Thermal Component Reference Guide

W A T L O W

Table of Contents Introduction Electric Heaters Resistance Temperature Detectors (RTDs)...... 49 This Application Guide is to assist you Thermistors ...... 52 in understanding the principles of electric thermal systems and compo- Non-Contact Temperature nents as they apply to various heating Sensor Basics ...... 54 tasks. Its purpose is to give you Defining an Application and theory, general calculations and Determining a Solution ...... 60 engineering data along with examples Reference Data ...... 61 for solving heating problems. This Thermocouple and Resistance Application Guide is not a how-to Wire RTD Initial Calibration manual or a substitute for specific Tolerances ...... 61 information related to complex RTD Resistance vs. Temperature and/or critical applications. Watlow Tables (Standard Thermistors) . . 63 engineers are available to provide you detailed information on engineering RTD Resistance vs. Temperature Tables (DIN Platinum RTDs). . . . . 70 approaches not included in this guide. When designing any thermal system, caution must always be exercised to Temperature Controllers comply with safety requirements, local Product Overview ...... 7 and/or national electrical codes, Power Calculations ...... 15 agency standards, considerations for Power Evaluation...... 19 use in toxic or explosive environments Review of Heater and sound engineering practices. Application Factors...... 20 Integrity and suitability of any Select Heater ...... 22 thermal system design/specification is ultimately the responsibility of those Reference Data ...... 24 selecting and approving system Heat Loss Factors and Graphs . . 26 components. Quick Estimates of This Application Guide is organized Wattage Requirements ...... 30 into sections dealing with the basic facets of an electric thermal system: Temperature Sensors the electric heaters, temperature sensors and temperature and power controllers. Information about wiring practices along with reference data and examples are also provided. Product Overview ...... 74 As always, Watlow Electric Manufac- Thermal Control Principles ...... 81 turing Company stands ready to Control Output Types ...... 88 provide you advice or engineering Control Output Comparison. . . . . 90 expertise to design and produce components to meet your electric Limit Control Protection for Temperature Process ...... 93 heating requirements. Agency Recognition for Controllers ...... 94 Customer Assistance Control System Tuning...... 94 Product Overview ...... 34 Typical Thermal Control System Manufacturing Facilities ...... 3 Contact Temperature Sensors Chart Recordings ...... 97 Sales Offices ...... 4 Types and Comparisons...... 36 Controller Overview ...... 99 Thermocouples ...... 37 Data Communications...... 100

1 Table of Contents

Power Controllers Reference Data Glossary

Celsius to Fahrenheit / Definitions of Commonly Used Fahrenheit to Celsius ...... 127 Terms Used in Heating, Sensing Ratings of Listed Heater Voltages and Controlling ...... 188 Operated on Other Voltages...... 129 Conversion Factors...... 130 Watlow Products and Commonly Used Geometric Technical Support Areas and Volume...... 133 Delivered Worldwide Physical Properties of Solids, Liquids and Gases ...... 134 Product Overview ...... 101 Watlow’s worldwide sales and Properties of Non-Metallic distributor network Five Basic Types ...... 102 Solids ...... 134 If you don’t find what you need in this Theory of SCR Power Controllers . . 108 Properties of Metals ...... 137 Application Guide, call the Watlow Methods of Firing SCRs ...... 109 Properties of Metals in office nearest you listed on the Enclosure Guidelines ...... 112 Liquid State ...... 139 following One phone call Heater Life and Selection of Power Properties of Liquids...... 140 gives you instant access to expert technical advice, application Handling Device ...... 113 Properties of Gases ...... 143 assistance and after-the-sale service. SCR Protective Devices ...... 114 Properties of Air ...... 143 In addition, more than 150 authorized Corrosion Guide ...... 144 distributors are located in the U.S. Wiring Practices Examples of Applications...... 156 and 42 other countries. Cabinet Freeze Protection . . . . . 156 For up-to-date information on Watlow’s new products or services, Heating a Steel Mold ...... 158 see Watlow’s home page on the Melting of Aluminum...... 164 Internet at http://www.watlow.com. Heating Liquid in a Tank...... 174 Heating a Flowing Liquid ...... 178 Air Duct Heater ...... 182 Drying a Moving Web of Cloth . . 186

Electrical Noise ...... 116 Helpful Wiring Guidelines...... 118 Input Power Wiring ...... 120 Output Wiring ...... 122 SCR Wiring Ð Tips and Special Considerations ...... 124

2 W A T L O W

Customer Assistance Watlow Manufacturing Hannibal, Missouri Winona, Minnesota - Controls Facilities Watlow Hannibal Watlow Winona, Inc. Manufactures: Manufactures: United States Manufacturing • Circulation Heaters • Custom Electronic Controllers Facilities • Duct Heaters • Power Controls Anaheim, California • Immersion Heaters • Safety and Limit Controls Watlow AOV, Inc. • Multicell Heaters • Single Loop Controls Manufactures: • Tubular Heaters 1241 Bundy Boulevard, P.O. Box 5580 • Silicone Rubber Heaters • Thick Film Heaters Winona, MN 55987-5580 1400 North Kellogg Drive, Suite A #6 Industrial Loop Road Phone: 507-454-5300 Anaheim, CA 92807 P.O. Box 975 FAX: 507-452-4507 Phone: 714-779-2252 Hannibal, MO 63401 FAX: 714-777-9626 Phone: 573-221-2816 Winona, Minnesota - Polymer Watlow Polymer Technologies, Inc. Batavia, Illinois FAX: Tubular/Process/Multicell 573-221-3723 Manufactures: Watlow Batavia • Polymer Heaters Manufactures: FAX: Thick Film 1265 East Sanborn Street • Cast-In Heaters 573-221-7578 Winona, MN 55987 1310 Kingsland Drive Richmond, Illinois Phone: 507-457-9797 Batavia, IL 60510 Watlow Richmond FAX: 507-457-9736 Phone: 630-879-2696 Manufactures: FAX #1: 630-879-1101 • RTDs, Thermocouples, Thermistors Wright City, Missouri FAX #2: 630-482-2042 • Thermocouple Wire and Cable 4/1/02 (formerly Troy, MO) • Temperature Measurement Devices Watlow Process Systems Columbia, Missouri 5710 Kenosha Street, P.O. Box 500 Manufactures: Watlow Columbia/Ceramic Fiber Richmond, IL 60071 • Process Heating Systems Manufactures: #10 Cooperative Way • Ceramic Fiber Heaters Phone: 815-678-2211 FAX: 815-678-3961 Wright City, Missouri 63390 2407 Big Bear Court Phone: 636-745-7575 Columbia, MO 65202 St. Louis, Missouri FAX: 636-745-0537 Phone: 573-443-8817 World Headquarters and FAX: 573-443-8818 Watlow St. Louis Asian Manufacturing Facilities Manufactures: Singapore Watlow Columbia/Flexible • Band Heaters Manufactures: • Cable Heaters Watlow Singapore Pte. Ltd. • Flexible Heaters • FIREROD® Heaters Manufactures: ® 2101 Pennsylvania Drive • Radiant Heaters • FIREROD Heaters Columbia, MO 65202 • Special Heaters • Thermocouples Phone: 573-474-9402 • Strip Heaters 55 Ayer Rajah Crescent, #03-23 FAX: 573-474-5859 12001 Lackland Road Singapore 139949 St. Louis, MO 63146 Phone: 65-67780323 Fenton, Missouri Phone: 314-878-4600 FAX: 65-67739488 Single Iteration FAX: 314-878-6814 A Consulting Services Division European Manufacturing Facilities of Watlow Watsonville, California France 909 Horan Drive Watlow Anafaze Watlow France, S.A.R.L. (Sales Office) Fenton, MO 63026 Manufactures: Immeuble Ampère Phone: 866-449-6846 • Multi-loop Controls Z.I. Rue Ampere FAX: 636-349-5352 • High Level Software 95307 Cergy Pontoise Cedex, France Phone: 507-454-5300 Phone: 33-1-3073-2425 FAX: 507-452-4507 FAX: 33-1-3073-2875 3 Customer Assistance Watlow Manufacturing Italy Latin American Manufacturing Facilities Watlow Italy, S.r.l. Facilities Manufactures: Mexico European Manufacturing Facilities • Thermocouples Watlow de Mexico, S.A. de C.V. (con’t.) Via Meucci 14 Manufactures: Germany 20094 Corsico - MI, Italy • FIREROD Heaters Watlow GmbH Phone: 39-02-4588841 (Cartridge and Metric) Manufactures: FAX: 39-02-45869954 • Ceramic Knuckle Heaters • Cable Heaters • THINBAND® Heaters • Cartridge Heaters United Kingdom • HV Band Heaters (FIREROD, EB Cartridge and Watlow Limited • Silicone Rubber Heaters Metric FIREROD) Manufactures: • Tubular Heaters • Silicone Rubber Heaters • Band Heaters • Cable Heaters • K-RING® Heaters • Cartridge Heaters Av. Epigmenio Gonzalez No. 5 • Pump Line Heaters • FIREROD Heaters • Electronic Assemblies • Flexible Heaters Col. Parques Industriales Queretaro C.P. 76130 Lauchwasenstr. 1 • Thermocouples Queretaro, Mexico Postfach 1165 Robey Close D 76709 Kronau, Germany Linby Industrial Estate Phone: 52-442-217-62-35 Fax: 52-442-217-64-03 Phone: 49-7253-94-00-0 Linby, Nottingham, England NG15 8AA FAX: 49-7253-94-00-44 Phone: 44-0-115-964-0777 FAX: 44-0-115-964-0071

Sales Support United States Sales Offices Chicago Denver 1320 Chase Street, Suite 2 5945 West Sumac Avenue Atlanta Algonquin, IL 60102-9668 Littleton, CO 80123-0886 1320 Highland Lake Drive Phone: 847-458-1500 Phone: 303-798-7778 Lawrenceville, GA 30045-8225 Fax: 847-458-1515 Fax: 303-798-7775 Phone: 770-972-4948 Fax: 770-972-5138 Cincinnati Detroit 4700 Duke Drive, Suite 125 155 Romeo Road, Suite 600 Austin Mason, OH 45040-9163 Rochester, MI 48307 12343 Hymeadow, Suite 2L Phone: 513-398-5500 Phone: 248-651-0500 Austin, TX 78750-1830 Fax: 513-398-7575 Fax: 248-651-6164 Phone: 512-249-1900 Fax: 512-249-0082 Cleveland Houston 28 West Aurora 3403 Chapel Square Drive Birmingham Northfield, OH 44067-2063 Spring, TX 77388 308 Honeysuckle Lane Phone: 330-467-1423 Phone: 281-440-3074 Chelsea, AL 35043-9669 Fax: 330-467-1659 Fax: 281-440-6873 Phone: 205-678-2358 Fax: 205-678-2567 Dallas Indianapolis PO Box 704011 160 W. Carmel Drive, Suite 204 Charlotte Dallas, TX 75370-4011 Carmel, IN 46032-4745 10915 Tara Oaks Drive Phone: 972-620-6030 Phone: 317-575-8932 Charlotte, NC 28227-5493 Fax: 972-620-8680 Fax: 317-575-9478 Phone: 704-573-8446 Fax: 866-422-5998

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Customer Assistance Sales Support Orlando Seattle 5514 Meadow Pine Ct. 1420 NW Gilman Blvd., Suite 2571 Kansas City Orlando, FL 32819 Issaqua, WA 98027 P.O. Box 15539 Phone: 407-351-0737 Phone: 425-222-4090 Lenexa, KS 66285-5539 Fax: 407-351-6563 Fax: 425-222-5162 Phone: 913-897-3973 Fax: 913-897-4085 Philadelphia Shreveport 85 Old Dublin Pike 149-1⁄2 Ockley Drive Los Angeles Doylestown, PA 18901-2468 Shreveport, LA 71105 1914 West Orangewood Avenue Phone: 215-345-8130 Phone: 318-864-2864 Suite 101 Fax: 215-345-0123 Fax: 318-864-2864 Orange, CA 92868-2005 Phone: 714-935-2999 Tampa/St. Petersburg Fax: 714-935-2990 Phoenix 831 Huntington Court 14830 North 10th Street Winter Park, FL 32789-4722 Maryland/Virginia Phoenix, AZ 85022-3751 Phone: 407-647-9052 85 Old Dublin Pike Phone: 602-298-6960 Fax: 407-647-5466 Doylestown, PA 18901-2468 Fax: 888-579-5222 Phone: 215-345-8130 Tulsa Fax: 215-345-0123 Pittsburgh 4444 East 66th Street, Suite 101 1241 West North Avenue Tulsa, OK 74136-4205 Milwaukee/Appleton Pittsburgh, PA 15233-1935 Phone: 918-496-2826 400 South Linwood Avenue, Suite 13 Phone: 412-322-5004 Fax: 918-494-8901 Appleton, WI 54914-4970 Fax: 412-322-1322 Phone: 920-993-2161 Portland Fax: 920-993-2162 Asian Sales Offices 1306 Northeast 149th Place Minneapolis Vancouver, WA 98684 Australia 14551 Judicial Road Phone: 360-254-1009 Watlow Australia Pty. Ltd. Suite 127 Fax: 360-254-2912 23 Gladstone Park Drive Burnsville, MN 55306 Tullamarine, VIC 3043 Phone: 952-892-9222 Sacramento Australia Fax: 952-892-9223 1698 River Oaks Circle Phone: 61 (39) 335-6449 Fairfield, CA 94533-7797 Nashville FAX: 61 (39) 330-3566 Phone: 707-425-1155 Sales Territory: Australia, New Zealand 212 Hidden Lake Road Fax: 707-425-4455 Hendersonville, TN 37075-5502 China Phone: 615-264-6148 Saint Louis Watlow China Fax: 615-264-5654 12001 Lackland Road Rm 1903, Chang De Building No. 478-5 St. Louis, MO 63146-4039 Chang Shou Road, Shanghai , China New England Phone: 636-441-5077 Tel: +(86) 21 62772138 4 John Tyler Street, Suite E Fax: 636-447-8770 Fax: +(86) 21 62278559 Merrimack, NH 03054-4800 Sales Territory : China Phone: 603-882-1330 San Francisco Fax: 603-882-1524 780 Montague Expressway, Suite 308 San Jose, CA 95131 New York/Upstate Phone: 408-434-1894 6032 Old Beattie Road Fax: 408-435-5409 Lockport, NY 14094-7943 Phone: 716-438-0454 Fax: 716-438-0082 5 Customer Assistance Japan Canadian Sales Offices Sales Territory: All Other European Countries Watlow Japan Ltd. Ontario Azabu Embassy Heights 106 Italy 1-11-12 Akasaka Watlow Ontario Minato-Ku, Tokyo, Japan 107-0052 60 Bristol Road East, Suite 460 Watlow Italy, S.r.l. Mississauga, Ontario L4Z 3K8 Via Meucci 14 Phone: 011-81-3-5403-4688 Canada 20094 Corsico - MI, Italy FAX: 011-81-3-5575-3373 Sales Territory: Japan Phone: 905-979-3507 Phone: +39-02-4588841 FAX: 905-979-4296 Fax: +39-02-45869954 Korea Sales Territory: Italy Quebec and Atlantic Canada Watlow Korea Co., Ltd. United Kingdom 3rd Fl., Taehong Bldg. Watlow Quebec & Atlantic Canada 20-6 Yangjae-dong, Seocho-gu C.P. 68084 Watlow Limited Seoul, Korea 137-130 Blainville, Quebec J7C 4Z4 Canada Robey Close Linby Ind. Estate Phone: 450-433-1309 Linby Nottingham Phone: 82 (2) 575-9804 England, NG15 8AA FAX: 82 (2) 575-9831 FAX: 450-433-0457 Sales Territory: Korea Phone: +44 (0) 115 964 0777 Western Canada FAX: +44 (0) 115 964 0071 Malaysia Watlow Western Canada Sales Territory: Great Britain, Ireland 9912 Lougheed Highway Watlow Malaysia Sdn Bhd Latin American Sales Office 38B Jalan Tun Dr Awang Burnaby, British Columbia V3J 1N3 Canada 11900 Bayan Lepas, Penang Mexico Phone: 604-444-4881 Malaysia Watlow de Mexico S.A. de C.V. Fax: 604-444-4883 Phone: 60 (4) 641-5977 Av. Epigmenio Gonzalez No. 5 FAX: 60 (4) 641-5979 European Sales Offices Col. Parques Industriales Sales Territory: Malaysia Querataro CP-76130 France Queretaro, Mexico Singapore Watlow France, S.A.R.L. Phone: + 52 442 217-62-35 Watlow Singapore Pte. Ltd. Immeuble Somag FAX: + 52 442 217-64-03 55 Ayer Rajah Crescent, #03-23 16 Rue Ampere Singapore 139949 Cergy Pointoise 95307 Sales Territory: Mexico and Latin America Phone: + (65) 67739488 Phone: 33 (1) 3073-2425 FAX: + (65) 67780323 FAX: 33 (1) 3073-2875 Corporate Headquarters Sales Territory: Singapore, South East Sales Territory: France Asia , Hong Kong, India Watlow Electric Manufacturing Sales Support Germany Company St. Louis, MO Watlow GmbH Taiwan 12001 Lackland Road Lauchwasenstr. 1 St. Louis, MO 63146 Watlow Taiwan Postfach 1165 10F-1 No. 189 76709 Kronau, Germany Phone: 314-878-4600 Chi-Shen 2nd Road FAX: 314-434-1020 Phone: +49-7253-9400-0 Kaohsiung, Taiwan, 801 Sales Territory: All countries and Canadian FAX: +49-7253-9400 Phone: 886-7-288-5168 provinces not specified. FAX: 886-7-288-5568 Sales Territory: Taiwan

6 Electric Heaters 7 ) 2 ) ) to 2 2 (230 W/in (30 W/in (55 W/in 2 2 2 and stainless steel. ® to 760°C (1400°F) 8.5 W/cm to 650°C (1200°F) wafer processing equipment 35.7 W/cm 4.6 W/cm Performance Capabilities • temperatures Maximum operating • watt densities from Typical maximum Applications • Extruders • Blown film dies • machines Injection molding • heating applications Other cylinder • Maximum operating temperatures Applications • Plastic injection molding nozzles • Semiconductor manufacturing and • Hot metal forming dies and punches • Sealing and cutting bars • Restaurant and food processing • Cast-in heaters • Laminating and printing presses • Air heating • Heating in a vacuum environment • Textile manufacturing Performance Capabilities • Typical maximum watt densities to heater and the standard mica band heater for specialized heater and the standard ® constructions, Watlow’s band and nozzle heaters are ideal for every type of band and nozzle heaters are constructions, Watlow’s equipment. plastic processing mica insulation, stainless include stainless steel with Sheath materials available with mica insulation. insulation and aluminized or zinc steel steel with mineral Cable Heaters be formed to a variety of shapes as The versatile Watlow cable heater can small diameter, high performance units dictated by its many applications. These to your desired configuration. are fully annealed and readily bent Sheath materials available include Inconel Heaters Heaters Band and Nozzle flexible MI Band heater, the patented, Led by the high performance THINBAND W A T L O W O L T A W is a registered trademark of the ® Inconel Product Overview Product Application Guide This section of the heaters; their is devoted to electric of use and different types, methods for determining general calculations unable to find specifications. If you’re type of Watlow or determine which your needs, call heater will best suit your nearest Watlow sales representative. Sales offices are listed on the back cover of this Application Guide. Application Guide Application Electric Heaters Special Metals Corporation. Application Guide Electric Heaters Cartridge Heaters The Watlow FIREROD® heater enters its 50th year of industry leading expertise Product Overview as the premier choice in swaged cartridge heating. With premium materials Continued and tight manufacturing controls, the FIREROD heater continues to provide superior heat transfer, uniform temperatures and resistance to oxidation and corrosion in demanding applications and high temperatures. Sheath materials available are Incoloy® and stainless steel. Performance Capabilities • Typical maximum watt densities up to 62 W/cm2 (400 W/in2) • Maximum operating temperatures to 760°C (1400°F) Applications • Molds • Life sciences • Dies • Aerospace • Platens • Semiconductor • Hot plates • Foodservice • Sealings equipment • Fluid heating

Cast-in Heaters When Watlow creates a custom-engineered cast-in product, the result is more than just a heater. It’s a “heated part” that becomes a functional component of your equipment, designed in the exact shape and size you need. The IFC heated part consists of a Watlow heater element built into custom metal shapes designed specifically for your application. Sheath materials available are 319 and 356 aluminum, pure aluminum and IFC (stainless, nickel, Inconel®, aluminum, copper and bronze). Performance Capabilities • Typical maximum watt densities to 15.5 W/cm2 (100 W/in2) • Maximum operating temperatures to 400°C (752°F) to 760°C (1400°F) depending on material Applications • Semiconductor manufacturing • Foodservice equipment • Plastics processing • Medical equipment • Hot glue melt • Circulation heating

Incoloy® and Inconel® are registered trademarks of the Special Metals Corporation.

8 Electric Heaters 9 ) 2 (11.5 W/in 2 1.8 W/cm to 1205°C (2200°F) applications Applications • Oil and gas field equipment • Refineries & petrochemical plants • Chemical and industrial gas plants • HVAC duct heating • Open tanks and heat treat baths • Textile drying • Heat transfer and lube oil systems • Semiconductor processing equipment • Precision cleaning equipment • Power generation systems • Emissions control systems • Supercritical fluid heating • In-line water boilers Performance Capabilities • Typical maximum watt densities to • Maximum operating temperatures Applications • High temperature furnaces • Metal melting, holding and transfer • Semiconductor processing • Glass, ceramic and wire processing • Analytical instrumentation • Fluidized beds • Laboratory and R&D • Other high temperature process Circulation and Process Heaters Circulation and Process for fluids such as heaters are compact heating solutions Watlow’s circulation like de-ionized water gases, supercritical fluids and liquids purified and inert well as for general liquid and electronics industries as for use in semiconductor heater lines of Watlow’s industrial process and gas heating applications. heat a myriad of high and and duct heaters are used to immersion, circulation water, oils, solvents, ranging from de-ionized and process low viscosity fluids like air, nitrogen, purified solutions, etc. to process gases rinse agents, caustic well. and inert gases as Ceramic Fiber Heaters temperature iron-chrome-aluminum Ceramic fiber heaters integrate a high fiber insulation. Numerous stock, (ICA) heating element wire with ceramic be provided, achieving the “heated standard and/or custom shapes can non-contact applications. The insulation” concept for your high temperature, high temperatures inside the heated ceramic fiber insulation isolates the are low mass, fast heating, with high chamber from the outside. The heaters of insulation values and the self-supported heating elements that offer some heater the highest temperature heating capabilities within the Watlow family of designs. The sheath material available is molded ceramic fiber. W A T L O W O L T A W Product Overview Product Continued Application Guide Application Electric Heaters Application Guide Electric Heaters Flexible Heaters Flexible heaters from Watlow are just what the name implies: thin, bendable and Product Overview shaped to fit your equipment. You can use your imagination to apply heat to the Continued most complex shapes and geometries conceivable without sacrificing efficiency or dependability. Sheath materials available include silicone rubber, Kapton®, HT foil and neoprene. Performance Capabilities • Typical maximum watt densities from 1.7 W/cm2 (11 W/in2) to 17.0 W/cm2 (110 W/in2) • Maximum operating temperatures to 595°C (1100°F) Applications • Medical equipment such as blood analyzers, respiratory therapy units and hydrotherapy baths • Freeze protection for military hardware, aircraft instrumentation and hydraulic equipment • Battery heating • Foodservice equipment • Factory bonding / subassemblies • Any application requiring a flexible shape or design Multicell Heaters The multicell heater from Watlow offers independent zone control for precise temperature uniformity, loose fit design for easy insertion in and removal from the equipment and extreme process temperature capability. The heaters are available with up to eight independently controllable zones and one to three internal thermowells for removable sensors. Custom assemblies are available. Incoloy® sheath material is available. Performance Capabilities • Typical maximum watt densities to 6.2 W/cm2 (40 W/in2) • Maximum operating temperatures to 1230°C (2250°F) Applications • Super plastic forming and diffusion bonding • Hot forging dies • Heated platens • Furnace applications • Superheating of air and other gases • Fluidized beds for heat treating • Glass forming, bending and tempering • Long heater needs (1219 cm (40 foot)) • Soil remediation ® Kapton is a registered trademark of • Aluminum processing E.I. du Pont de Nemours & Company.

10 Electric Heaters 11 ) 2 2 ) to (4.0 W/in 2 2 ) 2 ) 2 ) to 7.0 W/cm 2 (0.5 W/in 2 (60 W/in 2 (3.8 W/in (30 W/in 2 2 ) 2 1095°C (2000°F) (45 W/in 4.6 W/cm from 0.08 W/cm to 9.30 W/cm 0.59 W/cm 220°C (428°F) densities from 0.62 W/cm flexible shape • Maximum operating temperatures to Applications • Thermoforming • Food warming • Paint and epoxy curing • Heat treating • High temperature furnaces • Tempering and annealing processes Performance Capabilities • Typical maximum watt densities from Performance Capabilities • open watt densities Typical maximum • to Maximum operating temperatures Applications • Medical• Analytical• Aerospace• protection Freeze • Battery heating a • Any heated part application requiring Semiconductor • • Foodservice • Transportation • watt Typical maximum immersion heater line, we have a solution for almost any heater line, we have a solution for almost ® tubular, molded ceramic fiber, quartz tube and stainless steel emitter ® Radiant Heaters With Watlow’s diverse RAYMAX strip sheath materials are available. application requiring radiant heat. Our capabilities cover a wide range of application requiring radiant heat. Our panel heaters to fast-responding quartz needs, from contamination-resistant tubes to rugged tubular elements and high temperature ceramic panels. Incoloy Polymer Heaters a heated plastic part technology from Watlow, specify For the latest in heating resistive heating Watlow’s heated plastic parts combine in your next product. to yield a part that is range of thermoplastic compounds elements with a wide molding techniques Watlow utilizes typical injection both heater and structure. to produce heated plastic element construction methods and patented resistive safe and cost-effective. parts that are durable, W A T L O W O L T A W is a registered trademark of ® is a registered trademark of ® Ferro Corporation. Santoprene Advanced Elastomer Systems. Alcryn Product Overview Product Continued Application Guide Application Electric Heaters Application Guide Electric Heaters Strip Heaters Watlow’s mica and 375 strip heaters are the versatile solution for a number of Product Overview applications. They can be bolted or clamped to a solid surface for freeze and Continued moisture protection, food warming and other applications or utilized as a non- contact radiant heater. The 375 finned strip heaters are commonly used for air heating, drying ovens and space heaters. Performance Capabilities • Typical maximum watt densities from 7.8 W/cm2 (50 W/in2) to 15.5 W/cm2 (100 W/in2) • Maximum operating temperatures to 760°C (1400°F) Applications • Dies and molds • Tank and platen heating • Thermoforming • Packaging and sealing equipment • Ovens • Food warming equipment • Vulcanizing presses • Duct, space and air heaters • Incubators • Autoclaves • Freeze and moisture protection Thick Film Heaters Watlow layers thick film resistor and dielectric materials on quartz, stainless steel and ceramic substrates to produce high performance industrial heaters. The thick film heaters provide very fast temperature response and uniformity on a low-profile heater. Thick film heaters are ideal for applications where space is limited, where conventional heaters can’t be used, when heat output needs vary across the surface, or in ultra-clean or aggressive chemical applications. 430 stainless steel (open air), 430 stainless steel (immersion), aluminum nitride, quartz (open air) and quartz (clamp-on) sheath materials are available. Performance Capabilities • Typical maximum watt densities from 3 W/cm2 (20 W/in2) to 27 W/cm2 (175 W/in2) • Maximum operating temperatures to 550°C (1022°F) Applications • Ultra pure aggressive chemicals • Large panel processing • Analytical equipment • Foodservice equipment • Packaging sealing equipment • Life sciences sterilizers and GC/mass spectroscopy • Semiconductor wafer process equipment • Plastics hot runners nozzles and manifolds 12 Electric Heaters 13 Applications • Furnaces and ovens • Molten salt baths • Foodservice equipment • Semiconductor equipment • Die casting equipment • Metal melt and holding • Fluidized beds • Boilers • Radiant heating • Process air heating • Drying and warming and CSA component recognized elements available. and CSA component ® Tubular and Process Assemblies Tubular and Process elements are tubular heater elements and flat FIREBAR Watlow’s WATROD as water, oils, solvents for direct immersion in liquids such designed primarily and gases. By generating molten materials as well as air and process solutions, are virtually 100 percent the liquid or process, these heaters all the heat within formed and shaped into versatile heaters can also be energy efficient. These heating applications. for radiant heating and contact surface various geometries UL W A T L O W O L T A W Product Overview Product Continued Application Guide Application Electric Heaters Application Guide Electric Heaters Most electrical heating problems can be readily solved by determining the heat required to do the job. To do this, the heat requirement must be converted to electrical power and the most practical heater can then be selected for the job. Whether the problem is heating solids, liquids or gases, the method, or approach, to determining the power requirement is the same. All heating problems involve the following steps to their solution: Define the Heating Problem Calculate Power Requirements System Start-up and Operating Power Requirement System Maintenance Power Requirements Operating Heat Losses Power Evaluation Review System Application Factors Safe/Permissible Watt Densities Mechanical Considerations Operating Environment Factors Safety Factor Heater Life Requirements Electrical Lead Considerations

Defining the Problem Your heating problem must be clear- • Weights and dimensions of both And since the thermal system you’re ly stated, paying careful attention to heated material(s) and containing designing may not take into account defining operating parameters. Gather vessel(s) all the possible or unforeseen heating this application information: • Effects of insulation and its thermal requirements, don’t forget a safety • Minimum start and finish properties factor. A safety factor increases heater capacity beyond calculated temperatures expected • Electrical requirements—voltage requirements. For details on safety • Maximum flow rate of material(s) • Temperature sensing methods and factor, please see “Safety Factor being heated location(s) Calculation” under the portion of this • Required time for start-up heating • Temperature controller type section dealing with “Review of Heater and process cycle times • Power controller type Application Factors,” on page 20. • Electrical limitations

14 Electric Heaters 15 to ambient 3.412 Temp. differential

•

3.412 3.412 •

•

temperature rise (°F)

• )(°F) 2 (ft °F)

• Surface area of material Specific heat heat of fusion or vaporization (Btu/lb)

L + Safety Factor • • (Btu/lb 3 ⁄

hr)

• °F

Start-up or cycle time (hrs) • Start-up or cycle time (hrs)

2 Thickness of material or insulation (in.) in./ft

• working cycle to the operating point, within the time desired to the operating point, Watts required to melt or vaporize material during start-up period Watts required to melt or vaporize during working cycle Watts required to melt or vaporize material Watts required to raise temperature of the material during the raise temperature of the material during Watts required to Watts required to raise the temperature of material and equipment raise the temperature of material and Watts required to Watts lost from surfaces by: (Btu Thermal conductivity

of material or insulation • Conduction-use equation below • Radiation-use heat loss curves • Convection-use heat loss curves = = = = = Weight of material (lbs) Weight of material (lbs)

Short Method + C + Start-up watts = A C D watts-melting or vaporizing) Equation for C and D (Absorbed Equation for A and B (Absorbed watts-raising temperature) Equation for A and B (Absorbed B Operating watts = B + D + L + Safety Factor Operating watts = on application. 10 percent to 35 percent based Safety Factor is normally A L Equation for L (Lost conducted watts) ) for W A T L O W O L T A W 7 12 wer Calculations Desired Temperature o P Required Calculations for Heat Energy your own calcu- When performing Reference Data lations, refer to the page section (begins on covered by values of materials these equations. The total heat energy (kWH or Btu) required to satisfy the system needs will be either of the two values shown below depending on which calculated result is larger. A.Start-Up Heat Required for B. the Heat Required to Maintain The power required (kW) will be the heat energy value (kWH) divided by the required start-up or working cycle time. The kW rating of the heater will a be the greater of these values plus safety factor. The calculation of start-up and operating requirements consist of several distinct parts that are best handled separately. However, a short method can also be used for a quick estimate of heat energy required. Both methods are defined and then evaluated using the following formulas and methods: Application Guide Application Electric Heaters Application Guide Electric Heaters Equation 1 • • ∆ Power Calculations— QA or QB =w Cp T Conduction and Convection 3.412

Heating QA = Heat Required to Raise Temperature of Materials During Heat-Up (Wh)

Equation 1—Absorbed Energy, QB = Heat Required to Raise Temperature of Materials Processed Heat Required to Raise the in Working Cycle (Wh) Temperature of a Material w = Weight of Material (lb)

Because substances all heat differ- Cp = Specific Heat of Material (Btu/Ib • °F) ently, different amounts of heat are ∆T = Temperature Rise of Material (T - T )(°F) required in making a temperature Final Initial change. The specific heat capacity This equation should be applied to all materials absorbing heat in the of a substance is the quantity of heat application. Heated media, work being processed, vessels, racks, belts, needed to raise the temperature of a and ventilation air should be included. unit quantity of the substance by Example: How much heat energy is needed to change the temperature one degree. Calling the amount of of 50 lbs of copper from 10°F to 70°F? heat added Q, which will cause a Q= w • Cp • ∆T change in temperature ∆T to a weight = (50 lbs) • (0.10 Btu/Ib • °F) • (60°F) = 88 (Wh) of substance W, at a specific heat of 3.412 material Cp, then Q =w • Cp • ∆T. Since all calculations are in watts, an additional conversion of 3.412 Btu = 1 Wh is introduced yielding:

Equation 2—Heat Required to Equation 2 Melt or Vaporize a Material Q or Q =w • H w • H C D f OR v In considering adding heat to a 3.412 3.412 substance, it is also necessary to anticipate changes in state that might QC = Heat Required to Melt/Vaporize Materials During Heat-Up (Wh) occur during this heating such as QD = Heat Required to Melt/Vaporize Materials Processed in melting and vaporizing. The heat Working Cycle (Wh) needed to melt a material is known w = Weight of Material (lb) as the latent heat of fusion and H = Latent Heat of Fusion (Btu/Ib) represented by Hf. Another state f change is involved in vaporization Hv = Latent Heat of Vaporization (Btu/lb) and condensation. The latent heat of Example: How much energy is required to melt 50 lbs of lead? vaporization Hv of the substance is the energy required to change a sub- Q = w • Hf stance from a liquid to a vapor. This Q = (50 lbs) • (9.8 Btu/Ib) = 144 (Wh) same amount of energy is released as 3.412 Btu/(Wh) the vapor condenses back to a liquid. Changing state (melting and vaporizing) is a constant temperature process. The Cp value (from Equation 1) of a material also changes with a change in state. Separate calculations are thus required using Equation 1 for the material below and above the phase change temperature.

16 Electric Heaters 17 2 ) 2 ). 134 1.00 1.29 0.63 ). 2

= = = .

) 26 ) 0.09 = 0.22 W/in 2 • where the temperature of both surfaces 2 . Tabulated values of thermal conductivity are . Tabulated values of thermal conductivity , we find that a blackbody radiator (perfect 5 15 ) 2 ) hour) 2

• e t

• L °F

• • T F 2 ∆ e

C • • •

A ) Evaluated at Surface in./ft ) °F SL SL

3.412 • 2 1 • F F

• -T • 2 Surface Area (in Radiation Heat Losses (Wh) Blackbody Radiation Loss Factor at Surface Temperature (W/in Emissivity Correction Factor of Material Surface

Vertical Heated surface faces down horizontally Thickness of Material (in.) Thickness of Material Convection Heat Losses (Wh) Surface Area (in Conduction Heat Losses (Wh) Conduction Heat Thermal Conductivity (Btu Heat Transfer Surface Area (ft Heat Transfer Surface Exposure Time (hr) Vertical Surface Convection Loss Factor (W/in Surface Orientation Factor Heated surface faces up horizontally Temperature Difference Across Material (T Temperature (See Ref. 9, page

= =A = = =

= A =k =k = =

======

L3 L3 L2 L2 L1 L1 F

SL SL

e Equation 3C—Radiation Losses Q A L ∆ e Example: Using Reference 139, page radiator) at 500°F, has heat losses of 2.5 W/in F Q at the same temperature (2.5 W/in Q Equation 3A—Heat Required to Replace Conduction Losses Required to Replace Conduction Equation 3A—Heat Q Polished aluminum, in contrast, (e = 0.09) only has heat losses of 0.22 W/in Polished aluminum, in contrast, (e = 0.09) only has heat losses of 0.22 A Q k F A This expression can be used to calculate losses through insulated walls of This expression can be used to calculate containers or other plane surfaces can be determined or estimated (begins on page included in the Reference Data section Equation 3B—Convection Losses Q t C W A T L O W O L T A W dependent

not ) give emissivity ) includes graphs 27 1 127 wer Calculations o on orientation of the surface. Emissivity is used to adjust for a material’s ability to radiate heat energy. Radiation Heat Losses For the purposes of this section, graphs are used to estimate radiation losses. Charts in the Reference Data section (page values for various materials. Radiation losses are Convection Heat Losses Convection is a special case of conduction. Convection is defined as the transfer of heat from a high temperature region in a gas or liquid as a result of movement of the masses of the fluid. The Reference Data section (page and charts showing natural and forced convection losses under various conditions. Conduction Heat Losses Conduction Heat is Heat transfer by conduction of heat from the contact exchange temperature to one body at a higher another body at a lower temperature, or between portions of the same body at different temperatures. P Continued Application Guide Application Electric Heaters Application Guide Electric Heaters Equation 3D—Combined Convection and Radiation Heat Losses Power Calculations QL4 = A • FSL

Continued QL4 = Surface Heat Losses Combined Convection and Radiation (Wh) Combined Convection A = Surface Area (in2) and Radiation Heat Losses FSL = Combined Surface Loss Factor at Surface Temperature (W/in2) Some curves in Reference 139 (page 155) combine both radiation and convection losses. This saves This equation assumes a constant surface temperature. you from having to use both Equations 3B and 3C. If only the convection component is required, then the radiation component must be determined separately and subtracted from the combined curve.

Total Heat Losses Equation 3E—Total Losses

The total conduction, convection and QL = QL1+ QL2 + QL3 If convection and radiation losses are calculated radiation heat losses are summed separately. (Surfaces are not uniformly insulated together to allow for all losses in the and losses must be calculated separately.) power equations. Depending on the OR application, heat losses may make up only a small fraction of total power QL = QL1+ QL4 If combined radiation and convection curves are used. required... or it may be the largest (Pipes, ducts, uniformly insulated bodies.) portion of the total. Therefore, do not ignore heat losses unless previous experience tells you it’s alright to do.

Equations 4 and 5 Start-Up Equation 4—Start-Up Power (Watts) and Operating Power Required QA + QC 2 Both of these equations estimate Ps = + (QL) • (1 + S.F.) ts 3 required energy and convert it to power. Since power (watts) specifies QA = Heat Absorbed by Materials During Heat-Up (Wh) an energy rate, we can use power to QC = Latent Heat Absorbed During Heat-Up (Wh) select electric heater requirements. QL = Conduction, Convection, Radiation Losses (Wh) Both the start-up power and the S.F. = Safety Factor operating power must be analyzed before heater selection can take ts = Start-Up (Heat-Up) Time Required (hr) place. During start-up of a system the losses are zero, and rise to 100 percent at process temperature. A good approximation of actual losses is obtained when 2 heat losses (QL) are multiplied by ⁄3 .

Equation 5—Operating Power (Watts)

QB + QD Po = +(QL) • (1 + S.F.) tc QB = Heat Absorbed by Processed Materials in Working Cycle (Wh) QD = Latent Heat Absorbed by Materials Heated in Working Cycle (Wh) QL = Conduction, Convection, Radiation Losses (Wh) S.F. = Safety Factor

tc = Cycle Time Required (hr) 18 Electric Heaters 19

) ) ) L B D S.F. (Q (Q (Q 5 15 2 to T 1 Melting or Vaporizing Process Radiation — Convection Conduction Operating Losses 10% Safety Factor 10% ) 4 Operating Process Heat to Raise Product from T ) Process Heat f 1 e ) f Time (Hours) ( ) F 2 4 ) - known or assumed 2 ) (3.412 Btu/Wh) Plane Surfaces Concentric Cylinders Outer Radiating Inward Concentric Cylinders Inner Radiating Outward 2 - T

4 1 ) ) ) /ft C A L 2 (Btu/Hr. Sq. Ft. °R

(Q (Q (Q - 1 -8 S (T - 1 L 10 e 1 L

• (144 in e 1 • Conduction Convection Radiation { () Start-Up - 1 S L S L L D D e D D () of

3 / Stephan Boltzman Constant 0.1714 Emitter Temperature (°F + 460) Load Temperature (°F + 460) Power Absorbed by the Load (watts) - from Equation 4 or 5 by the Load (watts) - from Equation Power Absorbed Area of Heater (in Emissivity Correction Factor - see below 139, page Shape Factor (0 to 1.0) - from Reference Initial Heat to Raise Equipment and Materials 2 Initial Heat to Melt or Vaporize Losses + + + =

10% Safety Factor 10% S S S ======e e e

1 1 1 1

9 8 7 6 5 4 3 2 1 R

10 A =

= = P f f

f (°R) (°R) (Watts) Power

R e e

1 2 f Comparison of Start-Up and Operating Power Requirements Comparison of Start-Up and Operating Ref. 1 S T e A F T P Equation 6—Radiation Heat Transfer Equation 6—Radiation Size Parallel Surfaces Between Infinite Emissivity Correction Factor (e W A T L O W O L T A W Emissivity Tables) Emissivity Tables) = Load Diameter = Load Emissivity (from Material = Heater Diameter = Heater Emissivity (from Material wer Calculations— wer Calculations— Evaluate effects of lengthening start-up time such that start-up watts equals operating watts (use timer to start system before shift). Compare start-up watts to operating watts. L S o L S D e D • Power Evaluation Power After calculating the start-up and operating power requirements, a comparison must be made and various options evaluated. Shown in Reference 1 are the start-up and operating watts displayed in a graphic format to help you see how power requirements add up. With this graphic aid in mind, the following evaluations are possible: • e When the primary mode of heat trans- When the primary add a step after fer is radiation, we Equation 5. to calculate the net Equation 6 is used radiant heat transfer between two bodies. We use this to calculate either the radiant heater temperature required or (if we know the heater temperature, but not the power required) the maximum power which can be transfered to the load. P Radiant Heating Application Guide Application Electric Heaters Application Guide Electric Heaters • Recognize that more heating Having considered the entire system, capacity exists than is being a re-evaluation of start-up time, Power Evaluation utilized. (A short start-up time production capacity, and insulating Continued requirement needs more wattage methods should be made. than the process in wattage.) • Identify where most energy is going and redesign or add insulation to reduce wattage requirements.

Review of Heater Silicone Rubber Heater Example: These guards also serve a secondary Application Factors 1000 watts are required for heating purpose in that they may minimize a 150°C (300°F) block. convective heat losses from the back From the silicone rubber heater watt of heaters and increase efficiency of Safe/Permissible Watt Densities density chart in the flexible heater the system. section of the Watlow Heaters catalog, A heater’s watt density rating gives us In all applications where the heater page 170. an indication of how hot a heater will must be attached to a surface, it is operate. We use this information to Maximum Watt Density = extremely important to maintain as establish limits on the application of 16 W/in2 for wirewound on-off intimate a contact as possible to aid heaters at various temperatures and (2.5 W/in2) or 38 W/in2 (6 W/cm2) for heat transfer. Heaters mounted on the under a variety of operating etched foil exterior of a part should have conditions. This means 63 in2 of wirewound clamping bands or bolts to facilitate The maximum operating watt density (five 3 inch • 5 inch heaters) or 27 in2 this contact. Heaters inserted in holes is based on applying a heater such of etched foil (two 3 inch • 5 inch should have hole fits as tight as that heater life will exceed one year. heaters) are required. possible. Whenever possible, the holes should exit through the opposite In conjunction with desired life, watt Mechanical Considerations density is used to calculate both the side of the material to facilitate Full access must be provided (in the required number of heaters and removal of the heater. design process) for ease of heater their size. replacement. This is usually done with shrouds or guards over the heaters. Operating Environment Factors possible contaminants for this appli- choice of the external sheath ma- • Contaminants are the primary cation are as follows: terial is very important to heater cause of shortened heater life. a. molten zinc metal life. A corrosion guide is provided, page 144, and should be consulted Decomposed oils and plastics b. zinc vapor (hydrocarbons in general), con- in order to avoid using materials ductive pastes used as anti-seize c. hydraulic oils that are not compatible with a materials, and molten metals and d. high temperature anti-seize particular environment. metal vapors can all create situa- materials • Explosive environments generally tions that affect heater life. Some e. moisture, if die cooling is aided require that the heater be com- heater constructions are better by water circulation pletely isolated from potentially sealed against contaminants than All of these factors indicate that a dangerous areas. This is accom- others. In analyzing applications, highly sealed heater construction plished by inserting the heater in pro- all possible contaminants must be is required. tective wells and routing the wiring listed in order to be able to fully through sealed passage-ways out • The corrosiveness of the materials evaluate the proposed heater. of the hazardous area. Very close heated, or the materials that will fusing is recommended in these Example: Heat is required to main- contact the heater must also be cases to minimize the magnitude of tain molten zinc in the passageways taken into consideration. Even if the failure, should it occur. of a zinc die casting machine. The a heater is completely sealed, the

20 Electric Heaters 21 of the sheath by ” wetting “ 10 percent safety factor for large 10 percent safety when there are heating systems or variables. very few unknown factor for small to 20 percent safety where medium heating systems sure you you are not 100 percent have accurate information. heating 20 to 35 percent for systems where you are making many assumptions.

the liquid, act as an insulator, and possibly cause the heater to fail. Here are some general guidelines: Here are some general • • • section of the Watlow Heaters catalog, page 262, to ensure that the sheath material and watt density ratings are compatible with the liquid being heated. Immersion heaters used in tanks should be mounted horizontally near the tank bottom to maximize convective circulation. However, locate the heater high enough to be above any sludge build-up in the bottom of the tank. Vertical mounting is not recommended. The entire heated length of the heater should be immersed at all times. Do not locate the heater in a or restricted space where free boiling a steam trap could occur. Scale build-up on the sheath and sludge on the bottom of the tank must be minimized. If not controlled they will inhibit heat transfer to the liquid and possibly cause overheating and failure. Extreme caution should be taken not to get silicone lubricant on the heated section of the heater. The silicone will prevent the , the — 144 s cycle time ’ s DIN-A- ’ ), be sure to use the variable ® time base, burst-firing version. For Immersion Heaters Use the Corrosion Guide, page and the Selection Guides in the Tubular Elements and Assemblies Heaters utilizing lower temperature insulating materials (silicone rubber and mica) have life limiting factors associated with exceeding the temperature limits of the insulation and with thermal cycling. Flexible heaters and mica strip and band heaters must be properly sized and controlled to minimize the temperature swings during thermal cycling of the elements. Thermal Cycling Excessive thermal cycling will accelerate heater failure. The worst cycle rate is one which allows full expansion and full contraction of the heater at a high frequency (approximately 30 to 60 seconds on and off). Prevent excessive cycling by using solid state relays (SSRs) or SCR power controllers. If using SSRs, set the temperature controller to one second. If using SCR power controllers (like Watlow smaller the safety factor. smaller the safety MITE Safety Factor Calculation be sized for a Heaters should always the calculated higher value than to as adding in a figure, often referred safety factor. the fewer Generally speaking, influences variables and outside , F) internal ® Life ° W A T L O W O L T A W yrs. mos.

2 2 ⁄ ⁄ 1 1 2 days 1 wk. 1 yr. (2000 hrs.) 2 wks. 4 mos. 1 3 s r C (1600 ° , FIREBAR ® acto s service life. Mineral

’

(2100) (2000) (1900) (1700) (1800) (1500) (1600)*

¡C (¡F) w of Heater 925 980 815 870* Temperature Approximate e 1150 1095 1040 Internal Element vi e Below are the estimated life expect- ancies for mineral insulated heater types: FIREROD Tubular, MI Cable, MI Strip, MI Band. Ref. 2 Heater Life Requirements Temperature The higher the temperature, the shorter a heater insulated heaters using traditional alloys for resistance elements are subject to the life limiting factor of wire oxidation. The winding wire oxidizes at a rate proportional to the element temperature. If the element to temperature is known it is possible project a heater life as shown on the table in Reference 2. Application charts and operating recommen- temperature to insure expected heater life greater than one year. dations use maximum 870 Application R Continued Application Guide Application Electric Heaters * Application Guide Electric Heaters Lead Characteristics—Ref. 3 Review of Heater Maximum Lead Area Contamination Abrasion Relative Application Factors Lead Types Temperature Resistance Flexibility Resistance Cost Continued ¡C (¡F) Electrical Lead Considerations Lead Protection General considerations in selecting Metal Overbraid —— Average Good Excellent Moderate various lead types are: Flexible Conduit —— Good Average Excellent Moderate • Temperature of lead area Lead Insulation Ceramic Beads 650 (1200) Poor Poor Average High • Contaminants in the lead Mica-Glass Braid area (Silicone or Teflon¨ • Flexibility required Impregnated) 540 (1000) Poor Good Average High • Abrasion resistance Glass Braid required (Silicone Impregnated) 400 (750) Poor Good Average Low • Relative cost Silicone Rubber 260 (500) Good Good Poor Low Temperatures listed indicate actual Teflon¨ 260 (500) Excellent Good Good Low physical operating limits of various PVC 65 (150) Good Good Poor Low wire types. Wires are sometimes rated by CSA, UL® and other agencies for operating at much lower temperatures. In this case, the rating agency temperature limit is the maximum level Teflon® is a registered trademark of at which this wire has been tested. If E.I. du Pont de Nemours & Company. agency approvals are required, don’t UL® is a registered trademark of the exceed their temperature limits. Underwriter’s Laboratories Inc.

Select Heater Initial Installation Cost Replacement Cost Each heater type has specific The cost of a new heater, lost produc- Heater Costs installation costs to be considered. tion time, removal and installation of After calculating wattage required and • Machining required— the new heater must be considered. considering various heater attributes, mill, drill, ream Generally, these costs are actually much greater than expected. Heater the scope of possible heater types • Materials required— life must be such that replacement should be narrowed considerably. heater, brackets, wiring Now, several factors not previously can be scheduled and planned dur- • Labor to mount and wire ing off-peak production times to avoid examined must be considered before heating elements final heater type selection: installation, lost production. operation and replacement costs. Operating Cost • Removal of existing heater The total system operating cost is a • Equipment downtime cost composite of two factors. It is usually • Material cost— best to examine cost on an annual heater, brackets, wiring basis: • Labor to remove and install • Total cost of energy heating elements (kW Hours) ($/kWH) • Additional purchasing costs • Scrap products after heater failure and during restart of process • Frequency of burnouts

22 Electric Heaters 23 $50.00/hr = 200.00 • $0.07/kWH = $346.00 $0.07/kWH = $591.00 $20.00/hr = 80.00 • • • Total/Year = $931.00 Total/Year = $686.00 2.38 kW/H 4.06 kW/H • • $12.00 Each = 60.00 • A plastic extrusion barrel is operating 40 hours per week. Five barrel is operating 40 hours per week. A plastic extrusion Shrouded and Insulated = 2.38 kW/H Shrouded and Uninsulated = 4.06 kW/HShrouded and Uninsulated 2080 Hours Same as Case 1 = 340.00 4 Hours Lost Production Time 2080 Hours 5 Heaters 4 Hours Labor to Install Annual Energy Cost: less when insulation is used. Here, the cost of operation is much Case 2: Example: $0.07/kWH. Assume utilized, 1000 watts each. Energy cost band heaters are usage is as follows: or 2080 hours per year Actual power one shift operation Replacement Cost: Case 1: Annual Energy Cost: Annual Energy Cost: Replacement Cost: Replacement Cost: W A T L O W O L T A W Select Heater Type, Size Type, Select Heater and Quantity Application Guide Application Electric Heaters Application Guide Electric Heaters Reference Data Ohm’s Law Ref. 4

V Volts WR Amperes Volts = Watts x Ohms R Amperes = Volts W W Ohms Volts = Watts I R Amperes Amperes = Watts Volts Volts = Amperes x Ohms W IR VI Amperes = Watts (Volts) (Amps) V Ohms

(Ohms) (Watts) V VI Ohms I Watts R W 2 Ohms = Volts Watts = Volts Amperes Ohms W 2 2 I R Watts = Amperes2 x Ohms Ohms = Volts 2 Watts I 2 2 2 2 V V Watts = Volts x Amperes Ohms = Watts W R Amperes2

Wattage varies directly as ratio of voltages squared

2 W = W x V2 2 1 (V)1 3 Phase Amperes = Total Watts Volts x 1.732

24 Electric Heaters L V 25 L V P L01 I V PO V L02 I DELTA WYE WYE /R) /R) PO 2 2 I L03 LO L W W (No Neutral) I I /R) PO 2 3 2 (V ⁄ ⁄

L 2 1 2 3 LO2 2 / 1 2 (V /2 R PO1 R L P01 = 3 W = = I = I = = V LO P03 I = 2 (V = 2 I 1 = PO3 = R L 0WYE 0WYE PO PO Equations For Open Wye Only I V W W = I = 1.73 I = 1.73 1 = V 0DELTA R P PO1 LO3 Equations For Open Delta Only V I I W DELTA ODELTA OWYE Wye and Delta Equivalents W 3-Phase Open Delta Ref. 8 W W 3-Phase Open Wye (No Neutral) Ref. 6 L V L V L P I V P V )/R 2 P = L 3 I L I L L I 2 L L 3 I )/R P R /R = 3(V 2 I = R R 2 L L 2 V /1.73 L = 1.73 V = 1.73 3 = 2 V L P R I = 3(V V = 1.73 R I = R = L /1.73 WYE WYE = P L 1 P 1 W Equations For Wye Only I V W Resistance of each branch = V R DELTA DELTA = I P P W V W Equations For Delta Only I 1 = = Phase Voltage = Line Voltage = Phase Current = Line Current R P L P L W = Wattage 3-Phase Delta (Balanced Load) Ref. 7 3-Phase Wye (Balanced Load) Ref. 5 Typical 3-Phase Wiring Diagrams and Equations for Resistive Heaters Wiring Diagrams and Equations Typical 3-Phase Definitions Delta For Both Wye and (Balanced Loads) V V I I R R= W A T L O W O L T A W Reference Data Reference Continued Application Guide Application Electric Heaters Application Guide Electric Heaters Ref. 9

Heat Loss Factors Heat Losses from Uninsulated Surfaces and Graphs 2000

Heat Losses at 70¡F Ambient Convection—Vertical Surface Combined Radiation and Convection— How to use the graph for more Oxidized Aluminum accurate calculations 1800 Radiation—Black Body Combined Radiation and Convection— Ref. 9—Convection curve Oxidized Steel correction factors: 1600 For losses from Multiply convection top surfaces or curve value by from horizontal 1.29 pipes 1400 For side surfaces Use convection

and vertical curve directly F ° 1200 pipes — For bottom Multiply surfaces convection curve 1000 value by 0.63

Radiation Curve Correction Factors The radiation curve shows losses 800 from a perfect blackbody and are not Temperature of Surface dependent upon position. Commonly used block materials lose less heat by 600 radiation than a blackbody, so correction factors are applied. These cor- rections are the emissivity (e) values listed to the right: 400 Total Heat Losses = Radiation losses (curve value times e) 200 + Convection losses (top) + Convection losses (sides) + Convection losses (bottom) = Conduction losses 0.1 0.2 0.3 0.4 0.6 0.8 1 2 3 4 5 6 7 8 910 20 30 40 5060 80 100 (where applicable) Losses—W/in2

26 26 Electric Heaters 27 — — 0.80 0.85 0.28 0.25 Ref. 11 — Ref. 10 — 0.90 — — ——— — ——— ——— ——— ——— Surface Oxide Oxide Most non-metals: 0.-.. .-..2 -0.2 -0.2 -0.2 -0.2 -0.2 -0.2 -0.2 -0.2 0.2 — Specific Specific Emissivity Btu/lb-¡F Btu/lb-¡F 600 0.11 0.20 0.60 0.92 800 0.12 0.20 0.60 0.92 ® ® Material Heat Emissivity Material Heat Polished Medium Heavy mildstainless 304stainless 430 0.11 0.11 0.12 0.17 0.17 0.10 0.57 0.57 0.75 0.85 0.85 0.85 AsbestosAsphaltBrickworkCarbon 0.25 0.40 0.22 0.20 Glass 0.20 Wood, Oak 0.57 Textiles PaperPlasticRubberSilicon Carbide 0.20-0.23 0.45 0.2-0.5 0.40 BlackbodyAluminumBrassCopperIncoloy 0.24 0.10 0.10 0.09 0.04 0.04 0.11 0.75 0.35 0.03 0.22 1.00 0.60 0.65 Iron, Cast 0.12 Inconel Lead, solid 0.03 Zinc 0.10 Tin 0.056 MagnesiumNickel 200Nichrome, 80-20Solder, 50-50 0.23 Steel 0.11 0.11 0.04 Additional information on emissivities is available from Watlow. Some Material Emissivities/Non-Metals Some Material Emissivities/Metals F.) F. ° ° - 2 W A T L O W O L T A W insulated uninsulated insulated and are registered ® The graphs for losses 950 ) = ) = 200 2 2 Losses from an Losses from an F) rise above ambient F) rise above ambient and Inconel ° ° ® uninsulated F) T ( T ( ° ∆ ∆ Use only for surfaces less than 800 Losses (W/in Incoloy Losses (W/in surface (with an emissivity close to 1.0): (This applies only to temperatures between ambient and about 250 Heat Loss Factors and Graphs Continued Helpful Hint: from to read at low surfaces are hard to ambient. Here temperatures close calculations that are two easy-to-use are only rule-of-thumb approximations when used within the limits noted. Rule #1: Application Guide Application Electric Data trademarks of the Special Metals Corporation. Rule #2: surface: (This insulation is assumed to be one inch thick and have a K-value of about 0.5 Btu-in/hr - ft Application Guide Electric Heaters Ref. 12 Heat Losses from Vertical Insulated Surfaces Heat Loss Factors 2600 and Graphs 2400 Continued F —° 2200 4" Insulation 5" Insulation 6" Insulation 2000 3" Insulation 1800 1. Based upon combined natural convection 1600 2" Insulation and radiation losses into 70°F environment. 1400 2. Insulation characteristics k = 0.67 @ 200°F 1200 1" Insulation k = 0.83 @ 1000°F. 1000 3. For molded ceramic fiber products and 800 packed or tightly packed insulation, losses 600 will be lower than values shown. 400 For 2 or 3 inches Insulation multiply by 0.84 0" Insulation For 4 or 5 inches Insulation multiply by 0.81 Temperature of Insulated Surface 200 For 6 inches Insulation multiply by 0.79 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 Losses—W/in2 Ref. 13

Heat Losses from Horizontal Metal Surfaces 1400

0 1300 0.2 e= n F io 1200 iat n d * a .40 —° o R 0 i d = t n n e 110 0 c a tio e n ia v io d ct Ra n ve nd 1000 o n a C o n C tio l ec .0 a d v =1 r e n e n o ion 900 u i C iat t b ed Rad a m n d o bi an N on 800 C om ecti C onv d C ine 700 mb Co 600 Temperature of Surface

500

0 1234 56 7 8910 11 12 13 14 15 16 17 18 19 20 Losses—W/in2 Ref. 14

Combined Convection and Radiation—Losses from Water Surfaces 210

F 190 60% Humidity —° 40% Humidity 170

150

130

110

90 Temperature of Surface

* For losses of molten metal surfaces, 70 0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 use the curve e=0.40. Losses—W/ft2 28

Electric Heaters

MPH — Velocity Wind 29 5 2.5 25 20 35 15 10 30 300 700 1

200 1 ) T)

17 ∆ 00 1 600 1 F ( °

— 000 1

500 900

800

400 W/ft 700 factor from the curves below to determine total heat losses. conditions (ref. Equation #3, page Losses from Oil or Paraffin Surfaces Losses from Oil or Paraffin Calculate surface heat losses at still air

— . 2. Multiply result by proper wind correction Multiply 2. 1 —

600 Losses 300

500 How to Use:

400 200

300

200 00 Wind Velocity Effects on Exposed, Bare and Insulated Surfaces Wind Velocity Effects on Exposed, Bare and 1 Temperature Difference Between Exposed Surface and Air

00 1 Combined Convection and Radiation Combined Convection Ref. 16 Ref. 15 0 0 0 5 0

0 . .

1 1 600 500 400 300 200 1 3.0 2.5 2.0 3.5

Temperature of Surface of Temperature F —° Wind Velocity Correction Factor Correction Velocity Wind W A T L O W O L T A W s r acto F Heat Loss Continued Application Guide Application Electric Heaters and Graphs Application Guide Electric Heaters Kilowatt-Hours to Heat Steel*—Ref. 17 Temperature Rise ¡F Quick Estimates of Amount Wattage Requirements of Steel 50¡ 100¡ 200¡ 300¡ 400¡ 500¡ 600¡ The following tables can be used (lb.) Kilowatts to Heat in One Hour to make quick estimates of wattage 25 0.06 0.12 0.25 .37 0.50 0.65 0.75 requirements. 50 0.12 0.25 0.50 .75 1.00 1.25 1.50 100 0.25 0.50 1.00 1.50 2.00 2.50 3.00 For Steel: Use table or metric equation. 150 0.37 0.75 1.50 2.25 3.00 3.75 4.50 200 0.50 1.00 2.00 3.00 4.00 5.00 6.00 kW = Kilograms x Temperature Rise (°C) 250 0.65 1.25 2.50 3.75 5.00 6.25 7.50 5040 x Heat-up Time (hrs.) 300 0.75 1.50 3.00 4.50 6.00 7.50 9.00 400 1.00 2.00 4.00 6.00 8.00 10.00 12.00 500 1.25 2.50 5.00 7.50 10.00 12.50 15.00 kW = Pounds x Temperature Rise (°F) 600 1.50 3.00 6.00 9.00 12.00 15.00 18.00 20,000 x Heat-up Time (hrs.) 700 1.75 3.50 7.00 10.50 14.00 17.50 21.00 800 2.00 4.00 8.00 12.00 16.00 20.00 24.00 900 2.25 4.50 9.00 13.50 18.00 22.50 27.00 1000 2.50 5.00 10.00 15.00 20.00 25.00 30.00 * Read across in table from nearest amount Includes a 40 percent safety factor to in pounds of steel to desired temperature rise compensate for high heat losses and/or low column and note kilowatts to heat in one hour. power voltage.

Kilowatt-Hours to Heat Oil*—Ref. 18 For Oil: Amount of Oil Temperature Rise ¡F Use equation or table. Cubic kW = Gallons x Temperature Rise (°F) Gallons 50¡ 100¡ 200¡ 300¡ 400¡ 500¡ Feet 800 x Heat-up time (hrs.) 0.5 3.74 0.3 0.5 1 2 2 3 OR 1.0 7.48 0.5 1.0 2 3 4 6 kW = Liters x Temperature Rise (°C) 2.0 14.96 1.0 1.0 2 4 6 11 1680 x Heat-up time (hrs.) 3.0 22.25 2.0 3.0 6 9 12 16 4.0 29.9 2.0 4.0 8 12 16 22 1 cu. ft. = 7.49 gallons 5.0 37.4 3.0 4.0 9 15 20 25 10.0 74.8 5.0 9.0 18 29 40 52 15.0 112.5 7.0 14.0 28 44 60 77 20.0 149.6 9.0 18.0 37 58 80 102 25.0 187 11.0 22.0 46 72 100 127 30.0 222.5 13.0 27.0 56 86 120 151 35.0 252 16.0 31.0 65 100 139 176 40.0 299 18.0 36.0 74 115 158 201 45.0 336.5 20.0 40.0 84 129 178 226 50.0 374 22.0 45.0 93 144 197 252 55.0 412 25.0 49.0 102 158 217 276 60.0 449 27.0 54.0 112 172 236 302 65.0 486 29.0 58.0 121 186 255 326 70.0 524 32.0 62.0 130 200 275 350 75.0 562 34.0 67.0 140 215 294 375 * Read across in table from nearest amount Add 5 percent for uninsulated tanks. in gallons of liquids to desired temperature rise column and note kilowatts to heat in one hour.

Electric Heaters

hour/lb Ð Watt — Content Heat 31 ¡

140 140 150 160 170 180 190 200 0 10 20 30 40 50 60 70 80 90 100 110 120 130

Degrees of Superheat of Degrees

Quality W —° — F % R.h. %

¡ 900

120 800

700

95 100

100

200 600

85 500 400 300 ¡ F

100

lbs/in — Pressure Gauge 2 ¡ 80 400 300 150 100 50 25 10 0 P ¡

210

450 400 350 300 250

Temperature Rise

60 F —° Ref. 19 Temperature Saturated — Kilowatts to Heat in One Hour Kilowatts to Heat in One ¡ 40 ¡ 20 ) 1 -W . . 2 1 2 Gallons 3 ft 0.661.32.0 52.7 103.3 134.0 0.3 205.3 0.5 256.7 0.8 0.5 308.0 1.1 1.1 409.4 1.3 1.6 50 0.8 1.6 2.2 60 1.6 2.1 2.7 70 2.4 2.7 1.1 3.2 3.2 3.3 2.1 4.0 4.0 3.7 3.2 1.3 5.4 4.8 4.3 2.7 6.4 6.4 5.3 4.0 7.5 1.6 8.0 6.4 5.3 3.2 9.6 8.5 6.7 11.2 10.7 4.8 1.9 8.0 12.8 6.4 3.7 11.0 15.0 13.0 8.0 5.6 16.0 9.6 7.5 13.0 19.0 16.0 9.3 19.0 12.0 15.0 22.0 19.0 22.0 26.0 10.712.013.4 8016.7 9020.0 10023.4 4.3 12526.7 5.0 150 5.533.7 175 8.5 7.040.0 10.0 200 8.0 11.053.4 250 13.0 13.0 9.066.8 14.5 11.0 300 16.0 16.0 13.0 400 17.0 20.0 18.0 19.0 16.0 21.0 500 21.0 24.0 21.0 21.0 27.0 27.0 28.0 24.0 27.0 32.0 32.0 27.0 32.0 26.0 43.0 40.0 33.0 37.0 29.0 43.0 53.0 47.0 40.0 32.0 30.0 53.0 64.0 40.0 47.0 34.0 53.0 37.0 64.0 80.0 48.0 67.0 47.0 85.0 56.0 107.0 80.0 64.0 56.0 107.0 80.0 133.0 65.0 75.0 96.0 128.0 160.0 93.0 112.0 149.0 187.0 Amount of Liquid Kilowatt-Hours to Heat Water* Kilowatt-Hours to S to W. Read W P represents the inlet temperature (and saturation pressure) of the system. Q represents the liquid content of the water vapor. S indicates the outlet temperature minus the saturated temperature. W indicates the heat content of the water vapor. Q to W. Read W steam/hour x (W 3. Draw a straight line from P through Watt density is critical. Review temperature and velocity prior to heater selection. Reference is 80 percent quality at 20 psig. Kilowatt-Hours to Superheat Steam Ref. 20 1. Q and S. Plot points on lines P, 2. Draw a straight line from P through 4. Required watts = Weight (lbs.) of C) x 0.076 ° F) ° C) F) x 0.16 ° W A T L O W O L T A W ° Use equation or table. 375 x Heat-up Time (hrs) 790 x Heat-up Time (hrs) OR kW = Liters/min. x Temperature Rise ( kW = Gallons x Temperature Rise ( OR kW = Liters x Temperature Rise ( kW = GPM x Temperature Rise ( Quick Estimates of Quick Requirements Wattage Continued Application Guide Application Electric Heaters gallons of liquid to desired temperature rise gallons of liquid to desired to heat in one hour. column and note kilowatts 1 cu. ft. = 7.49 gallons For Heating Water in Tanks: For Heating Flowing Water: * across in table from nearest amount in Read Application Guide Electric Heaters Kilowatt-Hours to Heat Air—Ref. 21 Amt. Quick Estimates of Temperature Rise ¡F Wattage Requirements of Air Continued CFM 50¡ 100¡ 150¡ 200¡ 250¡ 300¡ 350¡ 400¡ 450¡ 500¡ 600¡ 100 1.7 3.3 5.0 6.7 8.3 10.0 11.7 13.3 15.0 16.7 20.0 200 3.3 6.7 10.0 13.3 16.7 20.0 23.3 26.7 30.0 33.3 40.0 300 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 45.0 50.0 60.0 400 6.7 13.3 20.0 26.7 33.3 40.0 46.7 53.3 60.0 66.7 80.0 500 8.3 16.7 25.0 33.3 41.7 50.0 58.3 66.7 75.0 83.3 100.0 600 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 120.0 700 11.7 23.3 35.0 46.7 58.3 70.0 81.7 93.3 105.0 116.7 140.0 800 13.3 26.7 40.0 53.3 66.7 80.0 93.3 106.7 120.0 133.3 160.0 900 15.0 30.0 45.0 60.0 75.0 90.0 105.0 120.0 135.0 150.0 180.0 1000 16.7 33.3 50.0 66.7 83.3 100.0 116.7 133.3 150.0 166.7 200.0 1100 18.3 36.7 55.0 73.3 91.7 110.0 128.3 146.7 165.0 183.3 220.0 1200 20.0 40.0 60.0 80.0 100.0 120.0 140.0 160.0 180.0 200.0 240.0 Use the maximum anticipated airflow. This equation assumes insulated duct (negligible heat loss). 70°F inlet air and 14.7 psia. For Air: Use equation or table. kW = CFM* x Temperature Rise (°F) 3000 OR kW = Cubic Meters/Min* x Temperature Rise (°C) 47 For Compressed Air: kW = CFM** x Density** x Temperature Rise (°F) 228 OR kW = Cubic Meters/Min** x Temperature Rise (°C) x Density (kg/m3)** 57.5

**Measured at normal temperature and pressure. **Measured at heater system inlet temperature and pressure.

32 Temperature Sensors 33 or substance (most notably the energy contained in the infrared portion of the electromagnetic spectrum) and detecting its intensity. This method is used to sense the temperatures of solids and liquids. IR sensors cannot be used to sense the temperature of gases due to their transparent nature. Temperature Sensing Methods Temperature Contact temperature sensing brings the sensor in physical contact with a substance or object. Contact sensing can be used with solids, liquids or gases. Non-contact temperature sensing (infrared temperature sensing or IR sensing) measures temperature by intercepting a portion of the electromagnetic energy emitted by an object W A T L O W O L T A W (°F - 32)] (°R - 0.6°); K = °C + 273] 9 ⁄ 5 9 ⁄ 5 the Celsius scale for scientific and engineering equations [K = throughout the world [°C = the Fahrenheit scale for scientific and engineering equations [°R = 1.8K + 0.6°; °R = °F + 460°] North America (°F = 1.8°C + 32) • Kelvin—used in conjunction with Temperature is the degree of “hotness” Temperature is the body or substance or “coldness” of a referenced to a as indicated on, or standard scale. of temperature is Another way to think in terms of heat energy. Heat energy is the amount of molecular activity which is the sum of an atom’s subatomic par- ticle vibration, oscillation and friction with other subatomic particles in the same molecule. The greater the molecular activity, the greater the amount of heat energy. Conversely, less molecular activity results in less heat energy. The theoretical point, or “temperature,” at which there is no molecular activity is called absolute zero. To measure “temperature” or the relative amount of heat energy, temperature scales have been devised to define arbitrary increments. There are four temperature scales commonly in use today: • Celsius—commonly used Defining Temperature— What Is It? Application Guide Application The Art of Temperature Sensing • Rankine—used in conjunction with • Fahrenheit—commonly used in Application Guide The Art of Temperature Sensors Sensing Thermocouples Product Overview Watlow provides more than 80 years of manufacturing, research and quality for your temperature sensing needs. A tremendous selection of general application, mineral insulated metal sheathed, base and noble metal thermocouples are available. Fiberglass insulated thermocouples are capable of temperatures up to 480˚C (900˚F) for continuous operation. Watlow provides grounded, ungrounded and exposed junctions, same day delivery on millions of products and custom manufactured thermocouples. Applications • Plastic injection molding machinery • Food processing equipment • Engine and turbine exhaust gas • Semiconductor processing • Heat treating and metals processing • Medical equipment • Aerospace industries • Packaging equipment • Test stands

RTDs and Thermistors Watlow’s platinum resistance elements are specially designed to ensure precise and repeatable temperature versus resistance measurements. The sensors are made with controlled purity platinum wire and high purity ceramic components, and constructed in a unique strain-free manner. Watlow RTDs and thermistors are accurate, sensitive, interchangeable, standardized and repeatable. Performance Capabilities • Temperature range of -200°C (-328°F) to 650°C (1200°F) • Specialty RTDs available to 850°C (1560°F) Applications • Air conditioning and refrigeration servicing • Furnace servicing • Foodservice processing • Medical research • Textile production • Plastics processing • Petrochemical processing • Microelectronics • Air, gas and liquid temperature measurement 34 Temperature Sensors 35 mineral insulated, metal-sheathed cable mineral insulated, XACTPAK cable is fireproof, high pressure XACTPAK cable is shock resistant, rated, cold and thermal proof, formable, gas tight, moisture resistant and high weldable, corrosion Cryogenic cable temperature rated. available upon request. mm Diameters are available down to 0.25 0 to (0.01 inch). Temperature ranges from 1480°C (32 to 2700°F). Applications • Atomic research / nuclear reactors • Blast furnaces / vacuum furnaces • Catalytic reformers • Diesel engines • Food and beverage • Glass and ceramic • Heat treating • Jet engines / rocket engines • Medical • Power stations / steam generators • Refineries and oil processing Insulation temperature ranges from -200 to 1290°C (-328 to 2350°F). SERV-RITE wire features NIST calibration certificates, solid or stranded wire constructions, wide selection of insulation types, color coding and select metallic overbraids and wraps. Applications • Aerospace industries • Composite component manufacturing • Automotive • Cryogenic applications • Electric power plants • Food processing • Glass, ceramic and brick manufacturing • Laboratories • Medical equipment • Petrochemical • Metal processing ® thermocouple wire and thermocouple ® Wire and Cable Cable ¨ ¨ make it ideally suited to solve a wide variety of problem applications. The outer to solve a wide variety of problem make it ideally suited hostile environments, and thermocouple from oxidation and sheath protects the dielectric strength. provides excellent high temperature the mineral insulation extension wire have been known for premium performance and reliability. extension wire have been known for is manufactured under ISO 9001 All Watlow Richmond SERV-RITE wire quality standards. SERV-RITE Since 1914, Watlow’s SERV-RITE XACTPAK The unique properties of XACTPAK The unique properties W A T L O W O L T A W Product Overview Product Continued Application Guide Application The Art of Temperature Sensing Application Guide The Art of Temperature Voltage Signals detectors (RTDs) and thermistors. Sensing Sensors generating varying voltage Resistive devices use metals or metal signals are thermocouples. Thermo- oxides that provide repeatable Contact Temperature Sensor couples combine dissimilar metallic changes of resistance with Types and Comparisons elements or alloys to produce a voltage. temperature. Thermocouples, RTDs and Using specific combinations of metals A variation of the thermistor not Thermistors and alloys in the thermocouple’s legs covered in this Application Guide is produces a predictable change in volt- the integrated circuit (IC). It’s a ther- Temperature sensors, aside from age based on a change in temperature. mistor that has a computer chip to capillary/bulb thermometers and bi- condition and amplify its signal. The Resistance Values metal sensors, use varying voltage computer chip limits the IC’s use to a signals or resistance values. Sensors generating varying resistance narrow temperature range. values are resistance temperature

Ref. 22

Thermocouple RTD Thermistor

V R R Voltage Resistance Resistance T T T Temperature Temperature Temperature • No resistance lead wire • Most stable, accurate • High output, fast problems • Contamination resistant • Two-wire ohms • Fastest response to • More linear than measurement temperature changes thermocouple • Point temperature sensing • Simple, rugged • Area temperature sensing • High resistance • High temperture • Most repeatable • High sensitivity to small operation 1704°C (3100°F) temperature measurement temperature changes • Point temperature sensing

• Non-linear • Current source required • Non-linear • Low voltage • Low absolute resistance • Limited temperature range • Least stable, repeatable • Self-heating • Fragile • Least sensitive to small • Slow response time • Current source required temperature changes • Low sensitivity to small • Self-heating Disadvantages Advantages temperature changes

Conclusion RTDs are best for most industrial Thermocouples are best suited to measurements over a wide temper- high temperatures, environmental ature range, especially when sensor extremes, or applications requiring stability is essential for proper control. microscopic size sensors. Thermistors are best for low temperature applications with limited temperature ranges.

36 Temperature Sensors 37 These thermocouples have been estab- inert and non-oxidizing Vacuum, hydrogen or inert atmospheres. couples. Not subject to corrosion at cryogenic temperatures. Iron leg subject to oxidation at elevated temperatures—use larger gauge to compensate. to oxidation and sulfur than Type K. Easily contaminated, require protection. Easily contaminated, require protection. ture ranges. Excellent in oxidizing and reducing atmospheres within temperature range. cryogenic temperatures, the thermocouple is not subject to corrosion. This thermocouple has the highest EMF output per degree of all the commonly used thermocouples. Additionally, there are non-ANSI/ASTM Additionally, there calibration types. and tungsten- are made from tungsten rhenium alloys. Generally used for measuring higher temperatures, but limited to use in atmospheres. Calibration types and the American lished by the ASTM Institute (ANSI) to National Standard vs. EMF define their temperature accordance with characteristics in or special the ITS-90, in standard calibrations. oxi- calibra- calibration Ref. 23 Ð are designed to deliver more suitable for sensor life E**J 95-900°C (200-1650°F) thermo- Highest output of base metal 95-760°C (200-1400°F)K**N Reducing atmosphere recommended. 95-1260°C (200-2300°F)R 650-1260°C (1200-2300°F)S Well suited for oxidizing atmospheres. For general use, better resistance 870-1450°C (1600-2640°F)T**atmosphere recommended. Oxidizing 980-1450°C (1800-2640°F) -200-350°C (-330-660°F) Laboratory standard, highly reproducible. Most stable at cryogenic tempera- BC* 1370-1700°C (2500-3100°F) 1650-2315°C (3000-4200°F) Easily contaminated, require protection. No oxidation resistance. Type Range Application Notes have different levels of compat- have different levels Thermocouple Useful/General Type E The Type E thermocouple is suitable for use at temperatures up to 900°C (1650°F) in a vacuum, inert, mildly dizing or reducing atmosphere. At Thermocouple Types subjected to high temperatures. Also, subjected to high calibration types line voltage curve as close to a straight application inside their temperature This makes it easier range as possible. or temperature con- for an instrument the received troller to correctly correlate temperature. voltage to a particular Additionally, thermocouple types ibility with different atmospheres. Chemical reaction between certain thermocouple alloys and the application atmosphere could cause metallurgy degradation, making another and accuracy requirements. tion types *Not an ANSI symbol * **Also suitable for cryogenic applications from -200 to 0°C (-328 to 32°F) W A T L O W O L T A W because they have Thermocouples previous page, As described on the voltage generating thermocouples are output increases sensors. Their voltage inside their in a predictable manner range. temperature application classified by Thermocouples are calibration type differing EMF (electromotive force) vs. temperature curves. Some generate considerably more voltage at lower temperatures, while others don’t begin to develop a significant voltage until Application Guide Application The Art of Temperature Sensing Application Guide The Art of Temperature Type J oxidize rapidly at temperatures over Sensing The Type J may be used, exposed or 540°C (1000°F), it is recommended that unexposed, where there is a deficien- larger gauge wires be used to compen- Thermocouples cy of free oxygen. For cleanliness and sate. Maximum recommended operat- Continued longer life, a protecting tube is recom- ing temperature is 760°C (1400°F). mended. Since JP (iron) wire will

Type K atmospheres, such as electric furnaces, Due to its reliability and accuracy, tube protection is not always necessary Type K is used extensively at tem- when other conditions are suitable; peratures up to 1260°C (2300°F). It’s however, it is recommended for cleanli- good practice to protect this type of ness and general mechanical protection. thermocouple with a suitable metal or Type K will generally outlast Type J ceramic protecting tube, especially in because the JP (iron) wire rapidly oxi- reducing atmospheres. In oxidizing dizes, especially at higher temperatures.

Type N provides better resistance to oxidation This nickel-based thermocouple alloy is at high temperatures and longer life in used primarily at high temperatures up applications where sulfur is present. to 1260°C (2300°F). While not a direct replacement for Type K, Type N

Type T this is a superior thermocouple for a This thermocouple can be used in wide variety of applications in low and either oxidizing or reducing atmos- cryogenic temperatures. It’s recommen- pheres, though for longer life a protec- ded operating range is—-200° to ting tube is recommended. Because 350°C (-330° to 660°F), but it can be of its stability at lower temperatures, used to -269°C (-452°F) (boiling helium).

Types S, R and B particularly damaging to the cali- Maximum recommended operating bration. Noble metal thermocouples temperature for Type S or R is 1450°C should always be protected with a (2640°F); Type B is recommended for gas-tight ceramic tube, a secondary use at as high as 1700°C (3100°F). tube of alumina and a silicon carbide These thermocouples are easily con- or metal outer tube as conditions taminated. Reducing atmospheres are require.

W-5 Percent Re/W-26 Percent 2315°C (4200°F). Because it has no Re (Type C*) resistance to oxidation, its use is This refractory metal thermocouple restricted to vacuum, hydrogen or may be used at temperatures up to inert atmospheres. *Not an ANSI symbol

Turn to page 46 for Thermocouple Conductor Gauge The larger the gauge size, the more recommended upper Thermocouple conductors come in a thermal mass the thermocouple will temperature limits for variety of sizes. Depending on your have with a corresponding decrease various thermocouple application, the gauge selected will in response. The larger the gauge conductor gauges. affect the thermocouple’s size the greater the stability and oper- performance. ating life. Conversely, a smaller gauge size will have a quicker response, but may not deliver the stability or operating life required. 38 Temperature Sensors 39 b b b b b b b b b (¡F) * * *

(±1.8) (±0.9) (±2.0) (±2.0)

Special

e e e

* * * ±0.25% ±1.0 ±0.5 ±1.1 ±1.1 ¡C Ref. 24 ±1.0 or ±0.4% ±1.1 or ±0.4% ±1.1 or ±0.4% ±0.6 or ±0.1% ±0.5 or ±0.4% Ð

b b b b b b b b b (¡F)

(whichever is greater)

(±7.6) (±3.0) (±1.8) (±9.0) (±4.0) (±4.0) (±12.2)

Standard

Tolerances

±0.5% ¡C ±4.2 ±1.7 ±6.8 ±1.0 ±5.0 ±2.2 ±2.2 ±1.7 or ±1% ±2.2 or ±2% ±1.7 or ±0.5% ±1.0 or ±1.5% ±1.5 or ±0.25% ±2.2 or ±0.75% ±2.2 or ±0.75% ±1.0 or ±0.75%

(¡F) h i (32 to 2700) (32 to 2300) (32 to 1400) (32 to 1600) (32 to 700) (32 to 400) (32 to 500) (32 to 400) (32 to 200) (32 to 400) (32 to 400) (32 to 400) (-328 to 32) (-328 to 32) (-328 to 32) (1600 to 3100) Tolerances in the table represent the maximum error contribution allowable from Tolerances in the table represent the maximum error extension wire when exposed new and essentially homogeneous thermocouple grade materials are not to the full temperature range given above. Extension intended for use outside the temperature range shown. to the total thermoelectric Thermocouple extension wire makes a contribution between the extreme signal that is dependent upon the temperature difference of any error introduced ends of the extension wire length. The actual magnitude connected extension into a measuring circuit by homogeneous and correctly at its two end wires is equal to the algebraic difference of the deviations pair. temperatures, as determined for that extension wire Tolerances in the table apply to new and essentially homogeneous thermocouple compensating extension wire when used at temperatures within the range given above. Thermocouple compensating extension wire makes a contribution to the total thermoelectric signal that is dependent upon the temperature difference between the extreme ends of the compensating extension wire length. Special compensating extension wires are not necessary with Type B over the limited temperature range 0 to 50°C (32 to 125°F), where the use of non- compensated (copper/copper) conductors introduces no significant error. For a somewhat larger temperature gradient of 0 to 100°C (32 to 210°F) across the extension portion of the circuit, the use of non-compensated (copper/copper) extension wires may result in small errors, the magnitude of which will not exceed the tolerance values given in the table above for measurements above 1000°C (1800°F). Proprietary alloy compensating extension wire is available for use over 0 to 200°C (32 to 400°F) temperature range.

* Special tolerance grade compensating extension wires are not available. * f g h i j

¡C Temperature Range f g a c 0 to 1480 0 to 1260 0 to 200 0 to 260 0 to 760 0 to 200 0 to 870 0 to 100 0 to 370 0 to 200 0 to 200 0 to 200 870 to 1700 and do -200 to 0 -200 to 0 -200 to 0

d d d J T E B JX TX EX T E CX K BX Type R or S K or N RX, SX KX or NX Tolerances on Initial Values of EMF vs. Temperature Tolerances on Initial Reference Junction 0°C (32°F) Reference Junction 0°C Extension Wires Thermocouples Compensating Extension Wires 118 in.) in diameter . Calibration e . The magnitude of such r thermocouples is likely to yield used W A T L O W O L T A W with new or known good ones to ascertain in Watlow’s Temperature Sensing Solutions in-situ 20 emperatu T : -200 to 0°C ±1.0°C or ±0.5 percent (whichever is greater); t of r Type E : Users should be aware that certain characteristics of thermocouple : Users should be aware that certain characteristics (No. 30 to No. 8 AWG) and used at temperatures not exceeding the (No. 30 to No. 8 AWG) and used at temperatures recommended limits on page Catalog. If used at higher temperatures these tolerances may not apply. Catalog. If used at higher temperatures these tolerances tolerance expressed in °F is At a given temperature that is expressed in °C, the Note: Wherever applicable, 1.8 times larger than the tolerance expressed in °C. from temperatures that are percentage-based tolerances must be computed expressed in °C. Caution materials, including the EMF vs. temperature relationship may change with time in use; consequently, test results and performance obtained at time of manufacture may not necessarily apply throughout an extended period of use. Tolerances given above apply only to new wire as delivered to the user not allow for changes in characteristics with use changes will depend on such factors as wire size, temperature, time of exposure and environment. It should be further noted that due to possible changes in homogeneity, attempting to recalibrate irrelevant results, and is not recommended. However, it may be appropriate to compare used thermocouples their suitability for further service under the conditions of the comparison. Thermocouples and thermocouple materials are normally supplied to meet the tolerances specified in the table for temperatures above 0°C. The same materials, however, may not fall within the tolerances given for temperatures below °C in the second section of the table. If materials are required to meet the tolerances stated for temperatures below 0°C the purchase order must so state. Selection of materials usually will be required. Special tolerances for temperatures below 0°C are difficult to justify due to limited available information. However, the following values for Types E and T thermocouples are suggested as a guide for discussion between purchaser and supplier: Type T: -200 to 0°C ±0.5 or±0.8 percent (whichever is greater). Initial values of tolerance for Type J thermocouples at temperatures below 0°C and special tolerances for Type K thermocouples below 0°C are not given due to the characteristics of the materials. Tolerances in this table apply to new essentially homogeneous thermocouple Tolerances in this table apply to new essentially homogeneous to 0 wire, normally in the size range 0.25 to 3 mm (0.010

Thermocouples Thermocouples Continued Application Guide Application The A Sensing b c d e a Industry specification have established the Industry specification thermocouples. accuracy limits of industrial sensor performance These limits define initial temperature and at time of manufacture.Time, environment operating conditions may cause sensors to change during use. Also, keep in mind that overall system accuracy will depend on the instrument and other installation parameters. Application Guide The Art of Temperature Thermocouple Junction The thermocouple’s physical con- Sensing All thermocouples have Hot and Cold struction may have its Hot junction junctions. Further, the Hot junction may exposed or unexposed. An exposed Thermocouples be physically exposed or unexposed junction has its bare thermoelements Continued (protected). in contact with the substance being measured. An unexposed junction The Hot junction is the junction subjected to the heat being measured. The has a shielding to protect it from hostile environments. Unexposed Cold, or reference junction, is another junction in the thermocouple circuit, junctions are commonly found in usually at, or compensated to, 0°C thermocouples made from mineral insulated, metal-sheathed cable. (32°F). Cold junctions are generally eliminated in the thermocouple circuit Another aspect of the unexposed by using electrical or hardware thermocouple junction is whether it’s compensating methods. grounded or ungrounded. In the A thermocouple’s thermoelectric volt- grounded construction, the thermocouple junction is electrically connect- age is generated between the Hot ed to the sheath or protecting tube and Cold junctions, not where the two thermoelements are physically joined. material. An ungrounded construction The Seebeck effect takes place in the has its junction electrically isolated temperature gradients between the from its sheath or protecting tube. isothermal portion at the Hot junction Each style has advantages and dis- end and the isothermal portion at the advantages depending on your par- Cold junction end. ticular application and electrical considerations.

Thermocouple Selection response at the expense of service life Thermocouple specifications are at elevated temperatures. Larger selected to meet the conditions of the gauge sizes provide longer service application. Only general recommen- life at the expense of response. As a dations on wire gauge size and type general rule, it is advisable to protect can be given. Some of the consider- thermocouple elements with a suitable ations involved are: protection method. • Length of service Note: Temperatures discussed are in • Application temperature relation to table #7, page 15, of ANSI MC96.1, August, 1982. • Atmosphere When ordering thermocouple wire or • Desired response time elements, be certain that the Type (K, • Accuracy J, E, etc.) corresponds to that of the The temperature ranges of the com- instrument with which it will be used. monly used thermocouple types are given in the (Initial Calibration Tolerances Table on pages 61 - 62.) Smaller wire gauges provide faster

40 Temperature Sensors 41 listed PLTC ¨ constructions. Conductors are insulated from the sheath using a variety of mineral oxide dielectric materials. The most common material is magnesium oxide (MgO). its Insulation is selected according to dielectric strength for the intended operating temperature and matched up with a sheath material selected to withstand the same temperature. MI cable has the advantage of being fabricated into a complete sensor assembly, combining sensing element and protective sheath in one. fibers. Each material or combination fibers. Each material to achieve the of materials is used shunts and objective of preventing given application. short circuits for a made to withstand Constructions are temperature and ambient operating with physi- electrical noise conditions; moisture, cal properties to withstand chemicals and abrasion. insulations, soft In addition to dielectric of wire can be supplied with a number metallic overbraids to increase abrasion resistance or provide additional electrical shielding. physical properties and on temperature ratings; information metallic overbraids; and information on UL See the Watlow Temperature Sensing Solutions catalog for information on soft wire constructions, insulations, is a registered trademark of insulation covering together and add resistance to electromagnetic interference ® Some materials that do not lend themselves to being drawn, such as molybdenum, are used in undrawn or “uncompacted” constructions. MI cable construction provides a protective sheath around the conductors, with the added advantage of a compacted insulation that improves thermal conductivity from the sheath to the conductors. Sheaths can be made from a wide variety of malleable metals, so matching sheath material to temperature range and chemical environment is relatively easy. Soft Wire and Cable use one or more Soft wire and cable materials to insulate flexible dielectric produce each conductor and constructions by: •with an additional Duplexing • (as with lamp cord) Duplex extruding •keep the conductors Twisted to Many different dielectric materials are used as insulation, from lacquers to elastomer plastics to high temperature Underwriter’s Laboratories, Inc. UL W A T L O W O L T A W ungrounded junction MI cable sensors MI cable See Watlow Temperature Sensing Solutions catalog for: ¥ MIcablecalibrations ¥ MIcablesheathmaterials ¥ MIcableinsulations ¥ Groundedand Fabricating sensorswith ¥ metal-sheathed cable Mineral Insulated, Metal-Sheathed Cable this Commonly referred to as MI cable, construction is well suited for demanding applications where elevated temperatures or hostile environments make soft insulated wire unsuitable. MI cable is most often made by placing crushable mineral oxide insulators around conductors and inserting them into a metal tube. This tube is then drawn down to the desired outside diameter and conductor gauge. Wire Insulations sensor’s elec- Due to a temperature to provide trical nature it’s important insulation conductors with sufficient short circuits. To to avoid shunts or wire, accomplish this, thermocouple wire and RTD thermocouple extension lead wire come in a variety of insulations and configurations. The two primary constructions are: • “Soft” wire and cable • Mineral insulated, Wire is generally understood to mean a one-or two-conductor soft insulated construction. Cable can be a soft construction with more than two conductors, excluding drain wires, or conductors encased in a metal sheath. Application Guide Application The Art of Temperature Sensing Application Guide The Art of Temperature greater versatility of smaller thermo- results. Errors which arise out of cyclic Sensing couples. Where high temperature heating are analogous to those stability is a substantial consideration, generated by changes in immersion, Rules of Good use the largest practical wire size and may range from two or three Thermocouple Practice consistent with the other requirements degrees Fahrenheit for thermocouples With proper installation and normal of the job. in good condition, to many degrees conditions, thermocouples can be 3. Install Thermocouple in Proper for badly corroded couples. Thus the depended upon to give trouble free Location—The location selected for type of heating cycle and condition of service and long life. Occasionally dif- installation of the thermocouple should the thermocouple mutually affect the ficulties may be encountered resulting insure that the temperatures being accuracy obtainable in a specific loca- from improper application or operation. measured are representative of the tion. Where cyclic heating cannot be The information presented here serves equipment or medium. Direct flame avoided, use top condition thermo- as a short guide to help thermocouple impingement on the thermocouple, couples for maximum accuracy. users obtain the accuracy and econ- for example, does not provide a 7. Establish Preventive Maintenance omy for which the thermocouple alloys representative temperature. Program—Thermocouples, protec- are produced. 4. Provide for Sufficient Immersion tion tubes and extension wire circuits 1. Protect Thermocouples in Depth—Since heat conducted away should be checked regularly. Experi- Service—Evaporation, diffusion, oxi- from the “hot” junction causes the ther- ence largely determines the frequency dation, corrosion and contamination mocouple to indicate a lower temper- of inspection, but once a month is induce EMF drift due to their effect ature, provide for sufficient depth of usually sufficient. on the composition of thermocouple immersion of the thermocouple into the Check out extension wire circuit by alloys. In as much as these environ- medium being measured to minimize making certain that it meets the estab- mental factors are destructive to all heat transfer along the protection tube. lished external resistance requirement. common thermocouple materials, it As a general rule, a minimum immersion Damaged or burned out protection is essential that proper protection be of 10 times the outside diameter of the tubes should be replaced to prevent provided whenever adverse conditions protection tube should be used. damage to the thermocouple. are encountered. In many applications, 5. Avoid Changing Depth of Thermocouples should be checked in this requirement can be met by the use Immersion—Under certain conditions, place, if possible. If it is necessary to of sheathed unit construction. If bare inhomogeneities may gradually devel- remove the thermocouple, it should be wire thermocouples are used, the ther- op in a pair of thermocouple wires due reinserted to the same depth or deeper moelements must be properly installed to oxidation, corrosion, evaporation, to avoid errors arising from placing an in suitable protection tubes. When the contamination or metallurgical changes. inhomogeneous segment of wire in a interiors of such tubes are clean and A change in depth of immersion, which steep temperature gradient. free of sulfur-bearing oils, refractories, shifts such inhomogeneous wire into a etc.—and when they are of the proper steep temperature gradient zone, can diameter-to-length ratios to permit alter the thermocouple output and pro- adequate ventilation inside, they serve duce erroneous readings. Therefore, admirably in overcoming the harmful avoid changing the depth of immer- effects of corrosive atmosphere. sion of a thermocouple after it has 2. Use Largest Practical Wire Size— been in service. It is generally true that heavy gauge 6. Recognize Effect of Heating thermocouples are more stable at high Cycles—For maximum accuracy, temperatures than their finer gauge a thermocouple should be used to counterparts. In many applications, control a single temperature, or suc- however, a heavy gauge thermo- cessively higher temperatures only. couple will not satisfy requirements for For various reasons, however, this flexibility, rapid response, equipment procedure cannot always be followed. geometry and the like. A compromise In many installations, thermocouples must then be struck between long- continually traverse a broad range of term stability of heavy sizes and temperatures, with wholly adequate

42 Temperature Sensors — 43 Meter Extension Wires C F) ° ° (300 Connector Block 4. Test Meter and Extension Wires 4. Test Meter and meter and exten- To check the working the extension wires sion wires, connect of known accu- to the test thermocouple the temperature racy and observe is not the same reading. If the reading the test meter, as that obtained with in the extension the trouble is either meter. wires or in the working are intended only The above checks as elementary guides in trying to pin- of point the possible cause or causes faulty temperature control. If the cause of erroneous readings can definitely be localized in the thermocouple itself, it should be removed and inspected. A visual inspection, plus a few tests which can readily be made with only hand instruments, will often reveal the condition which caused the thermocouple wires to go off calibration. Severely oxidized or corroded thermocouples should be replaced. It is usually more economical to replace a suspected thermocouple than to risk loss of costly time, product or equipment through inadequate temperature control. 148.8 Cool Zone Severely — F) ° Protection Tube (1800 Heat Zone Furnace Insulation Thermocouple Ref. 25 along side the working thermocouple along side the working as close together with the hot junction essential that the as possible. It is also the working and temperature of both the same. the test meter be the test meter If, under these conditions, that indicated by reading agrees with the source of trouble the working meter, circuit but is, is not in the pyrometry itself. If the perhaps, in the furnace test meter reading does not agree with the working meter reading, the following checks should be made to isolate the trouble. 3. Check Thermocouple oxidized or corroded thermocouples are always suspect. Changes in wire composition can result from corrosion and contamination by extraneous elements. Impurities such as sulfur and up iron plus other constituents picked from furnace refractories, oxide scale, brazing alloys and fluxes constitute potential sources of drift away from initial calibration. To check the working thermocouple, hook it up to the test meter of known If accuracy and observe the reading. the reading is the same as that previously obtained from the test thermocouple of known accuracy, then the working thermocouple is not the cause of trouble. W A T L O W O L T A W If the circuit — The first step is to — properly connected to the When a thermocouple installation is When a thermocouple erroneous readings, suspected of giving steps may be taken the following check of trouble. to isolate the source 1. Check Circuit Trouble-Shooting Installations Thermocouple Readings with Erroneous check the polarity of the thermocouple circuit and all connection contacts. The positive thermocouple wire should be properly connected to positive extension wire which, in turn, should be securely connected to the positive side of the meter. The negative thermocouple and extension wire should be sidenegative of the meter. A brief check at these points will often save a service call and delays in production. Wires can generally be identified by color coding or by verifying magnetism. 2. Check Instrument checks out all right, the next step is to check the control, meter or recording instrument. Verify instrument has been set for the thermocouple type being used. If checked as to room temperature setting (cold junction compensation). This is done by removing the extension wires, placing a jumper across terminals from the meter connection and observing the meter reading. It should coincide with the room temperature. If further diagnosis is required, should be checked by comparing its readings against those obtained with a test thermocouple of known accuracy connected to a portable meter also of known accuracy. In making such a check, it is important that the test thermocouple be inserted Application Guide Application The Art of Temperature Sensing Application Guide The Art of Temperature mocouple inspections before complete thermocouple element and the Sensing thermocouple failure occurs. tube wall. One or the other of the following condi- • Leaks in protecting tubes with Metallurgical Factors tions is usually found on examination refractory metal (titanium, colum- ® Ref. 26 of Chromel-Alumel thermocouples bium, tantalum) wires inside and experiencing early failure. sealed at the “cold end.” The pur- 1. Selective Oxidation—sometimes pose of the refractory metal wire is referred to as “green rot”—is typified to “sop up” all available oxygen by a greenish surface or subsurface creating an oxygen free atmosphere. scale that develops in nickel-chromium The atmosphere will become partially alloys, when subjected to a marginally oxidizing when the refractory metal oxidizing environment at high wire cannot absorb all the oxygen temperature. setting the stage for green rot. The formation of a thin nickel film will • Improperly degreased protecting give the non-magnetic KP magnetic tube interior. Residues of greases properties. and oils will decompose and release sulfur, a deadly enemy of nickel alloys. In applications where an abundant Inter-granular attack due to selective oxidation in • Leaky protecting tubes in reducing 8-gauge wire. (Unetched, X100) supply of oxygen is available, or where there is none at all, green rot does not (hydrogen for example) or carbona- Premature thermocouple failure is most occur. Reducing atmospheres such ceous gas containing furnaces, frequently a result of contamination or as pure dry hydrogen, will not adverse- where furnace atmospheres can corrosion due to uncontrolled furnace ly affect nickel thermocouple alloys. penetrate the tube and will cause atmosphere, unclean or leaking protec- partially oxidizing conditions within When green rot is apparent, check for tion tubes, or some other factor related the leaky tube. the following possibilities: to improper installation or operation. • Presence of zinc (galvanized tubes) • Protecting tubes having too small Damaging conditions can usually be or zinc-containing alloys, such as an inside diameter, or too great a detected and corrected through a pro- brass. Vapors from these metals length-diameter ratio, which prohibit gram of frequent and systematic ther- will accelerate deterioration of a reasonably free air circulation nickel thermocouple alloys. between the insulated (ceramic)

Ref. 27 2. Sulfur Attack—Sulfur is particularly hydrochloric acid containing a few harmful to high nickel alloys including pieces of metallic zinc. If sulfur is KN. In heat-treating operations, sulfur present in the sample, it can be may come from various sources such identified by the characteristic as furnace atmospheres, oil, mortar, hydrogen sulfide odor of rotten eggs cements and asbestos. In Type K that will evolve. Also, moistened lead thermocouples, sulfur attack often acetate paper held over the top of the reveals itself in breakage of the KN test solution will turn brown or black if wire. Thus, when normally ductile KN sulfur is present in the sample. wire appears to have become brittle in Where there is evidence of sulfur service, that is, if surface cracks attack in the thermocouple, it should appear when it is bent with the fin- be replaced, and an attempt made to gers, it is likely that sulfur corrosion eliminate the source of sulfur. If elim- has occurred. In case of doubt, the ination of the source is not feasible, presence of sulfur can be determined then the thermocouple should be com- Transverse inter-granular cracks due to sulfur positively by performing any one of pletely isolated from the contaminat- attack in 8-gauge wire. (Electrolytic etch, X35) several chemical tests. ing material. The possibility of a leak Alumel® is a registered trademark of A simple test for sulfur in a suspected in an existing protection tube should Hoskins Manufacturing Company. material is to immerse a sample of the not be overlooked. material in a solution of 20 percent 44 Temperature Sensors 45 error due to aging effects. values which is heat treated However, if pre-aged wire is subjected to temperature above the aging range, the effect of the heat treatment process is removed. For measurements above the aging range, the length of thermocouple in the gradient of aging temperatures needs to be minimized to keep aging effects small. To The effects of aging are reversible. remove the aging effects, heat the entire thermocouple to above 870°C (1600°F) for a minimum of five minutes and then rapidly cool to below the aging temperatures. This heat treating process should restore original wire calibration. to minimize temperature, errors due to aging temperature, errors When temperature should not occur. made in the aging measurements are errors due to range and undesirable applications a aging occur, in certain may be used. pre-aged thermocouple metal- (Not available in compacted A pre-aged sheath assemblies.) of specially thermocouple is one composition and selected chemical calibration W A T L O W O L T A W previous thermal history of the thermocouple temperature jected to the aging temperature Causes of Aging (Drift) refers to a positive The term “aging” of nickel ther- EMF shift (more output) to a temperature mocouple alloys due gradient along the thermocouple elements. Although the temperatures at which aging occurs are not absolutely defined, the temperature range of 370º to 540°C (700º to 1000°F) is generally used as the limit for the aging range. Several factors that will influence the amount of EMF shift are: • Temperature being measured, • Time and duration at aging • Specific thermocouple composition • Amount of the thermocouple sub- The thermocouple user must be aware that the amount of aging effect is dependent upon the specific application and temperature gradient in that application. When aging effects are believed to have occurred, an observation of thermocouple application should be made. First, the operating temperature of the thermocouple should be checked. If the entire thermocouple has never been subjected to aging Properties of Nickel Alloys Thermocouple Application Guide Application The Art of Temperature Sensing Application Guide The Art of Temperature Sensing Recommended Upper Temperature Limits for Protected Thermoelements Upper Temperature Limits for Various Wire Sizes (B & S Gauge), ¡F (¡C)—Ref. 28

No. 8 Gauge, No. 14 Gauge, No. 20 Gauge, No. 24 Gauge, No. 28 Gauge, No. 30 Gauge, 3.25 mm 1.63 mm 0.81 mm 0.51 mm 0.33 mm 0.25 mm Thermoelement (0.128 in.) (0.064 in.) (0.032 in.) (0.020 in.) (0.013 in.) (0.010 in.) JP 760°C 590°C 480°C 370°C 370°C 320°C (1400°F) (1100°F) (900°F) (700°F) (700°F) (600°F) JN, TN, EN 870°C 650°C 540°C 430°C 430°C 430°C (1600°F) (1200°F) (1000°F) (800°F) (800°F) (800°F) TP — 370°C 260°C 205°C 205°C 150°C — (700°F) (500°F) (400°F) (400°F) (300°F) KP, EP, KN 1260°C 1090°C 980°C 870°C 870°C 760°C (2300°F) (2000°F) (1800°F) (1600°F) (1600°F) (1400°F) RP, SP, RN, SN — — — 1480°C — — (2700°F) BP, BN — — — 1705°C — — (3100°F) NP, NN 1260°C 1090°C 980°C 870°C 870°C 760°C (2300°F) (2000°F) (1800°F) (1600°F) (1600°F) (1400°F)

Note: This table gives the recommended upper temperature limits for the various thermoelements and wire sizes. These limits apply to protected thermoelements, that is, thermoelements in conventional closed-end protecting tubes. They do not apply to sheathed thermoelements having compacted mineral oxide insulation. In any general recommendation of thermoelement temperature limits, it is not practical to take into account special cases. In actual operation, there may be instances where the temperature limits recommended can be exceeded. Likewise, there may be applications where satisfactory life will not be obtained at the recommended temperature limits. However, in general, the temperature limits listed are such as to provide satisfactory thermoelement life when the wires are operated continuously at these temperatures.

46 Temperature Sensors 47 Time

Time Constant

63 Percent Step Temp. Change Temp. Step Response is a function of the mass of Response is a function efficiency in trans- the sensor and its outer surfaces to ferring heat from its A rapid time the sensing element. for accuracy in response is essential temperature a system with sharp varies with changes. Time response the probe’s physical size and design. The response times indicated are representative of standard industrial probes. Time Constant (Thermal Response Time) Ref. 30 Ref. constant” (thermal response time). constant” (thermal thermal response Time constant, or of how quickly time, is an expression a sensor responds to temperature here, time changes. As expressed as how long it response is defined reach 63.2 percent takes a sensor to of a step temperature change (see Ref. 30). Average Response Time W A T L O W O L T A W 0.010 in.0.020 in.0.032 in.0.040 in.0.063 in.0.090 in. <0.020.125 in. <0.020.188 in.0.250 in. 0.020.313 in. 0.040.375 in. 0.220.500 in. 0.330.5 mm 0.50 <0.02 1.0 mm 1.001.5 mm 2.20 0.03 2.0 mm 5.00 0.07 3.0 mm 8.00 0.13 15.004.5 mm 0.40 6.0 mm <0.02 0.68 8.0 mm 0.04 1.10 <0.15 2.30 0.25 4.10 0.40 7.00 11.00 0.95 20.00 2.00 5.00 0.03 0.13 0.35 0.55 0.90 2.00 3.50 7.00 Sheath Still Water (seconds)* Diameter Grounded Junction Ungrounded Junction Ref. 29 Ref. Since you’re actually interested in the Since you’re actually surrounding medium, temperature of the on the ability of the accuracy depends heat from its outer sensor to conduct wire. sheath to the element into play.The Several factors come most commonly noted is “time Thermocouple Response Time Thermocouple Application Guide Application The Art of Temperature Sensing *Readings are to 63 percent of measured temperatures. Application Guide The Art of Temperature Sensing Thermowells and Material Selection significant effect on how a material will Protecting Tubes In selecting a thermowell or protecting hold up in actual conditions. Using thermowells and protecting tube, the first thing to do is determine Measuring a substance that’s flowing tubes will isolate a sensor from hostile the nature of the environment and what is another consideration. In this case, environments that could adversely material will best resist its destructive you need to determine the fluid’s vis- affect its operation or life. effects. To select the appropriate cosity at the process operating tem- material, see Watlow’s Temperature perature and combine that factor with Thermowells are machined from solid Sensing Solutions Catalog, pages its flow rate to determine the amount bar stock and come in a wide variety 127-131, for Thermowell Manu- of lateral (shear) force it will exert on of metals and alloys. facturing Standards and Material the face of the thermowell or protect- Protecting tubes are made up from Selection Guide. ing tube. Once the total shear force parts, either metallic or non-metallic The guide will help you determine what is figured, you must then be sure the materials, generally ceramics. material will best meet your protection size, shape and material will hold up. requirements. Please note that it’s not Don’t forget to include the effects of See Watlow Temperature just the corrosive agent, but also its erosion if the fluid has abrasive Sensing Solutions, temperature. Temperature can have a particulate material. Temperature Sensors, Wire and Cable catalog for: ¥ Thermowell Material Selection Guide Teflon¨ Coatings low-mass probe that would otherwise ¥ Ceramic and Silicon- If the thermal mass of a thermowell or be damaged in a hostile environment. Carbide Protecting Tube protecting tube slows response to an Such applications include electro- Application Data unacceptable level, Teflon® coatings plating and anodizing baths, and may provide a solution. Possessing many common acids like sulfuric, ¥ Typical Physical Data for a high resistance to many corrosive hydrochloric, nitric and chromic. Protecting Tubes agents, Teflon® coating can protect a ¥ Physical Properties of Hexoloy¨ Materials— Technical Data Hexoloy® is a registered trademark of Teflon® is a registered trademark of Carborundum Company. E.I. du Pont de Nemours & Company.

48 Temperature Sensors 49 C) ¡ / Ω / tant for Ω ) at 0°C 0.00672 at 0°C 0.00385 at 25°C 0.00427 Ω Ω Ω Ω ¡C ( Class B be taken into account. Ideally the be taken into account. measured will have substance being thermal conductivity enough mass and RTD’s self-generated so as to make the heat a negligible factor. the user to specify the TCR when ordering RTD probes. temperatures. Thus, it’s impor ) Ω ¡C ( Class A Ref. 32 vated Ð cause a are powered Ω RTDs Resistance Tolerance DIN-IEC-751 0 (32) 100.00 ±0.15 (±0.06) ±0.3 (±0.12) Nickel -100 to 205°C (-150 to 400°F) 120 Copper -100 to 260°C (-150 to 500°F) 10 Element Type Temperature Range Base Resistance TCR( ¡C (¡F) * * *Platinum DINto 650°C (-330 to 1200°F) -200 100 100200 (212)300 (392)400 (572) 138.51500 (752) 175.86600 (932) 212.05 (1112) ±0.35650 247.09 (±0.13) (1202) ±0.55 280.98 (±0.20) ±0.75 313.71 ±0.8 (±0.27) ±0.95 329.64 (±0.30) ±1.3 (±0.33) ±1.15 (±0.48) ±1.8 ±1.35 (±0.38) (±0.43) (±0.64) ±2.3 ±1.45 (±0.46) (±0.79) ±2.8 ±3.3 (±0.93) (±1.06) ±3.6 (±1.13) Temperature Value -200 (-328)-100 (-148) 18.52 60.26 ±0.55 (±0.24) ±0.35 (±0.14) ±1.3 (±0.56) ±0.8 (±0.32) RTDs generally have a positive temper- RTDs generally have ature coefficient. receiving devices. The instrument temperature as their “signal” reads Looked at the change in voltage. changes, another way, as temperature resistance. so does the sensor’s resistance devices, Because these are heat in addi- their operation generates measuring. tion to the heat they’re When specifying the use of an RTD, its mass and self-generated heat must Table of Tolerance Values of Resistance (TCR). Even a slight deviation in the TCR will significant error to result at ele Ref. 31 *Thin film element -50 to 550°C (-58 to 1020°F). W A T L O W O L T A W RTDs — is the actual temperature, in t RTDs are temperature sensors utilizing RTDs are temperature predictable change metals known and based on a rise in electrical resistance The sensing or fall in temperature. a deposited film or coil of is element wire, usually platinum, nickel, copper, or nickel-iron. Resistance Temperature Detectors Application Guide Application The Art of Temperature Sensing Where RTD Interchangeability Interchangeability is a commonly cited factor of RTD accuracy. It tells how closely the sensing element of an RTD follows its nominal resistance/temperature curve, and the maximum variation that should exist in the readings of identical sensors, mounted side-by-side under identical conditions. a Interchangeability consists of both tolerance at one reference temperature, usually 0°C, and a tolerance on the slope, or Temperature Coefficient RTD Tolerance Class Definitions DIN/IEC class A: ±(0.15 + 0.002 |t|°C DIN/IEC class B: ±(0.30 + 0.005 |t|°C °C, of the platinum elements. Application Guide The Art of Temperature Two-Wire Circuit Reference 33 shows a two-wire RTD Ref. 33 connected to a typical Wheatstone Sensing L1 bridge circuit. Is is the supply current; E is the output voltage; R , R , R are Resistance Temperature R1 o 1 2 3 R Detectors—RTDs T fixed resistors; and RT is the RTD. In L 2 this circuit, lead resistances L and L Continued IS EO 1 2 add directly to RT. Effects of Lead Wires R R on RTD Accuracy 2 3 The majority of RTD applications throughout industry today standardize on the three-lead wire systems. Three-Wire Circuit celing their resistance, since they’re Frequently the question arises— Ref. 34 in two separate arms of the bridge. L what is the difference in two-, three- 1 L2, connected to Eo, is used only as L a potential lead; no current flows or four-wire RTDs and how does the R1 2 R system operate? T through it when the bridge is balanced. L3 I This method of lead wire compen- The key issue is accuracy. Most manu- S EO facturers will specify accuracy as sation depends on close matching of R R 0.1 percent or a similar figure. This 2 3 the resistance in L1 and L3 and high number only refers to how tightly the impedance at Eo, since any current element (resistor) is calibrated at one In the three wire circuit shown in flow in L2 will cause errors. The two temperature and does not reflect the Reference 34, the identical measuring common leads, L2 and L3, are normally the same color for easy identification. total sensor accuracy after lead wire current flows through L1 and L3, can- has been added to the resistance element. Understanding how the bridge circuit operates should answer Four-Wire Circuit resistance become significant. Although these questions and further empha- many laboratory systems employ resis- Ref. 35 L1 size the value of three- and four-wire tive networks for four-wire compensation, the most common industrial circuit systems, when accuracy is important L2 to the user. drives a constant current through two I leads, and measures current drop across Because an RTD is a resistance type S EO RT the remaining two (see Reference 35). sensor, any resistance in the extension L3 Assuming that input impedance pre- wire between the resistive element L vents current flow in L and L , the and control instrument will add to the 4 2 3 only significant source of error is readings. Furthermore, this added Four-wire circuits offer the ultimate variation in the measuring current. resistance is not constant, since the performance over extreme distances, conductor in lead wires changes or where small errors such as contact resistance with changing ambient temperature. Fortunately, errors may be nearly canceled by using a three- Adding Extra Leads If necessary, you can connect a two or four-wire system. Ref. 36 wire RTD to a three-wire circuit, or a three-wire RTD to a four-wire circuit. Extension Leads RTD Leads Just attach the extra extension wires RED RED RED to the ends of the RTD leads, as shown in Reference 36. As long as these RT WHITE WHITE connections are close to the sensing element, as in a connection head, RED RED errors should be negligible. RED RED

WHITE R WHITE T WHITE

50 Temperature Sensors 51 fine / /¡C) to a Ω / TCR Ω ( 4.95 ohms 4.95 ohm (0.385 ohm/°C) 300 ft X 0.0165 ohm/ft (Avg. Ohm/¡C 0 to 100¡C)

0.00385 (DIN-IEC-60751), 0.00427 0.00672 = = = 12.9°C =

at 0°C at 0°C

at 25°C TCR

Ω Ω uniformly deposited in films and uniformly deposited Base Ω

Resistance 10 100 120 Gauge leads, 150 feet long: Total resistance Approx. error wire; temperatures can withstand extreme point of with its high melting (3700°F). approximately 2040°C RTDs have a positive All resistance wire resistance temperature coefficient—their increases. increases as temperature corrosion resistant and not easily corrosion resistant drawn oxidized. It can be

100500 0.003850 0.003850 0.3850 1.9250 1000 0.003850 3.8500 Base (Ohms) Resistance Sensitivity Benefits High sensitivity good linearity Best linearity Best stability, Low cost,

, aerospace y

0.0041 0.0065 0.0103 0.0165 0.0262 0.0418 0.0666 0.1058 at 25 Ohms/ft Range

Temperature -100 to 260°C (-148 to 500°F) -260 to 850°C (-436 to 1562°F) (-148 to 500°F) -100 to 260°C

16 18 20 22 24 26 28 30

Lead Wire B & S Gauge Metal Nickel Copper Platinum Element Ref. 38 Depending on the length of run, lead wire error can be significant. Particularly so if the gauge is small, or connected to a low sensitivity element. Using a three-wire circuit will reduce errors in most applications to a negligible level. Ref. 37 The table below contains resistance values for common copper lead wire gauges. To approximate the error in an uncompensated sensor circuit, multiply the length (in feet) of both extension leads by the approximate value in the table. Then divide it by the sensitivity of the RTD element to obtain an error value in °C. For example, assume a 100 ohm platinum element with 0.00385 TCR and 22 B & S The most notable advantage of The most notable their precise and platinum RTDs is to changes in predictable response is the most temperature. Platinum militar widely used RTD in and nuclear and many other and nuclear and many a high degree applications requiring also has the of precision. Platinum relatively advantage of being indifferent to its environment, e r

W A T L O W O L T A W for 63-72 61 tance vs. emperatu T TDs emperature R T — alter copper lead wire

Turn to pages for Resis Temperature tables. Turn to page RTD Initial Calibration Tolerances. t of s r r between sensor and instrument

ever, variations in ambient w Detecto Continued Resistance Application Guide Application The A Sensing RTD Lead Wire Compensation Because an RTD is a resistance device, any resistance in the lead wires will add resistance to the circuit and alter the readings. Compensating for this extra resistance with adjustments at the instrument may be possible. Ho temperature resistance, so this only works when lead wires are held at a constant temperature. RTD Resistance Comparisons RTD Resistance of electrical resis- Since the amount of a material’s tance is a function temperature, resistance of RTDs can theoretically be made from any metallic element or alloy. Most often they’re made from copper, nickel, nickeliron or platinum. The nonlinear response of nickel and limited temperature range of copper makes platinum the most commonly used resistance material. Application Guide The Art of Temperature In deciding to use a thermistor, it’s ature reading. Sufficient precautions Sensing important to be sure the application should be taken into account and safe- is within its temperature limits. Inside guards, like thermal fuses, designed Resistance Temperature their application range, thermistors into the sensor. Detectors—RTDs exhibit a great change in resistance Additionally, thermistors do not have Continued for a relatively small change in any established resistance vs. Thermistors temperature. temperature standards comparable Thermistors have the advantage to the DIN-IEC-60751 standards for Thermistors are semiconductor over RTDs of being available in both 100 ohm platinum wire RTDs. While devices made from oxides of metals positive and negative temperature different semiconductor manufacturers and other ceramics. As with almost all coefficients; although positive producing thermistors strive to have a semiconductors, heat is the primary temperature coefficients are less similar resistance at 25°C (77°F), their cause of failure. While this appears a common. curves can differ. little contradictory—using a semiconductor for measuring temperature— A drawback with thermistors is they can fail in a closed mode. This could Turn to pages 63-69 for thermistors do have properties that Thermistor Resistance vs. make them very advantageous. create problems if a failure produces a resistance value similar to a temper- Temperature charts.

52 Temperature Sensors 53 oad. frequently, When the heat demand fluctuates and creates a system between static and dynamic, place the sensor half- way between the heat source and work load to divide the heat transfer lag times equally. Because the system can produce some overshoot and/ or undershoot, we recommend that the electronic controller selected for this situation include the PID features (anticipation and offset ability) to compensate for these conditions. This sensor location is most practical in the majority of thermal systems. the system is static, placing the sen- the system is static, source will sor closer to the heat constant keep the heat fairly In this type throughout the process. between the of system, the distance sensor is small heat source and the (minimal thermal the lag); therefore, heat source will cycle for overshoot reducing the potential and undershoot at the work l With the sensor placed at or near the heat source, it can quickly sense temperature changes, thus maintaining tight control. the controller to take the appropriate output action more quickly. However, in this type of system, the distance between the heat source and the sensor is notable, causing thermal lag or delay. Therefore, the heat source cycles will be longer, causing a wider swing between the maximum (overshoot) and minimum (undershoot) temperatures at the work load. We recommend that the electronic controller selected for this situation include the PID features (anticipation and offset ability) to compensate for these conditions. With the sensor at or near the work load, it can quickly sense temperature rises and falls. Load Load Load Sensor Sensor Sensor Heater Heater Heater Ref. 41 Sensor in a Combination Static/ Dynamic System Ref. 40 Sensor in a Dynamic System We call a system “dynamic” when there is rapid thermal response from the heat source, rapid thermal transfer and frequent changes in the work load. When the system is dynamic, placing the sensor closer to the work load will enable the sensor to “see” the load temperature change faster, and allow Ref. 39 System Sensor in a Static We call a system “static” when there is slow thermal response from the heat source, slow thermal transfer and minimal changes in the work load. When W A T L O W O L T A W Placement of the sensor in Placement of the work load and relationship to the for heat source can compensate demands various types of energy from Sensor the work load. the effects of placement can limit thermal lags in the heat transfer process. The controller can only respond to the temperature changes the it “sees” through feedback from sensor location. Thus, sensor of placement will influence the ability the controller to regulate the temperature about a desired set point. Be aware that sensor placement cannot compensate for inefficiencies in the system caused by long delays in thermal transfer. Realize also that inside most thermal systems, temperature will vary from point-to- point. Application Hints Application should my Where placed? sensor be Application Guide Temperature Sensors Non-Contact Temperature Sensor Basics Many industrial applications require temperature measurement. A temperature value can be obtained either by making physical contact with the object or medium (see Contact Temperature Sensor Basics, page 37), or by applying a non-contact temperature sensor (infrared). An infrared temperature sensor intercepts heat energy emitted by an object and relates it to the product’s known temperature. An infrared temperature sensor offers many advantages and can be applied where contact temperature sensing cannot be used. Some of these include: • Can be mounted away from heat sources that could affect readings. • Can sense the temperature of a moving object. • The sensor will not heatsink, contaminate or deface the product. • The sensor doesn’t require slip rings. • Can be isolated from contaminated or explosive environments by view- ing through a window. time or until an operator indexes respond in a short amount of time. Additional benefits include: the process to the next stage can The process temperature can be • Quality: Quality of the finished be time killers. Processing time can controlled tighter with a faster product in many processes is vary due to differences in starting responding sensor, increasing the directly related to the heating of the temperature, humidity and other quality of the product and process. material. In many applications the factors. Without any method of • Reduced downtime: A thermocou- heater, mold or platen temperature monitoring the product, an estimate ple must make physical contact is controlled, not the temperature of of time or visual inspection is used. with the object that it is measuring. the product. Monitoring product By using an infrared sensor, the If that object moves or vibrates the temperature insures a more consis- product can be indexed when it thermocouple will fail and must be tent, repeatable and higher quality has reached its desired tempera- replaced. The replacement cost of product is produced. ture. The time factor is removed the thermocouple plus the cost of • Increased productivity: which gives the customer a higher downtime can be extremely high. Applications where a material is quality product with the fastest Since an infrared sensor does not processed based on period of time productivity. make any physical contact, there can hinder productivity. • Fast response: Infrared sensors is no cost associated with replace- Applications where a material is respond faster than thermocouples. ment and downtime. placed into a oven or chamber and This is important for moving prod- processed for a given amount of ucts where a thermocouple cannot

54 Temperature Sensors 55 Microns and sterilized before the device and sterilized before device is not can be used. If the must be clean, the entire process sensor does rejected. An infrared and can not contact the process not contaminate. — The Watlow Infrared sensor can also The Watlow Infrared Watlow temperature be interfaced with a closed-loop, controllers to provide control non-contact temperature system with options for serial data communications and data logging. There is a direct relationship between the amount of radiation given off by an object and its temperature value. An object at 540°C (1000°F) emits more radiation than an object at 260°C (500°F). An infrared sensor intercepts this radiation and produces an output signal based on the object’s temperature, see Ref. 43. F) °

F) Visible ° Ref. 42 Wavelength C (392 — ° C (1832 200 ° 1000 : Food pro- Ultraviolet Infrared Radio Waves X-rays

Cosmic Rays Gamma Rays

cessing, chemical and pharmaco- cessing, chemical that use logical applications contact devices to monitor temperature can be a nuisance. The contact device must be cleaned be done via an infrared sensor be done via an infrared The rather than an operator. also be used infrared sensor can inspector that as an automated of each checks the temperature the sensor, product passing under products. thus rejecting bad Contamination free Spectral Radiance Spectral 0.001 0.012 0.40 0.72 1000 10,000 S Constant = Stefan-Boltzmann T = Absolute Temperature of Object From this equation we see that the emissivity and absolute temperature influence the amount of emitted radiation. The radiation is proportional to the fourth power of the absolute if temperature of the source. That is, the absolute temperature of the source is doubled, the radiation is increased by a factor of 16. • Emitted Energy as a Function of Temperature Ref. 43 The Electromagnetic Spectrum W A T L O W O L T A W : An infrared sensor 4 Automation can be used to automate many can be used to automate An infrared existing processes. determine the sensor can not only temperature of an object, but can also determine absence or presence of an object. Indexing a product to the next operation can W = Energy e = Emissivity What is Infrared Energy? Infrared energy is radiation released by an object that is above absolute zero temperature. All objects with a temperature above absolute zero (0 Kelvin) emit radiant energy. As an object is heated, molecular activity more become molecules As increases. energy. release and collide they active, Infrared energy is emitted from an object as electromagnetic waves. These waves are invisible to the human eye, but have the same characteristics as visible light. Electromagnetic waves are produced over a wide range of frequencies as categorized in Reference 42. The infrared band that has any use- able level of intensity for temperature measurement is in the 0.72 to 20 micron range. There is a distinct relationship between the temperature of an object and the amount of energy emitted from the object. The theory behind infrared thermometry is that the amount of measurable emitted energy relates to an object’s temperature. The amount of energy emitted from an object is determined using the Stefan- Boltzmann Equation: W = eS T • Non-Contact Temperature Non-Contact Temperature Sensor Basics Continued Application Guide Application Sensors Temperature Application Guide Temperature Sensors Common Applications for Infrared Ref. 44 Temperature Sensing Non-Contact Temperature The following list represents areas Industry Application Sensor Basics where infrared temperature sensing Chemicals Drying powders, Adhesives Continued is successfully applied. However, Coatings, Film processing the application possibilities are Food Packaging/sealing much greater. Baking ovens, Mixing Cooking and sterilization Metals Extrusion, Cold rolling Automotive Paint preheating and drying ovens Plastics Thermoforming Vacuum forming Injection molding Packaging and sealing Ovens Coating, Paint curing Laminating, Forming truck bed liners Paper Roller temperature Printing, Drying Textiles Drying, Printing Silkscreening, Heat setting Medical Blood temperature Research Lumber Determining moisture content Packaging Heat sealing Preheating, Bottling Laminating Laminating TV, CRT cabinets

Emissivity Theoretically, a blackbody is an ideal A material’s emissivity value also surface, one that doesn’t really exist. affects the amount of radiation emit- All other surfaces have emissivities ted by an object. Emissivity is a mea- less than one and are referred to as sure of an object’s ability to either emit “graybodies.” The term blackbody is or absorb radiant energy. Emissivity somewhat of a misnomer. If a surface values range from 0 to 1.0 and are ty- is the color black, it doesn’t pically obtained from tables or deter- necessarily mean it has an emissivity mined experimentally. of 1.0. A surface having an emissivity of “0” When applying an infrared sensor, it indicates a perfect reflector. This sur- is best if the surface has an emissivity face neither absorbs nor emits radiant of at least 0.5. A surface with a low energy. One can conclude that sur- emissivity value can be enhanced by: faces having low emissivity values • Texturizing the surface (polished surfaces, highly reflective) (sanding or sandblasting) are not good candidates for infrared • Oxidizing the surface sensing. • Anodizing the surface A surface having an emissivity of 1.0 is called a “blackbody.” This surface • Painting the surface with a dull, emits 100 percent of the energy high absorbent coating supplied to it or absorbs 100 percent of the energy intercepted by it. 56 Temperature Sensors 57 350 0.80 Non-Contact Temperature Control System ) and transmitted R If the object in the above ) is 20 percent. The total of Sensor T Infrared ) R = 80 percent, then the sum of the A reflected energy (E emissivity, the wavelength of the energy striking the object and its angle of incidence. Example: illustration has an emissivity of 0.8, this implies the object absorbs 80 percent of the energy striking its surface. Relating back to the conservation of energy equation, if E all three is 100 percent of the energy intercepted by the object’s surface. As the object heats up, it starts to reradiate or emit energy on its own. The amount of energy reradiated depends on the temperature of the object and its emissivity. An infrared sensor produces its output signal by intercepting a combination of an object’s reradiated (emitted) and reflected energy. An emissivity adjustment on the sensor allows the sensor to compensate for the amount of emitted and reflected energy, thus detecting the “true” object temperature. energy (E 2. Reflected Energy (E ) T Product (E Energy 3. Transmitted Energy Reradiated = 1.0 Radiant Heater T + E ) R A (E Energy Emitted Energy sorbed by the object, causing its temperature to increase. by the object’s surface, and has no affect on the object’s temperature. transmitted through that object, having no effect on the object’s temperature. + E = Absorbed Energy = Reflected Energy = Transmitted Energy A A R T 1. Absorbed E E E The amount of energy absorbed by the object depends upon the object’s When the emitted energy is intercepted by an object, a combination of three events will happen: 1. Part of the emitted energy is ab- 2. Some of the energy is reflected 3. Some of the energy will be The energy values of all three of these events will always total the amount of energy originally intercepted by the object. This is called the conservation of energy. As a formula, it’s expressed as: E Emitted Energy Ref. 45 W A T L O W O L T A W Non-Contact Temperature Non-Contact Temperature Sensor Basics Continued Emitted Energy? What Happens to what happens Reference 45 illustrates once it has been to emitted energy object. intercepted by an Application Guide Application Sensors Temperature Application Guide Temperature Sensors Characteristics of an Infrared System: Non-Contact Temperature Ref. 46 Sensor Basics Heat Temperature Source Non-Contact Controller/Indicator Continued Temperature Sensor

Optics How Does an Infrared Infrared Sensor Work? Detector A non-contact temperature control system consists of: • Precision Optics • Infrared Detector • Sensor Housing intercepts a portion of the total is then transmitted to the support • Support Electronics emitted energy and concentrates it electronics through a cable. The onto an infrared detector. The signal is amplified, linearized and There is a distinct relationship be- detector produces a signal output conditioned by the support tween an object’s temperature and proportional to the amount of electronics. the amount of energy that is given off incoming infrared energy. This signal by the object. An infrared sensor

Factors to Consider When Using Where not to apply a Watlow IR 2. Sensor/Target Distance Infrared Temperature Sensing sensor: Position the infrared sensor so the 1. Material • Transmissive materials object fills the sensor’s entire field- The sensor should be used to measure Thin film plastics usually less of-view. Position #1 in Reference 47 materials that have a high emissivity. than 10 mils shows proper sensor placement. The sensor is looking at the object The surface condition and the type of • Reflective materials material have an affect on the itself and not picking up background Polished, uncoated metals emissivity. Materials such as rubber, radiation (noise). Position #2 illus- textiles, paper, thick plastic (greater Brass, copper, stainless steel trates incorrect sensor placement. than 20 mils), painted surfaces, glass and wood are examples of materials Ref. 47 with a high emissivity. 2 The sensor can measure materials that 1 are transparent to visible light (materials that we can see through), assuming that the material is not too thin (less than 10 mils thick). Materials such as Non-Contact Temperature plate glass and clear acrylic sheets Sensor have a very high emissivity and are Correct Distance excellent infrared sensor application. Sensor Incorrect Placement Sensor Where can a Watlow IR sensor be Placement Background applied: “Noise” • Food • Rubber

• Plastic • Glass 51 mm (2 in.) • Paper • Wood Dia. Spot Size • Paint • Textiles Sensor • Liquids • Chemicals Minimum of 102 mm 457 mm (4 in.) Target • Any material that has a (18 in.) high emissivity

58 Temperature Sensors 59 s performance. ’ 5. Environment water vapor Dust, gases, suspended matter canand other particulate affect the infrared sensor absorb or These items can intercept, before it gets scatter infrared energy it is best if to the sensor. Therefore, kept fairly clean the environment is An air and free of contaminants. to purge the purge collar is available optics systems to prevent the accumulation of foreign material on the lens. Product Sensor ¡ 45 . The sensor output will . The sensor output angle normal to the surface ° Ref. 48 exposed to a dramatically changing exposed to a dramatically ambient ambient stabilize when the The sensor is temperature stabilizes. at a accurate when maintained temperature. constant ambient jackets may Air and/or water cooling maintain the be available to help operating sensor at an appropriate ambient temperature. 4. Sensor Placement Ideally, the temperature sensor should be placed at a right angle with respect to the target. This helps reduce the effects of reflected energy. Not all applications will lend themselves to perpendicular sensor placement. In these situations, do not position the sensor at more than a 45 (see Reference 48). W A T L O W O L T A W at the object ” it is normal for the looking “ as well as at background radiation; as well as at background background en- thus, it will average emitted by the ergy with the energy target object. All background surfaces around the target emit radiant energy according to the basic laws. If the background radiation is within the spectral transmission (eight-14 microns) of the sensor, an error in the indicated temperature will occur. This background radiation can be energy emitted from lamps, heaters, ovens, heat exchangers, motors, generators, steam pipes, etc. As a general rule of thumb, to minimize the effects of background radiation, the target size should be two times larger than the desired spot size. For example, if an object is 457 mm (18 in.) away and the spot size is rated be for 51 mm (2 in.), the target should at least 102 mm (4 in.) in size. 3. Ambient Temperature Check the operating ambient temperature of the infrared sensor. Due to the thermal dynamics of the infrared sensor, output to drift when the sensor is The sensor is Non-Contact Temperature Non-Contact Temperature Sensor Basics Continued Application Guide Application Sensors Temperature Application Guide The Art of Temperature This section deals with the major factors you an idea of how a decision on one Sensing you should consider when deciding on aspect of a sensor choice will affect a solution to an application problem. another. The objective is always to Defining an Application This is not meant to be all inclusive; arrive at an optimum solution... a solu- and Determining a Solution as the matrix of possible combinations tion that allows you to satisfy your tem- involved can lead to solutions too perature sensing needs, given the numerous to include in the limited limits of temperature sensing space available. However, it will give technology.

Determining Application Objective sensing; or the process moves making An integral part of thermocouple and Requirements contact sensing impractical, then in- responsiveness involves how long The first step is to establish an objec- frared temperature sensing will be the sensor needs to last and with what tive and determine the requirements to your method. degree of stability. The larger the con- reach that objective. These include: If you choose contact sensing, the ductor gauge, the longer the life with greater stability. This also affects • Does the application require con- degree of accuracy and temperature response as larger gauges also pose tact or non-contact temperature range will help decide the type of sen- greater mass and thermal inertia. sensing? sor. In general, a platinum wire RTD will provide the best overall accuracy, When sensors are used in hostile • How accurate must the temperature for the largest temperature range, for environments and need protection to reading be? the longest time. However, its cost extend life, the style, size and material • What temperature range is involved? may prohibit its use if economy is a of the protecting device will affect the • What’s the maximum temperature factor. This leads to deciding among sensor’s response. Again, it’s a com- the sensor will be exposed to? thermocouples and thermistors. The bination of the protecting device’s size • How fast must the sensor respond limited temperature range of thermis- (or mass), the thermal conductivity of to a temperature change and deli- tors may preclude their use. In that its material, the effectiveness of the ver an accurate reading? case, you’re limited to selecting a sen- thermal contact between the sensor sor from the available types and/or and protecting device, and the thermal • How long should the stability and calibrations of thermocouples. contact between the protecting device accuracy of the sensor last? The degree of responsiveness with its surrounding substance. All this • What environmental restraints exist depends on both the type of sensor affects how efficiently heat energy is and what protection devices will and size. Sensor mass has thermal transferred back to the sensor element. solve those restraints with sufficient inertia that must be overcome. This Economy then dictates if the spec- ruggedness? also involves any protecting device ifications set to achieve accuracy, • What cost, or economic restraints used to shield the sensor from its envi- response and life requirements can are involved? ronment. The relationships between be financially justified. This has more Decisions resulting from the above the sensor’s mass and thermal conduc- impact on applications that use a sen- will tend to lead to one sensor type tivity, protecting device mass and sor in a product. Obviously, the more over others. thermal conductivity, and that of the expensive the sensor, and/or protect- If an object or process would be substance or object being measured ing device, the more expensive the defaced or contaminated by contact will affect the degree of responsiveness. final product.

Sensor Location contact to what’s being measured. Once the above have been considered In a thermally dynamic application, and an optimum sensor construction location of the sensor relative to the arrived at, sensor location is the next heat source and load has an impact application problem to determine and on accuracy and response. solve. If an application is isothermal, The following covers contact sensor sensor location is a simple matter of placement in a thermal system. convenient location with sufficient

60 W A T L O W

Application Guide Reference Data Thermocouple and Reference data for thermocouples derived Resistance Wire RTD Initial from ASTM E230. Reference data for RTD Calibration Tolerances sensors derived from IEC 60751.

Initial Calibration Tolerances for Thermoelements and Resistance Wire RTDs—Ref. 49

Initial Calibration Tolerances (±¡F) Thermocouple Temperature RTD, DIN or JIS Type B Type E Type J Type K, N Type R, S Type T ¡C (¡F) A B STD STD SPL STD SPL STD SPL STD SPL STD SPL -184 (-300) 0.93 2.2 3.32 6.64 4.98 -157 (-250) 0.83 1.95 3.06 5.64 4.23 -129 (-200) 0.73 1.7 3.06 4.64 3.48 Temperature Sensors -101 (-150) 0.63 1.45 3.06 3.96 2.73 -73 (-100) 0.53 1.2 3.06 3.96 1.98 -46 (-50) 0.43 0.95 3.06 3.96 1.80 0.90 -18 (0) 0.33 0.7 3.06 1.80 3.96 1.80 0.90 0 (32) 0.27 0.54 3.06 1.80 3.96 1.98 3.96 1.98 2.70 1.08 1.80 0.90 10 (50) 0.31 0.63 3.06 1.80 3.96 1.98 3.96 1.98 2.70 1.08 1.80 0.90 38 (100) 0.41 0.88 3.06 1.80 3.96 1.98 3.96 1.98 2.70 1.08 1.80 0.90 66 (150) 0.51 1.13 3.06 1.80 3.96 1.98 3.96 1.98 2.70 1.08 1.80 0.90 93 (200) 0.61 1.38 3.06 1.80 3.96 1.98 3.96 1.98 2.70 1.08 1.80 0.90 121 (250) 0.71 1.63 3.06 1.80 3.96 1.98 3.96 1.98 2.70 1.08 1.80 0.90 149 (300) 0.81 1.88 3.06 1.80 3.96 1.98 3.96 1.98 2.70 1.08 2.01 1.07 177 (350) 0.91 2.13 3.06 1.80 3.96 1.98 3.96 1.98 2.70 1.08 2.39 1.27 204 (400) 1.01 2.38 3.06 1.80 3.96 1.98 3.96 1.98 2.70 1.08 2.76 1.47 232 (450) 1.11 2.63 3.06 1.80 3.96 1.98 3.96 1.98 2.70 1.08 3.14 1.67 260 (500) 1.21 2.88 3.06 1.87 3.96 1.98 3.96 1.98 2.70 1.08 3.51 1.87 288 (550) 1.31 3.13 3.06 2.07 3.96 2.07 3.96 2.07 2.70 1.08 3.89 2.07 316 (600) 1.41 3.38 3.06 2.27 4.26 2.27 4.26 2.27 2.70 1.08 4.26 2.27 343 (650) 1.51 3.63 3.09 2.47 4.64 2.47 4.64 2.47 2.70 1.08 4.64 2.47 371 (700) 1.61 3.88 3.34 2.67 5.01 2.67 5.01 2.67 2.70 1.08 399 (750) 1.71 4.13 3.59 2.87 5.39 2.87 5.39 2.87 2.70 1.08 427 (800) 1.81 4.38 3.84 3.07 5.76 3.07 5.76 3.07 2.70 1.08 454 (850) 1.91 4.63 4.09 3.27 6.14 3.27 6.14 3.27 2.70 1.08 482 (900) 2.01 4.88 4.34 3.47 6.51 3.47 6.51 3.47 2.70 1.08 510 (950) 2.11 5.13 4.59 3.67 6.89 3.67 6.89 3.67 2.70 1.08 538 (1000) 2.21 5.38 4.84 3.87 7.26 3.87 7.26 3.87 2.70 1.08 566 (1050) 2.31 5.63 5.09 4.07 7.64 4.07 7.64 4.07 2.70 1.08 593 (1100) 2.41 5.88 5.34 4.27 8.01 4.27 8.01 4.27 2.70 1.08 621 (1150) 2.51 6.13 5.59 4.47 8.39 4.47 8.39 4.47 2.80 1.12 649 (1200) 2.61 6.38 5.84 4.67 8.76 4.67 8.76 4.67 2.92 1.17 677 (1250) 6.09 4.87 9.14 4.87 9.14 4.87 3.05 1.22 704 (1300) 6.34 5.07 9.51 5.07 9.51 5.07 3.17 1.27 732 (1350) 6.59 5.27 9.89 5.27 9.89 5.27 3.30 1.32 760 (1400) 6.84 5.47 10.26 5.47 3.42 1.37 788 (1450) 7.09 5.67 10.64 5.67 3.55 1.42 816 (1500) 7.34 5.87 11.01 5.87 3.67 1.47 843 (1550) 7.59 6.07 11.39 6.07 3.80 1.52 871 (1600) 7.84 7.84 6.27 11.76 6.27 3.92 1.57 CONTINUED

61 Application Guide Reference Data Thermocouple and Resistance Wire RTD Initial Calibration Tolerances Continued

Initial Calibration Tolerances (±¡F) RTD Thermocouple Temperature DIN or JIS Type B Type E Type J Type K, N Type R, S Type T ¡C (¡F) A B STD STD SPL STD SPL STD SPL STD SPL STD SPL 899 1650 8.09 12.14 6.47 4.05 1.62 927 1700 8.34 12.51 6.67 4.17 1.67 954 1750 8.59 12.89 6.87 4.30 1.72 982 1800 8.84 13.26 7.07 4.42 1.77 1010 1850 9.09 13.64 7.27 4.55 1.82 1038 1900 9.34 14.01 7.47 4.67 1.87 1066 1950 9.59 14.39 7.67 4.80 1.92 1093 2000 9.84 14.76 7.87 4.92 1.97 1121 2050 10.09 15.14 8.07 5.05 2.02 1149 2100 10.34 15.51 8.27 5.17 2.07 1177 2150 10.59 15.89 8.47 5.30 2.12 1204 2200 10.84 16.26 8.67 5.42 2.17 1232 2250 11.09 16.64 8.87 5.55 2.22 1260 2300 11.34 17.01 9.07 5.67 2.27 1288 2350 11.59 5.87 2.32 1316 2400 11.84 5.92 2.37 1343 2450 12.09 6.05 2.42 1371 2500 12.34 6.17 2.47 1399 2550 12.59 6.30 2.52 1427 2600 12.84 6.42 2.57 1454 2650 13.09 1482 2700 13.34 1510 2750 13.59 1538 2800 13.84 1566 2850 14.09 1593 2900 14.34 1621 2950 14.59 1649 3000 14.84 1677 3050 15.09 1704 3100 15.34

Notes: thermocouple materials. Purchase • To convert tolerances to Celsius order must state that materials are 5 multiply by ⁄9 (0.55555). to be used in cryogenic range. • Tolerances in the cryogenic range • Tolerances listed may not apply (<0°C) may not apply to standard after exposure to heat or cold.

62 Temperature Sensors 63 CONTINUED The following tables contain the Tem- The following tables values for perature vs. Resistance and JIS platinum thermistors, and DIN RTDs. Reference charts and tables for ther- Reference charts RTDs courtesy mistors and platinum for Testing of the American Society from publication and Materials. Taken on the Use of STP 470B, “Manual Temperature Thermocouples in Measurement.” W A T L O W O L T A W Ref. 50 — 300 Ohms — (¡C) Ohms (¡C) Ohms (¡C) Ohms (¡C) Ohms (-80)(-79)(-78)(-77)(-76) 50,763 47,473(-75) 44,417(-74) 41,576(-73) 38,935(-72) (-39)(-71) 36,477 (-38) 34,190(-70) (-37) 32,060(-69) (-36) 30,076(-68) (-35) 4,554 28,227(-67) (-34) 4,327(-66) 26,503 (-33) 4,113 24,895(-65) (-32) 3,910 23,394(-64) (-31) 3,719 21,993(-63) (2) (-30) 3,538 20,684(-62) (3) (-29) 3,367(-61) (4) 19,461 (-28) 3,205 (5) 18,318(-60) (-27) 3,052 (6) 17,249(-59) (-26) 2,907 709.5 16,248(-58) (7) (-25) 2,769 681.8 15,312(-57) (8) (-24) 2,639 655.3(-56) (9) 14,436 (-23) 2,516 630.0 (10) 13,614(-55) (-22) 2,400 605.8 (11) (43) 12,845(-54) (-21) 2,289 582.7 (12) (44) 12,123(-53) (-20) 2,184 560.5 (13) (45) 11,447(-52) (-19) 2,085 539.4 (14) (46)(-51) 10,812 519.1 (-18) 1,990 (15) (47) 10,216(-50) 499.7 (-17) 1,901 (16) 164.7 (48)(-49) (-16) 481.2 9,656 1,816 159.6 (17) (49)(-48) (-15) 463.4 9,131 154.7 1,735 (18) (50)(-47) 446.4 (-14) 8,637 (51) 149.9 1,659 (19)(-46) 430.1 (-13) (52) 8,173 145.3 1,586 (20)(-45) 414.5 7,737 1,516 (21) (53) (-12) 140.9 (-44) 399.6 7,326 1,451 (54) (-11) 136.6 (22)(-43) 385.2 6,940 (55) (-10) 132.5 1,388 (23)(-42) 128.5 371.5 6,576 (56) 1,328 (24)(-41) (-9) 124.7 358.3 (57) 6,234 (25)(-40) 1,272 (-8) 345.7 121.0 5,911 (26) (58) 1,218 (-7) 117.5 333.5 5,607 (59) (27) 1,167 (-6) 114.0 321.9 5,320 (60) (28) (-5) 110.7 310.7 5,050 1,118 (61) (29) (-4) 107.5 300.0 4,795 1,071 (62) (30) (-3) 289.7 104.4 1,027 (63) (31) (-2) 101.4 984.5 279.8 (64) (-1) 944.2 270.3 (32) (65) 98.5 (0) 905.8 (33) (66) 95.7 261.2 (1) 869.1 (34) (67) 93.0 252.4 834.2 (35) 244.0 (68) 90.4 800.8 (36) (69) 87.8 235.9 (37) 769.0 85.4 (70) 228.1 (38) 738.6 83.0 (71) 220.6 (39) 80.7 (72) 213.4 (40) 78.5 206.5 (73) (41) 76.4 199.8 (74) (42) 74.3 193.4 (75) 72.3 187.2 (76) 70.4 181.3 (77) 175.5 (78) 68.5 170.0 (79) 66.7 (80) 64.9 (81) 63.2 61.6 (82) (83) 60.0 58.4 56.9 55.4 54.0 52.7 Temp R Value Temp. R Value Temp. R Value Temp. R Value No. 10 RTD Resistance vs. RTD Temperature Tables Standard Thermistors Application Guide Application Data Reference Application Guide Reference Data RTD Resistance vs. Temperature Tables Standard Thermistors Continued

No. 10—300 Ohms—Ref. 50

Temp R Value Temp. R Value Temp. R Value Temp. R Value (¡C) Ohms (¡C) Ohms (¡C) Ohms (¡C) Ohms (84) 51.3 (101) 33.8 (118) 23.1 (135) 16.2 (85) 50.0 (102) 33.0 (119) 22.6 (136) 15.9 (86) 48.8 (103) 32.3 (120) 22.1 (137) 15.6 (87) 47.6 (104) 31.5 (121) 21.6 (138) 15.3 (88) 46.4 (105) 30.8 (122) 21.1 (139) 15.0 (89) 45.3 (106) 30.1 (123) 20.7 (140) 14.7 (90) 44.1 (107) 29.4 (124) 20.3 (141) 14.4 (91) 43.1 (108) 28.8 (125) 19.9 (142) 14.1 (92) 42.0 (109) 28.1 (126) 19.5 (143) 13.8 (93) 41.0 (110) 27.5 (127) 19.1 (144) 13.6 (94) 40.0 (111) 26.9 (128) 18.7 (145) 13.3 (95) 39.1 (112) 26.3 (129) 18.3 (146) 13.1 (96) 38.1 (113) 25.7 (130) 17.9 (147) 12.8 (97) 37.2 (114) 25.2 (131) 17.5 (148) 12.6 (98) 36.4 (115) 24.6 (132) 17.2 (149) 12.3 (99) 35.5 (116) 24.1 (133) 16.9 (150) 12.1 (100) 34.6 (117) 23.7 (134) 16.5

No. 11—1000 Ohms—Ref. 51

Temp R Value Temp. R Value Temp. R Value Temp. R Value (¡C) Ohms (¡C) Ohms (¡C) Ohms (¡C) Ohms (-80) 233,516 (-60) 60,386 (-40) 18,641 (-20) 6,662 (-79) 217,298 (-59) 56,717 (-39) 17,649 (-19) 6,350 (-78) 202,147 (-58) 53,294 (-38) 16,716 (-18) 6,053 (-77) 188,227 (-57) 50,099 (-37) 15,837 (-17) 5,773 (-76) 175,258 (-56) 47,116 (-36) 15,010 (-16) 5,507 (-75) 163,454 (-55) 44,329 (-35) 14,231 (-15) 5,255 (-74) 152,435 (-54) 41,725 (-34) 13,498 (-14) 5,016 (-73) 142,234 (-53) 39,289 (-33) 12,806 (-13) 4,709 (-72) 132,779 (-52) 37,012 (-32) 12,154 (-12) 4,574 (-71) 124,017 (-51) 34,881 (-31) 11,540 (-11) 4,369 (-70) 115,888 (-50) 32,886 (-30) 10,960 (-10) 4,175 (-69) 108,347 (-49) 31,016 (-29) 10,412 (-9) 3,991 (-68) 101,343 (-48) 29,266 (-28) 9,896 (-8) 3,816 (-67) 94,837 (-47) 27,624 (-27) 9,408 (-7) 3,649 (-66) 88,793 (-46) 26,085 (-26) 8,947 (-6) 3,491 (-65) 83,171 (-45) 24,642 (-25) 8,511 (-5) 3,341 (-64) 77,942 (-44) 23,286 (-24) 8,100 (-4) 3,198 (-63) 73,075 (-43) 22,014 (-23) 7,709 (-3) 3,061 (-62) 68,544 (-42) 20,819 (-22) 7,341 (-2) 2,932 (-61) 64,321 (-41) 19,697 (-21) 6,992 (-1) 2,808 CONTINUED

64 Temperature Sensors 65 W A T L O W O L T A W Ref. 51 cont. — 1000 Ohms — (0)(1)(2)(3)(4) 2,691(5) 2,579(6) 2,472(7) 2,371(8) 2,274(9) (38) 2,182 (39) 2,094 (40) 2,009 (41) 1,929 (42) 1,853 630.6 (43) 609.5 (44) 589.2 (45) 569.6 (46) 550.8 (76) (47) 532.8 (77) 515.4 (78) 498.7 (79) 482.6 (80) 194.9 467.1 (81) 189.5 (82) 184.3 (83) 179.3 (84) 174.5 (114) (85) 169.8 (115) 165.2 (116) 168.8 (117) 156.6 (118) 74.2 152.4 (119) 72.5 (120) 70.8 (121) 69.2 (122) 67.7 (123) 66.1 64.7 63.2 61.8 60.5 (¡C) Ohms (¡C) Ohms (¡C) Ohms (¡C) Ohms (10)(11)(12)(13)(14) 1,780(15) 1,710(16) 1,643(17) 1,579(18) 1,519(19) (48) 1,460 (49)(20) 1,405 (50)(21) 1,351 (51)(22) 1,300 (52)(23) 1,252 452.2(24) (53) 437.8 1,205 (54)(25) 424.0 1,160 (55)(26) 410.7 1,118 (56)(27) 397.8 1,077 (86) (57)(28) 1,038 385.5 (87)(29) (58) 373.5 1,000 (88) (59)(30) 362.0 964.0 (89) (60)(31) 351.0 929.5 (90) (61)(32) 148.4 340.3 896.3 (91) (62)(33) 144.6 864.6 330.0 (92)(34) 140.8 (63) 320.0 834.2 (93) 137.2 (64)(35) 310.4 804.9 (94) 133.6 (65)(36) (124) 301.2 776.9 (95) (66)(37) 130.2 (125) 292.3 750.0 (96) (67) 126.9 (126) 724.1 283.6 (97) 123.7 (68) (127) 275.3 699.3 (98) 120.6 (69) (128) 267.3 675.5 (99) 59.2 117.5 (70) (100) (129) 259.5 652.6 57.9 (71) 114.6 (130) (101) 252.0 56.6 (72) 111.7 (131) (102) 244.8 55.4 109.0 (73) (132) (103) 237.8 54.2 106.3 (74) (133) (104) 231.0 103.7 53.0 (75) (105) (134) 224.5 101.2 51.9 (135) (106) 218.1 50.8 98.7 (136) (107) 212.0 49.7 96.3 (137) (108) 206.1 (138) 48.7 94.0 (109) 200.4 (139) 47.7 91.7 (110) 46.7 89.6 (140) (111) 45.7 87.4 (141) (112) 44.8 85.1 (142) (113) 43.9 83.1 (143) 43.0 81.4 (144) 42.1 79.5 (145) 41.2 77.7 (146) 40.4 75.9 (147) 39.6 (148) 38.8 (149) 38.0 (150) 37.3 36.5 35.8 35.1 34.4 Temp R Value Temp. R Value Temp. R Value Temp. R Value No. 11 RTD Resistance vs. RTD Temperature Tables Standard Thermistors Continued Application Guide Application Data Reference Application Guide Reference Data RTD Resistance vs. Temperature Tables Standard Thermistors Continued

No. 12—3000 Ohms—Ref. 52

Temp R Value Temp. R Value Temp. R Value Temp. R Value (¡C) Ohms (¡C) Ohms (¡C) Ohms (¡C) Ohms (-80) 2,189,062 (-37) 82,682 (6) 7,251.8 (57) 831.97 (-79) 2,003,162 (-36) 77,492 (7) 6,904.8 (58) 802.16 (-78) 1,834,293 (-35) 72,658 (8) 6,576.5 (59) 773.56 (-77) 1,680,803 (-34) 68,159 (9) 6,265.6 (60) 746.12 (-76) 1,541,203 (-33) 63,966 (10) 5,971.1 (61) 719.82 (-75) 1,414,129 (-32) 60,055 (11) 5,692.1 (62) 694.55 (-74) 1,298,393 (-31) 56,408 (12) 5,427.8 (63) 670.31 (-73) 1,189,906 (-30) 53,005 (13) 5,177.2 (64) 647.02 (-72) 1,096,689 (-29) 49,827 (14) 4,939.5 (65) 624.69 (-71) 1,008,889 (-28) 46,860 (15) 4,714.2 (66) 603.23 (-70) 928,683 (-27) 44,088 (16) 4,500.3 (67) 582.62 (-69) 855,409 (-26) 41,497 (17) 4,297.4 (68) 562.81 (-68) 788,394 (-25) 39,073 (18) 4,104.8 (69) 543.78 (-67) 727,056 (-24) 36,806 (19) 3,915.9 (70) 525.49 (-66) 670,919 (-23) 34,684 (20) 3,748.1 (71) 507.90 (-65) 619,476 (-22) 32,697 (21) 3,583.0 (72) 490.99 (-64) 572,319 (-21) 30,836 (22) 3,426.0 (73) 474.72 (-63) 529,062 (-20) 29,092 (23) 3,276.8 (74) 459.08 (-62) 489,352 (-19) 27,458 (24) 3,135.0 (75) 444.04 (-61) 452,892 (-18) 25,924 (25) 3,000.0 (76) 429.56 (-60) 419,380 (-17) 24,486 (26) 2,871.6 (77) 415.61 (-59) 388,572 (-16) 23,136 (27) 2,749.4 (78) 402.20 (-58) 360,219 (-15) 21,868 (28) 2,633.1 (79) 389.29 (-57) 334,123 (-14) 20,678 (29) 2,522.3 (80) 376.85 (-56) 310,086 (-13) 19,559 (30) 2,416.8 (81) 364.87 (-55) 287,937 (-12) 18,508 (31) 2,316.3 (82) 353.33 (-54) 267,507 (-11) 17,519 (32) 2,220.5 (83) 342.21 (-53) 248,660 (-10) 16,589 (33) 2,129.2 (84) 331.50 (-52) 231,264 (-9) 15,714 (34) 2,042.1 (85) 321.17 (-51) 215,193 (-8) 14,890 (35) 1,959.0 (86) 311.22 (-50) 200,348 (-7) 14,114 (36) 1,879.8 (87) 301.62 (-49) 186,617 (-6) 13,383 (37) 1,804.3 (88) 292.37 (-48) 173,916 (-5) 12,694 (38) 1,732.1 (89) 283.44 (-47) 162,159 (-4) 12,044 (39) 1,663.2 (90) 274.83 (-46) 151,269 (-3) 11,432 (40) 1,597.5 (91) 266.52 (-45) 141,183 (-2) 10,854 (41) 1,534.7 (92) 258.51 (-44) 131,833 (-1) 10,309 (42) 1,474.6 (93) 250.78 (-43) 123,160 (0) 9,795.2 (43) 1,417.3 (94) 243.31 (-42) 115,114 (1) 9,309.1 (44) 1,362.5 (95) 236.10 (-41) 107,642 (2) 8,850.0 (45) 1,310.0 (96) 229.14 (-40) 100,701 (3) 8,416.3 (46) 1,259.9 (97) 222.41 (-39) 94,254 (4) 8,006.3 (47) 1,212.0 (98) 215.92 (-38) 88,258 (5) 7,618.7 (48) 1,166.1 (99) 209.65 CONTINUED

66 Temperature Sensors 67 CONTINUED W A T L O W O L T A W Ref. 53 — Ref. 52 cont. — 100,000 Ohms 3000 Ohms — — (¡C) Ohms (¡C) Ohms (¡C) Ohms (¡C) Ohms (¡C) Ohms (¡C) Ohms (¡C) Ohms (¡C) Ohms (-60)(-59)(-58)(-57) 17,400,000(-56) 16,093,000(-55) 14,892,000(-54) 13,788,000(-53) (-36) 12,773,000(-52) (-35) 11,839,000(-51) (-34) 10,979,000(-50) (-33) 10,186,000 3,061,000(-49) (-32) 9,455,001 2,862,000(-48) (-31) 8,782,000 2,678,000(-47) (-30) 2,506,000 8,160,000(-46) (-29) (-12) 2,347,000 7,587,999(-45) (-11) (-28) 7,059,001 2,198,000(-44) (-10) (-27) 6,570,000 2,060,000(-43) (-26) 6,117,000 (-9) 1,931,000(-42) (-25) 686,400 (-8) 5,698,000(-41) 1,811,000 (-24) 648,000 5,310,000 (-7)(-40) 1,699,000 (-23) 612,000 4,950,000 (-6)(-39) 1,594,000 (-22) 4,616,000 (-5) 578,000(-38) 1,497,000 (-21) 4,307,000 (12) 546,100(-37) (-4) 1,407,000 (-20) (13) 4,020,000 516,100 (-3) 1,322,000 (-19) (14) 3,753,000 488,000 1,243,000 (-2) (-18) 3,505,000 461,500 (15) (-1) 1,169,000 (-17) 3,274,000 (16) 188,100 1,100,000 436,600 (0) (-16) 179,000 1,036,000 (17) 413,200 (1) (-15) 170,300 (18) (2) 391,200 (-14) 975,800 (19) 370,500 (3) (-13) 162,100 919,500 (4) 154,300 (20) 351,000 866,700 (5) (21) 332,600 146,900 817,300 315,300 139,900 (22) 770,800 (6) 133,300 (23) 299,000 727,300 (7) 283,600 (24) 127,000 (8) 269,100 (25) 121,000 (9) (10) (26) 115,300 255,500 (11) (27) 109,900 242,600 (28) 104,800 230,400 (29) 100,000 218,900 208,000 (30) 95,440 197,800 (31) 91,120 (32) 87,010 (33) 83,110 (34) (35) 79,400 75,870 72,520 69,330 66,300 63,420 (100)(101)(102)(103)(104) 203.59(105) 197.73(106) 192.07(107) 186.60(108) 181.31 (113)(109) 176.19 (114)(110) 171.24 (115)(111) 166.46 (116)(112) 161.83 (117) 140.83 157.35 (118) 137.03 153.02 (119) 133.34 148.82 (120) 129.77 144.77 (121) 126.31 (126) (122) 122.96 (127) (123) 119.72 (128) (124) 116.57 (129) (125) 113.53 (130) 99.634 110.57 (131) 97.100 107.71 (132) 94.644 104.93 (133) 99.260 102.24 (134) 89.946 (139) (135) 87.703 (140) (136) 85.524 (141) (137) 83.410 (142) (138) 81.356 (143) 71.947 79.363 (144) 70.225 77.427 (145) 68.550 75.547 (146) 66.923 73.721 (147) 65.341 (148) 63.804 (149) 62.309 (150) 60.857 59.445 58.071 56.735 55.436 Temp R Value Temp. R Value Temp. R Value Temp. R Value Temp R Value Temp. R Value Temp. R Value Temp. R Value No. 16 No. 12 RTD Resistance vs. RTD Temperature Tables Standard Thermistors Continued Application Guide Application Data Reference Application Guide Reference Data RTD Resistance vs. Temperature Tables Standard Thermistors Continued

No. 16—100,000 Ohms—Ref. 53 cont.

Temp R Value Temp. R Value Temp. R Value Temp. R Value (¡C) Ohms (¡C) Ohms (¡C) Ohms (¡C) Ohms (36) 60,690 (80) 10,800 (124) 2,695 (168) 866.3 (37) 58,080 (81) 10,430 (125) 2,620 (169) 846.3 (38) 55,600 (82) 10,070 (126) 2,548 (170) 826.8 (39) 53,250 (83) 9,731 (127) 2,478 (171) 807.9 (40) 51,000 (84) 9,402 (128) 2,410 (172) 789.5 (41) 48,870 (85) 9,086 (129) 2,344 (173) 771.5 (42) 46,830 (86) 8,782 (130) 2,280 (174) 754.1 (43) 44,900 (87) 8,489 (131) 2,218 (175) 737.1 (44) 43,050 (88) 8,208 (132) 2,158 (176) 720.6 (45) 41,280 (89) 7,937 (133) 2,099 (177) 704.5 (46) 39,600 (90) 7,676 (134) 2,043 (178) 688.8 (47) 38,000 (91) 7,425 (135) 1,988 (179) 673.6 (48) 36,460 (92) 7,183 (136) 1,935 (180) 658.7 (49) 35,000 (93) 6,951 (137) 1,884 (181) 644.2 (50) 33,600 (94) 6,727 (138) 1,834 (182) 630.1 (51) 32,260 (95) 6,511 (139) 1,786 (183) 616.4 (52) 30,990 (96) 6,303 (140) 1,739 (184) 603.0 (53) 29,770 (97) 6,103 (141) 1,694 (185) 590.0 (54) 28,600 (98) 5,909 (142) 1,650 (186) 577.3 (55) 27,490 (99) 5,723 (143) 1,607 (187) 564.9 (56) 26,420 (100) 5,544 (144) 1,566 (188) 552.8 (57) 25,400 (101) 5,371 (145) 1,526 (189) 541.0 (58) 24,430 (102) 5,204 (146) 1,487 (190) 529.6 (59) 23,490 (103) 5,043 (147) 1,450 (191) 518.4 (60) 22,600 (104) 4,888 (148) 1,413 (192) 507.5 (61) 21,750 (105) 4,739 (149) 1,377 (193) 496.9 (62) 20,930 (106) 4,594 (150) 1,343 (194) 486.5 (63) 20,150 (107) 4,455 (151) 1,309 (195) 476.4 (64) 19,400 (108) 4,320 (152) 1,277 (196) 466.6 (65) 18,680 (109) 4,190 (153) 1,245 (197) 457.0 (66) 17,990 (110) 4,065 (154) 1,215 (198) 447.6 (67) 17,330 (111) 3,944 (155) 1,185 (199) 438.4 (68) 16,690 (112) 3,827 (156) 1,156 (200) 429.5 (69) 16,080 (113) 3,714 (157) 1,128 (201) 420.8 (70) 15,500 (114) 3,605 (158) 1,100 (202) 412.3 (71) 14,940 (115) 3,500 (159) 1,074 (203) 404.0 (72) 14,400 (116) 3,398 (160) 1,048 (204) 395.9 (73) 13,880 (117) 3,299 (161) 1,023 (205) 388.0 (74) 13,380 (118) 3,204 (162) 998.7 (206) 380.3 (75) 12,900 (119) 3,112 (163) 975.0 (207) 372.7 (76) 12,450 (120) 3,023 (164) 952.0 (208) 365.4 (77) 12,010 (121) 2,937 (165) 929.7 (209) 358.2 (78) 11,590 (122) 2,853 (166) 908.0 (210) 351.2 (79) 11,190 (123) 2,773 (167) 886.8 (211) 344.3 CONTINUED

68 Temperature Sensors 69 (300) 77.70 W A T L O W O L T A W Ref. 53 cont. — 100,000 Ohms — (¡C) Ohms (¡C) Ohms (¡C) Ohms (¡C) Ohms (212)(213)(214)(215)(216) 337.7(217) 331.1(218) 324.7(219) 318.5(220) 312.4(221) (234) 306.5 (235)(222) 300.6 (236)(223) 295.0 (237)(224) 289.4 (238)(225) 284.0 223.4(226) (239) 219.5 278.7 (240)(227) 215.6 273.5 (241)(228) 211.7 268.4 (242)(229) 208.0 263.4 (256) (243)(230) 258.6 204.4 (257)(231) (244) 200.8 253.8 (258) (245)(232) 197.3 249.2 (259) (246)(233) 193.9 244.7 (260) (247) 152.7 190.5 240.2 (261) (248) 150.2 235.9 187.2 (262) 147.8 (249) 184.0 231.6 (263) 145.4 (250) 180.9 227.5 (264) 143.0 (251) 177.8 (278) (265) (252) 140.7 174.8 (279) (266) (253) 138.4 (280) 171.8 (267) 136.2 (254) (281) 168.9 (268) 134.0 (255) (282) 166.1 (269) 131.9 107.5 163.3 (283) (270) 105.9 129.8 160.6 (284) (271) 104.3 127.7 (285) 157.9 (272) 102.7 125.7 (286) 155.3 (273) 101.2 123.7 (287) (274) 121.8 99.70 (288) (275) 119.9 98.20 (289) (276) 118.0 96.70 (290) (277) 116.2 95.30 (291) 114.4 93.90 (292) 112.6 92.50 (293) 110.9 91.10 (294) 109.2 89.80 (295) 88.50 (296) 87.20 (297) 86.00 (298) 84.70 (299) 83.50 82.30 81.10 80.00 78.80 Temp R Value Temp. R Value Temp. R Value Temp. R Value No. 16 RTD Resistance vs. RTD Temperature Tables Standard Thermistors Continued Application Guide Application Data Reference Application Guide Reference Data RTD Resistance vs. Temperature Tables DIN Platinum RTDs Resistance vs. Temperature for IEC 60751 100 Ohm Platinum RTDs with Temperature Coefficient of 0.00385—Ref. 54

(¡C)0-1-2-3-4-5-6-7-8-9

(-200) 18.49 —... —... —... —... —... —... —... —... —... (-190) 22.80 22.37 21.94 21.51 21.08 20.65 20.22 19.79 19.36 18.93 (-180) 27.08 26.65 26.23 25.80 25.37 24.94 24.52 24.09 23.66 23.23 (-170) 31.32 30.90 30.47 30.05 29.63 29.20 28.78 28.35 27.93 27.50 (-160) 35.53 35.11 34.69 34.27 33.85 33.43 33.01 32.59 32.16 31.74 (-150) 39.71 39.30 38.88 38.46 38.04 37.63 37.21 36.79 36.37 35.95 (-140) 43.87 43.45 43.04 42.63 42.21 41.79 41.38 40.96 40.55 40.13 (-130) 48.00 47.59 47.18 46.76 46.35 45.94 45.52 45.11 44.70 44.28 (-120) 52.11 51.70 51.29 50.88 50.47 50.06 49.64 49.23 48.82 48.41 (-110) 56.19 55.78 55.38 54.97 54.56 54.15 53.74 53.33 52.92 52.52 (-100) 60.52 59.85 59.44 59.04 58.63 58.22 57.82 57.41 57.00 56.60 (-90) 64.30 63.90 63.49 63.09 62.68 62.28 61.87 61.47 61.06 60.66 (-80) 68.33 67.92 67.52 67.12 66.72 66.31 65.91 65.51 65.11 64.70 (-70) 72.33 71.93 71.53 71.13 70.73 70.33 69.93 69.53 69.13 68.73 (-60) 76.33 75.93 75.53 75.13 74.73 74.33 73.93 73.53 73.13 72.73 (-50) 80.31 79.91 79.51 79.11 78.72 78.32 77.92 77.52 77.13 76.73 (-40) 84.27 83.88 83.48 83.08 82.69 82.29 81.89 81.50 81.10 80.70 (-30) 88.22 87.83 87.43 87.04 86.64 86.25 85.85 85.46 85.06 84.67 (-20) 92.16 91.77 91.37 90.98 90.59 90.19 89.80 89.40 89.01 88.62 (-10) 96.09 95.69 95.30 94.91 94.52 94.12 93.73 93.34 92.95 92.55 (0) 100.00 99.61 99.22 98.83 98.44 98.04 97.65 97.26 96.87 96.48 CONTINUED

70 Temperature Sensors 71 CONTINUED Ref. 54, cont. — W A T L O W O L T A W (0) 100.00 100.39 100.78 101.17 101.56 101.95 102.34 102.73 103.12 103.51 )1234 56 789 C)01 ¡ (10)(20)(30) 103.90(40) 107.79(50) 111.67 104.29(60) 115.54 108.18(70) 119.40 112.06 104.68(80) 123.24 115.93 108.57(90) 127.07 119.78 112.45 105.07 130.89 123.62 116.31 108.96 134.70 127.45 112.83 120.16 105.46 131.27 116.70 124.01 109.35 135.08 127.84 120.55 113.22 105.85 131.66 124.39 117.08 109.73 135.46 128.22 120.93 113.61 106.24 132.04 124.77 117.47 110.12 135.84 128.60 121.32 113.99 106.63 132.42 125.16 117.85 110.51 136.22 128.98 121.70 114.38 107.02 132.80 125.54 118.24 110.90 136.60 129.37 114.77 122.09 107.40 133.18 118.62 125.92 111.28 136.98 129.75 122.47 115.15 133.56 126.31 119.01 137.36 130.13 122.86 133.94 126.69 137.74 130.51 134.32 138.12 ( (190) 172.16 172.53 172.90 173.26 173.63 174.00 174.37 174.74 175.10 175.47 (100)(110)(120) 138.50(130) 142.29(140) 146.06 138.88(150) 149.82 142.66(160) 153.58 146.44 139.26(170) 157.31 150.20 143.04(180) 161.04 153.95 146.81 139.64 164.76 157.69 150.57 143.42 168.46 161.42 154.32 147.19 140.02 165.13 150.95 158.06 143.80 168.83 154.70 161.79 147.57 140.39 165.50 158.43 151.33 144.17 169.20 162.16 155.07 147.94 140.77 165.87 158.81 151.70 144.55 169.57 162.53 155.45 148.32 141.15 166.24 159.18 152.08 144.93 169.94 162.90 155.82 148.70 141.53 166.61 159.55 152.45 145.31 170.31 163.27 156.19 149.07 141.91 166.98 152.83 159.93 145.68 170.68 156.57 163.65 149.45 167.35 160.30 153.20 171.05 164.02 156.94 167.72 160.67 171.42 164.39 168.09 171.79 Resistance vs. Temperature for IEC 60751 100 Ohm Platinum RTDs for IEC 60751 100 Ohm Resistance vs. Temperature Coefficient of 0.00385 with Temperature RTD Resistance vs. RTD Temperature Tables DIN Platinum RTDs Application Guide Application Data Reference Application Guide Reference Data RTD Resistance vs. Temperature Tables DIN Platinum RTDs Resistance vs. Temperature for IEC 60751 100 Ohm Platinum RTDs with Temperature Coefficient of 0.00385—Ref. 54, cont.

(¡C)01 234 56 789

(200) 175.84 176.21 176.57 176.94 177.31 177.68 178.04 178.41 178.78 179.14 (210) 179.51 179.88 180.24 180.61 180.97 181.34 181.71 182.07 182.44 182.80 (220) 183.17 183.53 183.90 184.26 184.63 184.99 185.36 185.72 186.09 186.45 (230) 186.82 187.18 187.54 187.91 188.27 188.63 189.00 189.36 189.72 190.09 (240) 190.45 190.81 191.18 191.54 191.90 192.26 192.63 192.99 193.35 193.71 (250) 194.07 194.44 194.80 195.16 195.52 195.88 196.24 196.60 196.96 197.33 (260) 197.69 198.05 198.41 198.77 199.13 199.49 199.85 200.21 200.57 200.93 (270) 201.29 201.65 202.01 202.36 202.72 203.08 203.44 203.80 204.16 204.52 (280) 204.88 205.23 205.59 205.95 206.31 206.67 207.02 207.38 207.74 208.10 (290) 208.45 208.81 209.17 209.52 209.88 210.24 210.59 210.95 211.31 211.66 (300) 212.02 212.37 212.73 213.09 213.44 213.80 214.15 214.51 214.86 215.22 (310) 215.57 215.93 216.28 216.64 216.99 217.35 217.70 218.05 218.41 218.76 (320) 219.12 219.47 219.82 220.18 220.53 220.88 221.24 221.59 221.94 222.29 (330) 222.65 223.00 223.35 223.70 224.06 224.41 224.76 225.11 225.46 225.81 (340) 226.17 226.52 226.87 227.22 227.57 227.92 228.27 228.62 228.97 229.32 (350) 229.67 230.02 230.37 230.72 231.07 231.42 231.77 232.12 232.47 232.82 (360) 233.17 233.52 233.87 234.22 234.56 234.91 235.26 235.61 235.96 236.31 (370) 236.65 237.00 237.35 237.70 238.04 238.39 238.74 239.09 239.43 239.78 (380) 240.13 240.47 240.82 241.17 241.51 241.86 242.20 242.55 242.90 243.24 (390) 243.59 243.93 244.28 244.62 244.97 245.31 245.66 246.00 246.35 246.69

72 Temperature Controllers 73 Heat Source Load Work Heat Transfer MediumTemperature Input Sensor Output Sensor temperature controlling device The directs its output to add, subtract, or or maintain heat by switching heaters cooling apparatus on and off. The controlling system usually includes sensory feedback. Device Ref. 55 Controlling is the work load, heat transfer is the device which the temperature is that which must be and the heat source heat transfer medium work load heat source, heated or cooled. The material (a solid, liquid or gas) through which the heat flows from the heat source to the work. delivers heat to the system. The controlling device(s). The medium the Thermal System Components To understand the principles of regulating process temperature, let’s examine the components of the thermal system. They include the nearest

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emper Watlow Representative. Sales offices Watlow Representative. Sales offices are listed on pages Generally speaking, a temperature controller receives an input signal from a temperature sensor, compares that signal to a preset value and then produces an output signal. of Watlow manufactures a wide variety user-oriented temperature controllers. Each is designed with our philosophy of Control Confidence Cont This section of the Application Guide This section of the controllers, is devoted to temperature methods of use their types, styles, for and general considerations If you’re determining applications. unable to find or controller will or model of temperature best Application Guide Application T sure trouble-free, reliable operation sure trouble-free, reliable operation in the most hostile industrial environments. Available in standard DIN to sizes, they lend themselves readily design considerations or replacement of existing temperature controllers. The full line of Watlow controllers include ramping controllers, microprocessor based digital controllers, digital indicators, non-indicating controllers and alarms and limits. For specific information on each control model, see Watlow’s controller catalog, Power Controllers. Application Guide Temperature Controllers Controllers Single-Loop Auto-tuning 1 1 1 1 Product Overview Available in ⁄32, ⁄16, ⁄8 and ⁄4 DIN sizes, agency approved Watlow single-loop, auto-tuning temperature controllers automatically set PID control parameters for optimum system performance. Manual settings also permit on-off, P, PI or PID control modes. All Watlow auto-tuning controllers are designed and manufactured to withstand harsh industrial environments and come with a three-year warranty for Control Confidence®. SERIES SD 1 1 ¥ ⁄32 to ⁄4 DIN size • ±0.10 percent accuracy • Operating environment from 0 to 65°C (32 to 150°F) SERIES 96 1 • ⁄16 DIN size • ±0.10 percent accuracy • Operating environment from 0 to 65°C (32 to 150°F) SERIES 988/989 1 • ⁄8 DIN size • ±0.10 percent accuracy Applications • Operating environment from • Batch process 0 to 65°C (32 to 150°F) • Electroplating SERIES V4 1 • Environmental chambers • ⁄4 DIN size • Foodservice equipment • ±0.10 percent accuracy • Furnace / ovens • Operating environment from 0 to 65°C (32 to 150°F) • Medical and dental equipment SERIES F4P • Packaging 1 • ⁄4 DIN size • Plastics processing • ±0.10 percent accuracy • Pulp and paper • Operating environment from • Semiconductor manufacturing 0 to 65°C (32 to 150°F) SERIES PD • DIN Rail • ±0.10 percent accuracy • Operating environment from 0 to 65°C (32 to 150°F)

74 W A T L O W

Application Guide Temperature Basic Controllers Watlow’s agency approved basic temperature controllers are compact and offer an economical cost effective control solution for less demanding Product Overview applications requiring basic on-off control. Reliability is further enhanced with Continued either a NEMA 4X front panel or totally enclosed electronics. All Watlow basic controllers are designed and manufactured to withstand harsh industrial environments, and come with a three-year warranty for Control Confidence®. SERIES CF

1 • Open board, DIN Rail or ⁄8 DIN Square • ±1.00 percent accuracy • Operating environment from 0 to 55°C (32 to 131°F) SERIES CV

1 • Open board, DIN Rail or ⁄8 DIN Square • ±1.00 percent accuracy • Operating environment from 0 to 55°C (32 to 131°F) SERIES 101 • ±1.00 percent accuracy • Operating environment from Applications 0 to 55°C (32 to 131°F) • Foodservice equipment SERIES 102 Temperature Controllers 1 • General process control • ⁄16 DIN size • Percent power, open loop • ±1.00 percent accuracy control • Operating environment from • Plastics and textile processing 0 to 55°C (32 to 131°F) • Heat or cool control SERIES 103 •HVAC • DIN rail mount • ±1.00 percent accuracy • Operating environment from 0 to 55°C (32 to 131°F) SERIES 104 • Open board • ±1.00 percent accuracy • Operating environment from 0 to 55°C (32 to 131°F)

75 Application Guide Temperature Time/Temperature Profiling Controllers Ideal for applications that change temperature over time, Watlow’s agency approved time/temperature profiling (ramping) controllers set new standards of Product Overview performance. PID auto-tuning makes setup easy. All are available with a broad Continued range of industry standard I/O and communication options. All Watlow time/temperature profiling controllers are designed and manufactured to withstand harsh industrial environments, and come with a three-year warranty for Control Confidence®. SERIES SD

1 1 • ⁄32 to ⁄4 DIN size • ±0.10 percent accuracy • Operating environment from 0 to 65°C (32 to 150°F) SERIES 96

1 • ⁄16 DIN size • ±0.10 percent accuracy • Operating environment from 0 to 65°C (32 to 150°F) Applications SERIES 981/982

1 • Environmental chambers • ⁄8 DIN size • Complex process furnaces • ±0.10 percent accuracy • Any process that changes • Operating environment from variables over time 0 to 55°C (32 to 130°F) • Semiconductor manufacturing SERIES F4S

1 • Processes needing data • ⁄4 DIN size logging • ±0.10 percent accuracy • Processes requiring slidewire • Operating environment from control of valves or positions 0 to 55°C (32 to 130°F) SERIES F4D

1 • ⁄4 DIN size • ±0.10 percent accuracy • Operating environment from 0 to 55°C (32 to 130°F)

76 W A T L O W

Application Guide Temperature Limits and Alarms Controllers Watlow limit controllers provide agency approved performance in safety limit applications, including UL®, CSA, A.G.A. and FM (on some models). All are Product Overview available with industry standard I/O options. All Watlow limit/alarm controllers are Continued designed and manufactured to withstand harsh industrial environments, and come with a three-year warranty for Control Confidence®.

Applications • High and low safety limit control • Environmental chambers • Furnace / ovens • Semiconductor • Boiler

SERIES LF SERIES 145

1 1 • Open Board, DIN Rail or ⁄8 DIN • ⁄16 DIN size Square • ±1.00 percent accuracy

• ±1.00 percent accuracy • Operating environment from Temperature Controllers • Operating environment from 0 to 55°C (32 to 131°F) 0 to 565°C (32 to 131°F) SERIES 146 SERIES LV • DIN rail mount 1 • Open Board, DIN Rail or ⁄8 DIN • ±1.00 percent accuracy Square • Operating environment from • ±1.00 percent accuracy 0 to 55°C (32 to 131°F) • Operating environment from SERIES 147 0 to 565°C (32 to 131°F) • Open board SERIES SD • ±1.00 percent accuracy 1 1 • ⁄32 to ⁄14 DIN size • Operating environment from • ±0.10 percent accuracy 0 to 55°C (32 to 131°F) • Operating environment from SERIES TLM-8 0 to 65°C (32 to 150°F) • Sub-panel or DIN rail SERIES 97 • 5 percent accuracy 1 • ⁄16 DIN size • Operating environment from • ±0.10 percent accuracy 0 to 60°C (32 to 140°F) • Operating environment from 0 to 65°C (32 to 150°F) SERIES 142 • ±1.00 percent accuracy UL® is a registered trademark of • Operating environment from Underwriter’s Laboratories, Inc. 0 to 55°C (32 to 131°F)

77 Application Guide Temperature Multi-Loop Controllers 2-Loop Agency approved Watlow two-loop, auto-tuning temperature controllers Product Overview automatically set PID control parameters for optimum system performance. Continued Manual settings also permit on-off, P, PI, or PID control modes. Data communications or remote operation or data logging. All are available with a broad range of industry standard I/O options. All Watlow two-loop controllers are designed and manufactured to withstand harsh industrial environments, and come with a three-year warranty for Control Confidence®. SERIES PD • DIN Rail • 0.10 percent • 0 to 65°C (32 to 150°F) SERIES 733/734 • 0.10 percent at 25°C accuracy SERIES 998/999

1 • ⁄8 DIN size • 0.10 percent at 25°C accuracy SERIES F4D

1 • ⁄4 DIN size • 0.10 percent at 25°C accuracy MINICHEF¨ Applications 1 •3⁄4 x 2 DIN size • Any process requiring two • 0.20 percent for Type J T/C and control loops RTD at 25°C • Foodservice equipment 0.35 percent for Types K and • Complex process furnaces E T/C at 25°C • Environmental chambers • Processes requiring control / monitoring from a computer

78 W A T L O W

Application Guide Temperature 4- to 48-Loop Controllers With up to 48 control loops, Watlow Anafaze PID controllers deliver the options and performance demanded by complex process applications. Each controller offers a Product Overview wide range of I/O options with exceptional accuracy. Inputs can be multiple and Continued mixed, including thermocouple, RTD and process. Multiple job/recipe storage makes batch setups fast. Auto-tuning PID control sets optimum control parameters. Versatile alarms and serial communications round out the features. In addition, the PPC-2000 and CPC400 controllers gives users the ability to add ladder-logic programs to the PID control.The SERIES D8 controller offers DeviceNet communications in four and eight loop models. Optional Windows®-based software permits remote operation and monitoring with standard Windows® operating systems. Three-year warranty. 4- to 48-Loop PPC-2000 • Panel or DIN rail mountable • 0.1 percent at 25°C accuracy • 0.14 second channel scan time (4 channel module) MINICHEF 4000 • Panel or DIN rail mountable • 0.05 percent at 25°C accuracy • 1.00 second channel scan time Alarm Scanner and Data Logger 4-Loop 16-Channel CLS204, CPC404, SERIES D8 CAS200 Temperature Controllers 1 1 • ⁄8 DIN size • ⁄8 DIN size • 0.07 percent at 25°C accuracy • 0.07 percent at 25°C accuracy • 0.17 second channel scan time • 0.67 second channel scan time 8-Loop 8-Channel CLS208, CLS408, SERIES D8 TLM8 1 • ⁄8 DIN size • Panel or DIN rail mountable • 0.07 percent at 25°C accuracy SERIES D8 1 • 0.17 to 0.33 second channel • ⁄8 DIN size scan time • 0.07 percent at 25°C accuracy 16-Loop • 0.17 second channel scan time CLS216, MLS316 Applications 1 • ⁄8 DIN size • Electronics • 0.07 percent at 25°C accuracy • Plastics • 0.67 second channel scan time • Rubber 32-Loop • Textiles MLS332 • Packaging applications 1 • Metals • ⁄8 DIN size • Paper industry • 0.07 percent at 25°C accuracy • Automotive • 1.33 second channel scan time • Chemical • Sealing • Foodservice ® Windows is a registered trademark of • Semiconductor equipment Microsoft Corporation.

79 Application Guide Temperature Control Panels and Boxes Controllers Watlow control panels and boxes are convenient, ready-to-connect packages that utilize temperature controllers, power controllers, multi-loop controllers and Product Overview related safety limit controllers in NEMA-rated enclosures. Control panels and Continued boxes can be designed to meet your particular application. Controller options include auto-tune, PID, on-off and percent power. Industry standard I/O options meet virtually all applications. Agency approved temperature, limit and power controllers mean built-in reliability. Enclosure NEMA ratings meet application environments. Solid state power controllers available in single-phase, and three-phase/two and three leg configurations with phase angle or burst fire switching. Control boxes are available in ratings up to 50 amps, while standard control panels are available in ratings up to 300 amps. Custom control panels are available up to 1600 amps or more may be available upon request. UL® 508 panel listings and CE certifications are also available. Applications • System applications requiring agency approved controllers • Applications requiring specific NEMA rated enclosures • Applications requiring easy controller package installation Features • Designed per UL®508 and NEC standards • Complete I & M documentation with component manuals and CAD circuit drawings • Enclosure cooling with fans, vortex coolers or air conditioners • Circuit protection with fuses or circuit breakers • Ground fault protection • Real-time data acquisition for process validation

80 Temperature Controllers 81 direct Process set A needle moving over refer to the controller’s signal refer to the controller’s have gained in prominence in are the volume leader in deviation indicator. point is established by adjusting a scale setpot. Display of actual pro- on cess temperature is then detected a separate deviation (null) meter that indicates temperature relative to the set point. Digital Digital indication of the process and set point temperatures is now predominant in the industrial world. Two types of digital displays are the light emitting diodes (LED) and the liquid crystal display (LCD). Each one has certain advantages that may make it more desirable than the other. LEDs industrial applications. They provide a bright display that is easily seen in poor or no light conditions. LEDs come in many sizes and colors. They are rugged and reliable. LCDs recent years. They require very little power to function. Therefore, they are very desirable in portable equipment. The LCD does not emit light, but rather reflects existing light. Control Indicators display their Temperature controllers two forms—analog operating status in referring to indi- and digital. When analog and digital cators, the terms do not the style processing method—just of display. Analog Analog indication of process temperature can be achieved with a reading meter. a dial scale reads actual process temperature. The desired control point is set by adjusting a separate pointer over this same scale. Another form of analog readout is the Set point resolu- is the minimum interval between controller’s accuracy. Common acc- controller’s accuracy. are input voltages uracy parameters temperature and frequency, ambient forth. conditions, and so of accuracy Standard categories ratings are: Calibration Accuracy refers to the Calibration accuracy the tem- amount of error between perature displayed and the actual temperature. It is usually expressed in terms of degrees, or percent of input span. Set Point Assembly Accuracy Set point assembly accuracy refers to the amount of error that could exist the between the indicated setting and set point signal sent to the controller. It is usually expressed in terms of degrees, or percent of set point span. Indication Resolution Indication resolution is the minimum interval between two marks on the temperature scale. tion two adjacent hash marks on the set point potentiometer scale. Indication resolution affects readability. Set point potentiometer scale resolution affects setability. Repeatability Repeatability is stated as the amount of agreement among several output measurements at all levels of input signal under identical operating conditions. It is usually expressed in terms of percent of input span. Repeatability is one of the determinants of accuracy. It does not include variables such as hysteresis. (Hysteresis is a change in the process variable required to re-energize the control or alarm output.) W A T L O W O L T A W Thermal Control Principles Thermal Control temperature The selection of a first of all by controller is determined required. the degree of controllability the temperature It’s best to select model that gives controller type and you need to you the optimum control to achieve desired results. You’ll want avoid selecting more control than is required. Doing so will only add to needless expense and complexity your heating system. Control Accuracy What is Accuracy? Accuracy is a measure of controller capability alone, exclusive of external factors.It is usually expressed in terms of percent of span. (Span is the algebraic difference between the upper and lower input range values.) Accuracy is the limit of error which the controller can introduce into the control loop across the entire span. Be careful, there is a great difference between specified controller accura- cies and the overall accuracy of your thermal system. System accuracy is extremely sensitive to the overall system design. It must be a major factor in the planning stage of a system. Accuracy is influ- enced by the size of the system’s heating source, system heat transfer delays, type of sensor and its location, type of controller modes selected, noise in the system, and other factors. We provide you with controller accuracy specifications to help you select system components for the overall system accuracy you need. Accuracy specifications are stated in conjunction with parameters whose values determine the characteristics of the Application Guide Application Temperature Controllers Application Guide Temperature Ref. 56 Temperature controllers are of two Controllers basic types—open loop and closed Temperature loop. An open loop, or manual, control Thermal Control Principles Controller device is one that has no self-correct- Continued ing feedback information. The closed loop, or automatic, controller uses Control Types, Power feedback information from the sensor Power Sensor Open or Closed Loop Controller Controller to properly regulate the system. As process temperature changes, the feedback loop provides up-to-date Heating Device status information that allows the Heating Device Heat Transfer Medium Heat Transfer Medium Work Load controlling device to make self-cor- Work Load recting adjustments. The closed loop control device is a much more desira- Closed Loop Control Open Loop Control ble approach to temperature control.

Control Modes On-off Ref. 57 the control action between the on and There are a variety of control modes off switching points. This temperature that provide differing degrees of con- hysteresis is established to prevent trollability. The most common modes On - Off switching the output device on and off are on-off and PID control. The PID within a temperature span that is too Switching narrow. Switching repeatedly within control category includes devices of Hysteresis varying degrees of complexity that are Temperature such a narrow span will create a capable of providing accurate, stable Set condition known as output control under a variety of conditions. Point “chattering” (intermittent, rapid switching). Temperature is always controlled “about set point.” This is dictated by Time the switching hysteresis (also sensitivity or switching differential) of the on- Time vs. Temperature Profile off control. The control action further Developed by On-Off Control dictates that there will always be a The operation of the on-off control is certain amount of temperature just as the name implies; the output overshoot and undershoot. The device turns full on or it turns full off degree of overshoot and undershoot when reaching set point. Temperature will be dependent on the character- hysteresis (sensitivity) is designed into istics of the entire thermal system.

Proportional method of controlling effective power. which results in less process Proportional control is required for a It delivers proportional control with a temperature overshoot. At that time, more precise control of process nonproportional output device (on- the system will be stabilized such that temperature. A proportional control off), such as electromechanical relay, process temperature is controlled at operates in the same way as an on-off solenoid valve, MDR or zero-cross a point below set point. control when a process temperature is fired SSR. At the lower limit of the The process temperature stabilizes far enough away from set point to be band, as the process temperature with a resultant droop. This condition outside the proportional band. When more closely approaches set point, will remain providing there are no work process temperature approaches set the ratio of on to off time changes; the load changes in the system. point and enters the proportional amount of on time decreases as the band, the output effective power level off time increases. This change in Refer to page 90 “How the is reduced. effective power delivered to the work Process Output Works.” Time proportioning is an output load provides a throttling-back effect 82 Temperature Controllers 83 Manual reset is an adjustment that must be made by the operator which compensates for droop. This adjustment brings the process temperature into coincidence with the set point by shifting the proportional band. If the set point or thermal system is changed, coincidence between set point and process temperature will be lost; therefore, the manual reset again. be made to will have adjustment If the temperature droop cannot be If the temperature ways to compen- tolerated, there are manual reset and sate for it. They are Reset, or automatic reset (integral). for droop. “integral,” compensates Overshoot Overshoot Droop Time Droop — Time With Manual Reset Time Proportioning Ref. 59 Ref. 58 Time Proportioning Band Manual Reset Adjusted, Heat Application Band Proportional Band Shifted Proportional Proportional With Manual Reset in a Developed by Proportional

Control in a Heat Application

Time vs. Temperature Profile Time vs. Temperature Profile Temperature Temperature Developed by Proportional Control Manual Reset Set Point Integral (Reset) Droop Compensating For Set Point W A T L O W O L T A W Thermal Control Principles Thermal Control Continued Application Guide Application Temperature Controllers Application Guide Temperature Automatic Reset Automatic reset (integral) is an auto- Controllers Ref. 60 matic adjustment that is made by the control output power level to Time Proportioning Thermal Control Principles With Automatic Reset compensate for a droop condition Continued when it exists. An integration function Proportional Band Overshoot takes place that automatically com- Temperature pensates for the difference between Set set point and actual process temper- Point ature. This integration automatically adjusts output power to drive the process temperature toward set point. Automatic reset action is prevented Time until the process temperature enters Time vs. Temperature Profile the proportional band. If it was allow- Developed by a Proportional Plus ed to take place at any point in the Integral Control in a Heat span of control, a condition of ex- Application treme temperature overshoot would occur. This function of eliminating the auto-reset is referred to as “anti-reset windup.” Note that the condition of droop does not exist in this graph.

Derivative (Rate)— Rate Derivative (rate) is an anticipatory Compensating for Overshoot Ref. 61 function in a temperature control that

As all of the process temperature PID -Time Proportioning measures the rate of change of pro- graphs have illustrated, temperature With Auto Reset & Rate cess temperature and forces the overshoot occurs with any control controller to adjust output power on Proportional an accelerated basis to slow that mentioned thus far. This condition Band Reduced Overshoot may be hazardous to certain pro- Temperature change. This action prevents a large cesses and therefore cannot be Set degree of overshoot or undershoot on tolerated. It is preventable with a Point start-up and also functions to prevent control function known as “rate.” overshoot or undershoot when system disturbances would tend to drive the process temperature up or down. Time A proportioning control with the Time vs. Temperature Profile automatic reset and rate (PID control) Developed by a Proportional Plus provides the type of control required Integral Plus Derivative (PID) for difficult processes which result Control in a Heat Application in frequent system disturbance, or applications which need precision temperature control. Note the effect of automatic reset by the lack of droop and the effect of rate by the reduced amount of process temperature overshoot on start-up.

84 Temperature Controllers 85 See

infrared. change in resis-

thermistors. . and a

3 3 and

RTDs

are

thermocouples the “Temperature Sensors” section of this Application Guide for specific information, page Think of it in terms of a closed loop Think of it in terms system. The (automatic) thermal of a heat single loop is comprised sensor and a final source, controller, One input power switching device. control the heat and one output signal the set point. source relative to has two output The controller now used for heat/cool signals that can be output sig- output signals, heat/heat nals, heat/high alarm output signals and many other combinations. tance environment. Sensors generating a small voltage input signal are generally Sensors generating This controller can handle two independent process control loops having two separate inputs (measured variables) and output action signals. The controller now has two output A signals for each independent loop. common example of this configuration is one loop of temperature control with heat/cool output signals and a separate loop of humidity control with humidify/dehumidify output signals. For a multi-loop controller with more than eight loops, repeat this configuration for the number of loops in the packaged system. and

Output Signal Output 2 Signal Output 1 Signal Output Signal B Output Signal A Output Signal B2 Output Signal B2 Up to eight loops Output Signal A2 Output Signal B1 Output Signal A2 Output Signal B1 Output Signal A1 Output Signal A1 sensors Controller Controller Controller Controller Controller Set Point Generator Set Point Generator Set Point Generator B Set Point Generator A Set Point Generator B Set Point Generator B Set Point Generator A Set Point Generator A Input Input Variable Process Variable Process their selection depends on economy, the type of work being measured, its temperature range, the desired response time and operating through two basic methods—a change in small voltages, or a change in resistance. There are four basic types of temperature Single Loop Controller Single Loop Controller Dual Outputs Ref. 63 Single Loop Controller Ref. 62 Dual Loop Quad Outputs Ref. 65 8-Loop Controller/Multi-Loop Controller Ref. 66 Dual Loops Ref. 64 Process Variable Input A Process Variable Input B Process Variable Input A Process Variable Input A Process Variable Input B Process Variable Input B , s single W A T L O W O L T A W and and other

e ol Principles r r . dual loop with quad sensors and

ollers . Reference 66 represents r 16 outputs emperatu measurable process variables such as pressure, humidity and location. However, temperature sensing is the most common with signals created dual loop outputs multi-loop control with eight loops and Control Input Signal Basics Input signals can be generated by temperature Thermal Cont Continued Control Configuration variables) and Inputs (measured signals can be output control action package to combined in a controller device meet nearly make a controlling any system demand. The four most common configurations are the loop, single loop with dual output Application Guide Application T Cont Application Guide Temperature Output Signal Terminology for the final switching device. The Controllers We have already looked at the part output signal, in turn, achieves the of a controller which decides if the desired value for the process variable Thermal Control Principles actual process variable is above or or an alarm-related action. Common Continued below the desired set point. We’ve types of output or signals are the Control Output Signal Basics also examined the varying percentage direct acting output and the reverse of the available output signal. This acting output. signal provides deliberate guidance

Direct Acting Output (Cool Mode) This is the controller action in which Cool Mode Example: Ref. 67 the value of the output signal increas- ¥ Temperature controller on-off es as the value of the input (measured ¥ Cool mode (direct acting) relay variable) increases. Falling type switching device Temperature This function is termed direct because Process Relay is De-energized the relay is de-energized or the con- Variable Below Threshold (Temperature) tacts drop out (output decreases) as Set Point the temperature decreases. Think of Cool Action Off N.O. Contacts Open this in terms of refrigeration. The re- Time frigerator compressor is on, removing heat energy. When the freezer temperature is below set point, the output action decreases.

Reverse Acting Output (Heat Mode) This is the controller action in which Heat Mode Example: Ref. 68 the value of the output signal ¥ Temperature controller on-off decreases as the value of the input ¥ Heat system Heat Power Off (measured variable) increases. Set Point N.O. Contacts Open ¥ Relay switching device This function is termed reverse be- Process Relay is Energized cause the relay is de-energized or the Variable Below Set Point contacts drop out (output decreases) (Temperature) Rising Temperature as the temperature increases. Think of it in terms of cooking in an oven. As Time the temperature rises, the heat source is turned off at a predetermined set point.

High Alarm Output alarm (set point). The output signal High Alarm Example: (Heat or Cool System) may use a “latching” output feature ¥ Alarm output on-off Ref. 69 that requires operator action to stop ¥ Heat or cool system the alarm signal, thereby removing Alarm Action Occurs ¥ Relay switching device Alarm High N.C. Contacts Close the “latch.” Set Point The high alarm function will warn an Process Relay is Energized Variable operator if a heat mode system is too Below Set Point (Temperature) Rising hot and will cause damage to the Temperature process (heat fails to turn off). It also could warn an operator if a Time cooling mode system has failed to This controller action warns of danger remove the heat from the system in the system when the value of the (cooling fails to turn on), resulting in input (measured variable) increases, damaged product. passing through a predetermined 86 Temperature Controllers 87 passing through a predetermined set point. A limit controller must have a separate power supply, sensor and a latching output feature requiring operator action to restart the process. Note the major difference when comparing the low limit and low alarm function. The limit output is always a latching output and uses the normally open relay contacts in a de-energized state below the set point. That way, if the limit itself fails or has no power, the system will shut down in a safe condition. alarm (set point). The output signal alarm (set point). output feature may use a “latching” action to stop that requires operator remove the the alarm signal, or “latch.” will warn an The low alarm function process operator before the low enough to temperature drops the process (heat cause damage to also will warn an fails to turn on). It operator if the cooling system removes too much heat from the system (cooling fails to turn off) resulting in a temperature so cold it causes damage to the process. the process as the value of the input (measured variable) increases, passing through a predetermined set point. Note the major difference when comparing the high limit and high alarm a function. The limit output is always latching output and uses the normally open relay contacts in a de-energized if state above the set point. That way, the limit itself fails or has no power, the system will shut down in a safe condition. Falling Temperature Rising Temperature Falling Temperature Relay De-energizes N.O. Contacts Open Relay De-energizes N.O. Contacts Open Alarm Action Occurs N.C. Contacts Close Time Time Time High Limit Set Point Relay is Energized Below Set Point Relay is Energized Above Set Point Low Limit Set Point Alarm Low Set Point Relay is Energized Above Set Point Variable Process Variable Process Variable Process This controller action prevents the process from exceeding a predetermined low value by shutting down the process as the value of the input (measured variable) decreases, Ref. 72 Ref. 71 Low Limit (Cooling System) Ref. 70 This controller action warns of danger in the system when the value of the input (measured variable) decreases, passing through a predetermined This controller action prevents the process from exceeding a predetermined high value by shutting down Low Alarm Output Low Alarm Output (Heat or Cool System) High Limit (Heat System) (Temperature) (Temperature) (Temperature) W A T L O W O L T A W Limit on-off Latching output Relay switching device Alarm output on-off Heat or cool system device Relay switching Limit on-off Latching output Relay switching device Low Limit Example: ¥ ¥ ¥ Thermal Control Principles Thermal Control Continued Low Alarm Example: ¥ ¥ ¥ High Limit Example: ¥ ¥ ¥ Application Guide Application Temperature Controllers Application Guide Temperature Electromechanical relays provide a Advantages: Controllers positive circuit break (with the excep- • Low initial cost tion of small current leakage through Control Output Types • Positive circuit break (with the noise suppression components, RC exception of minimum leakage The Mechanical, or suppression). This is important in with noise suppression devices) many circuits. This contrasts with solid Electromechanical Relay • May be mounted in any position Control Output state devices which almost always have a minute amount of current • Available with normally open and/ The Watlow temperature controller’s leakage. Mechanical relays usually or normally closed contacts mechanical relay output is an electro- cost less initially, but must be mechanical device. When power is • Electrical isolation between coil replaced more often. Solid state applied to the relay coil, contact circuit and load circuit devices can potentially last closure is created through movement • Switches ac or dc indefinitely, if not misapplied, so the of the “common” (COM) contact of the eventual cost of the mechanical relay Disadvantages: relay. can surpass that of the solid state • Higher cost over time Because this relay has moving parts, device. • Relatively short life, depending it is susceptible to vibrations and even- Mechanical relays can be mounted on percent of rated load tual mechanical failure. The repeated in almost any position and are much closure of the contacts finally results • Contact arcing is a source of elec- easier to install and service than many in contact failure through burning and tromagnetic interference (EMI) solid state switches. They are offered pitting. General guidelines to project • May be sensitive to environmental with normally open (N.O.) and nor- the life of Watlow mechanical relay conditions, such as dust and mally closed (N.C.) contacts. Many outputs are: vibrations Watlow controllers with mechanical • 100,000 cycles at full rated load relay outputs have RC suppression to • Derating with ambient temperatures 2 above stated specification • 500,000 cycles at ⁄3 rated load prevent electrical noise. Watlow 1 recommends using a Quencharc® • Can fail in either a closed or • 1,000,000 cycles at ⁄3 rated load across the terminals of an output open state switching device if the controller has • Warranted for 100,000 cycles only no internal RC suppression. at rated current

The Solid State Relay switching device, the speed limitation • Used for tighter process control Control Output of that device must be accounted for. • No arcing; clean switching In addition, the second device must Watlow’s solid state relay outputs Disadvantages: change state at zero volts, which is tolerate the low current leakage of the • Initial cost burst firing. They are also optically solid state control output. isolated, which means the output Like any other control output, the solid • No positive circuit break; circuitry is energized by infrared light state output must have redundant limit output current leakage striking a photo sensitive device. This control or other protection because • Cannot be used with low results in the virtual absence of elec- it may fail in the closed state. Solid power factor inductive loads trically generated noise, plus output- state devices are subject to damage • Tend to fail in the “closed” position to-input electrical isolation. from shorts in the load or load circuitry, • Cannot switch dc Because solid state devices can op- as wellas from transients and over- • Requires minimum load current erate much faster than electrome- heating. to operate chanical relays, they are employed Advantages: where extremely tight process control • Electrically noise-free burst firing is required. However, with the solid • Faster cycle times state devices connected to a second • Optically isolated from the Quencharc® is a registered trademark control circuitry of ITW Pakton.

88 Temperature Controllers 89 (dc)) to drive Î failure with no damage isolated requires additional contactor, opto-isolator or switch wired to it for the internal and external switching devices to generate noise spikes that require RC suppression. AC input solid state relays (SSRs), ac input SCRs, and other high impedance loads are subject to output leakage and false firing—choose solid state relay without RC suppression. If you need more information, including how to remove or add noise suppression to or from a solid state relay control output, call you Watlow sales agent, authorized distributor, or a Watlow application engineer. signal (4-20mA or 0-5V the final load device. No external low volt source is required. The process output in most cases is a non-isolated output. The device this output drives must provide isolation to prevent interaction with other power, input or output circuits. Advantages: • parts, no mechanical No moving • shock and vibration Resistant to • a direct short circuit Can withstand Disadvantages: • alone in most cases; Non-isolated • Must match the specifications (dc) (dc) Î Î non- load; maximum , like a Ω Ω The device this will interface directly The absence of the RC network eliminates ® ¨ output leakage across the contacts, and thus the possibility of false firing. Another way to phrase the question is: Do you need RC suppression with your solid state relay control output, or will your output device tolerate output leakage? Solenoids, MDR, and mechanical relays or contactors tend with the process output from the Watlow temperature controller. The control provides the electrical solid state relay. The input solid state relay. The power switching specifications of the those listed for the device must match output. The solid solid state switch open collector, state switch is an that provides a switched dc signal of 3V minimum turn on voltage than 32V on voltage not greater to output drives must provide isolation prevent interaction with other power, input or output circuits. Watlow’s dc input solid state power controllers provide this isolation. into an infinite load. The switched into an infinite load. dc output is in most cases a isolated output. On the other hand, if you are switching an acinput solid state relay (SSR), an ac input SCR (Watlow DIN-A-MITE, QPAC), or other high impedance loads (typically 5K piezoelectric buzzer, or neon lamp), you need Watlow’s 0.5A solid state relay (SSR) without contact suppression. Quencharc into a minimum 500 power device such as a silicon controlled or equipment rectifier (SCR) requiring a current or voltage input. Specific versions of the Watlow QPAC, VPAC, POWER SERIES and DIN-A-MITE (dc) Î ® Ω W A T L O W O L T A W have no (dc),1-5V minimum. This Î Ω (dc) input with an input Î solid state switches brand) suppression for noise immunity. This integral RC network dampens any noise generated by the downstream output device. Choosing the Right Solid State Relay Control Output for Your Application The key to selecting the correct Wat- low controllers solid state relay output is knowing the application. What downstream device will you switch with the controller’s solid state relay output? If you are switching a solenoid, a mercury displacement relay (MDR), or a mechanical relay or contactor, you need Watlow’s 0.5A solid state relay (SSR) with RC (Quencharc The Process Control Output The process output on Watlow controllers is wired through a device requiring a 4-20mA/0-20mA input with an input impedance of 600-800 Control Output Types Control Continued Control Output The Switched DC Since have no mechani- moving parts, they cal failures. These solid state switches to shock and vibra- are more resistant tion than mechanical relays. The absence of moving parts provides silent operation. Watlow’s switched dc output provides a small dc signal to trigger an external power switching device such as a maximum; or a 0-10V Application Guide Application Temperature Controllers may be a valve positioner, variable or 0-5V impedance of 1-5K Application Guide Temperature toward set point and enters the pro- Advantages: Controllers portional band, the output signal • No moving parts decreases proportionately. Ideally, • Silent operation Control Output Types the system will proceed to set point Continued without overshoot. As the system • Resistant to interference; low noise stabilizes at set point, the process susceptibility; low impedance, How the Process Output Works output signal becomes constant at a current loop When the control calls for an increase value between 0-5VÎ(dc) or 4-20mA. Disadvantages: in the actual process value (heat, flow System thermal characteristics and • Non-isolated in most cases requires or pressure, etc.), and when the actu- control PID settings combine to al value is outside the controller’s pro- isolated contactor or power device determine the final, stable value of the connected external to control portional band, the process output process output signal. turns full on. With a 0-5VÎ(dc) process • Maximum load impedance output, full on measures five volts; The control output power level is 600-800Ω for current output represented by a linear process with 4-20mA, full on measures 20mA. • Minimum load impedance 1-5kΩ signal: 0% power = 4mA or 0VÎ(dc) In a reverse acting, or heat mode, for voltage output 100% power = 20mA or 5VÎ(dc) as the actual process value moves 50% power = 12mA or 2.5VÎ(dc) Control Output Comparison—Ref. 73

I want to switch… Output I want to control… Controller Output Life • Solenoid coil/valve Solid state relay • Mercury displacement relay (MDR) with RC suppression • Electromechanical relay • General purpose contactor

• AC input solid state relay (SSR) Solid state relay • AC input solid state contactor without contact suppression • High impedance load, typ.≥ 5kΩ • Piezoelectric buzzer • Indicator lamps • Various devices in on-off mode Electromechanical relay with RC suppression • Various devices in on-off mode (high Electromechanical relay impedance or inductive devices with coils without contact suppression suppressed) • Indicator lamps • Small heaters • AC input solid state contactor • A safety limit circuit with contactor, Electromechanical relay electromechanical relay or with RC suppression mercury displacement relay (MDR) • Various devices in on-off mode Electromechanical relay • Solenoid coil/valve with RC suppression • Mercury displacement relay (MDR) • Electromechanical relay • General purpose contactor • Pilot duty relays

90 Temperature Controllers 91 N/A Output (dc), Î (dc), Î (dc), non-isolated (dc), non-isolated Î Î (dc), non-isolated (dc), 1-5V Î Î (dc), isolated Controller Output Life Î (dc), 0-20mA Î (dc) @ 30mA Î Watlow power controller process inputs calibrated for 4-20mA unless otherwise specified with order. a (dc) or 0-10V Î valve positioner … … a Best Life Better Life Good Life (dc) valve positioner (dc) Î Î (dc) valve positioner (dc) valve positioner 4-20mA (dc), 1-5V Î Î Î impedance or inductive devices with coilsimpedance or inductive suppressed) without contact suppression W A T L O W O L T A W I want to control I want to switch • Cascade control • Cascade instruments • Other • Phase angle or burst fire SCR Process 4-20mA • in on-off mode (high Various devices lamps Electromechanical relay • Indicator heaters • Small • AC input solid state contactor • DC input solid state relay (SSR)input • PLC-dc • Low voltage panel lamp • DC input solid state relay (SSR)input • PLC-dc Switched dc, isolated • Low voltage panel lamp • DC input solid state relay (SSR)• input PLC-dc Switched dc, non-isolated • voltage panel lamp Low • 100mA minimum load• Electric resistance heaters isolated Open collector, • Phase angle or burst fire SCR Process 0-20mA Triac • 4-20mA • 0-20mA • 0-5V • Cascade control, • Cascade instruments • Other • fire Multiple SCRs, phase angle or burst Process 0-5V • 0-10V • 0-10V • Cascade control • Cascade instruments • Other • Sensor transmittersdevices• Ancillary Power supply, 5, 12 or 20V • Cascade control • Cascade instruments • Other • fire Multiple SCRs, phase angle or burst Process 0-10V Ref. 73 continued Control Output Types Control Continued Application Guide Application Temperature Controllers Application Guide Temperature Controllers Control Output Types Continued Control Output Comparison—Ref. 73 continued Retransmit/Alarms

I want to switch… Output I want to control… Controller Output Life • 1 or 2 devices, impedance dependent 0-20mAÎ(dc), 4-20mAÎ(dc), • Chart recorder non-isolated • Master-remote (slave) system • Data logging device • 1 or 2 devices, impedance dependent 4-20mAÎ(dc), non-isolated • Chart recorder • Master-remote (slave) system • Data logging device • Multiple devices, impedance dependent 0-5VÎ(dc), non-isolated • Chart recorder • Master-remote (slave) system • Data logging device • Multiple devices, impedance dependent 0-5VÎ(dc), 1-5VÎ(dc), • Chart recorder 1-10VÎ(dc), Isolated • Master-remote (slave) system • Data logging device • Various devices in on-off mode Electromechanical relay, Form A or B, with RC suppression

Best Life

Better Life

Good Life

92 Temperature Controllers 93 Install — , of this n 115 Warning express or implied, is hereby made, express or implied, protection dis- that the limit control herein will be cussed and presented application effective in any particular or that addi- or set of circumstances, precautions will not tional or different for a parti- be reasonably necessary cular application. to consult with We will be pleased application you regarding a specific upon request. Limit Controller Applicatio high or low temperature limit con- an trol protection in systems where overtemperature or undertemperature fault condition could present a fire hazard or other hazard. Failure to install temperature limit control protection where a potential hazard exists could result in damage to equipment and property, and injury to personnel. Application Guide. switches, or both. Consult the wiring examples contained in the “Wiring Practices” section, page by a defective or worn sensor, power controller, heater or temperature a controller. Limit controllers can take if process to safe, default conditions equipment failure occurs. because

no repre- use a

controller and

using

which

applied

873-recognized as

be temperature processes.”

under ®

for

may

97. Certain models of these

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quality, agency-approved limit controller where one is required. Redundant control- separate power supply, power lines and sensor, the limit controller can take the process to a safe, default condition when an over- or undertemperature fault occurs. Limit control reliability-

of the differences in components and of the differences methods of their installation, sentation or warranty of any kind, products • SERIES are either UL ment and time lost in an accident are usually well worth the extra level of protection limit controllers provide. Limit control protection has two keys: • Disclaimer of Warranty and state- This is a general overview need for ment of the safety-related “limit control and methods of applying protection Because of the diversity of conditions Because of the diversity and temperature regulating controllers or FM-approved as temperature limit control loop where a potential fault condition could result in damage to equipment, property and personnel. All devices have a finite life. Conse- quently, system faults can be caused are

W A T L O W O L T A W 94 and here

, ocess consequences

r end

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r r that

from

ol P r ollers r recover suggestions for protecting emperature P

o t is a registered trademark of Underwriter’s T n ® emperatu or Laboratories, Inc. UL of a serious system fault. In addition, the value of the process equipment, the value of the product in the equip- Watlow Limit Control Products Watlow offers three limit controllers suitable for use in environments where hazards exist, the SERIES some undertemperature against over- and conditions. Keys to Safe Limit Control Protection Limit control protection is a system safeguard often required for agency approval, government regulation or for insurance protection. In other systems where potential faults also exist, limit control protection makes good sense, like wearing a life jacket or a hard hat. It’s easier in the long run to have a limit control in place rather tha Introduction to Limit Control Protection What follows will define limit control and provide recommendations on limit control protection in a temperature Good engineering can minimize sys- Good engineering first” is a good tem failures. “Safety rule to follow. To Limit Cont f Application Guide Application T Cont Application Guide Temperature •UL® 873: Temperature Indicating • CE: 89/336/EEC Electromagnetic Controllers and Regulating Equipment Compatibility Directive and •UL® 197: Commercial Cooking 73/23/EEC Low Voltage Directive Agency Recognition Appliances • ®: UL® Tested to Applicable for Controllers •UL® 508: Industrial Control CSA C22.2 Standard In certain applications, the circum- Equipment • NRTL* approved to ANSI Z 21.23- stances require the control circuit •UL® 3101: Laboratory Equipment 1993: Gas Appliance Thermostats electronics and associated system •UL® 3121: Process Control • FM: Class 3545 Approved hardware to be tested by an indepen- Equipment Temperature Limiting Switch dent laboratory to meet specific con- Watlow furnishes many stock prod- struction and operation requirements •UL® 991: Tests for Safety-Related ucts that have recognition for various with respect to hazards affecting life Controls Employing Solid State agency file numbers. and property. There are several inde- Devices pendent test laboratories in the U.S. • CSA Std C22.2 No. 24-93: Please check the product catalog and many throughout the world. The Temperature Indicating and listing or, for special assistance following are the common standards Regulating Equipment; C22.2 No. regarding your unique requirements, to which most of our products are 109-M1981 Commercial Cooking consult your local Watlow sales office. designed and built: Appliances; C22.2 No. 14-M1973 •UL® 50: Type 4X Enclosure and C22.2 No. 14-M1987 Industrial *Nationally Recognized Testing Laboratory (NEMA 4X) Control Equipment

Control System Tuning Tuning Methods possible through the use of digital, microprocessor-based, electronic In this phase of making the system Tuning temperature controllers is circuitry. With auto-tuning, the con- work, we will focus on the process accomplished either manually or troller has a “program” inside its controller as the primary component automatically. Manual tuning is just memory that will calculate the correct of a closed loop system that must be that—manually setting each of the setting for each of the controller adjusted for optimum performance. controller’s operating parameters. parameters. These adjustments provide a means Automatic tuning, or auto-tuning, is to compensate for system problems. For instance, when the sensor cannot Auto-Tuning representative. Any change to set be placed in the most desirable loca- For Watlow controllers, the auto-tuning point, while in auto-tune, reinitiates the tion because of physical limitations, a automatically sets the PID parameters auto-tune process. PID controller can compensate for the to fit the characteristics of your Some Watlow temperature controllers, sensor’s resulting thermal lag problem. particular thermal system. featuring auto-tune, will not auto-tune Once the auto-tune sequence has while in remote set point. Transferring begun, the heat proportional band is from local to remote set points takes set to 0 and the controller goes into the controller out of auto-tune. an on-off mode of control typically at Generally, to complete auto-tuning, 90 percent of the established set the process must cross the 90 point. The display set point will percent set point four times within remain unchanged. approximately 80 minutes after Once the controller learns the thermal auto-tune has started. system response, it returns to a stan- The following graph visually repre- dard PID control using PID values sents the auto-tune process. Note automatically set as a result of auto- that tuning is effected at 90 percent tuning. Output 2 cool PID values are of temperature set point. Once auto- also set on certain Watlow products, tuning is completed, the controller such as the SERIES 93, 96, 935, 988, then brings the process to temperature. and F4 family. Consult your Watlow

94 Temperature Controllers 95 controller has a switching on-off trol adjustment at a time, allowing the system to settle down and reach a state of equilibrium before making another change. tuning the electronic controller system is relative to the precision of control you need. • Do not change more than one con- • Remember that the time you spend An controller will not tune a loop that is controller will not When auto-tune is already at set point. sets the heat started, the controller and holds control output to MANUAL percent (or at the the output at 100 output limit output limit if a continuous The response of has been selected). (PV) as it rises is the process variable the PID con- analyzed to calculate process is com- stants. When this plete, the controller puts the loop into AUTO with the new constants. To avoid excessive overshoot, the controller will abort the auto-tune function if the PV goes above 75 percent of setpoint. It will also abort if it fails to calculate PID constants to within a 10 minute time period (due a related failure). If aborted, the loop will return to its previous control state. hysteresis that is used to define switching thresholds where the unit will change its output status. Decreasing switching hysteresis will cause the output to change status more frequently (faster cycling) and reduce the excursions above and below set point. Increasing the hysteresis will produce the opposite results (slower cycling). Actual Process Value Set Point Switching Hysteresis Contact Closes control system. It will work a long time without further attention if done right. Contact Opens Ref. 75 with auto-tune temperature controllers. These manual steps are generally what’s taking place in an auto-tuning controller. Please take note of a few precautions: • Take your time in tuning the When auto-tuning is complete, the When auto-tuning to their previous displays will return the controller will state. At this point, PID tuning note the appropriate them in its non- parameters and save volatile memory. please refer to To abort auto-tuning, manual, or cycle the controller’s user on. the power off and specific For auto-tuning procedures to a particular temperature controller, always refer to that controller’s user manual for details. Auto-tune for Multi-loop Controllers (Watlow Anafaze) Multi-loop controllers have an auto- tune feature that is designed to tune loops from a cold-start (or a stable state well below set point). A On-off Control Hysteresis Diagram 203 202 201 200 199 198 197 Set Point any Auto-tune Complete W A T L O W O L T A W Process Time ° 90% of Set Point Auto-tune Begins

100 180 200

Temperature ° Manual On-Off Tuning Factors Manual Tuning The following steps for manual tuning are general and applicable to most manually set temperature controllers. Each is taken in sequence. However, when manually tuning controller, always refer to and follow the recommended steps in that controller’s User Manual. Many of these steps are accomplished “transparently” Ref. 74 Control System Tuning Control Continued Application Guide Application Temperature Controllers Application Guide Temperature Proportional Band controller cycle time, the better the Controllers The proportional band adjustment is system response, but it must be bal- the means of selecting the response anced against the maximum switching Control System Tuning speed (gain) or sensitivity of a propor- life of the controller’s output. Continued tioned controller to achieve stability in The tuning procedure is very simple if Manual PID Tuning Factors the system. The proportional band, a recorder is available to monitor the Conventional control parameter measured in degrees, units, or per- actual process variable. If a recorder adjustments (PID), listed in the cent of span, must be wider than the is not available, observe the process sequence in which they should be natural oscillations of the system and response and record readings over a adjusted, are as follows: yet not wide enough to dampen the defined time period. system response. A side note: if the Set the proportional band to 25º and controller has a “time proportional” allow the system time to stabilize. output, the cycle time should be set If there are oscillations, double the as short as possible while tuning, and proportional band. If no oscillations then reset longer to reduce wear on are present and the system is stable, the system, but not so long as to de- cut the proportional band in half. grade system response. Allow time for the system to stabilize. The time proportioning output must Continue to double or halve the be set to switch faster than the natural proportional band until the system oscillation of the system, sometimes again becomes unstable. Adjust the called, “system cycle time.” One sys- proportion band in the opposite tem variable that can limit the cycling direction in small increments. Allow speed of the control output is the time between adjustment for the switching device. A mechanical relay system to stabilize. Continue until the is hundreds of times slower than a process is stabe ±1˚ and power is solid state device. The shorter the stable ±5 percent.

Integral (Reset) Please make small changes in tem cycle time). Thus, the auto The reset adjustment, manual or auto- the reset adjustment and allow the reset time constant (repeats per matic, is tuned at this point to correct system to return to a state of equi- minute) must be tuned to match for the droop that is caused by the librium before making additional the overall system response time. proportional output. changes. This may take several Begin by setting automatic reset to • Controllers with manual reset system cycle times. Also, manual 0.50 repeats per minute. Then should have this parameter adjust- reset will have to be changed if the allow the system time to stabilize. ment set initially at the “mid-range” set point or other thermal charac- If there are oscillations, cut the setting. The operator will make teristics are changed substantially. reset value in half. If no oscillations small increment adjustments in • Automatic reset would seem to im- are present and the system is the proper direction (increase or ply that it would not require adjust- stable, double the reset value. decrease) to bring about coinci- ment. While it does automatically dence between the actual process make correction for offset errors, it temperature and the desired set has to be tuned to each unique point. system. Each system has its own characteristic response time (sys-

96 Temperature Controllers ” 97 Heater Silicone Rubber PID Without the Math “

Limit Sensor ” Limit SERIES 142 Chart Recorder Oscillations reduced by adding a proportional band Proportional control with a set point change Droop correction with reset Set point change in a control with proportional and reset action More rapid and less stable response to set point change, caused by increased reset action Controller Tuning and Control Loop by David W. St. Clair Available from: Straight-Line Control Co., Inc. 3 Bridle Brook Lane Newark, DE 19711-2003 increase the set point moderately. of the actual Observe the approach to set point. If it process temperature to increase the overshoots, continue increments. If the rate integer in small cut the rate value in system oscillates, and stablizes, half. If it overshoots Then increase double the rate value. moderately the set point temperature to set point is until optimum approach achieved. “ Performance • • • • • Relay Output 0.5A Solid State s function Retransmit ’ Typical Temperature Controller 4 F 1 2 1A1A 1B1B With SERIES F4 Driving a Chart Recorder Type J Thermocouple Input i SERIES F4 is the last control parameter ad- is the last control Oscillations of an on-off control, and response to a set point change Ref. 76 Derivative (Rate) Rate Rate justment to be made. is to reduce or eliminate overshoot or is to reduce or eliminate above or undershoot (excursions has a time base below set point). lt which must be (measured in minutes) the overall system tuned to work with cycle time). response time (system for rate should be at The initial setting 0.5 minutes after each adjustment Recommended Tuning Reference There are many reference books on the art of tuning electronic controllers to the systems they control. If you are not an instrument technician qualified to tune thermal systems, we suggest that you obtain and become familiar with the following reference before attempting to tune your system. These charts represent one type of system response. Nonetheless, they provide a representative look at a real thermal system. The charts go from on-off control, through proportional control with no reset or rate, to proportional control with reset and no rate. Phenomena exhibited on the charts are: • W A T L O W O L T A W s sensor so that the ’ and tuning of Watlow controllers. chart recorders in tuning thermal systems. several tuning settings quickly. in one PID parameter can affect system stability and response. Control System Tuning Control Continued Application Guide Application Temperature Controllers Sample chart recordings on the following page will assist you in: 1. Understanding the application 2. Demonstrating the usefulness of 3. Providing a means of observing 4. Demonstrating how a change This section contains typical chart a recorded temperature responses of temperature controller output plotted A 20 watt silicone by a chart recorder. rubber heater on a small aluminum J thermocouple load block with a Type input provides the heat source, load and feedback system. We connected the chart drive sensor input in parallel with the controller Typical Thermal Control Thermal Typical System Chart Recordings recorder would read the same system response. Application Guide Temperature Controllers Typical Thermal Control System Chart Recordings Continued Ref. 77 Ref. 78 Oscillation Difference Between 0 10 20 30 40 50 60 70 80 90 100 100 90 80 70 60 50 40 30 20 10 0 0 10 20 30 40 50 60 70 80 90 100 100 90 80 70 60 50 40 30 20 10 0

On-off Control With Set Point Change 0 10 20 30 40 50 60 70 80 90 100 100 90 80 70 60 50 40 30 20 10 0 0 10 20 30 40 50 60 70 80 90 100 100 90 80 70 60 50 40 30 20 10 0 ° On-off Control and Proportional Control 270 F 270°F 2 Minute Per Major Division ° 10 F Per Major Division ° Starting Point 70°F 250 F 250°F Set Point = 175°F Proportional Band = 0°F (on-off) Reset = 0.00 Rate = 0.00 Minute Temp Rise Rate Band = 0 Change in Temp Cycle Time = 4 Second Fluctuation Temp Fluctuation 175°F 175°F Proportional Band 1 = 5°F Change Set Point = 250°F 2 Minute Per Major Division Temp Rise 10°F Per Major Division Starting Point 70°F Set Point = 175°F Proportional Band = 0°F (On-Off) Reset = 0.00 Rate = 0.00 Minute Rate Band = 0 Cycle Time = 4 Second ° 70 F 70°F Ref. 79 Ref. 80 0 10 20 30 40 50 60 70 80 90 100 100 90 80 70 60 50 40 30 20 10 0 Droop Correction w/Reset in Proportional Control 0 10 20 30 40 50 60 70 80 90 100 100 90 80 70 60 50 40 30 20 10 0

0 10 20 30 40 50 60 70 80 90 100 100 90 80 70 60 50 40 30 20 10 0 20¡F Proportional Band w/Set Point Change 0 10 20 30 40 50 60 70 80 90 100 100 90 80 70 60 50 40 30 20 10 0 270¡F 270¡F

250¡F Change Set Point = 175¡F 250¡F

175¡F 175¡F Reset Action Change Set Point = 250¡F Change Set Point = 250¡F Reset 1 = 0.10 Correcting Droop 2 Minute Per Major Division 2 Minute Per Major Division 10¡F Per Major Division 10¡F Per Major Division Starting Point 70¡F Starting Point 70¡F Set Point = 175¡F Set Point = 175¡F Proportional Band = 20¡F Proportional Band = 30¡F Reset = 0.00 Reset = 0.00 Rate = 0.00 Minute Rate = 0.00 Minute Rate Band = 0 Rate Band = 0 Cycle Time = 4 Second Cycle Time = 4 Second 70¡F 70¡F

Ref. 81 Ref. 82

0 10 20 30 40 50 60 70 80 90 100 100 90 80 70 60 50 40 30 20 10 0 Set Point Changes w/2.00 Reset 0 10 20 30 40 50 60 70 80 90 100 100 90 80 70 60 50 40 30 20 10 0

0 10 20 30 40 50 60 70 80 90 100 100 90 80 70 60 50 40 30 20 10 0 Set Point Changes w/30¡F Proportional Band and 0.50 Reset 0 10 20 30 40 50 60 70 80 90 100 100 90 80 70 60 50 40 30 20 10 0 270¡F 270¡F Overshoot Created by Faster Reset Change Set Point = 175¡F Change Set Point = 175¡F 250¡F 250¡F

175¡F 175¡F Change Set Point = 250¡F Change Set Point = 250¡F Reset 1 = 2.00 Reset 1 = 0.50 Reset 1 = 1.00 2 Minutes Per Major Division 2 Minutes Per Major Division 10¡F Per Major Division 10¡F Per Major Division Starting Point 70¡F Starting Point 70¡F Set Point = 175¡F Set Point = 175¡F Proportional Band = 30¡F Proportional Band = 30¡F Reset = 0.10 Reset = 1.50 Rate = 0.00 Minute Rate = 0.00 Minute Rate Band = 0 Rate Band = 0 Cycle Time = 4 Second Cycle Time = 4 Second 70¡F 70¡F

98 W A T L O W

Application Guide Temperature Single-Loop Time/Temperature Profiling Controllers Auto-Tuning (Ramping) Used to automatically set PID Programmable auto-tuning controllers Controller Overview parameters for optimum thermal (see auto-tuning above) are able to Watlow offers controllers of two system performance. Capable of execute ramp and soak profiles such different types, temperature accepting a variety of sensor inputs, as temperature changes over time, controllers and power controllers. including thermocouple, RTD and along with hold, or soak/cycle Control panels are pre-assembled process. The controller senses the duration. Selected controllers are temperature and power controller rate of temperature increase (reverse available in CE compliant versions. packages mounted in a suitable acting) or decrease (direct acting) Applications include heat treating, electrical enclosure. and adjusts the output action to complex process furnaces and A temperature controller produces an minimize set point over- and under- environmental chambers. output action based on the input shoot. PID output action requires a Limits/Alarms signal received from a sensor. solid state power controller to These controllers are specifically Controllers used in cooling withstand rapid switching cycles. designed to provide safety limit applications are called direct acting. Auto-tuning controllers can have more control over process temperature. Controllers used in heating than one output channel for alarms, They are capable of accepting applications are called reverse acting. retransmit and serial communications. thermocouple, RTD or process inputs Depending on the controller, output Selected controllers are available in with limits set for the high or low actions can control a heating or CE compliant versions. temperature. Limit control is latching cooling device, or some other aspect Some controllers feature a percent and part of a redundant control circuit of a process (ratio mixing, conveyor power default operation or will de- to positively shut a thermal system speed, etc.). energize the system upon sensor down in case of an over-limit Temperature controllers are either break. Controllers with NEMA 4X front condition. single-loop or multi-loop. Single-loop panels are well suited for wet or Multi-Loop Temperature Controllers corrosive environments. temperature controllers are good for Two-Loop basic temperature control. Various Applications include batch These units can receive two inputs levels of sophistication can reduce processing ovens and furnaces, and produce two or more outputs for temperature under-and over-shoot, environmental chambers and direct and reverse acting control. produce alarm actions and perform analytical equipment. They accept thermocouple, RTD, data logging functions as well as Basic serial communications. process and event inputs. Auto-tuning Used for non-critical or (see auto-tuning above) automatically Multi-loop temperature controllers unsophisticated thermal systems to sets PID parameters for optimum (also called process controllers) are provide on-off temperature control for performance. Outputs include alarms, good for applications where direct or reverse acting applications. events, process, serial temperature and other process The basic controller accepts communications and data logging. variables need to be controlled in a thermocouple or RTD inputs and Selected controllers are available in coordinated fashion. offers an optional percent power CE compliant versions. Applications Temperature controllers are either control mode for systems without include foodservice equipment, single-loop or multi-loop. Single-loop temperature sensors. This category complex process furnaces and controllers have one input, and one or also includes cartridge thermostats. environmental chambers. more outputs to control a thermal These units operate on their sheath's Four to 32-Loop system. Multi-loop controllers have thermal expansion and are available Available in versions that supply four, multiple inputs and outputs, and are in reverse and directing acting modes. eight, 16 and 32 control loops, the capable of controlling several aspects They can be wired interconnected or controllers can accept thermocouple, of a process. More control loops for pilot duty with a relay. The cartridge RTD, process, linear and pulse inputs. permit controlling and coordinating thermostat can also serve as a non- A selected eight loop version also more process system functions. latching limit controller. Applications accepts carbon potential. Auto-tuning include foodservice and general automatically sets PID parameters for process control.

99 Application Guide Temperature facilities; our focus on electronics Software Design Controllers means we put significant investment • High level language for flexibility in state-of-the-art technology. Our and fast development Four to 32-Loop con’t engineers participate in a continuing • Software demo design optimum performance. Job recipe education and training program that • Communications keeps our team on the cutting edge of storage permits preprogramming to • Application overview screens innovation. We work with your team to speed batch setup. Outputs include • Custom menus and functions digital, alarms, events, process, serial give your company that competitive • Custom logic functions communications and data logging. edge. Optional PC communications permits Custom Controllers • Custom communication protocols Resources remote operation and monitoring. Capabilities Custom Controls • Hardware engineers Hardware Design • Software engineers Watlow Custom Controls Group • Microprocessor, analog and • Technicians provides design, engineering, discreet digital testing/debugging and production. • PC designers • Surface mount technology But more than that, Watlow provides • Mechanical designers • Through-hole technology you with a cooperative partnership • Account managers • Qualification lab based on service, ongoing product • Customer service agents • Electromagnetic compatibility support and electronic controllers Additional Custom Capabilities • Environmental testing solutions. We have the experience, • Customization of standard single stability and total thermal system • Shock and vibration and multi-loop controllers expertise to produce the controller • Agency approvals • Custom electronic contract that’s right for your application. PC Board Design assembly and system integration Watlow offers the most modern • Multi-layer • Custom control panels with or engineering, testing and production • Double-sided without turnkey heating systems Data Communications and manually operating many phys- Protocol, based on ANSI X3.28- 1976, ically isolated controls. Other uses Subcategories 2.2 and A3. For more In addition to data logging, many include monitoring and controlling information on Data Communications digital, microprocessor-based temper- processes for SPC (statistical process you can download a copy of the ature controllers offer serial (data) control), or gather data to prepare “Data Communications Reference: communications. This feature allows a certificates of compliance. This Electronic Users Manual” for the central computer to monitor and control eliminates the task of manual data Watlow web site. Both of these are one or several temperature controllers. collection and processing. based on the ASCII character code. The uses of serial communications are Serial communication is the exchange ASCII (American Standard Code for many and varied, depending on your of data in a one-bit-at-a-time, sequen- Information Interchange) is almost application requirements. Space tial manner on a single data line or universally used to represent each letter, doesn’t permit a detailed explanation channel. It relies on the controller’s punctuation mark and number we use. of this temperature controller feature. and computer’s ability to use a com- A third protocol is referred to as However, the main benefit of con- mon protocol to govern their inter- Modbus™ RTU. This expands the necting temperature controllers to a action, or communication. Because communications ability of the central computer is the ability to they are less prone to both operator controller by enabling a computer to more fully automate a process. and noise induced error, protocol- read and write directly to register Depending on the central computer’s driven communications are more containing the controller’s parameters. programming, it can be set to operate accurate than other forms of com- For specifics on how serial communi- in different capacities. The most computer communications. cations can meet your process tem- mon is to have the computer act as Protocols perature control and monitoring a single “control panel” for multiple Watlow uses three protocols, two of needs, please contact your Watlow temperature controllers. This relieves which are the simple XON/XOFF sales engineer, or the factory. production personnel of monitoring Protocol (flow control), and Full Modbus™ is a trademark of Schneider Automation Incorporated. 100 W A T L O W

Application Guide Power Controllers The discrete output device that acts in response to a deliberate guidance from the temperature controller is the power controller. There are four common power controllers: electromechanical relays, mercury displacement relays, solid state relays and silicon controlled rectifiers (SCRs). The first two use magnetic devices to actuate power switching. The latter two use solid state electronics to effect the switching function. The selection of a specific power controller type depends on the method of control being used, system power demands, degree of temperature control (accuracy to set point), the heater type and heater life requirements. Watlow manufactures a wide range switching needs. Each is manufac- controller types, models and ratings, of mercury displacement relays, solid tured to the highest standards of see the “Power Controllers” product state relays and SCR power control- reliability and performance. For more section of Watlow’s Temperature and lers in ratings to meet almost all power information specific to power Power Controller’s catalog, page 121. Temperature Controllers Product Overview Power Controllers Watlow solid state power controllers complement the rapid switching required by PID temperature controllers and help deliver optimum system performance and service life. Available in 1-phase and 3-phase/2-leg and 3-leg configurations, Watlow power controllers meet most industrial heating applications. Random, zero cross or phase angle fire options match the power controller to the application requirement. DIN-A-MITE SCR power controllers provide a convenient DIN rail mount package in current ratings from 18 to 100 amperes – a good replacement for equal mercury displacement relays. Qpac SCR power controllers rated up to 1,000 amperes for those large process heating applications. POWER SERIES microprocessor based SCR power controllers with ratings from 65 to 250 amperes. The POWER SERIES offers extensive system and heater diagnostics features and agency approvals. SERIES CZR is a CSA, VDE and UL® recognized contactor with ratings from 18 to 50 amperes single phase. Single solid state relays from 10 to 75 amperes. E-SAFE® relay is a 3-pole hybrid solid state/mechanical relay with current ratings of 20 and 40 amperes and is UL®-508 listed and C-UL®. E-SAFE is a good mercury displacement relay replacement in the amperages it serves.

101 Application Guide Power Controllers Applications SSR • Ratings from 10 to 75 amps Product Overview • Semiconductor processing Continued • Plastics processing • Single-phase configuration • Heat treating • VÅ(ac) or VÎ(dc) contactor • Drying ovens firing options • Foodservice equipment QPAC • Petroleum / chemical • Ratings from 30 to 1,000 amps • Lighting equipment • Single- and three-phase configurations • Glass processing • Contactor, burst fire and phase • Furnace / oven angle firing options DIN-A-MITE A POWER SERIES • Ratings to 25 amps • Ratings from 65 to 250 amps • Single-phase configuration • Single- and three-phase • Contactor or burst fire firing options configurations DIN-A-MITE B • Contactor, burst fire and phase • Ratings to 40 amps angle firing options • Single- and three-phase configuration SERIES CZR • Contactor or burst fire firing options • Ratings from 18 to 50 amps DIN-A-MITE C • Single-phase configuration • Ratings to 80 amps • VÅ(ac) or VÎ(dc) contactor • Single- and three-phase configurations firing options • Contactor, burst fire and phase angle E-SAFE firing options • Ratings from 20 to 40 amps DIN-A-MITE D • Three-phase configuration • Ratings to 100 amps • 24, 120 and 220 input, VÅ(ac) • Single-phase configuration Contactor • Contactor or burst fire firing options

Five Basic Types: Ref. 83 1. 100,000 cycles at full rated load 2 The electromechanical contactor, or Screw 2. 500,000 cycles at ⁄3 rated load 1 Contacts 3. 1,000,000 cycles at ⁄3 rated load relay is an electrical and mechanical Normally device with moving parts. When Closed Electromechanical contactors pro- power is applied to the relay solenoid, Contact vide a positive circuit break. This is contact closure is created through Normally important in many circuits. This con- Open movement of the relay’s “common” Contact trasts with solid state devices which contact. almost always have a small amount Screw of leakage current flow. 1. Electromechanical Relay Common Electromechanical contactors can be Because this contactor has moving Contact Field Coil mounted in almost any position and parts, it is susceptible to vibration or are much easier to install and service mechanical failure. The closure of the reason for failure of an electrome- than many solid state switches. They contacts when powered results in chanical relay. A general guideline for are offered with normally open and contact failure through burning and projecting the life of higher quality normally closed contacts, with a very pitting, which, in fact, is the primary mechanical relays is as follows: slight cost differential for both contacts.

102 W A T L O W

Application Guide Power Controllers Mercury displacement relays have The mercury displacement relay com- completely encapsulated contacts bines the best features of the electro- Five Basic Types that rely on mechanical movement to mechanical relay and the solid state Continued function. However, the relays are de- switch. The primary advantage of the 2. Mercury Displacement Relay signed so that the moving parts are electromechanical relay is its ability to (MDR) restricted to a confined area and any switch considerable amounts of power contact as a result of this movement is at a low cost. One of the primary ad- Ref. 84 between Teflon® and metal. The con- vantages of the solid state device is In-bound Electrode tacts do not wear due to the mercury long life. The MDR combines these within the capsule. Mercury does not features. While the electromechanical 1 1 pit and burn like metal. The mercury relay costs less (by ⁄3 to ⁄2), the MDR Plunger contacted is actually ever-changing. will provide the long life desired. The Field Coil Mercury displacement relays provide MDR can typically outlasts the electro- Liquid a positive circuit break, are small in mechanical relay by a factor of 100 Mercury size, are low in cost and provide a to one or more. The MDR is rated to Out-bound barely audible noise when switching. operate at full load for up to 15 million Electrode cycles, which provides extended life as with solid state relays.

3. Solid State Relays Solid state switching devices have Because solid state relays can oper- Ref. 85 no moving parts and consequently, ate at much faster cycle times than no mechanical failures. Solid state electromechanical relays, they should AC Output switches are resistant to shock and be employed where extremely tight vibration. The absence of moving process control is required. parts also makes them noise-free Disadvantages of solid state relays (they produce no audible sound). include the inability to provide a pos- Temperature Controllers The most important factor affecting itive circuit break, the initial cost, and service life is its ambient operating their failure mode when misapplied or temperature. Solid state devices are subjected to overrated conditions. very durable, if they are operated The failure modes include burnout of within tolerable ambient tempera- the switch if the system heater shorts tures. Failure to dissipate the heat out; reduction in switching capabilities generated by any solid state compo- as the ambient temperatures rise; and nent will quickly destroy it. Location susceptibility to failure caused by line and heatsinking must be adequate. transients and inductive loads. Watlow solid state relays accept a These failure modes can be eliminat- time proportioned or on-off signal from ed to a great degree by proper fusing a controller. of switches for overload conditions, Watlow’s solid state relays change increasing the heat sinking (the overall size) for high ambients, and filter- DC Input state near zero volts, which is burst firing. They are also optically isolated, ing for the transients and inductive which means the output circuitry is loads. Each of these will increase energized by infrared light striking a the cost of the solid state relay. photosensitive device. This minimizes electrically generated noise, plus output to input electrical isolation.

Teflon® is a registered tradmark of E.I. du Pont de Nemours & Company.

103 Application Guide Power Controllers The E-SAFE¨ relay is a long life turn off sequence when the triac again hybrid relay that uses a mechanical turns on for one cycle and then turns Five Basic Types relay with a triac in parallel with the off at zero cross. This eliminates the Continued contacts to turn on and off the load at contacts from arcing and greatly 4. E-SAFE Relay ¨ the zero cross point in the sine wave. increases the life of the mechanical Once the triac has turned on the load relay. for one cycle, the mechanical relay is energized to pass the current until the

Ref. 86 E-SAFE Relay In Operation

Normally Normally Normally Normally Normally Open Open Open Open Open Relay Relay Relay Relay Relay

Off Off On Off Off

Triac Triac Triac Triac Triac

Off On Off On Off

Load Load Load Load Load 240VÅ(ac) 240VÅ(ac) 240VÅ(ac) 240VÅ(ac) 240VÅ(ac) Å Å Å Å Å OFF ARC ABSORBED OPERATING ARC ABSORBED OFF

Conduction Path

104 W A T L O W

Application Guide Power Controllers SCR Power Control Watlow SCR power controllers can Ref. 87 accept two types of input signals; time Five Basic Types proportioned (or on-off) and process Continued signals (either 4-20mA or 1-5VÎ(dc) 5. SCR (Silicon Controlled Rectifier) from any temperature control. SCRs The Watlow SCR (silicon controlled Input: accepting time proportioned (or on- rectifier) is a solid state switching Time Proportioning off) signals are generally called device that can switch up to a (on-off) Switched “power contactors.” SCRs accepting Output 1200 amp load. A correctly chosen or process signals (4-20mA or SCR can reduce system cost by 4-20mA 1-5VÎ(dc) are generally called “power improving heater life and process controllers.” They control the power by controllability. two methods of firing, phase angle and variable time base burst firing. QPAC 3¯-2 Leg Power Control The primary advantages of SCR power controllers are their flexible input options, lack of moving parts, Reduced Temperature Excursions long life, improved controllability and Ref. 88 tremendous current handling capability. A Watlow SCR can improve system performance with increased heater life through the rapid switching an SCR provides. All SCRs, including Watlow’s, require

Process Input a proper heat sink. Heat is the inevit- T Phase Angle able by-product of solid state power emperature Cont Long Cycle Time Short Cycle Time or Burst Fired switching. The Power Switching Device Comparison Chart on page 114, details differences among the controllers listed above. The criteria for judging these devices, as well as

some basics for understanding SCRs, r will follow in this section. olle r s Proper Heat Sinking • Vertical fin orientation Ref. 89 Thermal Joint • Proper size Compound • Thermal compound between heat sink and solid state device

Proper Sizing (Consult Watlow Representative)

Vertical Fin Orientation

105 Application Guide Power Controllers Ref. 90 Power Output Types: Five Basic Types Continued One pole Single-phase loads ¨ 5a. DIN-A-MITE SCR Two pole Three-phase ungrounded loads only Power Controller Two pole multizone for two independent single-phase loads The DIN-A-MITE® power controller combines SCR control, heat sink, Three pole Three phase grounded Y loads, inside delta wiring and a touch safe exterior in one Three pole multizone for three independent single-phase loads complete package. The DIN-A-MITE controller configured with variable Type of Control: variable voltage and current time base switches as fast as three ac • Contactor (C input) is on-off; on when control. This option includes soft wave cycles (less than 0.1 seconds). the command signal is present, off start, line voltage compensation Set point deviation is virtually when the command signal is absent. and will work with a mA signal, a eliminated, providing the finest The temperature controller does the linear voltage signal or a pot input. control, lowest power consumption proportioning. It is available with ac It will also control the primary of a and longest heater element life. or dc command signal. step down transformer. (This is single phase only.) • Variable time base (V input) is loop powered and requires an analog • The shorted SCR alarm option uses input (4 to 20 mA only) to set the a current transformer to sense load power. The DIN-A-MITE controller current and a comparator to look at does the proportioning. At 50 load current and command signal. percent power the load is on for If there is command signal and three cycles and off for three cycles. load current, everything is OK. If At 25 percent power it is on three there is load current but no cycles and off nine. Cannot use command signal, the alarm will voltage or pot input. activate. The alarm output is a 0.25 amp triac that can be used to turn • Phase angle (P input) control is on a relay. The alarm will not work infinitely variable from full off to full on the phase angle option and also on. It varies the turn-on time inside will not work on a three pole DIN-A- the sine wave. This provides a MITE with an ungrounded load.

Ref. 91 L3 480V 43A L2 Inside Delta Connection 43A L1 43A Three-Phase-Three Leg DIN-A-MITE Breaker CR1 Notes 480V

1. SCR current is same as one heater. 120V 2. Circuit breaker and CR1 are line LP2 Alarm 120V High current. L1 L2 L3 Shorted DIN-A-MITE SCR 11 12 3 Leg 3 RY1 965 Reset + Signal CT Alarm RY1 Advantage 9 - + - 5 10 T1 T2 T3 1. A smaller DIN-A-MITE can be used. Control T/C 25A 25A 25A 1 2 LP1 SERIES 92 Alarm Over HIGH LIMIT Temp. 5

RY1 3 13 14 10 11 CR1 4 Coil Example: Three Single-Phase Heaters AC HIGH Wired Inside Delta 36kW AC Com Reset High Limit T/C 106 W A T L O W

Application Guide Power Controllers The POWER SERIES is a state-of-the- However, with the POWER SERIES 5b. POWER SERIES art microprocessor based silicon you can now “bake out” the moisture controlled rectifier (SCR) power in a wet heater before applying full controller intended for controlling power and destroying the heater. industrial heaters. This product is During heater “bake out” the POWER Ref. 92 based on one package with several SERIES slowly increases voltage to configurations that include single- the heater while monitoring the output phase, three-phase and single-phase- current. If the heater achieves full multizone capabilities. Each package output before the bakeout time configuration has a specific current expires, then the heater is dry and rating depending on the number of can be put into service. At all times, phases switched. The switching the output will not exceed the capabilities include 65 to 250A rms at temperature controller set point. 50˚C from 24 to 600VÅ(ac) depending If output current reaches a user- on the configuration or model number specified trip point during the bakeout selected. (as it would if arcing occurred in the It is available in the following heater), then the POWER SERIES configurations: shuts off the output and activates an 1. Single-phase for zero cross or over-current trip error. The operator phase control applications. should then lengthen the bakeout time and restart or just restart, depending 2. Three-phase, two-leg for zero cross on how long the initial bakeout ran. To applications. start heater bakeout you must cycle 3. Three-phase, three-leg for zero the controller power. After a successful cross or phase control.

heater bakeout, the POWER SERIES Temperature Controllers 4. Single-phase, multi-zone for two or automatically switches to the operator three single zones that can be pre-selected control mode (phase either zero cross or phase control. angle or zero cross). Options include heater diagnostics, Note: Heater bakeout is intended for heater bake out, communications and magnesium oxide filled nichrome retransmit of current or KVA. elements. A nichrome element heater Heater Bakeout can have a tolerance up to ±10 percent. This tolerance could add to If a system is shut down for long the maximum heater current during periods, some heaters can absorb normal operation. For example, a moisture. With a standard power 50-amp heater could draw 55 amps controller, turning the full power “on” and still be a good and dry heater. when moisture is present, can cause Heater bakeout may be selected in the fuses or the heater to blow. single phase (phase to neutral) and three-phase, six SCR systems with any preselected control mode. You must always have the heater diagnostics option installed on your POWER SERIES.

107 Application Guide Power Controllers Diode A diode allows current to flow in one Ref. 94 direction. It’s on or current is flowing, Theory of SCR Power when the anode is positive with Controllers + Anode - Cathode respect to the cathode.

AC voltage changes polarity accord- Current Flow ing to the frequency of the current. In North America this is usually 60 times a second. In Europe and many other parts of world, this is 50 times a sec- SCR The SCR, like a diode, can only pass ond. Polarity changes at zero voltage Ref. 95 current in one direction. The voltage potential. Circuits which detect this polarity (anode-to-cathode) must be zero point are called “zero cross + Anode - Cathode positive when applying a signal to the detectors.” gate. Once on, it latches and will only Current Flow Alternating Current turn off when the cathode becomes Ref. 93 more positive then the anode. This happens after passing through zero into the opposite polarity on the alternating current (ac) sine wave.

Back-to-Back SCRs Energizing the gate will turn the Ref. 96 SCR on for one half ac cycle. Going through zero will turn it off; correspondingly, the second SCR (facing the opposite direction) must be turned on.

Hybrid (SCR & Diode) Three-phase applications require two Ref. 97 or three pair of back-to-back SCRs, or may utilize SCRs and diodes. For some three-phase applications, there is an economy, as well as simplicity, in using three pair of hybrid thyristors. The diodes will conduct only if there is a return path. This return path exists when SCRs are gated on.

Forward Voltage Drop An SCR requires a small amount of Ref. 98 voltage to turn on. Without a load connected, it will never turn on. Each time the SCR is turned fully on, there is a 1.2 volt forward drop on the ac voltage sine wave. This generates heat and produces some electrical noise.

108 W A T L O W

Application Guide Power Controllers • Fixed Time Base Phase Angle Firing Ref. 102 Methods Of Firing SCRs Burst-firing (zero cross) controllers are available with either a one 1. Zero Cross second or four second time base. Zero cross (also known as burst firing) In either case, the SCR is turned provides even output power with the on for a time proportional to the Soft Start is accomplished by delay- lowest levels of noise generation command signal. In the example ing the turn on, and slowly increasing (RFI). Zero cross is the preferred just mentioned (assuming 60 cycle the on time in subsequent cycles with method for controlling a resistive load. ac current), the 40 percent would less delay. This allows heaters that be 24 cycles on and 36 cycles off The power controller determines when change resistance with temperature to with a one second time base. the ac sine wave crosses the 0-volts turn on slowly. This typically occurs point, then switches the load, over a 10 second period. minimizing RFI. Fixed Time Base Ref. 99 A. Solid State Contactor Soft Start Ref. 103 Temperature controllers with a “time 24 Cycles ON 36 Cycles ON proportioning” output proportion heat to the process with an on and off • Variable Time Base command signal to the power control- Burst-firing (zero cross) controllers Current Limiting utilizes the same ler. Proportioning is accomplished by are also available with a variable delay, and also has a transformer to turning the heat off for a longer time time base. The on and off time is sense current. A limit to the accept- period as the actual temperature proportional to the command able amount of current is established approaches set point. This is not to be signal, but the time base changes and the logic in the controller will not confused with an on-off temperature according to the demand. At 50 allow current above this predeter- control, where there is no percent it’s a two cycle time base, mined value. However, if a short in the proportioning. one cycle on and one cycle off. heater occurs during this on time, the Temperature Controllers SCR controllers designed to respond The example of 40 percent is two resulting high current cannot be to this on or off signal are solid state cycles on and three cycles off. restricted from passing through the contactors. They are capable of SCR. The only protection possible for operating from a cycle time as short 50 Percent Variable Time Base, the SCR is an I2t fuse that will blow as one ac cycle. This rapid response 1 Cycle On, 1 Cycle Off Ref. 100 within the ac cycle. to a fast proportioning signal Current Limiting Ref. 104 produces excellent process control.

B. Burst Firing or Zero Cross 40 Percent Variable Time Base, AC power alternates plus and minus 2 Cycles On, 3 Cycles Off Ref. 101 60 or 50 times per second (depending on power generation standards), thus 60/50 cycle . An SCR can accu- 3. Combination rately control each cycle. Burst firing Burst firing is also called “zero cross Utilizing the advantages of phase provides a proportional output to the firing” or “cycle proportioning.” angle firing to turn heater loads on heater by turning on for a number of and switching to burst firing to main- cycles and then remaining off for a 2. Phase Angle Firing tain power appears to offer the best number of cycles. The proportion on The SCR, once turned on, latches on of both worlds. This has been tried and off is according to the tempera- and only turns off when the polarity where burst firing cannot be used at ture controller’s command signal. A changes. If the turn on point is not turn on. Unfortunately, the bursts of zero to 5VÎ(dc) signal with the output zero, but is delayed inside the sine power have also been found to short- at two volts would have the SCR on 40 wave, then the amount of power en the life of silicon carbide elements percent of the time. There are two allowed to pass through the SCR can or transformers that the SCR is types of burst-firing controllers: be controlled. This is called “phase controlling. angle firing.”

109 Application Guide Power Controllers SCR Firing Method Selection Methods Of Firing SCRs Ref. 105 Continued Characteristics of the Load

Stable *1 Resistance *2 Inductance *3 Resistance Change Example

Nichrome Tungsten Transformer Cartridge Quartz Circulation Silicon Carbide Strip Glo Bars Tubular Molybdenum Mica Strip Graphite Quartz Radiant Firing Method

Solid State Burst Phase Phase Contactor Firing Angle Angle

Temperature Control Output

Time Process Process Process Proportioning (Analog) (Analog) (Analog)

Notes: *1. Nichrome heater elements change resistance less than two times in their operating temperature range. *2. Heaters that change resistance include: • Tungsten changes over 16 times from cold to hot • Silicon carbide changes with temperature and age • Molybdenum and graphite change resistance with the temperature and are often used on the secondary of a transformer *3. Transformers can become dc saturated if two pulses of the same polarity are applied in sequence which can cause overheating and high currents that will damage the SCR. Burst firing should not be applied.

110 W A T L O W

Application Guide Power Controllers 1. Single-Phase Controllers All single phase SCR controllers use Ref. 106 one pair of “back-to-back” SCRs. This Methods Of Firing SCRs combination can be used for solid L1 Continued state contactors and burst firing or Single- and Three-Phase phase angle controllers. Controllers L2

2A. Three-Phase Controllers This is for use with phase angle con- Six SCRs trollers only. Because no two phases Ref. 107 go through zero at the same time, it cannot be used with burst firing. L1 There is no return path for the current at zero potential. With phase angle, this is the preferred control when the L2 load is unbalanced, or for less common delta-to-delta transformers.

L3 Potential shock hazard (line to ground) is line ÷ √3.

2B. Three Pair SCR/Diodes Hybrid This is recommended for phase Ref. 108 angle only. Because of the uncontrolled diode (dc), potential shock L1 hazard is line X √2. It can be used for burst firing but the two leg control

L2 is recommended. The advantage of Temperature Controllers a hybrid over a “back-to-back” is less cost and fewer components. L3

2C. Two-Leg Controller Two Pair This is recommended for burst firing SCRs and cannot be used with phase angle. Ref. 109 Potential shock hazard is line ÷√3. It 1 L1 has ⁄3 fewer parts, which means it is less expensive, requires less maintenance, and generates less heat. L2

2D. Three-Leg, Four-Wire Controller This is more common in comfort heat- Grounded Wye Only ing applications where it is desirable Ref. 110 to have only one heater on each leg

L1 that is grounded and burst firing is desired. For use only with burst firing and grounded wye. L2

N 111 Application Guide Power Controllers Power controllers must be mounted in To determine how much cooling is a suitable electrical enclosure. It must required: Enclosure Guidelines have adequate wire bending space 1. Determine the amperage load on and cooling. The maximum ambient the power controller. Multiply the temperature in the enclosure must not amperage by 1.2 and then by the exceed 50˚C (122˚F) for name plate number of phases controlled. This rating. is the output power dissipated by To maintain the proper cooling, the the SCRs in watts. Add the watts enclosure must be large enough to dissipated by the controller’s power dissipate the heat generated by the supply (21W) and multiply the total power controller, or there must be power in watts by 3.41 to get BTUs some form of active cooling. per hour. Vortex coolers, heat pipe 1. Air circulation — fans bring air into coolers, and air conditioner cooling the bottom of the enclosure and are rated in BTUs removed. louver plates to allow the air to exit 2. Add up the watts generated by the top of the enclosure. Filters are other electronics in the enclosure not recommended as they can and multiply by 3.41 to get BTUs become plugged and block air per hour. flow. To maintain 80 percent of the 3. Add up the total BTUs inside the CFM of a fan, the outlet must be enclosure and pick a cooling four times the area of the fan inlet. device that will remove that amount Ensure that each power controller of BTUs. is within an unobstructed airstream. 4. For fan cooled enclosures, 2. Vortex coolers operate on enclosure and fan manufacturers compressed air and provide good usually have free software cooling on a sealed enclosure, but programs and application notes to are noisy and consume a lot of air. help size the fans for enclosures. If 3. Cabinet air conditioners work well necessary, contact the Application on sealed enclosures. Engineers at Watlow Winona for 4. Heat pipe coolers work well on assistance. sealed enclosures, but do not provide as much cooling as vortex coolers or air conditioners.

112 W A T L O W

Application Guide Power Controllers Heater Construction between two values in a means to Nichrome wire of computer-calculated maintain the process temperature, this Heater Life and Selection gauge, length and spacing is wound repeated excursion causes expansion of Power Handling Device on a supporting core. The resistance and contraction of the resistance wire. is precisely centered in the unit- This stress on the element will reduce equidistant to the sheath of all points. heater life. The higher the excursion, If the heater temperature cycles the shorter the life.

Effect of Time Base on Temperature Excursion Ref. 111 Ref. 112 Ref. 113 2000°F

1700°F

1600°F

1500°F

1300°F Electromechanical 30 Second Cycle Time MDR 5 Second Cycle Time Solid State Relay 1 Second Time Base Process Set Point: 1600°F Process Set Point: 1600°F Process Set Point: 1600°F Overshoot: 300°F (1900°F) Overshoot: 50°F Overshoot: 4°F Droop: 254°F (1346°F) Droop: 30°F Droop: 5°F Internal Temperature 2100°F Internal Temperature 1830°F Internal Temperature 1730°F Temperature Controllers

Ref. 114 Ref. 115 2000°F

1700°F

1600°F

1500°F

1300°F SCR (with burst firing) 16.6 millisecond time base SCR (with phase angle) Less than 8.3 millisecond time base Process Set Point: 1600°F Process Set Point: 1600°F Overshoot: 0 Overshoot: 0 Droop: 0 Droop: 0 Internal Temperature 1720°F Internal Temperature 1680°F

113 Application Guide Power Controllers fuses need to be in all controlled legs. happens, the temperature controller They are only intended to protect the can no longer control the SCR and a SCR Protective Devices SCR’s and are not legal for cable or runaway condition exists. An inde- load (branch circuit) protection. pendent high limit controller must be 1. Semiconductor Fuses 2. Current Limiting used that will sense unsafe temperature and disengage the power. Semiconductor fuses are a specialty A means of sensing current through a fuse that is intended for SCR current transformer. Some heater ele- 4. Heat Sink Thermostat protection only. They are very fast ments change resistance during their Removes signal from an SCR in clearing and will open a short circuit operation, (i.e., silicon carbide). In case of fan failure, filter blockage, or in less than two milliseconds. The order to control at a slow ramp, it is excess heat in the enclosure. SCRs clearing time and clearing current are often advantageous to limit the current. that incorporate a fan for forced designated by I2t. Current squared 3. High Limit Control cooling can reach unsafe temper- times time. This rating must be at or atures if the fan fails. All Watlow SCRs 2 The most common failure mode of below the I t rating of the SCR to with fan cooling incorporate a heat an SCR is in the shorted state. If this insure protection. Semiconductor sink thermostat.

Power Controller Comparisons The following chart is an abbreviated comparison of power controllers along with their suitability for use.

Power Switching Device Comparison Chart—Ref. 116

Device Initial Cost 3 Year Controller Heater EMI Control- Response Options Comments Cost* Life Life Generation lability Rate Electro- Low for low Highest Limited Shortest Yes, coil Poor Slowest None To extend contactor life the mechanical current (elec. and and contacts cycle time is normally Relay and mech.) extended to 30 seconds or Contactor more. This shortens heater life. Mercury Low Medium High Good Yes, coil Medium Medium None Silent Operation. Mercury Displace- and contact to Good to Fast may not be desirable. ment Relay Minimum cycle time is two seconds. Position sensitive. Solid State Medium Medium Extended Extended Minimal Good Fast None Excellent control with one Relay with burst second cycle time. firing Requires heat sink. May require snubber. SCR Solid Medium Low Extended Extended Minimal Good Fast None Excellent control with one State second cycle time. Contactor SCR Burst High Low Extended Longest Minimal Very Very Fast None one second time base or Firing Longest Excellent variable time base unit. SCR Phase High Lowest Extended Longest High Excellent Fastest Current Required for tungsten Angle Limit elements, transformers, or for current limiting. Saturable Highest Low Extended Longest Minimal Very Fast Current Cannot be turned full ON Core Good Limit or OFF, inefficient. Reactor

*Includes heater replacement and lost production.

114 Wiring Practices 115 practices just weren’t a concern. With the advent of today’s electronic controllers, awareness of techniques to minimize the disrupting effects of electrical “noise” is critical. Wiring Practices for a Successful Control System Not long ago the majority of industrial thermal systems were controlled by electrical/mechanical devices that were fairly immune to the negative effects of electrical noise. The shortest path for the wire was the best and only path. Noise resistant wiring is not W A T L O W O L T A W This section of the Application Guide This section of the system wiring is devoted to thermal are general practices. In this section integration guidelines for successful system com- of the different thermal temperature sen- ponents—heaters, controllers and sors, temperature This section power controllers. manual. It is a step-by-step, how-to your responsibility to be sure your wiring is safe and meets the requirements of applicable agency standards along with national and local electrical codes. If you’re unable to determine which method of wiring will best suit your needs, call your nearest Watlow Sales Representative. Their experience with all types of thermal systems makes them an invaluable source for advice. Sales of offices are listed on the back cover this catalog. System wiring is divided into two main areas—signal wiring and power wiring. Signal wiring deals with input signals (generated by the temperature sensor) and output signals (generated by the temperature controller). Power wiring deals with supply power to the temperature and power controllers and the current that’s ultimately delivered to the heating element. Signal wiring is less straight forward than power wiring. Not only does it have to conform to circuit designs, but must also be installed in such a way as to minimize the negative effects of electrical noise present in any thermal system. This section will start with wiring sensors to controllers and then wiring power controllers to temperature controllers. It also offers limit control wiring examples which provide a comprehensive system overview. Application Guide Application Wiring Practices Application Guide Wiring Practices caused by lightning or other sources allow “coupling” or the transfer of of electrical arcing. Electrical noise electrical noise into the control circuit. Electrical Noise from all sources and its effects on An outstanding resource for informa- What is Electrical Noise? controllers are very difficult to define, tion about wiring guidelines (source It is electrical signals which produce let alone give exact rules on how to for this summary) is the IEEE Stand- undesirable effects in the electronic prevent. Noise sensitivity is a function ard No. 518-1982 and is available circuits of the control system. The of more recent electronic controller from IEEE, Inc., 345 East 47th Street, term “electrical noise” originated designs. However, the majority of New York, NY 10017; phone number: with AM radios when the extraneous noise problems stem from crude wir- 800-678-4333. Internet: www.ieee.org “noise” heard in the speaker was ing practices and techniques which

When is Electrical Noise problem appearing consistently. Even indicators, control instability about set a Problem? worse, the system may exhibit several point and outputs turning on or off Symptoms resulting from an electric- different symptoms. unexpectedly. Another “red flag” of ally noisy environment are difficult to Some other commonplace symptoms electrical noise raises when high or predict. One common symptom is an of noise-related problems are fluctu- low limits trip with no limit fault erratic system, with no evidence of a ating digital indicators, blanked digital condition.

Why is Electrical Noise Sensitivity as mechanical relays or mercury dis- trollers has improved the accuracy of a Problem? placement relays have low noise sen- control and expanded immensely their How accurately a controller can sitivity, while low power controllers capabilities, but they are more com- differentiate between desired system that use electronic logic, especially plex and operate at very low power signals and electrical noise is a good those using integrated circuits, are levels. Electrical noise is more likely to indicator of its sensitivity to noise. In more sensitive to noise. The develop- affect them because of their lower general, high power controllers such ment of all-electronic solid state con- operating power levels.

Where Does Electrical Noise Noise Sources: • Chemical voltage produced by Come From? • Switches and relay contacts electrolyte action between poorly Our industrial world is full of equip- operating inductive loads such connected leads and interconnect ment capable of generating many as motors, coils, solenoids and cables types of electrical noise. A typical relays, etc. • Thermal noise from increased noise source is any piece of equip- • Thyristors or other semiconductor ambient temperatures around the ment that can cause or produce very devices which are not burst fired circuit electronics rapid or large amplitude changes in (randomly-fired or phase angle- • Noise could be introduced if the voltage or current when turned on and fired devices) control circuit includes the option of off. • All welding machinery a mechanical relay output and is used to switch high load currents • Heavy current carrying conductors over two or three amps. This • Fluorescent and neon lights presents a significant source for • Thermal voltages between noise, including inductive noise dissimilar metals that influence the from the coil and contact arcing, low voltage thermocouple input depending on how much power is signal brought inside the controller

116 Wiring Practices 117 sources of such radiation are TV or radio broadcasting towers. This type of interference is not experienced often because the circuit must be very close to the source. It is also difficult to eliminate if present, because shielding must be 100 percent complete. level) circuits. The best way to elim- is inate magnetic (inductive) coupling in to run leads from separate circuits separate bundles, taking special care to keep ac* (high voltage level) wires separated from dc (low voltage level) wires. If it is at all possible, twisted pair leads and shielding cables (with termination of shield at the controller end only) should be used to reduce magnetic coupling of noise. each other, the distance between the wires and wire diameter. The most effective way of reducing electrostatic (capacitive) coupling is to properly shield the wire runs. Again, separation of wires carrying ac* (high voltage level) and those carrying dc (low voltage level) signals will effectively reduce the noise in sensitive circuits. circuits sharing the common line. circuits sharing the this type of The best way to prevent the common coupling is to eliminate leads for line and use independent each return circuit. associated Another noise problem impedance coupling with the common Ground loops occur is a ground loop. exist for ground when multiple paths should the solenoid currents. Not only return lines be run as independent leads to the same electrical potential point, but they should also be terminated at the same physical point. In the same manner, safety ground lines should be returned to the same electrical and physical point. Safety ground (chassis ground) should never carry return currents. Coupling 4. Electromagnetic (Radiation) Electromagnetic (radiation) coupling occurs when the control circuit is very close to a high energy source that is capable of magnetic or electrostatic induction of a voltage. Common 2. Magnetic Inductive Coupling Magnetic (inductive) coupling generally appears where there are wires running parallel or in close vi- cinity to each other. This happens when the wires from several different circuits are bundled together in order to make the system wiring appear neat. However, without proper wire separation and shielding, magnetic coupling will introduce severe noise problems into sensitive (low voltage 3. Electrostatic (Capacitive) Coupling Electrostatic (capacitive) coupling appears where wires are running parallel with each other, similar to magnetic coupling. That is where the similarities end. Electrostatic, or capacitive, coupling is a function of the distance the wires run parallel to 1. Impedance Coupling Common coupling occurs Common impedance share a common when two circuits (even conductor or impedances A frequently common power sources). coupling is used common impedance one long com- the practice of using wire. An mon neutral or ground five relay contacts example would be solenoids operating five separate where the switching runs dependent- ly. The return lines from all the solenoids are connected together and run back to the power source with one conductor. This example of impedance coupling has a tendency to induce noise in circuits that do not have noise, or to am- the plify the noise from one or more of W A T L O W O L T A W Special attention should be given to the ac power line because it is a source of unusual types of noise-related problems in control circuits. Phenomena such as unbalanced power lines, brownouts, power surges, lightning and other “dirty” input power can cause the ac power supply line to fluctuate and momentarily drop below the operating specifications for the ac input to the control circuitry. When the type of noise on the ac supply line can be identified as purely electrical noise and it does not cause the line voltage level to drop, line filtering devices can be purchased to take care of the problems. However, if power surges, brownouts, inadequate wire size, etc., are causing the ac line voltage to drop below the levels recommended by the control circuit manufacturer, the only solution is to correct the wiring size or the voltage distribution. Note: Electrical Noise Continued Noise Get In? How Does Electrical must be consid- The control circuitry total system in an ered in terms of the The electrically noisy environment. power output lines sensor input and source line, all as well as the power the have the potential to couple or link control circuit to a noise source. Depending on the type of electrical noise and its intensity, noise can be coupled to other equipment by one of the following four methods: Application Guide Application Wiring Practices * Application Guide Wiring Practices Potential Noise Entry Paths The sensitivity or susceptibility to Ref. 117 noise coupling will be different among Helpful Wiring Guidelines Electromagnetic Radiation the four paths and may even vary on Overview the same path, depending on the type A quick review shows that electrical of electrical noise and its intensity. Output noise can enter the control circuit Input Control Signal Following simple wiring techniques through four different paths: Signal Circuit Power will greatly decrease the control 1. Input signal lines (most sensitive) Input system’s sensitivity to noise. 2. Output signal lines 3. Power input lines 4. Radiation (least likely to be a problem)

Physical Separation and • Another important practice is to B. If the shield is broken at a ter- Wire Routing look at the system layout and minal and the line continues, the • Physical separation and wire rout- identify electrical noise sources shield must be reconnected to ing must be given careful consid- such as solenoids, relay contacts, maintain shield continuity. eration in planning the layout of the motors, etc., and where they are C. If the shield is used as a signal system. For example, ac power physically located. Then use as return (conductor) no electrostatic supply lines should be bundled much caution as possible to route shielding can be assumed. If this together and kept physically the wire bundles and cables away must be done, use a triaxed cable separate from input signal lines from these noise sources. The (electrostatically shielded coaxial (very low power level). Keep all control circuits, of course, should cable). also be physically separated from switched output signal lines (high D. Twisted wire should be used these sources. voltage level) separate from current any time control circuit signals control loop signals (low voltage • Whenever possible, low level signal must travel over two feet, or when level). If lines must cross, do so lines should be run unbroken from they are bundled in parallel with at right angles. signal source to the control circuit. other wires. • Shielded cables should be used for Power and Signal Line Twisted Pair Wire Ref. 120 Separation Example Ref. 118 all low power signal lines to protect from magnetic and electrostatic A.C. Power Lines coupling of noise. Some simple Twisted pointers are as follows: Pair { A. Connect the shield to the control circuit common end only. Never leave the shield unconnected at E. Acceptable twisted wire should L1 L2 L1 L2 L1 L2 both ends. Never connect both have at least 12 to 16 twists per ends of the shield to a common. foot.

Shielded Twisted Pair Wire Ref. 119

Shield Input Signal Lines Twisted Pair {

118 Wiring Practices 119 use un- ® “ (UPS). ” This device senses the ac power line, and when it fluctuates, a battery powered 60Hz inverted circuit takes over supplying power within one-half to one cycle of the ac line. interruptable power supply media (electromagnetic filtering), other than electric circuits to filter out electrical noise. Care must be taken in matching the power capabilities of the filter with the power demands of the circuit. The ultimate protection is an circuit and at the same time buffer the control circuit from ac line noise. Devices like an Islatrol • Earth Ground Ensure optimum controller a good earth performance by having have ground. Some controllers requirements. specific grounding controller Refer to the specific connection manuals for terminal instructions. No Daisy Chains avoid daisy For best noise immunity, or chaining ac power (or return) lines output signal (or return) lines to multiple control circuits. Use direct, individual pairs of lines from the power source to each device requiring ac power. Avoid paralleling L1 (power lead) and L2 (return lead) to load power solenoids, contactors and control circuits. If L1 (power lead) is used to switch a load, the L2 line (return lead) will have the same switched voltage potential and could couple unwanted noise into a control circuit. to ” spikes “ that occur on ” spikes “ , and other similar ® (Metal Oxide Varistor) can ” (ac) lines. The MOV wiring diagram, one can wiring diagram, one ” Å MOV “ ground. However, MOVs have a limited life, because repeated action deteriorates the device. An Islatrol diode with the proper voltage rating for the circuit wired in reverse across the coil to suppress back emf. A be installed across the ac line to limit voltage the ac supply lines as a result of lightning strikes, switching large motors, etc. The MOV is available in several varieties for 115 or 220V dissipates the voltage power line filters are designed to carry the power for the control as-built • • with a grounded sensor input. By ob- with a grounded sensor schematic for the taining an internal identifying how control equipment, are done, and common connections to the transferring that information “ ground loops easily determine if are created. Ground Each Chassis of each piece of Ground the chassis equipment in the system. Connect each individual chassis to the overall equipment chassis immediately adjacent to that piece and tie all major chassis ground terminals together with one lead (usually green wire) to ground at one single point. Chassis Grounds vs. Commons Do not confuse chassis grounds (safety ground) with control circuit commons or with ac supply lines L2 (return or neutral line). Each return system wiring must be kept separate. Make sure the chassis ground (safety) is never used as a conductor to return circuit current. s ’ W A T L O W O L T A W watt 2 ⁄ 1 wiring diagram. ” is a simple RC sup- may be placed ® ® as-built “ is a registered trademark of (ac), non-polar capacitor in ® Å is a registered trademark of ® A Quencharc pression device using a 0.1µ f 600V series with a 100 ohm, across the terminals of devices such as relays, relay contacts, solenoids, motors, etc., to filter out noise generated by such devices. A Quencharc resistor. This device can be used on ac or dc circuits to effectively dampen noise at its source. Any dc relay solenoids, etc., should have a Get lt at the Source Other techniques to prevent problems include eliminating the noise at, or as close to the source as possible. These include the following: • There are also the not-so-obvious ground loops that result from the technique of connecting internal circuits common in the manufacturer equipment. An example would be if a equipment. An example would be if control circuit is designed to work ITW Pakton. Islatrol Quencharc Helpful Wiring Guidelines Helpful Wiring Continued Application Guide Application Wiring Practices Wire Gauge of wire should be The size or gauge the maximum selected by calculating choosing the circuit current and requirement. gauge fulfilling that Using sizes a great deal larger than required will generally increase the likelihood of electrostatic (capaci- tance) coupling of noise. Ground Loops In an optimized system, ground loops would be eliminated in the entire control system. There are obvious loops which can be spotted by studying the Control Concepts Corporation. Application Guide Wiring Practices For Clean Input Power: Don’t— Input Power Wiring Do— • Don’t Connect computer ground to • Do Keep line filters as close to the safety ground or any other ground Microprocessors require a clean en- controller as possible to minimize points in the electrical system— vironment to operate to their full po- the area of interference (noise except at the ground rod. tential. A clean environment means on pick up). • Don’t Mount relays or switching one level an environment that is free • Do Use twisted pair wire and devices close to a microprocessor of excessive dust, moisture and other possibly shielded wire from line controller. airborne pollutants. But primarily it filters to the controller to keep the means a clean source of input power • Don’t Run wires carrying line line “clean.” from which to base all its operations. voltage with signal wires (sensor • Do Keep low power controller wires communications or other low power Clean power is simply a steady, physically separated as far as lines) going to the control. noise-free line voltage source that possible from line voltage wires. meets the rating specifications of the • Don’t Use conduit for computer Also, keep all controller wiring equipment using it. Without clean ground. separate from other nearby wiring. power to the integrated circuitry, any • Don’t Connect ground to a metal Physical separation is extremely microprocessor chip is doomed to control case if the control is effective for avoiding noise. A malfunction. mounted in grounded enclosure to 300 mm (12 in.) minimum prevent ground loops. The recommendations provided separation is usually effective. here for you are ways to achieve an • Don’t Fasten line filters with metal • Do Use a common mode, acceptable level of clean input power cases to more than one ground. differential mode or a combination protection. In almost all cases these This prevents ground loops and of the two filters wherever power guidelines will remove the potential maintains filter effectiveness. may have electrical noise. for input power problems. If you’ve applied these measures and still do • Do Cross other wiring at 90 degrees not get results, please feel free to call whenever crossing lines is us at the factory. unavoidable. • Do Have a computer ground line separate from all other ground lines. The computer ground line should ideally terminate at the ground rod where the electrical service is grounded.

How to Check for Ground Loops If you find continuity, begin looking for To check for ground loops, discon- the ground loops. Disconnect nect the ground wire at the ground grounds in the system one at a time, termination. Use a volt/ohm meter to checking for continuity after each measure the resistance from the wire disconnection. When the meter reads to the point where it was connected. continuity “open,” you’ve eliminated The ohmmeter should read a high the ground loop(s). As you reconnect ohm value. If you have a low ohm grounds, keep making the continuity value across this gap, there is at least test. It is possible to reconnect a one ground loop present in your ground loop. system.

120 Wiring Practices 121 Controller Controller Controller Shield Shield Shield 0804-0147-0000 Ω For very dirty or critical applications—use microcomputer-regulated power supply or uninterruptible power supply. Load (ac), 100 Å Load Load D.M. Line Filter D.M. Line 0.1µ f, 600V D.M. Line Filter D.M. C.M. Line Filter C.M. MOV Line Line L1 L2 L1 L2 Ground Ground t Fasten line filters with ’ C.M. Line Filter C.M. ® Item Electrical Ratings Part Number Keep filters 300 mm (12 in.) Don L1 L2 Ground Quencharc Internet sites: www.cor.com www.aerovox.com www.filternetworks.com www.control-concepts.com or less from the control. Minimize the line distance where noise can be re- introduced to the control. Note: metal cases to more than one ground. This prevents ground loops and maintains filter effectiveness. Noise Suppression Devices Available Noise suppression devices are available from Watlow and local Watlow distributors. Ref. 122 Note: Combination Differential/Common Mode Filter Diagram Combination Differential/Common Ref. 121 W A T L O W O L T A W Input Power Wiring Input Power Continued Line Filtering Configurations for Controllers show filter con- These three diagrams input power figurations for removing noise. Application Guide Application Wiring Practices Application Guide Wiring Practices How to Wire the Mechanical Relay Control Output Output Wiring Electromechanical Relay Output Wiring Example Ref. 123 While there is always an ideal way to - TC wire each output type, we can’t cover + Sensor N.O. every situation. However, we can pro- Quencharc¨ vide the most important points. Not RC Noise Suppression Heater just so the wiring looks neat, but so it’s COM Thermal Fuse electrically “clean” as well. Incorrect wiring may cause damage to system components or threaten system relia- L2 L1 bility. Such problems take time and cost money. L1 Wiring Temperature Controllers L2 to Power Controllers How the Mechanical Relay Output Mechanical Relay Output Tips and These diagrams cover connecting Works Special Considerations temperature controller output signals The normally open (N.O.) and com- 1. The specified current rating for to power controls. mon (COM) contacts of the mechan- mechanical relays is usually at 120/ Note: Some controllers offer built-in ical relay operate as switch contacts. 240VÅ(ac) and can be rated RC noise suppression. Check the When a temperature controller calls differently at other voltages. product ordering information. for heat, the contacts will close and 2. In UL® applications, the relay out- there will be continuity. put may be derated with ambient temperature.

How to Wire the Solid State Relay Control Output Solid State Output Wiring Example Ref. 124 Fuse L1 Mercury Resistive Load (Heater) Displacement Thermal Relay Fuse L2

S.S Relay N.O. Zero Quencharc¨ sw (Noise Suppression) COM Fuse

How the Solid State Relay tion but does not exceed the maximum Output Works current rating for the solid state The COM and N.O. terminals of the output device. solid state relay output operate like a 2. Watlow solid state relays will switch switch. When a temperature con- only ac voltages. troller is calling for heat, there will be 3. Always provide overtemperature ac power conducted between the limit protection to circumvent the terminals. shorted solid state relay output Solid State Relay Output Tips and failure mode. Special Considerations

1. Make sure the load device meets UL® is a registered trademark of the “minimum load current” specifica- Underwriter’s Laboratories, Inc. 122 Wiring Practices 123 Wye VAC Delta Power L1 L2 Load Heater Limit Limit Contactor Contactor L1 L2 L3 L1 L2 T1 T2 L1 L2 L3 T1 T2 T3 QCD Q01 Be sure the input specifications QPAC - QPAC Single Phase QPAC Solid State Contactor + - 2. for the solid state relay are compatible with the specification of the Watlow solid state switch output. + 4 - 20mA Internal Power Source Switched DC Switched Be sure to route output wiring from How to Wire the Process Output Process Output Wiring Examples Ref. 126 Solid State Switched DC Tips and Special Considerations 1. the temperature controller to the load a power switching device in as short run as possible while avoiding any wires carrying line voltage. How to Wire the Solid State Switch Control Output How to Wire the DC Wiring Examples Solid State Switched Ref. 125 Note: Most Watlow controllers use power from their internal supply to power process outputs. W A T L O W O L T A W (dc) or 4-20mA. Î s proportional band, the ’ (dc) process output, full on Î How the Process Output Works When the controller calls for an increase in the actual process value (heat, flow or pressure, etc.), and when that actual value is outside the controller process output turns full on. With a process output turns full on. With a 0-5V Output Wiring Continued Switched How the Solid State DC Works calls for tem- When a heating control switched dc output perature rise, the on, developing a (a transistor) turns the output positive voltage across terminals, which turns on the solid state contactor and then the load. Application Guide Application Wiring Practices System thermal characteristics and control PID settings combine to determine the final, stable value of the process output signal. measures 5 volts; with 4-20mA, full on measures 20mA. As the actual process value moves toward set point and enters the proportional band, the output signal decreases proportionately. Ideally, the system will proceed to set point without overshoot. As the system stabilizes at set point, the process output signal becomes constant at a value between 0-5V Application Guide Wiring Practices Fusing Mounting Location Two types of fuses are required to Selecting a mounting location for an SCR Wiring—Tips and properly protect SCRs. Branch circuit SCR is important. They’re larger than Special Considerations fuses and semiconductor fuses mechanical relays and MDRs of com- Warning should be used together in the circuit parable ratings. More importantly, Whenever installing or working on an to ensure short circuit and overload SCRs must be mounted in such a way SCR, always disconnect the power. protection. to insure adequate ventilation. Exces- Carefully read the accompanying in- Semiconductor fuses are very fast sive ambient heat will dramatically structions for information specific to and will blow in less than one shorten an SCR’s life. the particular SCR being installed/ millisecond on very high fault Enclosures serviced. Failure to do so could cause currents, i.e. short circuits. They are It’s a good idea to mount SCRs in serious injury or death. made up of parallel silver links protective enclosures meeting NEMA The following are general installation/ packed in a low temperature silica ratings to prevent the possibility of service tips and considerations to sand. When they blow, the silver links electrical shock and the accumulation make your SCR use easier, better produce heat and melt the sand of contaminants. Enclosure must be and longer lasting. which forms a glass seal to stop the vented to allow for cooling with vents arc produced from the blown links. located above the top of the heatsinks. Semiconductor fuses are rated by the Vibration I2T value which is determined by current squared times time (I2T). If the Any location experiencing excessive I2T rating of the fuse is at or below the vibration should be mounted using rating of the SCR, it will protect the industry standard shock mounting SCR from a short circuit in the load or techniques. Excessive vibration can wiring. Semiconductor fuses do not also affect wire connections. Make have a defined overload rating, sure the connectors used can with- therefore, they are not legal or safe to stand the vibration and remain tight. use for branch circuit protection. A Wiring Considerations semiconductor fuse will pass 400 to Wire should be sized to meet NEC 500 percent of its base current rating and local electrical codes. Ambient for an hour or more. operating conditions should be taken Branch circuit fuses or circuit into account. breakers are different from Cable Routing and Connection semiconductor fuses in that they are Route all large power cables to the sized by their overload rating. These SCR in such a manor to allow access fuses are required to protect the for inspection, I2t fuse replacement wiring and the load from partial and other maintenance not requiring overload conditions. A branch circuit removal of the SCR. Wire connectors fuse should clear in one minute at should be conveniently located to 125 percent of its base rating. allow use of a wrench for tightening. Branch circuit fuses should be sized Heat generated by the flow of elec- such that they pass only 80 percent of tricity will heat and expand the wire its base. The way to insure this is to and the connector. This could cause pick a fuse rating that is 125 percent resistance to increase, generating of the connected load, or the next even more heat. To minimize the available fuse size up to a maximum effects of heat, use spring, or of 160 percent of connected load. “Belleville” washers on all electrical The semiconductor fuse base rating junctions to insure a tight connection. can be determined as shown above Additionally, all connections should or it can be rated to the power have an electrical compound applied controller provided that the I2T rating to improve both thermal and electrical of the SCR is not exceeded. conductivity. 124 Wiring Practices 125 ” control system “ Control Panels of configurations Available in a variety control and levels of sophistication, smaller versions panels, and their all temperature control boxes, contain devices and power controlling system. This necessary for a thermal temperature limit includes a separate that is required for control circuit. All power supply operation is mounting, and load connections, and connecting the temperature and limit sensors to their respective controllers. Enclosures can be specified to meet application environments. Control Panel Guide Control panels combine temperature, limit and power controllers in a self- contained enclosure, ready for mounting and hook-up. Control panels are generally for large thermal systems. Capacities range up to 1600 amps or more. Temperature, limit and power controllers are carefully matched to application requirements while enclosures feature NEMA ratings to match application environment. Control panels require four to five week lead times for shipment. Control panels can be made to comply with agency approvals and can have agency certification when required. Applications include large industrial furnaces, petrochemical plants and heat treating furnaces. Control Boxes With capacities up to 50 amps, control boxes provide temperature, limit and power controller packages in a NEMA rated enclosure. Availability is fast with a five to 10 working day lead time for shipment on most models. Popular temperature, limit and power controller options make control boxes a hassle free alternative to specing, buying and assembling the individual components. t fuses used in the SCR are 2 designed to prevent surge or transient currents from damaging the semiconductors in the SCR. They are oversized to prevent nuisance fuse blowing and, for this reason, cannot be used or relied upon for steady state overload protection. Noise Considerations Industrial environments and phase angle fired SCRs can produce electrical noise that could create signal error in the sensor wiring or temper- of ature control. If unacceptable levels electric noise are present, use MOV, resistor-capacitor networks and other noise suppression devices. Heater Type vs. Firing Method Many loads that change resistance over time and temperature require phase angle firing. Most other loads can use burst firing. Consult with the heating element manufacturer for most appropriate firing method recommendation. Temperature Control Compatibility Not all temperature controllers will work with all SCRs and vice versa. Be sure the type of temperature controller is suitable for use with your selected SCR. Consult the manufacturer for details on compatibility. After the first 48 hours of use, re- After the first 48 hours to spec- tighten all wire connections an installation ifications. Additionally, air from cooling design which directs wire connectors will fans to pass over and help cool the connections improve reliability. and SCR Power Disconnect Protection should be Disconnect means provided through circuit breaker, fused disconnect or fuses. These should be installed ahead of the SCR. The I W A T L O W O L T A W Tips and — t) ’ Special Considerations (con SCR Wiring Application Guide Application Wiring Practices 126 Reference Data 127 CONTINUED Space limits don’t permit this infor- Space limits don’t If mation to be all encompassing. the information you’re unable to find you consult you need, we suggest reference materials additional Watlow specific and engineering textbooks working on. These to the areas you’re of this section. If are listed at the end immediate, please your need is more Represen- call your nearest Watlow tative. Sales offices are listed on the back cover of this guide. This section of the Application Guide This section of the helpful in under- contains information of standing the thermodynamics heating systems. section contains The first half of this conversion technical references, other data used in tables, formulas and The second solving heating problems. of applications half contains examples draw all the to illustrate how to information in this Application Guide together for solving heating problems. 65.6 150 302.0 315.6 600 1112.0 565.6 1050 1922.0 71.1 160 320.0 321.1 610 1130.0 571.1 1060 1940.0 76.7 170 338.0 326.7 620 1148.0 576.7 1070 1958.0 W A T L O W O L T A W ...... 4.4 40 104.0 254.4 490 914.0 504.4 940 1724.0 754.4 1390 2534.0 -6.7-1.1 20 30 68.0 86.0 243.3 248.9 470 480 878.0 896.0 493.3 498.9 920 930 1688.0 1706.0 743.3 748.9 1370 1380 2498.0 2516.0 -95.6-90.0-84.4 -140-78.9 -130-73.3 -120 -220.0-67.8 -110 -202.0-62.2 -100 -184.0 154.4-56.7 -166.0 -90 160.0-51.1 -80 -148.0 165.6-45.6 310 -70 171.1-40.0 -130.0 320 -60 176.7-34.4 -112.0 330 -50 590.0-28.9 340 182.2 -94.0 -40 608.0-23.3 187.8 350 -76.0 -30 626.0-17.8 404.4 -58.0 -20 193.3 360 644.0-12.2 410.0 -40.0 -10 198.9 370 662.0 415.6 -22.0 204.4 760 380 421.1 0 680.0 210.0 -4.0 770 10 390 426.7 698.0 14.0 215.6 780 1400.0 400 432.2 716.0 790 1418.0 221.1 410 32.0 437.8 734.0 226.7 800 50.0 1436.0 420 654.4 752.0 443.3 1454.0 660.0 810 430 232.2 770.0 448.9 1472.0 665.6 237.8 440 820 1210 788.0 454.4 671.1 1220 1490.0 830 450 460.0 806.0 676.7 1230 1508.0 460 840 2210.0 824.0 465.6 1240 2228.0 682.2 850 1526.0 471.1 1250 2246.0 687.8 842.0 860 1544.0 476.7 860.0 2264.0 870 1260 1562.0 693.3 2282.0 1270 1580.0 698.9 482.2 880 487.8 890 1598.0 2300.0 704.4 1280 2318.0 710.0 1290 1616.0 900 1634.0 715.6 910 1300 2336.0 1310 2354.0 721.1 1652.0 726.7 1320 1670.0 2372.0 2390.0 1330 732.2 2408.0 1340 737.8 2426.0 1350 2444.0 1360 2462.0 2480.0 to ¡C ¡F/¡C to ¡F to ¡C ¡F/¡C to ¡F to ¡C ¡F/¡C to ¡F to ¡C ¡F¡/C to ¡F -184.4 -300 NA -178.9 -290 NA -173.3 -280 NA -167.8-162.2-156.7 -270-151.1 -260-145.6 -250 -454.0-140.0 -240 -436.0-134.4 -230 -418.0-128.9 -220 82.2 -400.0-123.3 -210 87.8 -382.0-117.8 -200 93.3 -364.0 180-112.2 -190 98.9 -346.0 190 104.4-106.7 -180 -328.0 200 110.0-101.1 -170 356.0 -310.0 210 115.6 -160 374.0 220 -292.0 121.1 230 -150 392.0 332.2 -274.0 126.7 240 410.0 337.8 -256.0 132.2 428.0 250 343.3 -238.0 137.8 446.0 630 260 348.9 143.3 464.0 640 354.4 270 148.9 482.0 360.0 280 650 1166.0 500.0 365.6 290 660 1184.0 670 518.0 371.1 300 1202.0 582.2 680 536.0 376.7 1220.0 587.8 690 554.0 1238.0 382.2 593.3 1080 700 572.0 1256.0 387.8 598.9 1090 710 1274.0 393.3 604.4 720 1100 1976.0 1292.0 610.0 398.9 730 1110 1994.0 1310.0 615.6 1120 740 1328.0 2012.0 621.1 1130 750 1346.0 2030.0 626.7 1140 2048.0 1364.0 632.2 1150 2066.0 1382.0 637.8 1160 2084.0 643.3 1170 2102.0 648.9 1180 2120.0 1190 2138.0 1200 2156.0 2174.0 2192.0 Celsius to Fahrenheit/Fahrenheit to Celsius—Ref. 127 Celsius to Fahrenheit/Fahrenheit Application Guide Application Data Reference Application Guide Reference Data

to ¡C ¡F/¡C to ¡F to ¡C ¡F/¡C to ¡F to ¡C ¡F/¡C to ¡F to ¡C ¡F/¡C to ¡F

10.0 50 122.0 260.0 500 932.0 510.0 950 1742.0 760.0 1400 2552.0 15.6 60 140.0 265.6 510 950.0 515.6 960 1760.0 765.6 1410 2570.0 21.1 70 158.0 271.1 520 968.0 521.1 970 1778.0 771.1 1420 2588.0 26.7 80 176.0 276.7 530 986.0 526.7 980 1796.0 776.7 1430 2606.0 32.2 90 194.0 282.2 540 1004.0 532.2 990 1814.0 782.2 1440 2624.0 37.8 100 212.0 287.8 550 1022.0 537.8 1000 1832.0 787.8 1450 2642.0 43.3 110 230.0 293.3 560 1040.0 543.3 1010 1850.0 793.3 1460 2660.0 48.9 120 248.0 298.9 570 1058.0 548.9 1020 1868.0 798.9 1470 2678.0 54.4 130 266.0 304.4 580 1076.0 554.4 1030 1886.0 804.4 1480 2696.0 60.0 140 284.0 310.0 590 1094.0 560.0 1040 1904.0 810.0 1490 2714.0 815.6 1500 2732.0 954.4 1750 3182.0 1093.3 2000 3632.0 1232.2 2250 4082.0 821.1 1510 2750.0 960.0 1760 3200.0 1098.9 2010 3650.0 1237.8 2260 4100.0 826.7 1520 2768.0 965.6 1770 3218.0 1104.4 2020 3668.0 1243.3 2270 4118.0 832.2 1530 2786.0 971.1 1780 3236.0 1110.0 2030 3686.0 1248.9 2280 4136.0 837.8 1540 2804.0 976.7 1790 3254.0 1115.6 2040 3704.0 1254.4 2290 4154.0 843.3 1550 2822.0 982.2 1800 3272.0 1121.1 2050 3722.0 1260.0 2300 4172.0 848.9 1560 2840.0 987.8 1810 3290.0 1126.7 2060 3740.0 1265.6 2310 4190.0 854.4 1570 2858.0 993.3 1820 3308.0 1132.2 2070 3758.0 1271.1 2320 4208.0 860.0 1580 2876.0 998.9 1830 3326.0 1137.8 2080 3776.0 1276.7 2330 4226.0 865.6 1590 2894.0 1004.4 1840 3344.0 1143.3 2090 3794.0 1282.2 2340 4244.0 871.1 1600 2912.0 1010.0 1850 3362.0 1148.9 2100 3812.0 1287.8 2350 4262.0 876.7 1610 2930.0 1015.6 1860 3380.0 1154.4 2110 3830.0 1293.3 2360 4280.0 882.2 1620 2948.0 1021.1 1870 3398.0 1160.0 2120 3848.0 1298.9 2370 4298.0 887.8 1630 2966.0 1026.7 1880 3416.0 1165.6 2130 3866.0 1304.4 2380 4616.0 893.3 1640 2984.0 1032.2 1890 3434.0 1171.1 2140 3884.0 1310.0 2390 4334.0 898.9 1650 3002.0 1037.8 1900 3452.0 1176.7 2150 3902.0 1315.6 2400 4352.0 904.4 1660 3020.0 1043.3 1910 3470.0 1182.2 2160 3920.0 1321.1 2410 4370.0 910.0 1670 3038.0 1048.9 1920 3488.0 1187.8 2170 3938.0 1326.7 2420 4388.0 915.6 1680 3056.0 1054.4 1930 3506.0 1193.3 2180 3956.0 1332.2 2430 4406.0 921.1 1690 3074.0 1060.0 1940 3524.0 1198.9 2190 3974.0 1337.8 2440 4424.0 926.7 1700 3092.0 1065.6 1950 3542.0 1204.4 2200 3992.0 1343.3 2450 4442.0 932.2 1710 3110.0 1071.1 1960 3560.0 1210.0 2210 4010.0 1348.9 2460 4460.0 937.8 1720 3128.0 1076.7 1970 3578.0 1215.6 2220 4028.0 1354.5 2470 4478.0 943.3 1730 3146.0 1082.2 1980 3596.0 1221.1 2230 4046.0 1360.0 2480 4496.0 948.9 1740 3164.0 1087.8 1990 3614.0 1226.7 2240 4064.0 1365.6 2490 4515.0

128 Reference Data 129 (°F - 32°) (°R - 0.6°) 9 9 ⁄ ⁄ 5 5 K = °C + 273° °R = °F + 460° 120 Volts 240 Volts 480 Volts 110 115 208 220 230 440 460 Volts Volts Volts Volts Volts Volts Volts RankineKelvin °R = 1.8K + 0.6° K = FahrenheitCelsius °F = 1.8°C + 32° °C = Temperature Scale Convert to by... The Kelvin scale uses no “°” symbol. kW Output kW of Heater When Operated On: 1.02.03.04.0 0.844.5 1.695.0 2.53 0.927.5 3.36 1.84 3.78 2.76 0.75 4.20 3.67 1.50 6.30 4.13 2.25 4.59 0.84 3.00 6.89 1.69 3.38 2.53 0.92 3.5 3.36 1.84 5.6 3.78 2.76 0.84 3.68 4.2 1.69 4.14 6.3 2.53 0.92 3.36 1.84 4.6 3.78 2.76 6.9 3.68 4.14 4.2 6.3 4.6 6.9 10.012.515.020.025.050.075.0 7.5 9.4 11.3 15.0 8.4 10.5 18.8 12.6 37.6 16.9 56.3 9.2 11.5 21.0 13.8 42.0 18.4 63.0 10.5 8.4 23.0 12.6 46.0 16.9 11.5 69.0 21.0 13.8 9.2 42.0 18.4 63.0 23.0 46.0 69.0 Rating 100.0 75.1 84.0 92.0 84.0 92.0 of Heater Note: Ratings of Listed Heater Voltages Operated on Other Voltages—Ref.Ratings of Listed Heater Voltages 129 Ref. 128 2 W A T L O W O L T A W NEW RATED V V () RATED = W NEW W Equation: Application Guide Application Data Reference Application Guide Reference Data

Conversion Factors—Ref. 130

To Convert To... Multiply... By...

Atmospheres (atm) Bar 0.9869 Atmospheres (atm) Inches Mercury (in Hg) 0.03342 Atmospheres (atm) Pounds/square inch (psi) 0.06805 Atmospheres (atm) Torr 0.001316 Bar Atmospheres (atm) 1.0133 Bar Pounds/square inch (psi) 0.06895 British Thermal Units (Btu) Joules (J) 0.000948 British Thermal Units (Btu) Kilowatt-hours (kWh) 3412 British Thermal Units (Btu) Watt-hours (Wh) 3.412 British Thermal Units/hour (Btu/h) Kilocalories/hour (kcal/h) 3.969 British Thermal Units/hour (Btu/h) Watts (W) 3.412 British Thermal Units—inches (Btu—in) Watts/meter—°C (W/m—°C) 6.933 hour-square foot—°F (h-ft2—°F) British Thermal Units/pound (Btu/lb) Kilojoules/kilogram (kJ/kg) 0.4299 British Thermal Units/pound—°F (Btu/lb—°F) Kilojoules/kilogram—°C (kJ/kg—°C) 0.2388 Calories (cal) Joules (J) 0.2388 Centimeters (cm) Feet (ft) 30.48 Centimeters (cm) Inches (in) 2.54 Centimeters/second (cm/s) Feet/minute (fpm) 0.508 Cubic centimeters (cm3 or cc) Cubic feet (ft3) 28,320 Cubic centimeters (cm3 or cc) Cubic inches (in3) 16.39 Cubic centimeters (cm3 or cc) Milliliters (ml) 1.0 Cubic feet (ft3) Cubic meters (m3) 35.32 Cubic feet (ft3) Gallons, U.S. (gal) 0.1337 Cubic feet (ft3) Liters (l) 0.03532 Cubic feet/minute (cfm) Cubic meters/hour (m3/h) 0.5885 Cubic feet/minute (cfm) Cubic meters/second (m3/s) 2119 Cubic feet/minute (cfm) Liters/second (l/s) 2.119 Cubic inches (in3) Cubic centimeters (cm3 or cc) 0.061 Cubic meters (m3) Gallons, U.S. (gal) 0.003785 Cubic meters (m3) Liters (l) 0.001 Cubic meters (m3) Cubic feet (ft3) 0.02832 Cubic meters/hour (m3/h) Cubic feet/minute (cfm) 1.699 Cubic meters/hour (m3/h) Gallons/minute (gpm) 0.2271 Cubic meters/second (m3/s) Cubic feet/minute (cfm) 0.000472 Feet (ft) Centimeters (cm) 0.03281 Feet (ft) Meters (m) 3.281 Feet/minute (fpm) Centimeters/second (cm/s) 1.969 Feet/minute (fpm) Meters/second (m/s) 196.9 Gallons, Imperial Gallons, U.S. (gal) 0.8327

CONTINUED

130 Reference Data 131 CONTINUED ) 1000 ) 0.001 ) 27.68 3 3 ) 0.01602 ) 16.02 3 3 3 ) 1000 )/h) 264.2 4.403 ) 28.32 ) 7.481 3 3 3 3 3 ) Pounds/square inch (psi) 0.07031 2 ))) meter Kilograms/cubic foot Pounds/cubic inch Pounds/cubic (kg/m (lb/ft (lb/in )) Grams/cubic centimeter Pounds/cubic foot (g/cm (lb/ft 3 3 3 3 3 W A T L O W O L T A W To Convert To... Multiply... By... Grams/cubic centimeter (g/cm Kilograms/square centimeter (kg/cm Kilograms/cubic meterKilojoulesKilojoules/kilogramKilojoules/kilogram—°CKilometers/hour (kg/m KilopascalsKilowattsKilowatts (kJ/kg—°C) (kJ/kg)Kilowatt-hoursKilowatt-hours (kJ)Liters British Thermal Units/pound—°F (km/h) (Btu/lb—°F) British Thermal Units/pound (kPa) (Btu/lb) Watt-hours (kW) 4.187 (kWh) Miles/hour (kW) (kWh) inch Pounds/square 2.326 (l) Thermal Units British British Thermal Units/hour Watt-hours Watts (Wh) (psi) (mph) (Btu/h) (Btu) Cubic Feet 3.6 (Wh) 1.609 0.0002931 6.895 (W) 0.0002931 (ft 0.001 0.001 Grams/cubic centimeterInchesInchesInches Mercury (g/cm Inches MercuryJoulesJoulesJoulesJoules/secondJoules/secondKilocalories/hour (in Hg) (in) (in Hg)Kilograms (in)Kilograms/cubic meter Atmospheres (J) (J/s) Torr (J) (J/s) Centimeters (J) (kcal/h) (kg/m Millimeters (kg) Thermal Units/hour British British Thermal Units (atm) Btu/hour Watts Calories Watt-hours (cm) (Btu/h) (mm) (Btu) Pounds 29.92 0.2931 (Btu/h) 0.3937 (cal) (Wh) 1055 (W) 0.03937 25.4 (lb) 0.252 3600 4.187 1 0.4536 Gallons, U.S. (gal) Cubic feet (ft Liters (l) Cubic Meters (m LitersLiters/secondLiters/second (l/s) (l/s) (l) Cubic feet/minute Gallons/minute Gallons, U.S. (cfm) (gpm) (gal) 0.4719 0.06309 3.785 Gallons, U.S. (gal) meters Cubic (m Gallons, U.S.Gallons, U.S.Gallons/minuteGallons/minuteGramsGramsGrams/cubic centimeter (gal) (gal) (gpm) (gpm) (g/cm Imperial Gallons, (g) Cubic meters/hour Liters (g) Liters/second (m Ounces Pounds (l/s) (l) 1.201 15.85 (oz) (lb) 0.2642 28.35 453.6 Conversion Factors Application Guide Application Data Reference Application Guide Reference Data

Conversion Factors

To Convert To... Multiply... By...

Meters (m) Feet (ft) 0.3048 Meters/second (m/s) Feet/minute (fpm) 0.00508 Miles/hour (mph) Kilometers/hour (km/h) 0.6215 Millimeters (mm) Inches (in) 25.4 Newtons/square meter (N/m2) Pounds/square inch (psi) 6,895 Ounces (oz) Grams (g) 0.035274 Pounds (lb) Grams (g) 0.002205 Pounds (lb) Kilograms (kg) 2.205 Pounds/cubic foot (lb/ft3) Grams/cubic centimeter (g/cm3) 62.43 Pounds/cubic foot (lb/ft3) Kilograms/cubic meter (kg/m3) 0.06243 Pounds/cubic inch (lb/in3) Grams/cubic centimeter (g/cm3) 0.03613 Pounds/square inch (psi) Bar 14.504 Pounds/square inch (psi) Kilograms/square centimeter (kg/cm2) 14.22 Pounds/square inch (psi) Kilopascals (kPa) 0.145 Pounds/square inch (psi) Newtons/square meter (N/m2) 0.000145 Square centimeters (cm2) Square feet (ft2) 929 Square centimeters (cm2) Square inches (in2) 6.452 Square feet (ft2) Square centimeters (cm2) 0.001076 Square feet (ft2) Square meters (m2) 10.76 Square inches (in2) Square centimeters (cm2) 0.155 Square meters (m2) Square feet (ft2) 0.0929 Torr Inches Mercury (in. Hg) 0.03937 Torr Pounds/square inch (psi) 51.71 Watts (W) British Thermal Units/hour (Btu/h) 0.2931 Watts (W) Joules/second (J/s) 1 Watt-hours (Wh) British Thermal Units (Btu) 0.2931 Watt-hours (Wh) Joules (J) 0.0002778 Watt-hours (Wh) Kilojoules (kJ) 0.2778 Watts/meter—°C (W/m—°C) British Thermal Units—inches (Btu—in) 0.1442 hour-square foot—°F (h-ft2—°F) Watts/square centimeter (W/cm2) Watts/square inch (W/in2) 0.155 Watts/square inch (W/in2) Watts/square centimeter (W/cm2) 6.452

132 Reference Data 133 ) 2 h 2 3 2 - d d d 2 2 d d + h) ) π π . 2 2 4 / 1 h + h

2 2 = - r r 3 r 2 h = 2 r r 2 π r r π π 3 (R / π 4 3 6 1 π π

A = Cone V = volume A = area of conical surface V = Cylinder V = volume S = area of cylindrical surface V = S = 6.28rh = 3.14dh Total area A of cylindrical surface and end surfaces: A = 6.28r(rh) + = 3.14d( V = volume A = area of surface V = abc A = 2ab + 2ac + 2bc Sphere V = volume A = area of surface V = A = 4 Cube or Square Prism

Circular Ring A = area A = = 0.7854 (D = 0.7854

r r c d d

r b

D d

d a

h h R 2 4 - s 2 2 R D d π π n = ÷

r = 2 2 ¡ rl r 2 π / 1 π (a + b)h bh 2 nsr ns 2 2 a = 57.3l r Circular Sector A = area l = length of arc a = angle, in degrees r = radius l = ra3.14 180 A = 2 C = 2 Circle A = area C = circumference A = Square, Rectangle, Parallelogram A = area A = ab Note that dimension a is measured at right angles to line b. Trapezoid A = area A = A = area A = Triangle A = = A = Regular Polygon A = area n = number of sides s = length of side a = 360

s a r r l a b

b d a r

h R b Commonly Used Geometric Areas And Volumes Commonly Used of Plane Figures Areas and Dimensions Ref. 131 the surfaces of show the areas of plane figures, The following illustrations of solids. solids, and the volumes h W A T L O W O L T A W Application Guide Application Data Reference Application Guide Reference Data Properties of Non-Metallic Solids—Ref. 132 Physical Properties of Solids, Specific *Thermal Melting Latent Liquids and Gases Heat Conductivity Point Heat of *Density Btu Btu-in ¡F Fusion Material lb./ft3 lb.-¡F hr.-ft2-¡F (Lowest) Btu/lb. Allyl, Cast 82.5 0.55 12.1 Alumina 96% 232 0.20 110.9 3812 Alumina 99.9% 249 0.20 270 3812 Aluminum Silicate 149 0.2 9.1 3690 (Lava Grade A) Aluminum Nitride 199 0.19 1179 3992 Amber 65.6 Asbestos 36 0.25 0.44 Ashes 40-45 0.2 0.49 Asphalt 65 0.4 1.2 250± 40 Bakelite Resin, Pure 74-81 0.3-0.4 Barium Chloride 240 0.10 1697 Beeswax 60 1.67 144± 75 Boron Nitride (Compacted) 142 0.33 125 5430 Brick, Common Clay 100 0.23 5 Brick, Facing/Building 140 0.22 8 & Mortors Calcium Chloride 157 0.17 1422 72 Carbon 138 0.20 165 6700 Carnauba Wax 62.4 0.8 Cement, Portland Loose 94 0.19 2.04 Cerafelt Insulation 3 0.25 @ 1000° 1.22 Ceramic Fiber 10-15 0.27 *** Chalk 112-175 0.215 5.76 Charcoal Wood 17.5-36 0.242 0.612 Chrome Brick 0.17 9.6 Clay 90±10 0.224 9 3160 Coal (Course Anthercite) 80 0.32 11 Coal Tars 78 0.35-0.45 Coke 62-88 0.265 Concrete (Cinder) 100 0.16 5.3 Concrete (Stone) 144 0.156 9.5 Cordierite (AISI Mag 202) 131 0.35 9.12 2680 Cork 13.5 0.5 0.36 Cotton (Flax, Hemp) 92.4 0.31 0.41 Delrin 88 0.35 1.56 Diamond 219 0.147 13872 Earth, Dry & Packed 94 0.44 0.9 *** At or near room temperature *** Thermal conductivity will decrease with age Ethyl Cellulose 67-74 0.32-0.46 and use Fiberglass 0.75 0.28 To convert to kg/m3 multiply lb/ft3 by 16.02 Microlite Duct Insulation To convert to kJ/kg multiply Btu/lb by 2.326 Fiberglass 3 0.26 To convert to kJ/kg-°C multiply Spin-Glas 1000 Insulation Btu/lb-°F by 4.187 To convert to W/m-°C multiply CONTINUED Btu -in/hr-ft2-°F by 0.1442

134 Reference Data 135 Fusion CONTINUED (sublimination) ¡F (Lowest) Btu/lb. 2- ¡F hr.-ft - Btu Btu-in ¡F 2.28 Heat Conductivity Point Heat of lb. Specific *Thermal Melting Latent 3 lb./ft 3.48 *Density Material Butyrate 74 0.3-0.4 1.2-2.3 AcrylicCellulose AcetateCellulose Acetate Epoxy 76-83FluoroplasticsNylonPhenolic 69-74 0.3-0.5PolycarbonatePolyester 131-150 1.2-2.3 Polyethylene 0.34 66-88Polyimides 0.28 74-78Polypropylene 85-124 67-72 0.25-0.3 1.0 57-60 66-92 1.68 0.3 0.3-0.5 1.2-2.4 0.35 0.2-0.35 55-57 0.54 90 1.68 1.38 1.02 3.96-5 0.46 0.27-0.31 2.28 2.5-6.8 1.72 Before CompactionAfter Compaction 147 190 0.21 0.21 3.6 14.4Laminated 5165 5165 ABS 78 0.3-0.5 69-76 2.4 0.35 1.32 IceIsoprene (Nat’l Rubber)LimestoneLitharge 58MagnesiaMagnesite BrickMagnesium Oxide 0.48 130-175 57Magnesium Silicate 159Marble 0.217 1.0 225Marinite I @ 400°FMelamine Formaldehyde 0.46 0.222 175Mica 3.6-9 0.234Nylon Fibers 93 0.055Paper 10.8-30 46 15.36Paraffin 1472 0.48 150-175Phenolic Resin, Cast 0.4Phenolic Formaldehyde 0.29Phenolic, Sheet or Tube 32 0.21 5070 72 78-92 15.6 84Pitch, Hard 185 3 1627 Plastics: 0.89 0.38-0.42 14.4 0.4-0.5 58 0.3-0.4 56 0.20 0.45 1.1 0.70 83 3 0.82 1.56 133 63 300± Firebrick, FireclayFirebrick, SilicaFloursparForsterite (AISI Mag 243) 137-150Garnet 175Glass 144-162 0.243GraniteGraphite 0.258 6.6 7.2 2900 25.5 160-175 165 0.21 130 3000 0.192 0.176 3470 0.20 0.20 13-28 5.4 1.25 2200 1202 by 16.02 W A T L O W O L T A W 3 multiply lb/ft 3 -°F by 0.1442 2 and use To convert to kg/m To convert to kJ/kg multiply Btu/lb by 2.326 To convert to kJ/kg-°C multiply Btu/lb-°F by 4.187 To convert to W/m-°C multiply Btu-in/hr-ft * At or near room temperature ** Thermal conductivity will decrease with age ** * Physical Properties Solids, of Physical Liquids and Gases Continued Application Guide Application Data Reference Application Guide

Reference Data Specific *Thermal Melting Latent Physical Properties of Solids, Heat Conductivity Point Heat of *Density Btu Btu-in ¡F Fusion Liquids and Gases Material lb./ft3 lb.-¡F hr.-ft2-¡F (Lowest) Btu/lb. Continued Plastics: Polystyrene 66 0.32 0.36-0.96 Polyvinyl Chloride Acetate 72-99 0.2-0.3 0.84-1.2 Porcelain 145-155 0.26 6-10 Potassium Chloride 124 0.17 1454 Potassium Nitrate 132 0.26 633 Quartz 138 0.26 9.6 3137 Rock Salt 0.219 1495 Rubber Synthetics 58 0.40 1.0 Sand, Dry 88-100 0.191 2.26 Silica (fused) 124 0.316 10.0 3137 Silicon Carbide 112-125 0.20-0.23 866 4892 (sublimination) Silicone Nitride 197 0.16 208 3452 (sublimination) Silicone Rubber 78 0.45 1.5 Soapstone 162-174 0.22 11.3 Sodium Carbonate 135 0.30 520 Sodium Chloride 135 0.22 1474 Sodium Cyanide 94 0.30 1047 Sodium Hydroxide Bath 110 0.28 550 72 (75% NaOH and Mixed Salts) Sodium Nitrate 141 0.29 584 Sodium Nitrite 135 0.30 520 Sodium/Potassium Nitrate Baths: Draw Temp 275 Solid 132 0.32 275 94 Liquid 110 0.37 2.4± @ 600°F Draw Temp 430 Solid 130 0.29 430 49 Liquid 115 0.38 2.4± @ 600°F Soil, Dry Including Stones 127 0.40 3.6 Steatite 162 0.20 17.4 2500 Stone 0.20 Stone, Sandstone 130-150 0.22 Sugar 105 0.30 320 *** At or near room temperature *** Thermal conductivity will decrease with age Sulphur 125 0.203 1.8 230 17 and use Tallow 60 90± To convert to kg/m3 multiply lb/ft3 by 16.02 Teflon® 135 0.25 1.7 To convert to kJ/kg multiply Btu/lb by 2.326 Urea, Formaldehyde 97 0.4 To convert to kJ/kg-°C multiply Vinylidene 107 0.32 Btu/lb-°F by 4.187 To convert to W/m-°C multiply Vinylite 73 0.29 Btu-in/hr-ft2-°F by 0.1442 Wood, Oak 50 0.57 1.2 Wood, Pine 34 0.67 0.9 Teflon® is a registered trademark of E.I. du Zirconia 368 0.12 17.3 4892 Pont de Nemours & Company.

136 Reference Data 137 6 ± - in/in/¡F CONTINUED 40 6.0 Fusion ± -¡F (Lowest) Btu/lb. X10 2 204 636 -°F by 0.1442 2 Btu Btu-in ¡F Heat Conductivity Point Heat of Expansion lb.-¡F hr.-ft Specific *Thermal Melting Latent Thermal by 16.02 3 3 Ref. 133 — lb./ft Density are registered multiply lb/ft ® 3 and Inconel ® Material (Cemented Carbide) 875 0.052(55% Cu, 45% Ni) 420 555 >6422 0.098 2237-2372 8.3 (75% Cu, 25% Sn) 541 0.082 180 1832 75 To convert to kJ/kg multiply Btu/lb by 2.326 To convert to kJ/kg-°C multiply Btu/lb-°F by 4.187 To convert to W/m-°C multiply Btu-in/hr-ft Iron, WroughtLeadLinotypeLithium 480MagnesiumManganese 0.12MercuryMolybdenum 627 708 109 367 432 463 0.04 0.032 0.232 638 0.79 0.115 844 240 2800± 1092 0.061 0.033 516 80.6 980 620 1202 60.8 2268 480 367 155 9.8 4750 116 -38 59 16.4 14.0 126 12.7 5.0 31 2.9 33.8 GoldIncoloy 800Inconel 600Invar 36% NiIron, Cast 501 1203 525 506 0.12 0.030 0.11 450 0.126 2028 97 0.13 109 73 1945 396 2475 2470 2600 29 2300 7.9 7.9 5.8 1.1 CopperGerman Silver 537 559 0.109 0.10 168 2688 1761 1981 44.2 91 10.6 9.8 CadmiumCalciumCarbonCarboloy 540Chromium 96.7 0.055Cobalt 138Constantan 0.149 660 0.165 450 912 173 0.11 554 610 1564 0.099 >6422 23.8 484 140 499 17.2 12.2 2822 2696 111.7 2.3 115.2 3.6 6.9 Babbitt-Tin BaseBariumBeryllium 462BismuthBoron 0.071Brass (80-20)Brass (70-30) 225Brass (Yellow) 113.5 278.4Bronze 610 0.052 535 0.068 525 144 0.031 529 465 0.091 1121.0 0.10 0.309 0.096 59 2345 82 672 828 1562 58 1700± 520 1700± 24 1710 6.6 4172 22.4 10.0 898 7.4 10.6 4.6 11.2 Aluminum 1100-0Aluminum 2024Antimony 169Babbitt-Lead Base 173 0.24 640 0.24 413 0.039 1536 1344 0.049 165.6 1190 131 935 169 470 167 1166 13.1 12.6 69 10.9 5.0 To convert to kg/m Properties of Metals trademarks of the Special Metals Corporation. Incoloy * At or near room temperature W A T L O W O L T A W Physical Properties Solids, of Physical Liquids and Gases Continued Application Guide Application Data Reference Application Guide

Reference Data Specific *Thermal Melting Latent Thermal Physical Properties of Solids, Heat Conductivity Point Heat of Expansion Density Btu Btu-in ¡F Fusion in/in/¡F Liquids and Gases Material lb./ft3 lb.-¡F hr.-ft2-¡F (Lowest) Btu/lb. X10-6 Continued Monel® 400 551 0.11 151 2370 6.4 Muntz Metal (60% Cu, 40% Zn) 523 0.096 852 1660 11.5 Nickel 200 554 0.11 468 2615 1335.8 7.4 Nichrome (80% Ni, 20% Cr) 524 0.11 104.4 2550 7.3 7.8 Platinum 1338 0.32 492 3225 49 4.9 Potassium 750 0.058 720 146 26.2 4.6 Rhodium 776 0.059 636 3570 90 4.7 Silicon 14.5 0.162 600 2570 709 4.2 Silver 655 0.057 2904 1760 38 10.8 Sodium 60 0.295 972 207 49.5 39 Solder (50% Sn, 50% Pb) 552 0.040 336 420 17 13.1 Solder (60% Sn, 40% Pb) 540 0.045 355 375 28 13.3 Steel, Mild Carbon 490 0.12 456 2760 6.7 Steel, Stainless 304, 316, 321 500 0.12 105.6 2550 9.6 Steel, Stainless 430 475 0.11 150 2650 6.0 Tantalum 1036 0.036 372 5425 74.8 3.6 Tin 455 0.056 432 450 26.1 13.0 Titanium 283 0.126 111.6 3035 156.9 4.7 Tungsten 1200 0.032 1130 6170 79 2.5 Type Metal (85% Pb, 15% Sb) 670 0.040 180 500 14 Uranium 1170 0.028 193.2 3075 22.5 7.4 Zinc 445 0.095 112 787 43.3 22.1 264 Zirconium 400 0.066 145 3350 108 3.2 * At or near room temperature To convert to kg/m3 multiply lb/ft3 by 16.02 To convert to kJ/kg multiply Btu/lb by 2.326 To convert to kJ/kg-°C multiply Btu/lb-°F by 4.187 To convert to W/m-°C multiply Btu-in/hr-ft2-°F by 0.1442

Monel® is a registered trademark of the Special Metals Corporation.

138 Reference Data 139 -¡F 2 Btu Btu-in. lb.-¡F hr.-ft Specific Heat Thermal 3 752662 618.7680752 0.0354 498.8 495932 0.0632 107.4 752 0.0632 0.0632 648.7 307.7 0.037 31212 305 320 1.0 392 107.4 833.6752 818.8 0.03279 0.03245 46.6400752 0.1826768 56.2783 53.3 277.5 81 932 0.320 426.6 0.301 556.8 493.8 229.3 400.6 12921454 147.71112 0.26 603.1 0.26 0.0376 717 842 107.4 13281341 94.3 0.321 18322000 578.1 574.4 0.0692 0.0692 1112 425 0.117 394.8 Ref. 134 — -°F by 0.1442 Heat of Capacity Conductivity 2 by 16.02 3 ¡F (¡C) Btu/lb. ¡F lb./ft Melting Point Fusion Temperature Density multiply lb/ft 3 W A T L O W O L T A W Material Aluminum 1220.4Bismuth (660.2) 173Cadmium 520 (271) 1220 609 21.6 (321)Gold 148.6Lead 23.8 572 0.26 Lithium 1945 (1063) 621 626Magnesium 626.2 (327.4) 354 26.9 1204 (179) (651) 10.6 0.034 @ 520°FMercury 500 2012 284.4 148 119 700 0.0632 -38Potassium 1076 392 (-38.9) 1204 655.5Silver 147 5 0.0355 31.7 (63.8) 0.038 98Sodium 1761 26.3 1.0 32 (960.5) 0.317 Tin 208 300 44.8 111.6 (97.8)Zinc 1761 48.7 262 50.6 449 0.03334 (231.9)Solder 580.6 212 0.19010.5 Sn, 0.5Pb 787 26.10.6 Sn, 0.4Pb 421 (419.5) 0.0692 375 (216) 57.9 57 43.9 482 (190.6) 312 17 28 0.331 787 432 596.5 0.058 0.12 0.0556 0.0584 To convert to kg/m Properties of Metals in Liquid State Properties of Metals To convert to kJ/kg multiply Btu/lb by 2.326 To convert to kJ/kg-°C multiply Btu/lb-°F by 4.187 To convert to W/m-°C multiply Btu-in/hr-ft Continued Physical Properties Physical of Solids, Liquids and Gases Application Guide Application Data Reference Applications Guide Reference Data Properties of Liquids—Ref. 135 Physical Properties Specific *Thermal of Solids, Liquids Heat Conductivity Boiling Heat of Substance *Density Btu Btu-in Point Vaporization and Gases lbs./ft3 lb.-¡F hr.-ft2-¡F ¡F Btu/lb. Continued Acetic Acid, 100% 65.4 0.48 1.14 245 175 Acetone, 100% 49.0 0.514 1.15 133 225 Allyl Alcohol 55.0 0.665 207 293 Ammonia, 100% 47.9 1.1 3.48 -27 589 Amyl Alcohol 55.0 0.65 280 216 Aniline 64.6 0.514 1.25 63 198 Arochlor Oil 89.7 0.28 650 Brine-Calcium Chloride, 25% 76.6 0.689 3.36 Brine-Solium Chloride, 25% 74.1 0.786 2.88 220 730 Butyl Alcohol 45.3 0.687 244 254 Butyric Acid 50.4 0.515 345 Carbon Tetrachloride 98.5 0.21 170 Corn Syrup, Dextrose 87.8 0.65± 231 Cottonseed Oil 59.2 0.47 1.2 Ether 46.0 0.503 0.95 95 160 Ethyl Acetate 51.5 0.475 180 183.5 Ethyl Alcohol, 95% 50.4 0.60 1.3 370 Ethyl Bromide 90.5 0.215 101 108 Ethyl Chloride 57.0 0.367 54 166.5 Ethyl Iodide 113.0 0.161 160 81.3 Ethylene Bromide 120.0 0.172 270 83 Ethylene Chloride 71.7 0.299 240 139 Ethylene Glycol 70.0 0.555 387 Fatty Acid-Aleic 55.4 0.7± 1.1 547 Fatty Acid-Palmitic 53.1 0.653 0.996 520 Fatty Acid-Stearic 52.8 0.550 0.936 721± Fish, Fresh, Average 55-65 0.76 Formic Acid 69.2 0.525 213± 216 Freon 11 92.1 0.208 0.600 74.9± Freon 12 81.8 0.232 0.492 -21.6± 62 Freon 22 74.53 0.300 0.624 -41.36± Fruit, Fresh, Average 50-60 0.88 Glycerine 78.7 0.58 1.97 556± Heptane 38.2 0.49 210± 137.1 Hexane 38.2 0.6 155± 142.5 CONTINUED

** At or near room temperature. ** Average value shown. Boils at various temperatures within the distillation range for the material. Verify exact value from application originator. To convert to kg/m3 multiply lb/ft3 by 16.02 To convert to kJ/kg multiply Btu/lb by 2.326 To convert to kJ/kg-°C multiply Btu/lb-°F by 4.187 To convert to W/m-°C multiply Btu-in/hr-ft2-°F by 0.1442

140 Reference Data 141 70 95 90 170 117 176.5 142 918 207 142.2 CONTINUED ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± Point Vaporization -¡F ¡F Btu/lb. 2 Btu Btu-in Heat Conductivity Boiling Heat of lb.-¡F hr.-ft Specific *Thermal 3 -°F by 0.1442 2 lbs./ft by 16.02 3 multiply lb/ft 3 Substance *Density SAE 10-30SAE 40-50 55.4 55.4 0.43 0.43 Fuel Oil #1 (Kerosene)Fuel Oil #2Fuel Oil Medium #3, #4Fuel Oil Heavy #5, #6 50.5 55.7 58.9 0.47 53.9 0.425 0.41 1.008 0.44 0.918 **440± 0.852 **580± 0.96 86 67 Propane (Compressed)TolueneTransformer Oils 0.13 0.576 56.3 53.7 1.81 0.42 0.42 -48.1 0.9 1.032 NapthaleneParaffin, Melted (150°F+) 56 54.1 0.69 0.396 1.68 572 424± 103 GasolineMachine/Lube Oils: 41-43 0.53 0.936 **280± 116 Fuel Oils: AsphaltBenzene 62.3 56 0.42 0.42 5.04 1.04 175 Phosphoric Acid, 10%Phosphoric Acid, 20% 65.4 69.1 0.93 0.85 Phenol (Carbolic Acid) 66.6 0.56 346 HoneyHydrochloric Acid, 10%IceIce CreamLardLinseed Oil 66.5Maple SyrupMeat, Fresh, AverageMercuryMethyl Acetate 0.93Methyl Chloroform 90± 56 57.9 57.4 0.34 0.70 0.70 54.8 82.7 0.5 0.44 221 845 0.64 0.48 0.47 0.26 0.033 3.96 59.64 552 675 133 165 Methylene Chloride 82.6 0.288 104 Milk, 3.5%MolassesNitric Acid, 7%Nitric Acid, 95%NitrobenzeneOlive OilPerchlorethylene 64.2 64.7 87.4 93.5 0.90 0.92 101.3 0.60 0.5 58 0.21 0.35 0.47 220 220± 187 250 412 570 Petroleum Products: Verify exact value from application originator. To convert to kg/m To convert to kJ/kg multiply Btu/lb by 2.326 To convert to kJ/kg-°C multiply Btu/lb-°F by 4.187 To convert to W/m-°C multiply Btu-in/hr-ft W A T L O W O L T A W * At or near room temperature. * ** at various temperatures within the distillation range for the material. Average value shown. Boils Continued Physical Properties Physical of Solids, Liquids and Gases Applications Guide Applications Data Reference Applications Guide

Reference Data Specific *Thermal Physical Properties Heat Conductivity Boiling Heat of Substance *Density Btu Btu-in Point Vaporization of Solids, Liquids lbs./ft3 lb.-¡F hr.-ft2-¡F ¡F Btu/lb. and Gases Polyurethane Foam Components Continued (MDI System): Part A Isocyanate 77 0.6 1.14 Part B Polyoil Resin 74.8 0.7 1.32 Potassium (1000°F) 44.6 0.18 260.40 1400 893 Propionic Acid 61.8 0.56 286 177.8 Propyl Alcohol 50.2 0.57 208 295.2 Sea Water 64.2 0.94 Sodium (1000°F) 51.2 0.30 580 1638 1810 Sodium Hydroxide (Caustic Soda) 30% Sol. 82.9 0.84 50% Sol. 95.4 0.78 Soybean Oil 57.4 0.24-0.33 Starch 95.4 Sucrose, 40% Sugar Syrup 73.5 0.66 214 Sucrose, 60% Sugar Syrup 80.4 0.74 218 Sulfur, Melted (500°F) 112 0.24 832 120 Sulfuric Acid, 20% 71 0.84 218 Sulfuric Acid, 60% 93.5 0.52 2.88 282 Sulfuric Acid, 98% 114.7 0.35 1.8 625 219 Trichloroethylene 91.3 0.23 0.84 188 103 Trichloro-Trifluoroethane 94.6 0.21 118 63 Turpentine 54 0.42 319 133 Vegetable Oil 57.5 0.43 Vegetables, Fresh, Average 50-60 0.92 Water 62.4 1.00 4.08 212 965 Wines, Table & Dessert, Average 64.2 0.90 Xylene 53.8 0.411 288 149.2 ** At or near room temperature. ** Average value shown. Boils at various temperatures within the distillation range for the material. Verify exact value from application originator. To convert to kg/m3 multiply lb/ft3 by 16.02 To convert to kJ/kg multiply Btu/lb by 2.326 To convert to kJ/kg-°C multiply Btu/lb-°F by 4.187 To convert to W/m-°C multiply Btu-in/hr-ft2-°F by 0.1442

142 Reference Data ) 143 3 -¡F 2 Btu-in. (¡F) (Btu/lb.-¡F) (lb./ft 600650700750 0.252800 0.253850 0.254900 0.037 950 0.256 0.035 0.257 0.034 0.258 0.260 0.033 0.261 0.032 0.030 0.029 0.028 10001050110011501200 0.262 0.264 0.265 0.266 0.027 0.267 0.026 0.025 0.025 0.024 Temperature Specific Heat Density Heat at *Thermal *Specific Constant Conductivity Btu/lb. - ¡F hr.-ft ) 3 3 lb./ft Ref. 136 — Ref. 137 — Substance *Density Pressure 0 0.240 0.086 50 0.240 0.078 (¡F) (Btu/lb.-¡F) (lb./ft 100150200250 0.240300 0.241350 0.242400 0.071 450 0.243 0.065 0.244500 0.060 0.245550 0.247 0.056 0.248 0.052 0.049 0.249 0.046 0.250 0.043 0.041 0.039 Temperature Specific Heat Density AcetyleneAirAlcohol, Ethyl (Vapor)Alcohol, Methyl (Vapor)AmmoniaArgonButaneButylene 0.073Carbon DioxideCarbon MonoxideChlorine 0.35 0.4534 Chloroform 0.076 0.4580 0.044ChloromethaneDichlorodifluoromethane (F-12)Ethyl Chloride 0.113 0.240 0.103 0.329 0.078 0.1623 0.523 0.129 Ethylene 0.148 Ethyl Ether 0.199 0.124Helium 0.143 0.248 0.18 Hydrochloric Acid 0.1309 0.184 0.16 HydrogenHydrogen Sulfide 0.1703 0.24 0.12 0.12 0.058 0.18 Methane 0.115Nitric Oxide 0.0876 Nitrogen 0.1441 0.0946 0.0728Nitrous Oxide 0.0636 Oxygen 0.06 0.096 0.0104 0.191 0.40Sulfur Dioxide 0.046 0.0056Water Vapor (212°F) 1.25 0.4380 0.2451 0.066 0.0779 0.0447 3.43 0.1212 0.1143 0.075 0.0372 0.0924 0.231 0.60 0.091 1.10 0.179 0.221 0.13 0.082 0.482 0.249 0.155 0.1656 0.21 0.218 0.1056 0.16 0.19 0.07 0.18 Properties of Gases Properties of Air* W A T L O W O L T A W by 16.02 3 multiply lb/ft 3 -°F by 0.1442 2 To convert to kg/m To convert to kJ/kg multiply Btu/lb by 2.326 To convert to kJ/kg-°C multiply Btu/lb-°F by 4.187 To convert to W/m-°C multiply BTU-in/hr-ft * At 60°F and atmospheric pressure (14.7 psia) Physical Properties Solids, of Physical Liquids and Gases Continued Applications Guide Applications Data Reference Application Guide Reference Data Rating System 4. Direct immersion heaters not A—Good practical. Use clamp-on heaters Corrosion Guide on outside surface of cast iron pot. The Watlow Corrosion Guide repre- B—Fair 5. Element surface loading should sents a compilation of available data C—Conditional—Performance is not exceed 3 W/cm2 (20 W/in2). and application experience on the dependent upon specific appli- relative compatibility of common cation conditions such as solution 6. For concentrations greater than 15 heater sheath materials and concentration and temperature. percent, element surface loading should not exceed 3 W/cm2 corrodants. This can be valuable in X—Unsuitable—Should not be used. the initial selection of a heater sheath (20 W/in2). Notes to Corrosion Guide material to be used with a listed corro- 7. See suggested watt density chart. 1. This solution involves a mixture dant. Final selection, however, should 8. Remove crusts at liquid level. be made based upon the specific of various chemical compounds 9. Clean often. exposure conditions, recommen- whose identity and proportions are dations of the corrosive agent’s unknown or subject to change 10. Do not exceed 2 W/cm2(12 W/in2). manufacturer and preliminary testing. without our knowledge. Check 11. Passivate stainless steel, Inconel® supplier to confirm choice of and Incoloy®. sheath material plus alternate Note: Blank spaces indicate an sheath materials that may be absence of data to establish used. a rating. 2. Caution—Flammable material. 3. Chemical composition varies widely. Check supplier for specific recommendations. Ref. 138 B ¨ 800 600 400 ¨ ¨ ¨ ¨ Corrodant Boiling Point Flash Point Auto Ignition Comments B.P. F.P. A.I. Nickel 200 304, 321, 347 Stainless Steel 316 Stainless Steel Type 20 Stainless Steel Incoloy Inconel Titanium Hastelloy Iron Steel Cast Iron Grey Cast Iron NI Resist Aluminum Copper Lead Monel ¡F¡ ¡F¡ ¡F¡ Quartz Graphite Teflon Acetaldehyde 69 -33 365 B X B B B A A A B A C A A Note 2 Acetic Acid 244 109 800 X X C X X B C C BACCA AAA Crude X C A/B B X B B A/B A/B A C C A Pure X A B B A B A ACCAA Vapors X C B X B B X X A C C A/B A A A Hastelloy® C-276 Acceptable 150 PSI, 400°F C B X B B CC Aerated X X X C X X X X X BB XA No Air X X C B X A B C BB XA Acetone 134 0 1000 C X B B A A/B A A A A A AAAAAAANote 2 Actane™ 70 A A Note 1 TM: Enthone, Inc. Acid additive for pickling of metals. Actane™ 80 A A Note 1 Actane™ Salt A Note 1 Alboloy Process A Alcoa™ R5 Bright Dip A A Note 1 TM: This is a proprietary process licensed to individuals by Alcoa. Allyl Alcohol 207 70 713 A A B A B A A A A A/B A A A/B A A Alcohol B B B A A A A B A A AAAAAA Note 2 CONTINUED

Hastelloy® is a registered trademark of Haynes Teflon® is a registered trademark of E.I. du Pont International. de Nemours & Company. 144 Reference Data 145 CONTINUED C-276 Acceptable C-276 Acceptable C-276 Acceptable C-276 Acceptable ® ® ® ® Chemical Co. Aluminum conversion coating. Protective coating chemical for aluminum. Comments

Note 1

Teflon

X Note 1

Graphite Quartz

A A Note 1

Hastelloy B

A Note 1 TM: Fredrick Gumm

Titanium

Inconel 600 ¨

Incoloy 800 ¨

Stainless Steel Stainless

Type 20 Type 316 Stainless Steel Stainless 316 XB XXXAXAA X X X X X A A A A Note 1 Hastelloy X X CBAAAA

A A/BAA XXX A AAA B A B AB B BBABAA XBXAAA A X A A A AA A BBABAAA AA A A A A Hastelloy A B A AB B B X X X X AAA B Notes 1, 9 A AA A A Note 1 A Note 1 TM: Amchem Products Inc. A A A BAA A A A A A A Hastelloy CA A C C C C A A A A A Hastelloy

Sulfate A/B A/B A A A/B A A A B/C B B A/B A A A/B A/B A A B B A A

Stainless Steel Stainless

304, 321, 347 321, 304,

Nickel 200 Nickel

Monel 400 ¨

Lead

Copper

Aluminum

Cast Iron NI Resist NI Iron Cast

Cast Iron Grey Iron Cast

Iron Steel Iron Ignition

¡ Auto F ¡

W A T L O W O L T A W Point

Flash F

¡ Point

¡ Boiling F ¡ B.P. F.P. A.I. Corrodant ColdHot C C A A C A B A A A X A A A C 200°F A347 Ammonia and OilAmmonium AcetateAmmonium BifluorideAmmonium ChlorideAmmonium HydroxideAmmonium Nitrate 640Ammonium PersulfateAmmonium SulfateAmyl Acetate A Amyl Alcohol A X B XAniline X B X A/BAniline, Oil X B B X X B X 298 A X B X B/X A X C 77 X X X 280 B X A/B X 714 C X 91 B B B X B 572 X X X B/X X X X A A X X 364 B C B 158 X A 1418 X X B X A C X X B A/B A/B B A A B/X B A A B A B B A304 C X A A B B B X X A Aluminum (Molten)Aluminum AcetateAluminum Bright Dip 3732Aluminum ChlorideAluminum CleanersAluminum Potassium 356Sulfate (Alum)Aluminum SulfateAlumAmmonia XAmmonia(Anhydrous)(Gas) X X -28 X Contact B Factory C B 1204 X C A X B B X X B X X A/B X X X X X A X X X X A X X X A X A/B X B B B X X B X X A X B C X See Aluminum Potassium C X X X Alkaline SolutionsAlkaline CleanersAlkaline Soaking CleanersAlodine™ A A A A Alcorite™ Application Guide Application Data Reference Application Guide Reference Data B ¨ 800 600 400 ¨ ¨ ¨ Boiling Point Flash Point Auto Ignition Corrodant ¨ Comments B.P. F.P. A.I. Inconel Titanium Hastelloy Iron Steel Cast Iron Grey Cast Iron NI Resist Aluminum Copper Lead Monel Nickel 200 304, 321, 347 Stainless Steel 316 Stainless Steel Type 20 Stainless Steel Incoloy ¡F¡ ¡F¡ ¡F¡ Quartz Graphite Teflon Aniline, Dyes A A A Anodizing X X X X A X X X XA XXX AAA Anodizing Solutions (10% Solution) Chromic Acid 96°F C A AA Sulfuric Acid 70°F 626 A A Sodium Hydroxide160°F 2534 A A A AA A A Nigrosine150°F Black Dye A B Nickel Acetate 200°F C A B Arp™ 28 A A Note 1 TM: Specialty Chemicals, Allied-Kelite Products Div., The Richardson Co. Arp™ 80 Blackening Salt A Note 1 Arsenic Acid X X X X X X X C BB XXX AAA Asphalt <878 400 905 A A X X X X A/B A/B AA AAA AAA + Barium Chloride 2840 X A B B ABB AA Barium Hydroxide B B X X X B A B A A/B B B X B A A A Carpenter 20 Acceptable Barium Sulfate B B B B B B B B B B B BBABAAA Barium Sulfide (Barium Monosulfide) B X X A/X A A/B BB AA Barium Sulfite B Black Nickel A A Note 5 Black Oxide A Note 5

1 Bleaching Solution (1 ⁄2 lb.

Oxalic Acid per gallon H2O at 212°F A F Bonderizing™ (Zinc C B A A TM: Parker Div., OMI Corp., Phosphate) Paint Base Boric Acid X X X C C C C C C C C C A A A A A Hastelloy® C276 Acceptable Brass Cyanide A Note 1 Bright Copper–Acid See Copper Bright Acid Bright Copper–Cyanide See Copper Cyanide Bright Nickel A A Notes 1, 5 Brine (Salt Water) A BAA Bronze Plating A A Note 1 Butanol (Butyl Alcohol) 243 84 689 A/B A B A/B A A A A A A A A A/B B A A A Note 1 Cadmium Black A Note 1 Cadmium Fluoborate A A Note 1 Cadmium Plating A A A Note 1 Calcium Chlorate B B B C C B B B BB BB A CONTINUED

146 Reference Data 147 CONTINUED C276 Acceptable C276 Acceptable C276 Acceptable C276 Acceptable C-276 Acceptable C-276 Acceptable C-276 Acceptable ® ® ® ® ® ® ® Comments Hastelloy Hastelloy Hastelloy Hastelloy

Note 1 Note 1 Note 2

Teflon ¨

A/X

Graphite Quartz

AA Notes 1, 6 Note 1 A A Note 1 A Note 1

Hastelloy B ¨ Titanium

A A Note 1

Inconel 600 ¨

Incoloy 800 ¨

Stainless Steel Stainless

Type 20 Type 316 Stainless Steel Stainless 316 X X XXABAAA X B BBAAAAA XX XXX AX XX XXA AAX XX XXA AAX X C C A A A A A Hastelloy

AABB AA AA A Note 1 BB XX BAAA BB BB AA B A/B Note 1 C X A B A A A Hastelloy B B AAAAAAA BA BAA AAA AX XXA AAX BA AAA AA AAA BB AAB B B BBAAAAA C C C B CC X A B A 6, 8 Notes C B B/X B A B B Note 2 C B BBAAAAA

A/B A/B X X X A A A A/B AA/B A/B A A A A X X AA/B A A A A X X A X X A A A A A Hastelloy

Stainless Steel Stainless

304, 321, 347 321, 304,

Nickel 200 Nickel

Monel 400 ¨

Lead

Copper

Aluminum

Cast Iron NI Resist NI Iron Cast

Cast Iron Grey Iron Cast Iron Steel Iron

XX XXXBB X Ignition

¡ Auto F ¡

W A T L O W O L T A W Point

¡ Flash F

None 548 Refined Point

¡ Boiling F ¡ B.P. F.P. A.I. 2912 Corrodant 2%10–30%, 210°F76%, 180°FDryWet(Monochloroacetic Acid) 372 B B -30 A -30 X X B B X B X X B A X X A X B X X X A X B X A B A X A X X B X X X X X B X C X C/X X X Chromic Acetate Chromic AcidChromium PlatingChromylite Citric AcidClear Chromate Cobalt Acetate at 130°FCobalt Nickel Cobalt PlatingCoconut Oil X XCod Liver Oil X CCopper Acid X XCopper Bright X X XCopper Bright Acid B B XCopper Chloride X X X 420 Crude XCopper Cyanide X C C X Copper Fluoborate 412 X CCopper Nitrate X BCopper Plating B BCopper Pyrophosphate B C Copper Strike A Copper Sulfate B A A X X A A C/X X A A C X X X X X A A X X X X C X X A X A B B A X X B B X X A/B B C/X A X X A B A Chlorine Gas: Chloroacetic Acid Carbolic Acid (Phenol)Carbon Dioxide–Dry Gas 362Carbon Dioxide–Wet Gas 175 1319Carbon Tetrachloride BCarbonic Acid BCastor Oil B BCaustic Etch XCaustic Soda (Lye) B X B(Sodium Hydroxide) 359 X B X 175 A 1319 X C A C C A 595 A X C 445 B X X A 840 B C A C A A X C A/B A A C X A A/B C A A/B C A A A A/B X A A C X A A A A/B X X X X X C C A A X A Calcium Chloride > B B C B X B B B Application Guide Application Data Reference Application Guide Reference Data B ¨ 800 600 400 ¨ ¨ ¨ ¨ Corrodant Boiling Point Flash Point Auto Ignition Comments B.P. F.P. A.I. Nickel 200 304, 321, 347 Stainless Steel 316 Stainless Steel Type 20 Stainless Steel Incoloy Inconel Titanium Hastelloy Iron Steel Cast Iron Grey Cast Iron NI Resist Aluminum Copper Lead Monel ¡F¡ ¡F¡ ¡F¡ Quartz Graphite Teflon Creosote 392 165 637 A B B C B X B B B B B B B A A Note 2 -482 Cresylic Acid (Cresol) 376 110 C C C C X B B B A A CBBBAAANote 2 -397 Deionized Water X X X X A A A A A A A Note 11 Deoxidine™ A TM: Amchem Products, Inc. Metal cleaner, rust remover Deoxylyte™ A TM: Amchem Products, Inc. Deoxidizer (Etching) A Note 1 Deoxidizer (3AL-13) A A Note 1 Non-Chrome Dichromic Seal X X Diethylene Glycol 474 255 444 B A B B A B B A AA BBA AAA Diphenyl 300°F–350°F 491 235 1004 A A A A A A A A A A ABB Disodium Phosphate A BA Diversey™–DS9333 A Note 1 TM: Diversey Chemical Co. Diversey™ 99 A Diversey™ 511 A Notes 1, 5 Diversey™ 514 A A Note 1 Dowtherm™ A A TM: Dow Chemical Co. Heat transfer agent Dur-Nu™ A A Note 1, 5 TM: The Duriron Co., Inc. Electro Cleaner A A Note 1 Electro Polishing A Note 1 Electroless Nickel A A Note 1 Electroless Tin (Acid) A Note 1 (Alkaline) A A Note 1 Enthone Acid–80 A A Note 1 Ether 94 -49 356 B B B B B B B B B A B B A A Note 2 Carpenter 20 Acceptable Ethyl Chloride (No Water) 54 -58 966 B B B A B B A B B A BAABAAANote 2 Ethylene Glycol 387 232 775 A B A B X B B B B B BBAAAAANote 5 Hastelloy® C-276 Acceptable Fatty Acids X X A C/X X B B C/B A A BBAAAAA Carpenter 20 Accep., Hastleloy® C-276 Accep. Ferric Chloride 606 X X X X X X X X X XX XXACAAA Ferric Nitrate X X X X X X B B A X X X A A A Carpenter 20 Acceptable Ferric Sulfate X X X X X A/B X C B BBCCAXAAA Fluoborate A A Note 1 Fluoborate (High Speed) A Note 1 Fluorine Gas, Dry -305 C X C/X X X A A C A/C A/C C A A B C X X Formaldehyde 27 122 806 X X B B B X B B A AA BBA AAA 185 Formic Acid 213 156 1114 X X X B X C C X C A B C X A A A A Carpenter 20 Accep., Hastelloy® C-276 Accep. Freon A A A A A A A A A AA AA Fuel Oil–Normal A A A/B A A B B A/B A/B A B B A B A A Notes 2, 3, 7 CONTINUED

148 Reference Data 149 CONTINUED C-276 Acceptable ® Protective coating, clear finish for all metals. Div,. Chromate treatment for ferrous and non-ferrous metals.

Comments

Hastelloy

Teflon ¨

Graphite Quartz

A AA A 1 Note A 1 Note Div., TM: Allied-Kelite Products A A 1 Note

Hastelloy B ¨ Titanium

A AA A Note 1 A Notes 1, 5

Inconel 600 ¨

Incoloy 800 ¨

Stainless Steel Stainless

Type 20 Type 316 Stainless Steel Stainless 316

XX XXX AA XX XXX AAA X C/XXC XXXB XA X X X XA XX XXXC C X A A Note 5 AAA AA Note 1 A A A A A AB A B A BB Note 1 A 2 Note 2 Note AAA BB BBACAXA A Note 1 TM: Allied-Kelite Products B AA A CB C A BA A A AAAAAAA B X X B A B A A A A Notes 2, 5 2, 3, 7 Notes A Carpenter 20 Acceptable Notes 2, 3, 5 Carpenter 20 Acceptable

Stainless Steel Stainless

304, 321, 347 321, 304,

Nickel 200 Nickel

Monel 400 ¨

Lead

Copper

Aluminum

Cast Iron NI Resist NI Iron Cast

Cast Iron Grey Iron Cast

Iron Steel Iron Ignition

¡ Auto F ¡

W A T L O W O L T A W Point

Flash F

¡ Point

¡ Boiling F ¡ B.P. F.P. A.I. >65%>65% B X X X X X X C X X X X X C X X Corrodant Hot <65% X X X X C X X Dichromate <150°F>150°FCold<65% X X X X X X X X X X X X X X X X X X X X X X C X X X #4-C, #4PC & S, #4P-4, #4-80, #4L-1, #4-2, #4-2A, #4-2P, #5P-1, #7-P, #8, #8-P, #8-2, #12-P, #15, #17P, #18P #40, #80 # 4-73, #14, #14-2, #14-9, #18-P Houghtone Mar Tempering SaltHydrocarbons–AliphaticHydrocarbons–AromaticHydrochloric Acid (No Air)Hydrocyanic Acid (No Air) AHydrofluoric Acid 78 A A C 0 A -120 100 A A X A 67 X A A A B A X A A X A B B C B Fuel Oil–AcidGasoline–RefinedGasoline–SourGlycerine (Glycerol) 280±Gold–Acid -45Gold–Cyanide 495 554Grey Nickel 320 A AHoldene 310A 739 A BTempering Bath A/B A/B A CHot Seal Sodium B B B A X B X A B C A C X A X A A C C C A C A X C X B A A Iridite™ #1, #2, #3, Iridite™ Dyes–#12L-2, Irilac™ Hydrogen PeroxideIndiumIridite™ #4-75, 3632 X X X A X X C B B Application Guide Application Data Reference Application Guide Reference Data B ¨ 800 600 400 ¨ ¨ ¨ ¨ Corrodant Boiling Point Flash Point Auto Ignition Comments B.P. F.P. A.I. Nickel 200 304, 321, 347 Stainless Steel 316 Stainless Steel Type 20 Stainless Steel Incoloy Inconel Titanium Hastelloy Iron Steel Cast Iron Grey Cast Iron NI Resist Aluminum Copper Lead Monel ¡F¡ ¡F¡ ¡F¡ Quartz Graphite Teflon Iron Fluoborate A A Note 1 Iron Phosphate (Parkerizing) C B A A Isoprep™ Deoxidizer Note 1 TM: Allied-Kelite Products #187, #188 A Div., Cleaners and surface preparation materials. Isoprep™ Acid Aluminum Cleaner #186 A Note 1 Isoprep™ #191 Acid Salts A A Note 1 Isopropanol (Isopropyl Alcohol) 180 53 750 C B A A A A A/B A A B A A Jetal™ A Note 1 TM: Technic Inc. Blackening Salt Kerosene 347 100 444 A A A A A A A A A A A B B A A Note 2 617 165 Kolene™ A TM: Metal Processing Co., Kolene process–metal cleaning Lacquer Solvent B A A A B A B B A A A B B A A Note 2 Lead Acetate X X X X X A A A/B A/BA/BAAABAAA Lead Acid Salts A Note 1 Lime Saturated Water B B X B X B B B AB BB XA Linseed Oil 649 432 650 X A B B X B B A A A BBBBAXANote 2 Raw 403 Boiled Magnesium Chloride 2574 X C B X B X B A B BA/BBAAAAAA Carpenter 20 Accep. Hastelloy® C-276 Accep. Magnesium Hydroxide A A A B A A B A A A A AAAAAAA Hastelloy® C-276 Acceptable Magnesium Nitrate B B B B C B B B B B BXBBAAA Magnesium Sulfate B B B B B A A A B B A/B B A A/B A A A MacDermid™ M629 A A Note 1 TM: MacDermid, Inc., Acid Salt–Contains Fluoride Mercuric Chloride 579 X X X X X X X X X B/XX XXBXAAA Mercury 674 A A A X X X B B B A A A B X B A A A Hastelloy® C-276 Acceptable Methyl Alcohol (Methanol) 149 52 867 B B C B B A A B A/B A/BBAAAAAANote 2 Hastelloy® C-276 Acceptable Methyl Bromide 38 None 998 C C X B B B B A AA BBA AAA Methyl Chloride -11 <32 1170 C C X A C C C C C C C C A B A A A Carpenter 20 Acceptable Methylene Chloride 104 1224 X C C C B C B C B A C B A C A A A Carpenter 20 Acceptable Mineral Oil 500 A A A/B A A A A A A/BA AAAAAAA Muriato A A Note 1 Naptha 300 100 900 A B B A A A A A A A A AAABAAA 421 950 Napthalene 424 176 979 A A A B B A B B A A A BBAB AA Nickel Acetate Seal A A Note 1 CONTINUED

150 Reference Data 151 CONTINUED Compounds for cleaning surface heating. Corrosion Res. Coating Industries Inc., Degreasing solvent and cleaning compound. Comments Carpenter 20 Acceptable TM: Parker Div., OMI Corp., TM: Detrex Chemical

Note 1 TM: Oakite Products Inc., Note 1

Teflon

X 9 Notes 1, 5,

Graphite Quartz

A A Notes 1, 5

Hastelloy B ¨ Titanium

A AA A A Notes 1, 5 A Notes 1, 5

Inconel 600 ¨

Incoloy 800 ¨

Stainless Steel Stainless

Type 20 Type 316 Stainless Steel Stainless 316

XX XXX AAA X B X B X B A A A Cupro Nickel Acceptable X B A B X C A A Tantalum Acceptable B B CBC XAAA AAA A A A A X A Note 1 A A AB A Note 2 BABBAAA A Note 1 AA AB B BAABAAA B A AA Notes 2, 7 Notes 1, 2 AA AA A Notes 2, 3, 7 BB A XA AA X Notes 1, 5, 9 X Notes 1, 5, 9 CB XXBXAXA C A A Note 1 CB AA AAXC C C C B B C A A A Notes 1, 5

Stainless Steel Stainless 304, 321, 347 321, 304,

347

Nickel 200 Nickel

Monel 400 ¨

Lead

Copper

Aluminum

Cast Iron NI Resist NI Iron Cast

Cast Iron Grey Iron Cast Iron Steel Iron

BB CBBAA B Ignition

¡ Auto F ¡

W A T L O W O L T A W Point

¡ Flash F

None Point

¡ Boiling F ¡ B.P. F.P. A.I. > 500°F>1000°F A X A A X X X X X X X X X A A Corrodant CrudePure <45%>45% Cold>45% Hot X C X X X X C X X C X X X C X B X B C X C C B C X C X C X C A X C X Petroleum–Crude < 500°F B B A A C C A C A Perm-A-Chlor™Phenol (See Carbolic Acid) Phosphate Phosphate CleanerPhosphatizing Phosphoric Acid A A Oakite™ #20, 23, 24, 30, 51, 90Oleic AcidOxalic AcidPaint Stripper (High Alkaline Type)Paint Stripper (Solvent Type) 680 372Paraffin 685Parkerizing™ C(See Iron Phosphate) C CPerchloroethylene C A C X A B X X B 250 X C B B X C B X A A A A B A Nickel ChlorideNickel Plate–BrightNickel Plate–DullNickel Plate–Watts Solution 1808Nickel SulfateNickel Copper Strike (Cyanide Free)Nitric AcidNitric Hydrochloric Acid X XNitric 6% Phosphoric Acid XNitric Sodium Chromate X XNitrobenzene COakite™ #67 C 187 X X X X A X X 412 X X 190 A B X 900 B X X A C X X A B X X A X X A B X X B X X X X A A C A A A Application Guide Application Data Reference Application Guide Reference Data B ¨ 800 600 400 ¨ ¨ ¨ ¨ Corrodant Boiling Point Flash Point Auto Ignition Comments B.P. F.P. A.I. Inconel Titanium Hastelloy Nickel 200 304, 321, 347 Stainless Steel 316 Stainless Steel Type 20 Stainless Steel Incoloy Iron Steel Cast Iron Grey Cast Iron NI Resist Aluminum Copper Lead Monel ¡F¡ ¡F¡ ¡F¡ Quartz Graphite Teflon Photo Fixing Bath C A Picric Acid >572 302 572 X X X X X X X B BBCC AAA Ex- plodes Potassium Acid Sulfate A A Note 1 Potassium Bichromate C B B B B B B A A A B BAAAA (Potassium Dichromate) 347 Potassium Chloride C X B X C C B B C B A C B A C A A A Carpenter 20 Acceptable Potassium Cyanide C X B X X X C B B BB BBXBACA Potassium Hydrochloric A A Note 1 Potassium Hydroxide 2408 X X X C X B A C CC CBXBXAA Potassium Nitriate (Salt Peter) B B B A B B B B B B B BBA XAAA Potassium Sulfate C C C A B A A B A A A BBACAAA Prestone™ 350°F A A TM: Union Carbide Corp., Anti-freeze/coolant R5 Bright Dip for Copper Polish at 180°F Reynolds Brightener A A Note 1 Rhodium Hydroxide AA Rochelle Salt Cyanide A A Note 1 Ruthenium Plating A A Note 1 Sea Water X X A X X A A C C A BBACAAA Silver Bromide X X X X C C X XC A AAA Silver Cyanide C C X X B A A A A AAAAA Silver Lume A Note 1 Silver Nitrate 831 X X X X X X X C C B C C A C A A A Hastelloy® C276 Acceptable Soap Solutions A A A X C A A A/B A/B A/B A B A A Note 3 Sodium–Liquid Metal C X X X X B A A AA XX Sodium Bisulfate X X X C B C C B X X A B C B A A Carpenter 20 Acceptable Sodium Bromide 2534 B C X B B B B C B B BBBCAAA Sodium Carbonate C C X A X B B B B A BBABCAA Sodium Chlorate X X B A B A A B B B B A A X A A A Cupro-Nickel Acceptable Sodium Chloride 2575 C X B X B B A B X X C B A C C A A A Cupro-Nickel Acceptable Sodium Citrate X X X X X C B B B ABAAA Sodium Cyanide 2725 A B C X X X C C A AA AACBACA Sodium Dichromate (Sodium Bichromate) B B B C X B BB CXAAA Sodium Disulfate X X C C C C X XB CC AA Sodium Hydroxide (See Caustic Soda) Sodium Hypochlorite X X X X X X X X X X B X X A A/X A C/A A Hastelloy® C276 Acceptable Sodium Nitrate B B A C C C B B A A A AAACAAA Sodium Peroxide B A B C X X B B B BB B C A CONTINUED

152 Reference Data 153 CONTINUED C-276 Acceptable ® Chemical to produce anti-galling coatings. Heat transfer fluid. Corp., Bright acid tin plating process. Comments TM: Amchem Products, Inc. Co., TM: Monsanto Hastelloy

Note 1

Teflon ¨ Graphite

A A Note 1 Quartz

A A 1 Note A A Note 1 TM: The Udylite Co., OMI

Hastelloy B ¨ Titanium

A A A 1 Note

Inconel 600 ¨

Incoloy 800

AA AA

Stainless Steel Stainless

Type 20 Type 316 Stainless Steel Stainless 316 XC CBXBAXA AA XX XBXB XB BXXA AA XC XXXC AA XX XX CA X X X X X X X X 4 Note

A A AB B A AAA XAAA ABBCCAXAAA A A A Note 7 BB XC AA A A BAABAAA BB AAA B ABBB AA A B X X A X X Note 4 A B BAABAAA B B BBA ABB BB A AAA A A A A C ABB A A Note 4 AA A B B AABA A AA/BBBBAAAA CBCXXA AA CC CC C CB CAB AA C C CCCCCAA

A/B B B B C B A A A

Stainless Steel Stainless

304, 321, 347 321, 304,

Nickel 200 Nickel

Monel 400 ¨

Lead

Copper

Aluminum

Cast Iron NI Resist NI Iron Cast

Cast Iron Grey Iron Cast

Iron Steel Iron Ignition

¡ Auto F ¡

W A T L O W O L T A W Point

Flash F

¡ Point

¡ Boiling F ¡ B.P. F.P. A.I. HotHotHot X X X X C X X X X X X X X X X X B X C C X X X X X Corrodant 10–75% Cold75–95% Cold X B B X B B X B B C B C X X X B 500–1000°F>1000°F<10% Cold C X C C X C X C X A X X X A X C A B B C X Steam <500°FStearic AcidSugar SolutionSulfamate Nickel SulfurSulfur Chloride 721Sulfur Dioxide 385Sulfuric Acid 743 A/B C C 280 C A/B 245 A/B C C 453 X A 832 14 405 X X A A 626 B 450 X A/B A C B C X X C A X C A B A C A X X C A C X A B C C C A C B C X X C Sodium PhosphateSodium SalicylateSodium SilicateSodium StannateSodium SulfateSodium SulfideSolder BathSoybean OilStannostar™ C C B B X C B B A B C 540 B A 833 C A B C C X B B C B C B X X B A C/B C B A B C X B B X X B A A B X B B B X C/X B A B X X X X X X A/B Therminol™ FR1–Non Flowing Tin (Molten)Tin-Nickel Plating Tin Plating–Acid Tin Plating–Alkaline A B B A X X X X X B A FumingSulfurous AcidTannic AcidTarTartaric AcidTetrachlorethylene (See Perchloroethylene) Thermoil Granodine™ 390 980 C 410 X C 802 X C X C/X C C C X X X B X C X C A B C X X X A/B X C C X B X X C B A/B B C A/B Application Guide Application Data Reference Application Guide Reference Data B ¨ 800 600 400 ¨ ¨ ¨ ¨ Corrodant Boiling Point Flash Point Auto Ignition Comments B.P. F.P. A.I. Inconel Titanium Hastelloy Nickel 200 304, 321, 347 Stainless Steel 316 Stainless Steel Type 20 Stainless Steel Incoloy Iron Steel Cast Iron Grey Cast Iron NI Resist Aluminum Copper Lead Monel ¡F¡ ¡F¡ ¡F¡ Quartz Graphite Teflon Toluene 231 40 947 A A A A C A A A A A A A A A A A A Hastelloy® C-276 Acceptable Triad Solvent C Trichloroethane A C C B B B B B A BB BBA AA Trichloroethylene 165 None BCCBCXCC B B B BAAAAAA Hastelloy® C-276 Acceptable Triethylene Glycol 556 350 700 A A A A A A A A A AA AAA A Trioxide (Pickle) A A Note 1 Trisodium Phosphate A A X C X C C C CC CXBX Turco™ 2623 A TM: Turco Products, Div., Purex Corp., Ltd. Turco™ 4008, 4181, 4338 A Note 1 Turco™ Ultrasonic Solution A Note 1 Turpentine Oil 309 95 488 C C C A B A A A A A A ABB AA -338 Ubac™ A Note 1 TM: The Udylite Co., OMI Corp., High leveling acid copper bath. Udylite #66 A A A Notes 1, 5 Unichrome™ CR-110 A A Note 1 TM: M & T Chemicals Inc., Plating Process, supplies and equipment. Unichrome™ 5RHS A A Note 1 Vegetable Oil 610 C C B X X A A A AAAABAA Vinegar C C A B A/B B A B A A Water (Fresh) X C A A A A A A C CA AAA AA Water (Deionized) (See Deionized Water) Water (Sea) (See Sea Water) Watt’s Nickel Strike A Note 1 Whiskey and Wines X C A A A A A A AAAA AA Wood’s Nickel Strike A Note 1 Yellow Dichromate A A Note 1 X-Ray Solution A Zinc (Molten) 1664 X X X X X X XX XXX X Zinc Chloride 1350 C C C X X B B B X XB XBCBAAA Zinc Phosphate A X Notes 1, 5 Zinc Plating Acid A Zinc Plating Cyanide A A Note 1 Zinc Sulfate C X A C B A B C C CC BAC AA Zincate™ A A Note 1 TM: Ashland Chemical, Alkaline salt for immersion zinc plating aluminum.

154 W A T L O W

Application Guide Reference Data Ref. 139 Shape Factor for Radiant Application Energy Calculations 1.0 10.0 4.0 0.7 2.0 0.5 0.4 1.0

0.3 0.6

0.2 0.4 N

0.1 0.2 Reference Data 0.07 Shape Factor F 0.05 0.1 0.04

0.03

0.02

0.01 0.1 0.2 0.3 0.4 0.5 1 2 3 4 5 10 20

M For Two Heated Length Heated Width Facing Panels: N = M = ( Distance to Material) ( Distance to Material)

Ref. 140

Radiation Energy Transfer Between Uniformly, Equally Spaced Parallel Surfaces (Planes and Concentric Cylinders) 2000

100 W/in2 90 W/in2 1800 80 W/in2 70 W/in2 60 W/in2 1600

50 W/in2

40 W/in2 1400

30 W/in2 1200

20 W/in2 1000 Heater Surface Temperature—°F 10 W/in2 800 2

0 W/in 5 W/in2 600 0 200 400 600 800 1000 1200 1400 1600 1800 2000 Load Temperature—°F

155 Application Guide Reference Data Cabinet Freeze Protection Ref. 141 Controller Examples of Applications Objective An insulated steel cabinet located outdoors on a concrete pad contains an electronic control system for out- door signaling equipment. The cabinet is three feet wide, two feet deep and four feet high with a two-inch thickness of insulation applied to the Power outer surfaces. Under the worst conditions the cabinet is exposed to temperatures of -20°F and 20 MPH winds. The objec-tive is to provide Heater heating to maintain the electrical equipment above the freezing temperature. The control system normally consumes 75 watts of power but must be protected even when not in operation. A terminal strip within the cabinet provides 120 volt, single- phase power. Power Requirements For this application, we only need to be concerned with how much power Determine Thermal System Heat Losses is required to make up the cabinet’s a. Conduction. Heat losses through the concrete base are negligible using heat losses. The heat losses are Equation 3A, (Page 17). continuous assuming a worst case situation (-20°F and 20 mph winds). b. Combined convection and radiation—losses from exposed surfaces— From Equation 3D, (Page 18).

QL4 = A • FSL • te

= (6624 in2) • (0.03 W/in2) • (2.75) • (1 hr)

QL = 546 Wh where: A = the exposed surface area = 2 ft • 3 ft + 2 • (3 ft • 4 ft) + 2 • (2 ft •4 ft) = 46 ft2 = 6624 in2 ∆T = temperature difference = 32°F - (-20°F) = 52°F

FSL = the heat loss coefficient for 2 inch insulation at ∆T= 52°F from Ref. 12, page 28 = 0.03 W/in2 multiplied by the wind velocity correction factor at 20 mph (2.75 from Ref. 16, Page 29). Since Ref. 12, Page 28 is based on 70°F ambient rather than -20°F, find the coefficient at an equivalent temperature of 122°F

te = the exposure time = 1 hour

156 W A T L O W

Application Guide Reference Data Calculate Operating Power Requirements From Equation 5, (Page 18) using a 10 percent safety factor, Examples of Applications Continued Q + Q Q Operating Power = B D + L • (1 + S.F.) [ tc te ]

546 Wh = • 1.1 = 601 W 1 hr where:

QB = 0 Re f QD = 0

QL = 546 Wh erence Data tc = assume 1 hour te = 1 hour

Cabinet Freeze Protection Power Evaluation Ref. 142

750

10% Safety Factor 500 Power (Watts) QL Radiation and Convection 250 Losses

Continuous Process (No Start-up) Time (Hours)

Heater Recommendation Control A flexible silicone rubber heater six This application requires only very inch X 20 inch rated at 600 watts, 120 simple control to ensure the insulated volts mounted near the bottom of the steel cabinet maintains a preset cabinet provides a simple and temperature above freezing. A Watlow inexpensive solution for enclosure basic controller preset to 40˚F will heating. The heater may be ordered protect the cabinet above the freezing with a pressure sensitive adhesive point. surface for easy mounting.

157 Application Guide Reference Data Heating a Steel Mold Ref. 143 Examples of Applications T/C Sensors Upper Mold Continued Temperature Contoller and Objective Power Switching Device A mild steel compression mold is 15" 10" 2" used to form plastic parts. Two- Upper Platen ounce charges of plastic at room temperature are inserted at a rate Mold 6" of 30 per hour. The steel mold is Mold six inch X nine inch X six inch overall 9" 6" and is placed between two steel Lower Platen platens, each 10 inch X 15 inch X two 2" inch. The platens are insulated from 1 Lower Mold the press with ⁄2 inch thick rigid Temperature Contoller and insulation board. The mold must be To Heaters Power Switching Device To Power pre-heated to 350°F in 45 minutes and Fusing while closed. Room temperature is 70°F. Power Requirements Step 1: Initial Heating of the Mold and Platens The following steps illustrate the calculations to estimate the power in From Equation 1, (Page 16). watts needed for initial heating and to w • Cp • ∆T maintain the operating temperature. QA = 3.412

• • • = (263 lbs) (0.12 Btu/lb °F) (280°F) 3.412 Btu/Wh = 2590 Wh where: w = weight of mold and platens = volume (in3) x density (lbs/in3) = [(6 in. • 9 in. • 6 in.) + 2 (10 in. • 15 in. • 2 in.)] (0.284 lbs/in3) = 263 lbs

Cp = specific heat of steel = 0.12 Btu/Ib • °F ∆T = temperature rise = 350°F - 70°F = 280°F

158 W A T L O W

Application Guide Reference Data Step 2: Heating of Plastic During the Operating Cycle From Equation 1, (Page 16). Examples of Applications Continued (0.125 lbs) • (0.4 Btu/lb • °F) • (280°F) QB = 3.412 Btu/Wh = 4.1 Wh

where: w = weight of plastic charge = 2 oz. = 0.125 lb

Cp = specific heat of plastic = 0.4 Btu/lb • °F ∆ T = temperature rise = 280 °F Re f erence Data Step 3: Heat Required to Melt or Vaporize Materials During Initial Heating Not required since plastic is not present during initial heat-up.

QC = 0

Step 4: Heat Required to Melt or Vaporize Materials During the Operating Cycle Not required since the plastic does not change phase during the molding operation.

QD = 0

Step 5: Determine Thermal System Heat Losses Energy is required to replace heat lost to conduction, convection and radiation: a. Conduction losses through the insulated surfaces From Equation 3A, (Page 17).

K • A • ∆T • te QL1 = 3.412 • L (5.2 Btu • in./ft2 • °F • hr) • (2.08 • ft2) • (280°F) • (1 hr) = (3.412 Btu/Wh) • (0.5 in.) = 1775 Wh

where:

1 K = the thermal conductivity of ⁄2 inch rigid insulation board = 5.2 Btu • inch/hr • ft2 • °F A = The total insulated surface area 2 • (10 • 15) in2 = 2.08 ft2 = 144 in2/1ft2 ∆T = the temperature differential between the heated platen and the outside insulation at ambient= 350°F - 70°F = 280°F L = the insulation thickness = 0.5 inch

te = exposure time = 1 hour 159 Application Guide Reference Data b. Convection losses From Equation 3B, (Page 17). Examples of Applications • • • Continued QL2 = A FSL CF te Sides:

QL2 = (180 in2 + 200 in2) • (0.64 W/in2) • (1 hr) = 243 Wh

where:

FSL = the surface loss factor for a vertical surface at 350°F is 0.64 W/in2 from Reference 9, (Page 26)

A1 = mold side area = 2 • (6 in. • 6 in.) = 2 - (6 in. • 9 in.) = 180 in2 A2 = platen side area = 4 • (2 in. • 10 in.) + 4 • (2 in. • 15 in.) = 200 in2 CF = correction factor = 1.0 te = exposure time = 1 hr

Bottom (of the top platen): QL2 = (96 in2) • (0.64 W/in2) • (0.63) • (1 hr) = 39 Wh where: A = exposed platen area = (10 in. •15 in.) - (6 in. • 9 in.) = 96 in2 FSL = 0.64 W/in2 CF = the correction factor for bottom surfaces (0.63 from Reference 9, Page 26) te = exposure time = 1 hr

Top (of the bottom platen): QL2 = (96 in2) • (0.64 W/in2) • (1.29) • (1 hr) = 79 Wh where:

CF = the correction factor for top surfaces (1.29 from Reference 9, Page 26)

160 W A T L O W

Application Guide Reference Data c. Radiation losses From Equation 3C, (Page 17) Examples of Applications Continued QL3 = A • FSL • e • te = (572 in2) • (1.3 W/in2) • (0.75) • (1 hr) = 558 Wh where: A = the total surface area of mold sides, platen sides and exposed platen top and bottom is 572 in2

FSL = the blackbody radiation loss factor at 350°F is 1.3 W/in2 from Reference 9 (Page 26) Re e = the emissivity of mild steel with a medium oxide finish f (0.75 from Reference 10 (Page 27) erence Data

te = exposure time = 1 hr

d. Total heat losses From Equation 3E, (Page 18) Conduction 1775 Wh Convection–sides 243 Convection–bottom 39 Convection–top 79 Radiation 558 Total QL 2694 Wh

Step 6: Calculate Start-Up Power Requirements Start-up power is required for initial heating of the mold and platens, to compensate for losses during start-up plus a 10 percent safety factor. From Equation 4, (Page 18)

Q + Q 2 Q Start-Up Power = A C + L • (1 + S.F.) [ ts 3 ( te )]

2590 Wh 2 2694 Wh = + • (1.1) [( 0.75 hr ) 3 ( 1 hr )]

= 5774 watts where:

QA = initial heating of mold and platens = 2590 Wh

QC = latent heat = 0 QL = heat losses = 2694 Wh ts = start-up time = 0.75 hours te = exposure time for losses = 1 hr S.F. = safety factor = 10% 161 Application Guide Reference Data Step 7: Calculate Operating Power Requirements Operating Power is required to heat each plastic charge and to compensate Examples of Applications for operating losses. From Equation 5, (Page 18) using a 10 percent safety factor, Continued

Q + Q Q Operating Power = B D + L • (1 + S.F.) [ tc te ]

4.1 Wh 2694 Wh = + • (1.1) [( 0.0333 hrs ) ( 1 hr )]

= 3099 watts where:

QB = Heating of plastic during operation = 4.1 Wh QD = Latent heat = 0 QL = Heat losses = 2694 Wh tc = Cycle time at 30 charges per hour = 0.0333 hrs te = Exposure time for losses = 1 hr S.F. = Safety factor = 10%

Heating a Steel Mold Power Evaluation Ref. 144

6000 10% Safety Factor 5000 2 /3 QL Losses 4000

3000 10% Safety Factor Power (Watts)

2000 QA Heating Molds Q and Platens L Losses 1000

QB = Heating Plastic During Operating Cycle

12 Start-up Time (Hours)

162 W A T L O W

Application Guide Reference Data Hole Fit and Watt Density should be derated to 126 W/in2 using 1 1 A normal tolerance for a ⁄2 inch drilled a 0.7 multiplier. The recommended ⁄2 Examples of Applications hole is ±0.005 inch; and the diameter inch X six inch, 1000 watt heaters are Continued 1 2 of a standard ⁄2 inch FIREROD car- rated at 117 W/in which is within Heater Recommendation tridge heater is slightly undersized the maximum of 126 W/in2 for this Heating capacity is determined at 0.496 inch ±0.002 inch. Therefore application. Therefore the heaters are by either the start-up power require- the worst-case clearance or “fit” is conservatively rated and should yield ment or the operating power needed, 0.011 inch (0.505 – 0.494 inch). extended life. whichever is larger. In this case, a Assuming close temperature control minimum of 5700 watts is required. with frequent on-off cycling of the Heater selection is dictated by a heater, the maximum watt density number of factors including efficiency, Reference Data even heat distribution, watt density Environmental Factors to protect against contamination. Both and availability. The biggest single cause of heater are effective at 400°F. For higher Since heating efficiency is optimized failure is contamination. This contam- temperature applications MI lead by heating the mold from within, six ination can come from many sources assemblies are available. cartridge heaters inserted into holes such as lubricating oil, cleaning sol- In addition, stainless steel hose, drilled in the molds are recommend- vents, plastic material or fumes, or- 1 stainless steel braid or galvanized ed. The heaters are stock ⁄2 inch ganic tapes, etc. As a heater cools BX conduit may be ordered with diameter X six inch length FIREROD® down, it “inhales” these contaminates. the heaters to protect the leads heaters rated 1000 watts at 240 volts. Upon reaching the heated zone, the against abrasion. Either right angle Three heaters each in the top and contaminates carbonize causing or straight terminations are available bottom molds should be arranged to electrical arcing and failure. for wiring convenience. surround the cavity. Holes will be drilled completely through the mold to The heaters may be specified with ® facilitate heater removal. a Teflon seal or with silicone rubber potting in the lead end of the heater

Control separate power switching device for The heaters may be controlled indi- each, will do the job. The Watlow vidually, or as a group, depending SERIES SD with a DIN-A-MITE® power on the need for precision in tempera- controller is the recommended control ture and heat distribution. The plastic solution. The SERIES SD offers auto- molding material itself and the config- tuning or manually-set PID values, as uration of the molded part will dictate well as a configurable alarm output. the level of temperature precision Two SERIES SDs, with switched DC and heat distribution precision neces- output, in conjunction with two Watlow sary. A Type J thermocouple is used DIN-A-MITE controllers control the as standard sensor for plastics heaters. molding. This application demands narrow temperature control. Two PID temperature controllers, one for the top and one for the bottom, plus a

Teflon® is a registered trademark of E.I. du Pont de Nemours & Company. 163 Application Guide Reference Data Melting of Aluminum Ref. 145 Examples of Applications

Continued Backup Insulation Objective C.F. Insulation Board Primary Control Thermocouple in Protective Tube Design a furnace to melt at least Crucible Molten Aluminum Heater Surface Control 250 lbs of aluminum ingots per hour Thermocouple and raise the crucible, furnace and Insulated Cover aluminum to a working temperature Temperature Controllers of 1350°F in five hours using ceramic fiber heaters. The aluminum is held in a 1000 Ib capacity silicon carbide crucible. The crucible is 26 inches in diameter at the top, 18 inches in 120VAC 1 ¯ diameter at the bottom and 24 inches Control in height. Wall thickness is two inches. Power In The crucible rests on a silicon carbide pedestal four inches thick. The Power Controllers crucible and pedestal together weigh Heated 300 lbs. Ambient temperature is 70°F. Silicon Carbide Pedestal Poured Ceramic Hearth Area 3 ¯ Load Power In Furnace Construction Ceramic Fiber Heater Load Power C.F. Insulation Board To Heaters The inside diameter of the furnace Limit Controller should be 30 inches, that is, an air gap between furnace wall and crucible of two inches, or four inches Step 1: Initial Heating and Melting of Aluminum, Initial Heating larger than the crucible diameter. of Crucible and Furnace Ceramic fiber heaters include two inch thick insulation and are sur- a. Aluminum from ambient to 1080¡F, the melting temperature rounded by four inches of additional of a typical aluminum alloy back-up insulation. The overall Using Equation 1, (Page 16) diameter is 42 inches. Total furnace w • Cp • ∆T height is 34 inches allowing 24 inches QA = for the crucible, four inches for the 3.412 pedestal, two inches for a hearth and (1000 lbs) • (0.24 Btu/lb • °F) • (1010°F) = four inches for the cover. Approxi- 3.412 Btu Wh mately 20 cubic feet of insulating = 71,043 Wh material is included. The chassis shell 1 is constructed of ⁄8 inch thick steel. where: Power Requirements w = aluminum weight = 1000 lbs

The following steps illustrate how to Cp = specific heat of solid aluminum calculate the power in watts needed = 0.24 Btu/lb • °F for initial heating of the aluminum, ∆T = temperature rise = 1080°F - 70°F = 1010°F crucible and furnace assembly. Also, the power required to maintain the holding temperature, and the power required to melt 250 lb/hr of aluminum on a continuous basis.

164 W A T L O W

Application Guide Reference Data b. Heat required to melt the aluminum during start-up From Equation 2, (Page 16) Examples of Applications w • Hf Continued QC = 3.412 (1000 lbs) • (167 Btu/Ib) = 3.412 Btu/Wh = 48,945 Wh where: w = weight of aluminum = 1000 lbs

Hf = aluminum heat of fusion = 167 Btu/lb Re f erence Data c. Aluminum from 1080¡F to the casting temperature of 1350¡F w • Cp • ∆T QA = 3.412 (1000 lbs) • (0.26 Btu/lb • °F) • (270°F) = 3.412 Btu/Wh = 20,574 Wh where: w = weight of aluminum = 1000 lbs ∆T = 1350°F - 1080°F = 270°F

Cp = 0.26 Btu/lb • °F for molten aluminum

d. Crucible and pedestal (300 lbs) • (0.19 Btu/lb • °F) • (1380°F) QA = 3.412 Btu/Wh = 23,054 Wh where: w = weight of crucible and pedestal = 300 lbs

Cp = specific heat of silicon carbide used = 0.19 Btu/lb • °F ∆T = 1450°F - 70°F = 1380°F (From experience, the average crucible temperature will be about 100°F hotter than the molten aluminum).

165 Application Guide Reference Data e. Insulation T1 + T2 w • C • -70° Examples of Applications p ( 2 ) QA = Continued 3.412 (300 lbs) • (0.27 Btu/lb • °F) • (880°F) = 3.412 Btu/Wh = 20,891 Wh where: density of ceramic fiber insulation = 15 lbs/ft3 w = weight of insulation = volume • density = 20 ft3 • 15 lbs/ft3 • 300 lbs Cp = specific heat of insulation = 0.27 Btu/lb • °F T1 = heater surface temperature = approx. 1700°F from experience. The actual heater temperature is calculated in later paragraphs.

T2 = chassis temperature = 200°F From “Insulation Effectiveness” on page 146 of the Watlow Heaters catalog. Use the graph at 1700°F heater temperature and 6 inch insulation. TA = average insulation temperature T + T = 1 2 = 950°F 2 ∆T = average temperature rise

= TA - 70°F = 880°F

f. Chassis and structure (258 lbs + 200 lbs) • (0.122 Btu/lb • °F) • (130°F) QA = 3.412 Btu/Wh = 2129 Wh where: density of steel = 490 lbs/ft2 = 0.284 lbs/in3

w1 = weight of steel chassis shell = surface area • thickness • density = (7257 in2) • (0.125 in.) • (0.284 lbs/in3) = 258 lbs

w2 = weight of additional steel supports, brackets, mounting pads = 200 lbs (assume)

CP = specific heat of steel used = 0.122 Btu/Ib • F ∆T = temperature rise = 200°F - 70°F = 130°F

166 W A T L O W

Application Guide Reference Data g. Total for initial heating: aluminum to 1080°F = 71,043 Wh Examples of Applications aluminum from Continued 1080°F to 1350°F = 20,574 Wh crucible and pedestal = 23,054 Wh insulation = 20,891 Wh chassis and structure = 2,129 Wh

Total QA = 137,691 Wh Total QC = 48,945 Wh

Step 2: Heating and Melting of Aluminum During Operating Cycle Re

a. Heat aluminum to the melting point f erence Data From Equation 1, (Page 16).

w • Cp • ∆T QB = 3.412 (250 lbs) • (0.24 Btu/lb • °F) • (780°F) = 3.412 Btu/Wh = 13,716 Wh where: w = 250 lbs of aluminum ingots ∆T = 1080°F - 300°F. Aluminum ingots are preheated to 300°F to eliminate moisture on the aluminum ingots.

b. Heat required to melt the aluminum during the operating cycle From Equation 2, (Page 16).

w • Hf QD = 3.412 (250 lbs) • (167 Btu/lb) = 3.412 Btu/lb = 12,236 Wh

c. Heat aluminum from melting point to operating temperature From Equation 1, (Page 16).

w • Cp • ∆T QB = 3.412 (250 lbs) • (0.26 Btu/lb • °F) • (270°F) = 3.412 Btu/Wh = 5,144 Wh

d. Total for operating cycle QB = 13,716 + 5,144 = 18,860 Wh QD = 12,236 Wh

167 Application Guide Reference Data Step 3: Determine Thermal System Heat Losses Power is required to replace heat energy lost from the surfaces of the furnace Examples of Applications by convection and radiation. Using Equation 3D, (Page 18). Continued a. Side losses Experience has shown that during long melting cycles, the internal heater wire temperature rises, which in turn raises the side surface temperatures of the furnace.

QL4 = A • FSL • te = (4486 in2) • (1.0 W/in2) • (1 hr) = 4486 Wh where:

A = side surface area = 42 in. dia • π • 34 in. height = 4486 in2

FSL = surface loss factor for the chassis at 260˚F (an increase of 60˚F during melting) = 1.0 W/in2

te = exposure time for losses = 1 hr

b. Top losses QL4 = A • FSL • CF • te = (1385 in2) • (0.4 W/in2) • (1.29) • (1 hr) = 715 Wh where: A = top surface area = (42. in. dia/2)2 • π = 1385 in2

FSL = surface loss factor for the top surface at 170°F = (170°F from page 146 of the Watlow Heater’s catalog for an inside surface temperature of 1350°F and four inch insulation.) = 0.4 W/in2 (Ref. 9, see Page 26 for oxidized steel)

CF = top surface correction factor of 1.29

te = exposure time for losses = 1 hr

168 W A T L O W

Application Guide Reference Data c. Bottom losses Q = A • F • C • t Examples of Applications L4 SL F e 2 • 2 • • Continued = (1385 in ) (0.95 W/in ) (0.63) (1 hr) = 829 Wh where: A = 1385 in2 (previously calculated)

FSL = surface loss factor for a surface at 250°F = (bottom temperature = 250°F; assume hotter than top or sides due to pedestal and poured ceramic hearth) = 0.95 W/in2 Re f CF = bottom surface correction factor of 0.63 erence Data te = exposure time for losses = 1 hr

d. Open furnace cover losses Opening and closing of the furnace cover to add additional ingots, causes significant power losses. The 22 inch diameter skin of the molten aluminum in a full crucible, the upper edges of the exposed crucible and other surfaces are all sources of heat losses when the cover is open. Assuming the cover is opened and closed several times per hour, we can say that the cover is open for 10 minutes during a one hour period. From Equation 3D, (Page 18).

QL4 = A • FSL • te = (380 in2) • (13 W/in2) • (0.167 hr) = 825 Wh where: A = molten aluminum surface area = (22 in. dia/2)2 • π = 380 in2

FSL = surface loss factor from Reference 13 (Page 28) at 1080°F = 13 in2

te = 10 minutes = 0.167 hr

e. Total losses Sides = 4486 • Wh Top = 715 • Wh Bottom = 829 • Wh Open Lid = 825 • Wh

Total QL = 6855 • Wh

169 Application Guide Reference Data Step 4: Calculate Start-Up Power Requirements From Equation 4, (Page 18). Examples of Applications Continued Q + Q 2 Q Start-Up Power = A C + L • (1 + S.F.) [ ts 3 ( te )]

137,691 + 48,945 Wh 2 6855 Wh = + • (1) 5 hrs 3 ( 1 hr )

= 41,900 watts where:

QA = 137,691 Wh QC = 48,945 Wh QL = 6855 Wh ts = start-up time = 5 hrs te = exposure time for losses = 1 hr S.F. = 0 for this example

Step 5: Calculate Operating Power Requirements From Equation 5, (Page 18). Q + Q Q Operating Power = B D + L • (1 + S.F.) [ tc te ]

18,860 + 12,236 Wh 6855 Wh = + • (1) 1 hr 1 hr

= 37,950 watts where:

QB = 18,860 Wh QD = 12,236 Wh QL = 6855 Wh tc = cycle time = 1 hr te = exposure time for losses = 1 hr S.F. = 0 for this example

170 W A T L O W

Application Guide Reference Data Melting of Aluminum Power Evaluation Ref. 146 Examples of Applications Continued 40 2 /3 QL (Losses) Heater Recommendation QL (Losses) QC Latent Heat Twelve standard eight inch X 24 inch 30 for Aluminum QD Latent high watt density, flat ceramic fiber Heat for QA Initial Heating Aluminum heaters arranged in a circle around of Crucible, Ingots the crucible will form an inside dia- 20 Block, Aluminum, Chassis and QB Heating meter of about 30 inches. Each Power (Kilowatts) Structure Up of Aluminum eight inch X 24 inch heater with 10 Ingots sinuated wire elements is rated at Re 3600 watts with furnace hot face f temperatures up to 1800°F. Twelve erence Data heaters will produce 43,200 watts. 1 2 3 456 7 8 9

Start-up Time (Hours)

Heater Performance Limits Crucible Surface Temperature Verification From Equation 3A, (Page 17) heat energy conducted through the crucible: It is necessary to verify the element • • • operating temperature and insure Q = K A T∆ te that the load can absorb the energy 3.412 • L produced by the heaters fast enough to prevent heater damage. Solve for T:∆ First, use the heat transfer equation ∆ Q 3.412 • L T = • = T1 - T2 for thermal conductivity through the te K • A crucible to calculate the outside surface temperature of the crucible. Then (35,445 W) • (3.412 Btu/Wh) • (2 in.) = = 160°F use the radiant heat transfer equation (112 Btu • in./hr • ft2 • °F) • (13.5 ft2) to calculate the heater element ∆ temperature. Then T1 = T2 + T = 1510°F Note that the thermal conductivity where: of new silicon carbide is reasonably Q = power available to melt the aluminum. This is calculated good at K = 112. However, as the by subtracting heat losses during operation from the rated crucible ages, thermal conductivity te power of the heaters. can decrease drastically to as little as 20 percent of original value. A = 42,300 - 6855 = 35,445 W 50 percent decrease in the thermal L = crucible thickness = 2 in. ∆ conductivity will cause the T across K = thermal conductivity of silicon carbide the crucible to double, simply to = 112 Btu - in./hr - ft2 - °F (From Ref. 132, Page 134) conduct the same amount of heat. This must be considered when A = crucible surface area = 13.5 ft2 designing the furnace and its control T1 = crucible outside surface temperature system. T2 = crucible inside surface temperature = 1350°F

171 Application Guide Reference Data Heater Surface Temperature From Equation 6, (Page 19) the heat energy radiated from the heater to Examples of Applications the crucible: Continued 1 44 S • (T - T ) • 1 • F Since the equation was originally 2 2 1 + - 1 written for equal size parallel plates, Watt Density Q e1 e2 )( 2 = = and we are dealing essentially with (W/in ) • te A 144 • 3.412 concentric cylinders, the proportional differences between the different For concentric cylinders, this equation becomes: diameters must be factored into the analysis. The ratio (R) takes this into 4 4 1 S • A • (T - T ) • account when the outer cylinder 1 2 1 • 1 e +R e - 1 (the heater, or source) radiates heat Power Q ( 1 2 ) toward the inner cylinder (the load). = = (watts) te • The shape factor (F) is assumed to be 144 3.412 one as end effects are negligible near the center of the crucible’s height. Now, solving for the heater element temperature T1: The best heat transfer condition occurs where there are small differ- 4 4 Q • (144) • (3.412) 1 1 T = T + • + R • - 1 1 2 e e ences in the shape/size of the source te • S • A ( 1 2 ) and load. Where the differences are large, the temperature of the source T1 = 2146°R = 1686°F must be significantly higher to transfer the same amount of heat energy. where: Q For this crucible application, the = power radiated to the crucible = 35,445 watts best heat transfer condition occurs te where the crucible diameter is largest. S = Stefan-Boltzman constant Similarly, the heat transfer near the = 0.1714 X 10-8 Btu/hr • ft2 • °R4 bottom of bowl shaped crucibles is T = heating element temperature poorest. Generally, design should be 1 based upon the worst case condition, T2 = crucible outside surface temperature however, for this example, we can = 1510°F = 1970°R ignore this situation, since convection e1 = heater emissivity = 0.88 effects cause the heat to rise from the e2 = silicon carbide crucible emissivity = 0.92 bottom of the bowl area, thus equaliz- D1 = heater diameter = 30 in. ing the energy flow between heater D2 = crucible diameter = 26 in. and crucible. D 30 R=1 = = 1.1538 D2 26 A = heater surface area = 12 • 8 in. • 24 in. = 2304 in2 To transfer 35,445 watts to the load, the heater must operate at 1686°F which is below the heater rating of 1800°F.

172 W A T L O W

Application Guide Reference Data

Conclusion period of time, reduced thermal con- effect on the heater temperatures. From the example presented here, it ductivity will require that a higher cru- Larger differences (especially at appears that the system will function cible surface temperature is required small sizes) can have a marked effect. well. It is important to note that all of to get heat transfer to the aluminum. Emissivities of the various surfaces the permutations have not been con- As the crucible temperature must in- can also have important effects on sidered in this example. To insure crease, the heater temperature must the resultant heater temperatures. satisfactory performance and life, the also increase. It is important to use values that are aging characteristics of the crucible From a practical standpoint, small accurate, or to test prototypes during must also be considered. Over a long differences in diameters have little the design and development stage. Reference Data

Control Requirements with Set Point 1 at 1350˚F and the High and Low Limit Control— Design—The aluminum crucible re- other set of six heaters with on-off Because both over- and undertem- quires a unique control system, a de- Set Point 2 at a differential 20˚F less. peratures are potentially damaging sign with cascaded control outputs, A Watlow DIN-A-MITE® switches to the crucible system and the alumi- which not only controls aluminum tem- power to each set of heaters. In num charge, a Watlow limit controller perature via “hold” and “high melt” addition, to extend the life of the two with a mercury displacement relay is heaters, but also controls the surface sets of heaters, a special set point used to ensure fail-safe protection for temperature of the heaters them- interchange switch enables monthly the system. The limit controller takes a selves. In addition, high and low rotation. The hold heaters become the Type K thermocouple input. It will limit control must provide fail-safe boost heaters and vice versa. sever power to the heaters at 1825°F protection for the crucible and the Heater Surface Control—To further heater surface temperature, and turn aluminum charge. protect the ceramic fiber heaters a on a red strobe alarm. Low alarm input comes directly from the input Primary Control—A Watlow SERIES second thermocouple is used to terminals of the SERIES 988. At 988 microprocessor based control is monitor the face temperature of the 1200˚F, the low limit SP of the 988 will the recommended primary control for heaters. This sensor is connected to also activate the red strobe indicator. the crucible. The SERIES 988 has a input 2 of the 988 which is set up for A feature of the SERIES 988 allows a dual output, heat PID-heat on-off cascade control. The rH2 value, range low alarm condition to be ignored on configuration with a Type N thermo- high Z is set to limit the heater to a start-up. couple sensor in a protective tube in maximum temperatures of 1800˚F. the molten aluminum. The Type N The Type N thermocouple sensor is thermocouple is excellent for long placed directly against the heater sensor life at high temperatures. The face. 988 controls half of the 12 heaters

173 Application Guide Reference Data Heating Liquid in a Tank Ref. 147 Examples of Applications Power Continued

Objective Power A manufacturing process requires nitrogen gas which is supplied from standard steel gas cylinders. The 40" system operates at low pressure, To Load 3 Pole Power below 120 psi, and the cylinders 34" Controller (2) must be heated to 140°F. A steel tank 52 inches long X 14 inches wide Temperature X 40 inches high holds four cylinders Controller plus 48 gallons of heated water. The To Heater tank weighs 100 lbs and is covered Reset To Sensor with two inch thick insulation. “Alarm Indicator” 52" One hour is allowed for preheating the Temperature Controller tank, water bath and two gas 14" cylinders. Two additional nitrogen cylinders are then put into the bath and allowed to warm-up for 15 minutes as the first pair is used. They Step 1: Initial Heating of Tank, Water and Gas Cylinders are then used during the following 15 From Equation 1, (Page 16) minutes while the next pair is warming up and so on. Each cylinder weighs a. Tank 55 lbs empty and 65 lbs when full. w • Cp • ∆T QA = Ambient temperature is 70°F. Power 3.412 available is 240 volts, 3-phase. (100 lbs) • (0.12 Btu/Ib • °F) • (70°F) Power Requirements = 3.412 Btu/Wh The following steps illustrate the = 246 Wh calculations to estimate the power required to preheat the system, to where: heat the gas cylinders and to replace w = weight of tank = 100 lbs heat losses. Cp = specific heat of steel = 0.12 Btu/lb • °F ∆T = temperature rise = 140°F -70°F = 70°F

b. Water (400 lbs) - (1.0 Btu/Ib • °F) • (70°F) QA = 3.412 Btu/Wh = 8206 Wh where: w = weight of water = volume • density = 48 gal • 1 ft3 • 62.3 lbs/ft3 = 400 lbs 7.48 gal

Cp = specific heat of water = 1.0 Btu /Ib • °F ∆T = 70°F

174 W A T L O W

Application Guide Reference Data c. Gas cylinders The energy requirements of both the steel cylinder and nitrogen gas Examples of Applications must be calculated. Continued Steel cylinder: (55 lbs) • (0.12 Btu/lb • °F) • (70°F) QA = 3.412 Btu/Wh = 135 Wh where: w = weight of each cylinder = 55 lbs

• Cp = specific heat of steel = 0.12 Btu/lb °F Reference Data ∆T = 70°F

Nitrogen gas: (10 lbs) • (0.249 Btu/Ib • °F) • (70°F) QA = 3.412 Btu/Wh = 51 Wh where: w = weight of nitrogen = 10 lbs CP = specific heat of nitrogen = 0.249 Btu/Ib -°F ∆T = 70°F

Total for two gas cylinders: QA = 2 • (135 + 51) = 372 Wh

d. Total QA = 246 + 8206 + 372 = 8824 Wh

Step 2: Heating of Gas Cylinders During the Operating Cycle Since two gas cylinders are used for each cycle, refer back to Step 1, part c.

QB = 2 • (135 + 51) = 372 Wh

Step 3: Heat Required to Melt or Vaporize Materials During Start-Up Not required as no materials change phase.

QC = 0

Step 4: Heat Required to Melt or Vaporize Materials During Operating Cycle Not required as no materials change phase.

QD = 0 175 Application Guide Reference Data Step 5: Determine Thermal System Heat Losses Examples of Applications a. Convection and radiation losses from insulated tank Continued From Equation 3D, (Page 18)

QL4 = A • FSL • te = (5280 in2) • (0.03 W/in2) • (1 hr.) = 158 Wh where: A = exposed surface area = (2 • 14 in. • 40 in.) + (2 • 52 in. • 40 in.) = 5280 in2

FSL = surface loss factor for 2 inch insulation at ∆T = 70°F = 0.03 W/in2

te = exposure time = 1 hour

b. Convection and radiation losses from water surface From Equation 3D, (Page 18).

QL4 = (728 in2) • (1.7 W/in2) • (1 hr) = 1238 Wh where: A = water surface area = 14 in. • 52 in. = 728 in2

FSL = surface loss factor for water at 140°F = 1.7 W/in2

c. Total Losses QL = 158 + 1238 = 1396 Wh

Step 6: Calculate Start-Up Power Requirements From Equation 4, (Page 18) using a 10 percent safety factor,

Q + Q 2 Q Start-Up Power = A C + L • (1 + S.F.) [ ts 3 ( te ) ]

8824 + 0 Wh 2 1396 Wh = + • (1.1) [( 1 hr ) 3 ( 1 hr )]

= 10,730 W

where:

QA = 8824 Wh QC = 0 QL = 1396 Wh ts = start-up time = 1 hour te = exposure time for losses = 1 hour S.F. = safety factor = 10 percent 176 W A T L O W

Application Guide Reference Data Step 7: Calculate Operating Power Requirements From Equation 5, (Page 18) using a 10 percent safety factor, Examples of Applications Continued Q + Q Q Operating Power = B D + L • (1 + S.F.) [ tc te ]

372 Wh 1396 Wh = + • (1.1) [ 0.25 hr 1 hr ] = 3172 W where:

QB = 372 Wh Re f

QD = 0 erence Data QL = 1396 Wh tc = cycle time = 15 min. = 0.25 hr te = 1 hr S.F. = safety factor = 10 percent

Heater Recommendation Heating Liquid in a Tank Power Evaluation The heating requirement is deter- Ref. 148 mined by either the start-up or the 11,000 operating power, whichever is great- 10% Safety er. In this case 10.7 kilowatts are 10,000 Factor required for start-up. 2 9000 /3 QL (Losses) A stock 12 kilowatts over-the-side immersion heater is recommended; 8000 an “L”-shaped configuration with Incoloy® elements rated at 48 W/in2. 7000 The element length is about 38 inches 6000 and is spaced four inches above the QA 5000 Initial

bottom of the tank. The elements Power (Watts) Heating should be protected against damage 4000 of Tank by the gas cylinders. and Water 10% Safety Factor Control 3000 QL The control requirements here do not 2000 Losses demand a high degree of controllability. The 48 gallons of water 1000 Q = Heating of Gas Cylinders represent a large thermal mass; B overshoot is not anticipated, nor is it a problem. The Watlow SERIES SD 2 31 digital indicating control with PID and Start-up Time (Hours) auto-tuning is the recommended controller. In addition, a Watlow limit controller will protect the heater when the tank is empty. A Watlow DIN-A- MITE power controller will provide power-switching for the SERIES SD.

Incoloy® is a registered trademark of the Special Metals Corporation.

177 Application Guide Reference Data Heating a Flowing Liquid Ref. 149 Examples of Applications Control Limit Continued Heater Power Temperature Power 3¿ Power Heater Power Objective 1¿ Power Controller Controller Power Control Power Controller (2) 3¿ Power A waste water treatment plant requires 120V 1¿ heating four gallons per minute of Power treatment water from 70-150°F. The Controller water contains traces of electrolytic 36" cleaners, so it is contained in a 36 Limit inch diameter by 84 inch tall, 350 Controller gallon polypropylene receiver tank. Reset A four inch -150 lb mating flange is 84" Thermocouple available at the bottom of the tank. The customer has expressed concern about the possibility of corrosion, and requests a lower watt density heater rated at 50 kW. Thermocouple

FIREBAR¨ Flange Heater

Step 1: Initial Heating of the Water and Tank Because the process is a continuous operation, there will not normally be any start-up period. When the process is interrupted for periodic maintenance though, a maximum of 12 hours for heat-up is requested. With this long of a start-up period, it is likely that the normal operating power will meet this requirement, but it is always advisable to check. From Equation 1, (Page 16). a. Tank The tank is made of polypropylene and we will assume it is an insulator, so heat-up of tank will be negligible.

b. Water w • Cp • ∆T QA = 3.412 (2915 lbs) • (1.0 Btu/lb • °F) • (80°F) = 3.412 Btu/Wh

QA = 68,350 Wh where: w = weight of water = volume • density 1 ft3 62.3 lbs = (350 gal) • • ( 7.48 gal ) ( 1 ft3 ) = 2915 lbs

Cp = specific heat of water = 1.0 Btu/lb • °F ∆T = 150°F - 70°F = 80°F

178 W A T L O W

Application Guide Reference Data Step 2: Heating of Water During the Operating Cycle The following is the energy needed to heat the treatment water during actual Examples of Applications operation. Even though the customer has specified a given value, it is advis- Continued able to check that rate with the given process parameters. From Equation 1, (Page 16).

w • Cp • ∆T QB = 3.412 (2000 lbs) • (1.0 Btu/lb • °F) • (80°F) = 3.412 Btu/Wh = 46,890 Wh

where: Re f

w = weight of water per hour erence Data = volume • density 1 ft3 62.3 lbs = (4 gpm) • (60 min) • • ( 7.48 gal ) ( 1 ft3 ) = 2000 lbs/hr Cp = specific heat of water = 1.0 Btu/lb • °F ∆T = 150° - 70° = 80°F

Step 3: Heat Required to Melt or Vaporize Materials During Initial Heating Not required since the water does not change phase.

QC = 0 Step 4: Heat Required to Melt or Vaporize Materials During Operating Cycle Not required since the water does not change phase.

QD = 0

Step 5: Determine Thermal System Heat Losses Because polypropylene is a poor thermal conductor, we will assume it acts as an insulator, and use one inch of insulation as an equivalent value. From Equation 3D, (Page 18).

QL4 = A • FSL • te = (10,520 in2) • (0.05 W/in2) • (12 hrs)

QL = 6312 Wh where: A = exposed surface area π • (36 in.)2 = (36 in. • π • 84 in.) + [ 4 ] = 10,520 in2

FSL = surface loss factor for 1 inch insulation at ∆T = 80°F = 0.05 W/in2

te = exposure time = 12 hrs

179 Application Guide Reference Data Step 6: Calculate Start-Up Power Requirements From Equation 4 (Page 18), using a 10 percent safety factor, Examples of Applications Continued Q + Q 2 Q Start-Up Power = A C + L • (1 + S.F.) [ ts 3 ( te ) ]

68,350 Wh 2 6312 Wh = + • (1.1) [( 12 hrs ) 3 ( 12 hrs )]

= 6050 W where:

QA = 68,350 Wh QC = 0 QL = 6312 Wh ts = start-up time = 12 hrs te = exposed time = 12 hrs S.F. = safety factor = 10%

Step 7: Calculate Operating Power Requirements From Equation 5 (Page 18), using 10 percent safety factor,

Q + Q Q Operating Power = B D + L • (1 + S.F.) [ tc te ]

46,890 Wh 526 Wh = + • (1 • 1) 1 hr 1 hr

= 52,100 watts = 52.1 kW where:

QB = 46,890 Wh QD = 0 QL = during operation, losses are evaluated on a per hour basis, therefore: (10,520 in2) • (0.05 W/in2) • (1 hr) = 526 Wh

tc = cycle time required = 1 hr te = exposure time = 1 hr S.F. = safety factor = 10%

180 W A T L O W

Application Guide 5000 W Reference Data W/in2 = = 93 W/in2 1 hr Examples of Applications Continued where: W Heater Recommendation W/in2 = active heater surface area The customer’s requested value of 50 kilowatts appears to be correct. heated length surface area in2 elements This specific installation will limit our = [in.] • • • element element in. flange choices to a four inch-150 Ib flange [ ] heater with a maximum immersed heated length = (30 inches immersed) • (2 lengths/element) length of 36 inches. A traditional approach would be a four inch flange surface area for 2 Reference Data with six 0.475 inch diameter tubular 0.475 inch diameter = 1.49 in /in. elements. The watt density would be: surface area = (30 in.) • (2) • (1.49 in2/in.) • (6 elements) = 536 in2

Control Heating a Flowing Liquid Power Evaluation A SERIES SD is used to switch a Ref. 150 50 power controller which in turn QL (Losses) 10% Safety Factor switches the heaters. A limit controller is used with a mechanical contactor 40 as over temperature protection. 30

20 Power (Kilowatts)

10 10% Safety Factor

QA Initial Heating of Water

1 2 3 4 5 6 7 8 9 10 11 12

Start-up Time (Hours)

Compare this traditional approach to a FIREBAR® flange heater, with six FIREBAR elements. 50,000 watts W/in2 = 60.4 = 828 in2 where:

surface area for FIREBAR = 2.3 in2/in. surface area = (30 in.) • (2) • (2.3 in2/in.) • (6 element) = 828 in2 Clearly the FIREBAR® flange heater provides a better solution with a 35 percent reduction in watt density. Incoloy® elements and a 304 stainless steel flange will be used because of the traces of corrosive cleaners.

181 Application Guide Reference Data Air Duct Heater

Ref. 151 Limit Control Examples of Applications Thermocouples Continued 3 ¯ Power Objective Alarm Indiction High Limit Reset Button A drying process for unfired ceramics Limit Controller requires 780 cubic feet per minute (CFM) of air at 560°F ± 20°F. The air temperature at the blower exit is 90°F and the air is delivered to the dryer through a duct 19 feet in length. The duct is 22 inches wide X 15 inches high and is wrapped with four inch thick insulation. Temperature The equipment layout dictates that Controller the duct heaters may be located no 1 ¯ Power 3 ¯ Power closer than 12 feet to the dryer. The Sensors plant ambient temperature is 70°F. 4" Insulation Primary Control SUR Power Controller Power Controller Power available is 240/480 volt three- Thermocouple for Heaters phase or single phase. Power Requirements The following steps illustrate the cal- Step 1: Initial Heating Of Materials culations to estimate the heat needed Not required, because this application is a continuous air flow process. for the process air and to compensate Q = 0 for duct losses. There is no start-up A heating required. Step 2: Heating of Air During Operation From Equation 1, (Page 16)

w • Cp • ∆T QB = 3.412 (1825 lbs) • (0.245 Btu/lb • °F) • (470°F) = 3.412 Btu/Wh = 61,591 Wh where: density of air at 560°F from Reference 137 (Page 143) = 0.039 lbs/ft3 w = weight of air per hour 60 min = volume per min (CFM) • • density (lbs/ft3) hr 60 min = 780 CFM • • 0.039 lbs/ft3 hr

= 1825 lbs/hr

Cp = specific heat of air at 90°F = 0.24 Btu/lb • °F, at 560°F = 0.25; average = 0.245 Btu/Ib • °F ∆T = temperature rise = 560°F - 90°F = 470°F

182 W A T L O W

Application Guide Reference Data Step 3: Heat Required to Melt or Vaporize Materials During Initial Heating Examples of Applications Not required as the air does not change phase during heating. Continued QC = 0

Step 4: Heat Required to Melt or Vaporize Materials During Operating Cycle Not required as the air does not change phase during heating.

QD = 0

Step 5: Determine Thermal System Heat Losses Re f Radiation and convection losses erence Data From Equation 3D, (Page 18)

QL4 = A • FSL • te = (74 ft2) • (20 W/ft2) • (1 hr)

QL = 1480 Wh where: A = exposed surface area (22 in. + 15 in.) = 12 ft • 2 • = 74 ft2 12 in./ft

FSL = surface loss factor at ∆T = 490°F and 4 inch insulation = 20 W/ft2 from Ref. 12 (Page 28)

te = exposure time = 1 hr

Step 6: Calculate Start-up Power Requirements Not required, because this application is a continuous air flow process. PS = 0

Step 7: Calculate Operating Power Requirements From Equation 5, (Page 18) using a 10 percent safety factor,

Q + Q Q Operating Power = B D + L • (1 + S.F.) [ tc te ]

61,591 Wh 1480 Wh = + • (1.1) [ 1 hr 1 hr ] = 69,378 watts = 69.4 kW where:

QB = 61,591 Wh QD = 0 QL = 1480 Wh tc = 1 hour te = 1 hour S.F. = safety factor = 10% 183 Application Guide Reference Data Air Duct Heater Power Evaluation Ref. 152 Examples of Applications Power Evaluation Continued 100,000

10% Safety Factor

QL Losses

50,000 Power (Watts)

QB = Heating of 780 CFM Air at 560°F and 1 atm.

10,000

Continuous Process (No Start-up) Time (Hours)

Heater Recommendations a. Air velocity v1 at the inlet to duct heater # 1 The duct size of 15 inch X 22 inch volume per min. (CFM) 422 v1 = = = 184 ft/min. is generally too small for a single duct area (ft2) 2.29 75 kilowatts unit. Therefore, two stock 36 kilowatts, 480 volt three phase units where: will be installed in series. Heating weight of air per hour (lbs) elements are tubular-type 0.430 inch CFM1 = 60 min/hr • density (lbs/ft3) diameter Incoloy® rated at 20 W/in2. Minimum air velocity of 180 ft/min 1825 lb/hr must be maintained to provide suffi- = = 422 CFM cient heat transfer to prevent exces- 60 min/hr • 0.072 lbs/ft3 sive element temperatures. The following are estimates of air velocity density = 0.072 lbs/ft3 @ 90°F from Reference 137 (Page 143) at the inlets of the two duct heaters to 22 in. • 15 in. verify that the air velocity is sufficient. duct area = = 2.29 ft2 2 2 While the mass flow rate through 144 in /ft the duct is constant, the CFM and velocity are not, because they are determined by the air density which varies with temperature. As previously calculated the weight of air per hour = 1825 lbs/hr.

184 W A T L O W

Application Guide

Reference Data b. Air velocity V2 at the inlet to duct heater #2 volume per min (CFM) 596 Examples of Applications v2 = = = 260 ft/min 2 Continued duct area (ft ) 2.29 where: weight of air per hr (lbs) CFM2 = 60 min/hr • density (lbs/ft3)

1825 lb/hr = = 596 CFM 60 min/hr • 0.051 lb/ft3

The temperature at the inlet to duct heater #2 is the average of the heated and Re f unheated air temperatures by assuming that each 36 kW heater supplies one- half of the heat: erence Data (560 + 90) T2 = = 325°F 2 density = 0.051 lbs/ft3 @ 325°F from Reference 137 (Page 143)

Control Requirements limit controller is recommended, Control accuracy in this application providing two channels of high limit is not critical (±20°F), but digital control with Type J thermocouple indication is required. In addition, limit inputs from the heaters. Each heater controllers with thermocouples must will be delta connected across the monitor the sheath temperature of 480 volt, three-phase line and each heater. The Watlow SERIES SD switched by a SCR power switching with Type J thermocouple input is the device for long, dependable service correct controller choice. A Watlow and heater life.

185 Application Guide Reference Data Drying a Moving Web of Cloth Examples of Applications 1. Collect the data, make assumptions. To uniformly heat the product, choose a Continued heater size that overlaps an amount equal to the distance between the heater and the sheet of steel, i.e.: Objective Heater Size = 28 in. • 28 in. A manufacturing process requires that ∆ 24 inch x 24 inch x 0.031 inch pieces - T = 300 - 60 = 240°F of 304 stainless steel be heated to - Weight/in2 = 500 lbs/ft3 • 1 ft3/1728 in2 • 0.031 in. thick = 0.00897 lbs/in2* 300˚F in one minute. The stainless - Specific heat = 0.12 Btu/lb°F* steel has a coating with an emissivity - Time = 1 minute = 0.0167 hrs of 0.80. A radiant panel can be located two inches above the metal. - Emissivity of product = Ep = 0.080

2. Determine the wattage required to heat one square inch of the material. Watts = w • specific heat • ∆T Time • 3.412 Btu/Wh

Watts = 0.00897 lbs/in2 • 0.12 Btu/lb°F • 240°F 0.0167 hrs. • 3.412 Btu/Wh Watts = 4.54 W/in2

3. Using the radiant heat transfer equation, determine the radiant heater temperature needed to transfer the required wattage found above. W/in2 = S(Th4 - Tp4) • E • F 144 in2/ft2 • 3.412 Btu/Wh

A. Compute the view factor F

The heater is 28 in. • 28 in., located two inches from the product. M = 28 - 14 N = 28 = 14 22 F = 0.85

B. Compute the effective emissivity (E). Emissivity of heater = Eh = 0.85

E = 1 = 1 = 0.70 1 + 1 - 1 1 + 1 - 1 Eh Ep 0.85 0.8

C. Determine the average product temperature (Tp) Tp = 300 + 60 = 180°F = 640°R 2

186 W A T L O W

Application Guide Reference Data D. Plug into the radiant heat transfer equation Examples of Applications W/in2 = S(Th4 - Tp4) • E • F Continued 144 in2/ft2 • 3.412 Btu/Wh From above we found: E = 0.70 F = 0.85 Tp = 640°R Required W/in2 = 4.54 Therefore:

2 4 4 • •

4.54 W/in = S(Th - (640) ) 0.7 0.85 Reference Data 144 in2/ft2 • 3.412 Btu/Wh 7.6 W/in2 = S(TH4 - (640)4) 144 in2/ft2 • 3.412 Btu/Wh

S = 0.1714 • 10-8 Btu/hr ft2°R4

E. Determine the required heater temperaure (Th) All information required to solve the above equation for the heater temperature (Th) is now available. Note that the equation gives Th in °R. Th (˚F) = Th (°R) - 460 From the graph or the calculation, find: Th = 780°F To transfer the required watts, the heater must operate at 780°F. Comments/Questions What is the required heater watt density? If selecting a Watlow RAYMAX® 1120 for this application, this heater requires about 9 W/in2 to maintain 780°F face temperature in open air. In this application, slightly less would be required since some of the radiant energy that is reflected off of the 0.80 emissivity surface of the metal is reflected back into the heater and re-absorbed. This would be a much more significant factor if the product surface had a lower emissivity, say 0.5. What about losses off the surface of the metal as it heats up? Generally, the air temperature between the heater and the product is higher than the product temperature, so some convection heating takes place. In this application, assume the plate is resting on a good heat insulator and there is very little air movement. If this is not the case, then these losses must be estimated and added to the required wattage determined above.

187 Glossary Definitions of active components An electronic Alloy #11¨ A compensating alloy Commonly Used device whose properties change with made of 99 percent copper and a change in the applied signal. one percent nickel. It is used to make Terms Used in Diodes, transistors and integrated the negative conductor that, in Heating, Sensing circuits are active components. conjunction with pure copper, forms and Controlling actual The present value of the thermocouple extension wire for controlled variable. ASTM Type R and S thermocouples Introduction (platinum, platinum/rhodium). address An identification, The terms contained in this glossary Alloy #11® is a registered trademark represented by a name, label or are defined according to their most of Harrison Alloys. See “compensating number, of a register or location in common use as they apply to heaters, alloy.” storage, or any other data source or temperature sensors, temperature Alloy 188¨ A cobalt-based austenitic controllers and power controllers. destination, such as the location of a station in a communication network. alloy that exhibits high strength and Also included are terms used in the resistance to oxidation and corrosion. Advance¨ A thermocouple alloy general discussion of thermodynamic It is commonly used in the aerospace, made of 55 percent copper and 45 theory, thermal systems and heat nuclear, chemical and process percent nickel, used as the negative energy. industries. Alloy 188® is a registered conductor in ASTM Type E, J, and trademark of Haynes International. A T thermocouples. Advance® is a registered trademark of Harrison Alloys Alloy 203/225 Alloys made up of A.G.A. See “American Gas Company. 90 percent nickel and 10 percent Association.” chromium (203), and 98 percent nickel alarm A signal that indicates that the and two percent chromium (225). They abrasion resistance The ability of a process has exceeded or fallen below form thermocouple extension wire material to resist mechanical wear. the set or limit point. For example, an conductors for Type D (W3Re/W25Re) absolute zero The temperature at alarm may indicate that a process is thermocouples for applications under which substances possess minimal too hot or too cold. energy. Absolute zero is 0 Kelvin or 200°C (400°F). Type D is not an ASTM alarm dead band An area of no calibration. 0° Rankine and is estimated to be control or alarm change. -273.15°C (-459.67°F). Alloy 214¨ A material that exhibits alarm delay The lag time before an ac (Å) See alternating current. excellent resistance to oxidation, alarm is activated. carburization and chlorine-bearing ac line frequency The frequency of alarm hysteresis A change in atmospheres. It is commonly used to the alternating current power line the process variable required to make sensor probe sheaths. measured in Hertz (Hz), usually 50 or re-energize the alarm output. Alloy 214® is a registered trademark 60Hz. alarm module 1) A controller of Haynes International. ac/dc (ı) Both direct and alternating hardware and software combination Alloy 230¨ A material that exhibits current. configured to alert an operator or excellent high temperature strength, accelerated aging A test that perform another function in response oxidation resistance and long-term simulates the effects of long-term to a problem in the thermal system. thermal stability. It works well in environmental and operating 2) A specific behavioral feature in the nitriding environments, and is conditions in a relatively short time NAFEM (National Association of Food commonly used to make sensor probe period. Equipment Manufacturers) data sheaths. Alloy 230® is a registered accuracy Difference between the protocol model that determines if an trademark of Haynes International. value indicated by a measuring alarm condition exists. It does this by instrument and the corresponding true providing criteria to compare against value. Sensor accuracy is based on alarm object attributes. US NIST (NBS) standards. alarm silence A feature that disables action The response of an output the alarm relay output. when the process variable is changed. See also “direct action,” and “reverse action.”

188 Glossary The 189 Pressure in A standard unit of The feature of a The ambient See “anti-reset windup.” American Society of American Society for Testing (Address Resolution Protocol) (14.22 psi). 2 anti-reset anti-reset windup that PID temperature controller (automatic reset) prevents the integral when the circuit from functioning the proportional temperature is outside feature helps band. This standard Also called “anti- stabilize a system. reset.” Application layer (OSI Layer 7) highest layer of the seven-layer OSI (Open System Interconnection) model where communication begins with a specific application that comm- unicates with another device or system. All application-specific functions occur here, such as user authentication and addressing. An e-mail application or web browser are examples of the application layer for exchanging data over the Internet. The Application Layer resides above the Presentation Layer. ARP The TCP/IP protocol that converts an IP address into a physical hardware address, such as an address for an address for an Ethernet card. ASME Mechanical Engineers. ASTM and Materials. atmosphere environment. atmosphere (atm) pressure representing the pressure exerted by a 760 mm (29.92 in.) column of mercury at sea level at 45 degrees latitude and equal to 1,000 g/cm grams per square centimeter or pounds per square inch exerted by the earth’s atmosphere on bodies located within it. atmospheric pressure (dc). Î (A.G.A.) (AWG) See A continuously A visual display that An instrument that measures (amp, A) A unit that defines A method of representing data To relieve stress in a solid American National Standards using the amplitude of a signal. analog output variable signal that is used to represent a value, such as the process value or set point value. Typical hardware configurations are 0 to 20mA, 4 to 20mA or 0 to 5V ambient temperature “temperature, ambient.” American Gas Association laboratory that Independent testing and tests gas-related appliances standards, or to accessories to ANSI in the absence of a A.G.A. standards standard. nationally-recognized nationally Watlow now uses recognized testing laboratories to ANSI standards for gas-related products, rather than A.G.A. American Wire Gauge the magnitude of an electric current. ampere in the rate of flow of electricity (current) a circuit. Units are one coulomb (6.25 x 1,018 electrons) per second. analog anneal material by heating it to just below its melting point and then gradually cooling it to ambient temperature. Annealing usually lowers the tensile strength while improving flexibility and flex life. Metals and glasses are commonly annealed. annunciator uses indicator lights to display the former or existing condition of several items in a system. ANSI A standard of the dimensional characteristics of wire used to conduct electrical current or signals. AWG is identical to the Brown and Sharpe (B & S) wire gauge. ammeter Institute. The United States government agency that defines and maintains technical standards. /°C Ω / Ω W A T L O W O L T A W See is a ® ) An electric /°C (JIS). ÅÅ Ω ( / Ω Alloys made of 94.5 A material that exhibits ¨ A multipurpose alloy that An alloy made of 95 percent ¨ is a registered trademark of is a registered trademark of ¨ ® ® (A) The temperature coefficient percent nickel, two percent percent nickel, two silicon and manganese, one percent (405), and 80 1.5 percent aluminum 20 percent copper percent nickel and (426). They form thermocouple for use with extension wire conductors thermocouples Type C (W5Re/W26Re) 870°C (1600°F). for applications under calibration. Type C is not an ASTM Alloy 556 Glossary Alloy 405/426 the Hoskins Manufacturing Company. ambient compensation “compensation, ambient.” Haynes International. alpha of the change in electrical resistance of a material measured in ohms/ohm/°C. It indicates the basic change in electrical resistance in a material for each °C in temperature. Alpha is a defining parameter for resistance temperature detectors (RTDs). For example, common alphas for platinum RTDs are 0.00385 (DIN) or 0.003916 current that reverses at regular intervals, and alternates positive and negative values. Alumel alternating current nickel, two percent aluminum, two percent manganese and one percent silicon. It forms the negative conductor of ASTM Type K thermocouples. Alumel exhibits good resistance to sulfidizing, carburizing and chlorine-bearing environments. Alloy 556 superior resistance to sulfides with good resistance in some salt bath applications. It is commonly used to make sensor probe sheaths. Alloy HR160 registered trademark of Haynes International. Alloy HR160 Glossary atmospheric pressure, standard B.T.E. thermocouple holes “Behind- block A set of things, such as words, Pressure exerted by the earth's the-element” ceramic tubes create characters or digits that are handled atmosphere on bodies located within electrically isolated thermocouple as a unit. it. Standard atmospheric pressure is holes through Watlow ceramic fiber Block Check Character (BCC) A 14.7 psi (1.013 bar abs.) measured at heaters. The holes are built into the serial communications error checking sea level and 15°C (60°F). heaters to very closely track element method. An acceptable method for automatic mode A feature that allows temperature for over-temperature most applications, BCC is the default the controller to set PID control outputs protection and to improve heater life. method. See “Cyclic Redundancy in response to the process variable bandwidth A symmetrical region Check (CRC).” (PV) and the set point. above and below the set point in which blocking voltage The maximum automatic power reset A feature in proportional control occurs. voltage a surge protector can accept latching limit controllers that does not base metal thermocouple without degrading its component recognize power outage as a limit Thermocouples with conductors made current-protective devices. condition. When power is restored, the of base metallic element alloys (iron, boiling point The equilibrium output is re-energized automatically, copper, and nickel). Base metal temperature between a liquid and a as long as the temperature is within thermocouples are ASTM Types E, J, gaseous state. For example, the limits. K, N and T. They are usually used in boiling point of water is 100°C (212°F) automatic prompts Data entry points lower temperature applications. at standard atmospheric pressure. where a microprocessor-based baud rate The rate of information bonding The process of joining two controller asks the operator to enter a transfer in serial communications, similar or dissimilar materials. In control value. measured in bits per second. temperature sensors and lead wires, automatic reset The integral function BCC See “Block Check Character.” bonding usually establishes a seal of a PI or PID temperature controller bend radius (standard) The specified against moisture. See “potting.” that adjusts the process temperature minimum radius to which a sensor (or braid A flexible covering formed from to the set point after the system wire) can be bent without stressing the plaited (served) textile or ceramic stabilizes. The inverse of integral. structure of the metal or damaging its fibers or metallic filaments. Textile and auto-tune A feature that automatically electrical transmitting characteristics. ceramic fibers are used to produce sets temperature control PID values to Standard bend radius is a function of electrical insulation around electrical match a particular thermal system. sensor (or wire) diameter. conductors. Metallic filaments are auxiliary output An output that beryllia/beryllium oxide (BeO) A used to add abrasion resistance or controls external activities that are not white crystalline powder with a high shielding from electrical noise. directly related to the primary control melting temperature (approximately bright annealing The description of output. For example, door latches, gas 2585°C or 4685°F, high thermal stainless steel or aluminum after final purges, lights and buzzers. conductivity and high dielectric surface treatment, produced by AWG See “American Wire Gauge.” strength. Used in high-temperature passing the metal between rollers with ceramic thermocouple insulation. Its a moderately smooth surface. This B dust and particles are toxic. Special surface treatment is used in the precautions are required when processing of aluminum sheets, B & S Gauge (Brown and Sharp handling BeO. stainless steel back plates, stainless Gauge) A standard of the dimensional blackbody An ideal surface that steel cold rolled sheets and cold characteristics of wire used to conduct absorbs all incident radiation, rolled strip steels. electrical current or signals. It is regardless of wavelength, the direction browser A software application that identical to the American Wire Gauge. of incidence and polarization. It finds and displays web pages. Also radiates the maximum energy possible called “web browser.” for given spectral and temperature BS British Standards. The United conditions. A blackbody has an Kingdom agency that defines and emissivity of 1.00. See “emissivity.” maintains technical standards.

190 Glossary 191 The ability of a Materials made An alloy made of See “control channel.” is a registered trademark of The rapid on-off cycling of an ¨ ® Any closed path for electrical The client half of a client-server Computational Fluid Dynamics. Computational Fluid Cubic feet per minute. The ceramic insulation are capable of of metal oxides that temperatures and withstanding high dielectric providing the desired used to insulate strength. They are thermocouple heater elements or wires. CFD to solve and Numerical technique simulate the behavior of the Navier- Stokes equation that describes fluid flow. Used by Watlow for thermal system simulation. cfm volumetric flow rate of a fluid. When used in gas flow, it is evaluated at a given process temperature and pressure. channel chatter electromechanical relay or mercury displacement relay due to insufficient controller bandwidth. It is commonly caused by excessive gain, little hysteresis and short cycle time. chemical resistance material to resist permeation, erosion or corrosion caused by base, acid or solvent chemicals. Chromel the Hoskins Manufacturing Company. circuit current. A configuration of electrically or electromagnetically-connected components or devices. client system where the client is typically an application (residing on a personal computer) that makes requests to a server, computer with one or more clients networked to it. E-mail is an example of a client-server system. approximately 90 percent nickel and 10 percent chromium that is used to make the positive conductors of ASTM Type E and K thermocouples. Chromel The The ability Compliant with the An alumina-silica fiber Formerly known as Control algorithm in which Control algorithm °C) + 32. X Category 5 wiring or cable Category 5 wiring Confidential Disclosure A manufacturer’s mark that carbon potential control carbon potential Agreement. A legal document that spells out the conditions and circumstances by which confidential information can be shared with another party, and the remedies required for violations. Companies typically use both general CDAs and detailed CDAs that cite specific intellectual property to protect. See “MCDA.” CE demonstrates compliance with European Union (EU) laws governing products sold in Europe. CE-compliant essential requirements of European directives pertaining to safety and/or electromagnetic compatibility. Celsius (C) Centigrade. A temperature scale in which water freezes at 0°C and boils at 100°C at standard atmospheric pressure. The formula for conversion to the Fahrenheit scale is: °F = (1.8 to control the carbon content in steel to control the carbon furnaces. inside heat treating cascade manufactured to the TIA/EIA 568-A standard. The standard Ethernet wiring in for 10 Mbps or 100 Mbps networks four twisted pairs; insulated, unshielded and jacketed cable. Terminated with RJ45 connectors in lengths of 100m or less. CDA the output of one control loop provides the output of one control loop. The the set point for another determines the second loop, in turn, control action. CAT.5 that is lightweight and low density. It is used as a refractory material. central processing unit (CPU) unit of a computing system that includes the circuits controlling the interpretation of instructions and their execution. ceramic fiber An W A T L O W O L T A W Difference A smooth An adjustment to The comparison of a A power control method The process of adding Gathering insulated electrical A unit of energy defined as the British Thermal Unit. A unit of British Thermal Unit. cabling conductors into a single cable. Methods include serving (braiding), extruding or wrapping. Calendar van Dusen equation interpolation equation that provides resistance values as a function of temperature for RTDs. calibration measuring device (an unknown) against an equal or better standard. calibration accuracy C between the value indicated by a measuring instrument and a physical constant or known standard. calibration offset eliminate the difference between the indicated value and the actual process value. calorie amount of heat energy required to raise the temperature of one gram of water 1°C at 15°C. Glossary Btu energy defined as the amount of heat energy defined as pound of water required to raise one at standard from 32°F to 33°F One Btu is atmospheric pressure. One equal to 0.293 watt-hours. to 3,412 Btus. kilowatt-hour is equal bumpless transfer (closed loop) to transition from auto operation. The manual (open loop) control output(s) does (do) not change during the transfer. burst fire ac that repeatedly turns on and off full cycles. Also called zero-cross fire, it switches close to the zero-voltage point of the ac sine wave to minimize radio frequency interference (RFI). Variable time-base burst fire selectively holds or transits ac cycles to achieve the desired power level. bushing additional sheath tubing to achieve a additional sheath tubing to achieve larger, non-standard diameter. Glossary closed loop A control system that common-mode rejection ratio The conductivity Electrical conductivity is uses a sensor to measure a process ability of an instrument to reject the ability of a conductor to allow the variable and makes decisions based electrical noise, with relation to ground, passage of electrons, measured in the on that input. from a common voltage. Usually current per unit of voltage applied. It is CMM 1) Cubic meters per minute, a expressed in decibels (dB). the reciprocal of resistivity. Thermal measure of airflow. 2) Coordinate communications The use of digital conductivity is the quantity of heat Measuring Machines, used for computer messages to link conducted through a body per unit dimensional inspection in components. See “serial area, per unit time, per unit thickness manufacturing and quality communications” and “baud rate.” for a temperature difference of 1 kelvin. applications. 3) Capability Maturity compensated connectors A Model®, a registered trademark thermocouple connector that uses connection head A housing on a software development management either actual thermocouple alloy sensor assembly. It provides a terminal model of the Software Engineering contacts or compensating alloy block for electrical connections, and Institute (SEI), a research and contacts. Maintaining metallic circuit allows the attachment of protection development center sponsored by the properties throughout the connection tubes and cables or conduit hook-ups. U.S. Department of Defense and circuit reduces errors due to connectivity Computer jargon that operated by Carnegie Mellon mismatched materials. describes the readiness or capability University. compensating alloy Any alloy that of a device for communicating with CNC Computerized Numerical has similar resistance to another other devices or systems. Control. The programmed instructions thermocouple alloy. Compensating Constantan A generic designation used by a class of cutting tool alloys are usually low cost alternatives for a thermocouple alloy made of 55 machines (usually driven by design for extension lead wire types. For percent copper and 45 percent software) for creating machined parts example, Alloy #11 is a compensating nickel that is used as the negative and molds. lead wire for platinum thermocouple conductor in ASTM Type E, J and T coaxial cable A cylindrical sensors. thermocouples. transmission cable made of an compensating loop An extra pair of continuity check A test of finished insulated conductor or conductors lead wires that have the same assemblies or wire that indicates centered inside a metallic tube or resistance as the actual lead wires, but whether electric current flows shield, typically of braided wires. It are not connected to the RTD element. continuously throughout the length of isolates the signal-carrying conductor A compensating loop corrects lead the material. It also shows a short from electrical interference or noise. wire resistance errors when measuring circuit between conductors. cold junction Connection point temperature. control accuracy The ability to between thermocouple metals and the compensated, ambient The ability of maintain a process at the desired electronic instrument. See “reference an instrument to adjust for changes in setting. This is a function of the entire junction.” the temperature of the environment system, including sensors, controllers, cold junction compensation and correct the readings. Sensors are heaters, loads and inefficiencies. Electronic means to compensate for most accurate when maintained at a control action The response of the the effective temperature at the cold constant ambient temperature. When control output relative to the difference junction. temperature changes, output drifts. between the process variable and the color code A system of standard computer ground A line for the set point. For reverse action (usually colors used to identify electrical ground connections to computers or heating), as the process decreases conductors. For example, a color code microprocessor-based systems. It is below the set point, the output identifies the thermocouple type in isolated from the safety ground. increases. For direct action (usually thermocouple circuits. Codes common conduction The mode of heat transfer cooling), as the process increases in the United States have ASTM within a body or between bodies in above the set point, the output designations. Color codes vary in contact, caused by the junction increases. different countries. between adjacent molecules. common-mode line filter A device to filter noise signals on both power lines with respect to ground.

192 Glossary 193 The programmed (D) The last term in See “resistance.” An output shift in the A method of recording a A method of recording The range through which The range through The rate of change in a Mass per unit volume of a The increments in a ) Direct current. An electrical ) Direct current. An ÎÎ ( current that flows in one direction. current that flows dc resistance dead band produces no a variation of the input in the output. In the noticeable change be deadband, specific conditions can placed on control output actions. decalibration thermocouple so that it no longer conforms to established standards. The shift is caused by the altering of alloys in the thermocouple conductors. default parameters values that are permanently stored in the microprocessor software. degree data logging a period of time. process variable over performance. Used to review process dc temperature scale, or the increments of rotation of a dial. The location of a in a reference point in electric or phase cycle, in mechanical or electrical cyclic scales. One cycle is equal to 360 degrees. density substance expressed in kilograms per cubic meter of pounds per cubic foot derivative process variable. Also known as rate. See “PID.” derivative control the PID control algorithm. Action that anticipates the rate of change of the process variable and compensates to minimize overshoot and undershoot. Derivative control is an instantaneous change of the control output in the same direction as the proportional error. This is caused by a change in the process variable (PV) that decreases over the time of the derivative (TD). The TD is in units of seconds. ) An ® file ® The ® ”. ® is a ® A transformer 508. In some instances, The time required for a ® A thermocouple alloy made The rate of flow of electricity. ¨ Canadian recognition of Canadian recognition approval may stand in lieu of approval may stand UL stem from the original ¨ ® ® C-UL second layer of the seven-layer OSI (Open System Interconnection) protocol model that handles data packet encoding and decoding to and from bits on a network. The Data Link Layer has two sublayers, Media Access Control (MAC), and Logical Link Control (LLC). The Data Link Layer resides between the Transport Layer and the Physical Layer. D Data Link Layer (OSI Layer 2) approval. See “CSA and “UL approval. See “CSA Canadian Standards Association Canadian Standards references to (CSA) approval. All C-UL Underwriters Laboratories, Inc. (UL Underwriters Laboratories, of 55 percent copper and 45 percent nickel. It is used in the negative conductor of ASTM Type E, J and T thermocouples. Cupron C-UL controller to complete one on-off-on cycle. It is usually expressed in seconds. Cyclic Redundancy Check (CRC) error checking method in communications. It provides a high level of data security, but is more difficult to implement than Block Check Character (BCC). See “Block Check Character.” designed for measuring electrical current. cycle time registered trademark of Carpenter Technology. current The unit of measure is the ampere (A). 1 ampere = 1 coulomb per second. current transformer Cupron only, resident at the location of UL only, resident at the approval of a particular product class, approval of a particular such as UL W A T L O W O L T A W Often synonymous See “accuracy” and The type of action that A control system with A mode of heat transfer in Related to low Audio frequency signal The positive conductor in an Canadian Standards See “Cyclic Redundancy Cycles per second. Frequency. Association. An independent testing laboratory that establishes commercial and industrial standards, tests and certifies products. temperatures. Generally in the range of 0° to -200°C (32° to -328°F). CSA a controller uses. For example, on-off, time proportioning, PID, automatic or manual, and combinations of these. controllability “control.” convection a fluid (gas or liquid) in which heat is transferred through movement of masses of the fluid from a region of higher temperature to one of lower temperature. copper Also referred to as Hertz. CRC Check.” crosstalk interference coupled from one signal- carrying conductor to an adjacent conductor. cryogenic feedback (closed loop) from a single feedback (closed or without load to the controller, from the load feedback (open loop) to the controller. control mode See T thermocouple. ASTM Type “OFHC.” cps with “control loop.” In some markets, with “control loop.” its use may such as life sciences, of a data indicate the presence communications feature. control loop Glossary control channel Glossary Deutsche Industrial Norm (DIN) A diffusion A gradual mixing of draw A manufacturing process action set of technical, scientific and molecules of two or more substances that pulls a material through a die to dimensional standards developed in through random thermal motion. compact the material. Germany. Many DIN standards have digital adaptive filter A filter that drift A change in reading or value that worldwide recognition. rejects high frequency input signal occurs over long periods. Changes in deviation Any departure from a noise (noise spikes). ambient temperature, component desired value or expected value or digital filter (DF) A filter that slows the aging, contamination, humidity and pattern. Sometimes referred to as response of a system when inputs line voltage may contribute to drift. delta. change unrealistically or too fast. droop In proportional controllers, the deviation alarm Warns when a Equivalent to a standard resistor- difference between set point and process exceeds or falls below a capacitor (RC) filter. actual value after the system stabilizes. certain range from the set point. DIN See “Deutsche Industrial Norm.” The integral (reset) component of PID Alarms can be referenced at a fixed control corrects droop. direct action An output control action number of degrees, plus or minus, the in which an increase in the process dual element sensor A sensor with set point. variable causes an increase in the two independent sensing elements. DHCP Dynamic Host Configuration output. Cooling applications usually Usually used to measure temperature Protocol. A protocol that assigns a use direct action. gradients or provide redundancy in a network device, a unique IP address single point sensor assembly. direct current (Î) An electric current each time it logs onto a network. that flows in one direction. duplex control With enhanced di/dt The time rate of change in software, duplex control splits a single display capability In an instrument current. Excessive di/dt can damage a process output into two individual with digital display, the entire possible phase-fired silicon controlled rectifier outputs. For example, a 4 to 20mA span of a particular parameter or (SCR) power controller when it is used output is split into a 4 to12mA direct value. for large resistive loads. In this case, action (cooling) output and a 12 to an inductor may be necessary to dissipation constant The ratio of the 20mA reverse action (heating) output, protect the SCR. change in internal power dissipation to thus allowing one control output to the resulting change in the body dielectric An insulating material with function as two. temperature of a thermistor. very low electrical conductivity. duplex wire A cable or wire with two distributed zero crossing (DZC) A dielectric breakdown The point at insulated conductors that are parallel form of digital output control used by which a dielectric substance becomes or twisted together. Duplex Watlow Anafaze in which the output conductive. Usually a catastrophic constructions may also include a on-off state is calculated for every insulation failure caused by excessive drain-wire conductor. cycle of the ac line cycle. Power is voltage. duty cycle The percentage of a cycle switched at the zero crossing point, time in which the output is on. dielectric strength The potential reducing electrical noise. See gradient at which electric failure or “zero cross.” dv/dt Time rate of change in voltage. breakdown occurs. Also known as Excess dv/dt can cause false turn on distributed zero crossing (DZC) A breakdown potential. and destroy a silicon controlled form of digital output control. Similar rectifier (SCR) power controller. Loose differential control A control to burst fire. algorithm where the set point wiring connections may arc and DNS Domain Name Server. A represents a desired difference produce this voltage change. computer that translates alphabetic between two processes. The controller internet domain names into IP (Internet then manipulates the second process protocol) addresses. to hold it at a set value relative to the E first controller. drain wire An uninsulated wire that is earth ground A metal rod, usually used as a ground conductor in wire differential mode line filter A device copper, that provides an electrical and cable construction. to filter electrical noise between two path to the earth, to prevent or reduce power lines. the risk of electric shock.

194 Glossary 195 An e-Solutions A system that allows A process that releases A property expressing the A property expressing Erasable, programmable, A local area network (LAN) Ethylene tetrafluoroethylene, or The difference between the See “electrostatic discharge.” , the DuPont brand. See An input or output signal ® enthalpy of a gas or vapor relative energy state pressure and at a given temperature, in units of Btu/lb or volume. Expressed to evaluate the Joules/gram. It is used occurs when a energy change that Steam heating vapor or gas is heated. solved using this problems are readily property. EPROM read-only memory inside the controller. error correct or desired value and the actual measured value. ESD e-Solutions Watlow's Authorized Distributors to complete business transactions with Watlow via the Internet. allows Watlow's Distributors to order products, to build products to meet specifications, to check order status a and stock availability, and to access variety of other features. ETFE Tefzel “Tefzel.” Ethernet protocol that supports a bus or star- to configured network with speeds up 1,000 Mbps (megabits per second). event representing an on or off state. Events can control peripheral equipment or processes, or act as an input for another control or control loop. exothermic heat. explosion-proof enclosure enclosure designed to withstand an explosion of gases inside, to isolate sparks inside from explosive or flammable substance outside, and to maintain an external temperature that will not ignite surrounding flammable gases or liquids. (EMI) A power (ESD) An (EMF) A Selectable units of Creating a bright, A process that absorbs The ratio of radiation See “electromagnetic See “electromotive force.” See “electromagnetic Electrical and magnetic noise imposed Electrical and magnetic are many possible on a system. There ac power causes, such as switching wave. EMI can on inside the sine of controls interfere with the operation and other devices. relay electromechanical completes or switching device that by physically interrupts a circuit opening or closing electrical contacts. Not recommended for PID control. electromotive force difference in electrical potential energy, measured in volts. Electronics Industries of America (EIA) An association in the US that establishes standards for electronics and data communications. electropolishing electromagnetic interference electromagnetic a smooth metal surface by depositing thin layer of another metal on it via electrolysis. Also, “electroplating.” electrostatic discharge electrical discharge, usually of high voltage and low current. For example, the shock that occurs when walking across a carpet. EMC compatibility.” EMF EMI interference.” emissivity emitted from a surface compared to radiation emitted from a blackbody at the same temperature. endothermic heat. engineering units measure, such as degrees Celsius and Fahrenheit, pounds per square inch, newtons per meter, gallons per minute, liters per minute, cubic feet per minute or cubic meters per minute. An An (EMC) See W A T L O W O L T A W Electrical See “noise.” Any material that returns to The ratio of useful output The ratio of useful See “Electronics Industries of See “Electronics Industries Electronics Industries of America (EIA)/Telecommunication Industry Association (TIA) standard for interface between data terminal equipment and data communications equipment for is serial binary data interchange. This usually for communications over a to a short distance (50 feet or less) and single device. EIA/TIA-485 (formerly RS-485) Electronics Industries of America (EIA)/Telecommunication Industry Association (TIA) standard for electrical characteristics of generators and receivers for use in balanced digital multipoint systems. This is usually used to communicate with multiple devices over a common cable or where distances over 50 feet are required. elastomer “relay” and “electromechanical relay.” electromagnetic compatibility The ability of equipment or a system to function as designed in its electromagnetic environment without introducing intolerable electromagnetic disturbances to that environment, or being affected by electromagnetic disturbances in it. Glossary efficiency energy. energy (work) to input EIA its original shape or dimensions after being stretched or distorted. electrical interference America.” -423 and -485 EIA/TIA -232, -422, standards set by Data communications of America the Electronic Industries Industry and Telecommunications referred to as RS Association. Formerly (Recognized Standard). EIA/TIA-232 (formerly RS-232) noise that can obscure desired information. electrical noise electrical-mechanical relay Glossary exposed junction A type of FEP Fluorinated ethylene propylene. Form A — A single-pole, single-throw thermocouple probe in which the hot, A fluorocarbon copolymer of relay that uses only the normally open or measuring, junction protrudes tetrafluoroethylene and (NO) and common contacts. These beyond the sheath material and is fully hexafluoropropulene. See “Teflon®.” contacts close when the relay coil is exposed to the substance being ferrule A tubular compression energized. They open when power is measured. It usually gives the fastest component used to mount a removed from the coil. response time. No electrical isolation is temperature sensing probe. It Form A or C — An electromechanical provided. creates a gas-tight seal. relay capable of Form A or Form C extension wire See “thermocouple fiber, insulation Any nonmetallic, function, selected with a jumper wire. extension wire.” nonconductive textile that is used to Form B — A single-pole, single-throw external transmitter power supply A insulate conductors. Fibers may be relay that uses only the normally dc voltage source that powers external braided or wrapped. closed (NC) and common contacts. devices. field of view The target size or These contacts open when the relay extrusion A process by which a distance necessary for an infrared coil is energized. They close when material is melted and pushed or sensor to receive 90 percent of the power is removed from the coil. pulled through a die to create a power radiated by a surface. Form C — A single-pole, double-throw desired shape. FIREROD¨ A registered tradename relay that uses the normally open (NO), for Watlow’s patented cartridge heater. normally closed (NC) and common contacts. The operator can choose to F firmware A combination of software wire for a Form A or Form B contact. Fahrenheit The temperature scale and hardware, where the software is that sets the freezing point of water at written (embedded) into a ROM (read fpm Feet per minute. A measure of 32°F and its boiling point at 212°F at only memory) chip, such as PROM flow velocity. When used in gas flow, it standard atmospheric pressure. The (programmable read only memory) or is evaluated at a specific process formula for conversion to Celsius is: EPROM (erasable programmable read temperature and pressure. 5 °C = ⁄9 (°F - 32°F). only memory). fps Feet per second. A measure of failed sensor alarm Warns that an fixed point A reproducible flow velocity. When used in gas flow, it input sensor no longer produces a temperature at the equilibrium point is evaluated at a specific process valid signal. For example, when there between the phase changes in a temperature and pressure. are thermocouple breaks, infrared material. For example, the triple point freezing point The fixed temperature problems, or resistance temperature of water at standard atmospheric point at which a material changes from detector (RTD) open or short failures. pressure is 0.01°C (32.02°F). a liquid to a solid state. This is the FEA Finite Element Analysis. A flexibility The relative ease with which same as the melting point for pure Watlow Research and Development a conductor can bend. See “bend materials. For example, the freezing method of using a computer simulation radius.” point of water is 0°C or 32°F. to create a thermal model of a heater flow area The unobstructed area in frequency The number of cycles over or heated part, saving the time and the cross section of a conduit that is a specified period of time, usually expense of multiple prototype builds. available for fluid flow. measured in cycles per second. Also referred to as Hertz (Hz). The FEA optimizes the heater design with flow rate The actual volume of a fluid reciprocal is called the period. an accurate prediction of the expected passing through a section of a conduit. temperature uniformity. Flow rate may be measured in cubic fuse A device that protects electric FEM Finite Element Method. A feet per minute, cubic meters per circuits by interrupting power in a numerical technique to solve and second or other units. circuit when an overload occurs. Silicon controlled rectifiers (SCRs) simulate the behavior of differential FM See “Factory Mutual Research require special, fast acting fuses, equations, used for thermal system Corporation.” simulation. sometimes referred to as I2t FNPT informal; Female (internal) (amps2-seconds) fuses. National Pipe Thread.

Teflon® is a registered trademark of E.I. duPont de Nemours & Company.

196 Glossary 197 See A A filter that See “process Warns that the Warns that the its final value within 3 ⁄ 2 An input level that A test that applies a high Any object that conducts The gap between the (Hz) Frequency, measured in heat treating thermocouple “heat treating.” “thermocouple” and filter heat/cool output in the response of slows the change The output the heat or cool output. change by going to responds to a step approximately the number of scans that the number of scans are set. concept heated insulation description of one of the major features line of the ceramic fiber heater product from Watlow Columbia, that the insulation and heater element exist in one package. heat sink and dissipates heat away from an object in contact with it. Also a finned piece of metal, usually aluminum, that by is used to dissipate heat generated electrical and electronic devices. Hertz cycles per second. high deviation alarm process exceeds the set point by the be high deviation value or more. It can used as either an alarm or control function. high process alarm be process exceeds a set value. It can used as either an alarm or control function. high process variable corresponds to the high process value. For linear inputs, the high reading is a percentage of the full scale input range. For pulse inputs, the high reading is expressed in cycles per second (Hertz, Hz). hi-pot test voltage to a conductor to assure the integrity of the surrounding insulation. See “dielectric breakdown.” hole fit cartridge heater sheath and the part it fits into. The smaller this gap, the better the heater transfer to the part. variable.” high reading is is a ® ® is a ® The electrical Type of The flow of heat energy A family of related alloys A thermocouple alloy made A thermocouple alloy made ¨ ¨ ¨ Chemical abbreviation Graphic User Interface. A Energy transferred between grounded potential potential of the earth. A circuit, terminal potential of the earth. to be at ground or chassis is said used as a reference potential when it is in the system. point for other potentials grounded junction in which the hot, thermocouple probe is an integral or measuring junction, material. No part of the sheath is provided. electrical isolation GUI representation, on a computer screen, of a system or process that allows the computer user to interact with the system or process. H HAI-KN of 90 percent nickel and 10 percent chromium used in the positive conductor of ASTM Type K and E thermocouples. HAI-KP of 95 percent nickel, two percent aluminum, two percent manganese as and one percent silicon that is used the negative conductor of ASTM Type K thermocouples. HAI-KN (X, Alloy B2 and C276). Hastelloy registered trademark of the Harrison Alloys Company. Hastelloy registered trademark of the Harrison Alloys Company. HAI-KP a registered trademark of Haynes International. HDPE representing high-density polyethylene plastics. heat material bodies as a result of a temperature difference between them. See “Btu,” “calorie” and “Joule.” heat transfer from one body of higher temperature to one of lower temperature. (one 9 W A T L O W O L T A W Alarm associated with A condition created A type of artificial See “preferential An electrical line with the Glass Glass Silicone. An The amount of amplification used The amount of amplification Gallons per minute. A measure (G) A prefix that means 10 Gallons per hour. A measure of G gain in an electrical circuit. Gain can also refer to the proportional (P) mode of PID. GGS optional heater lead wire covering, for Watlow cartridge or multicoil tubular heaters, made with two layers of fiberglass and a silicone binder. giga Glossary fuzzy logic uses a intelligence logic that to represent percentage match data, rather than variable or inexact or false (0) of the exactly true (1) binary logic. of the volumetric flow rate of a fluid. green rot oxidation.” ground billion in the US). Note: The word billion refers to different numbers in Europe and the US. In the US a billion is one thousand million (1,000,000,000). In Germany, England, is France and other countries, a billion one million million (100,000,000,000). That is a trillion in the US. global alarm a global digital output that is cleared a directly from a controller or through user interface. gph the volumetric flow rate of a fluid. gpm same electrical potential as the surrounding earth. Electrical systems are usually grounded to protect people and equipment from shocks due to malfunctions. Also called “safety ground.” ground loop when two or more paths for electricity are created in a ground line, or when one or more paths are created in a shield. Ground loops can create undesirable noise. Glossary hot change A feature of ceramic fiber IFC heated part Interference Fit infrared A region of the and band heaters that allows individual Construction. A manufactured part with electromagnetic spectrum with heater replacement without total a specially designed groove milled into wavelengths ranging from one to 1,000 system shutdown or disassembly. it with an IFC heater element microns. These wavelengths are most HTML Hypertext Markup Language. permanently formed into the groove, suited for radiant heating and infrared HTML uses tags and attributes to creating intimate contact between the (non-contact) temperature sensing. format documents displayed on a web element and the part. IFC heated parts initial calibration tolerance The browser. offer an alternative to milled groove allowable deviation from the theoretical heaters and brazed heater assemblies HTTP Hypertext Transfer Protocol. EMF value generated by any particular for application with temperatures too The protocol used by the worldwide thermocouple type at a given high for aluminum “cast-in” heated web that defines messages and temperature. See “limit of error.” parts, or for environments where cast transmissions between servers and input Process variable information aluminum cannot be used. clients. that is supplied to the instrument. i-key A toggle-action information key hub connecting point in a star- input scaling The ability to scale on controllers that provides context configured LAN (local area network). A input readings (readings in percent of sensitive help in a display. Typically hub gathers individual network nodes full scale) to the engineering units of colored as “highway information sign together. the process variable. blue,” i.e., Pantone 293C or equivalent. hunting Oscillation of a process value input type The signal type that is impedance (Z) The total opposition of near the set point. connected to an input, such as a circuit to the flow of alternating thermocouple, RTD, linear or process. Hypalon¨ A synthetic rubber, current. It includes resistance and chlorosulfonated polyethylene. reactance, and is measured in ohms. installed power Amount of power Hypalon® is a registered trademark of used for an application or process. It is Incoloy¨ A family of related alloys the E.I. duPont de Nemours & the same as the kilowatt (kW) rating of (800, 800X and 825). A registered Company. installed heaters. trademark of the Special Metals hysteresis A change in the process Corporation (formally Inco). Instrument Society of America (ISA) variable required to re-energize the An engineering society that defines Incoloy¨ 800 The standard heater control or alarm output. Sometimes and maintains standards for scientific protective sheath material, a nickel- called switching differential. and technical measuring devices. iron-chromium alloy, and registered tradename of Special Metals insulation A material that electrically Corporation, used for the Watlow isolates a conductor from its I FIREROD® heater. Incoloy® 800 is surroundings, or thermally isolates an I.D. Inside diameter. very corrosion- and temperature- object from its surroundings. ice point The temperature at which resistant, and a key to the long-lived insulation resistance The capacity of pure water changes from a liquid to a FIREROD® in high-temperature an insulation material to resist the flow solid (freezes). 0°C (32°F). applications. of electricity. Expressed in ohms. See “dielectric strength.” idle set point Desired control value Inconel¨ A family of related alloys after a timing period. (600, 601, 625, X750). A registered integral Control action that trademark of the Special Metals automatically eliminates offset, or IETF Internet Engineering Task Force Corporation (formerly Inco). droop, between set point and actual A collection of expert volunteers who process temperature. See “reset” and by consensus set the engineering indication accuracy Closeness “automatic reset.” standards for Internet technology. The between the displayed value and a IETF is overseen by the Internet measured value. Usually expressed as integral control (I) A form of Society, an international, non-profit, a + or -, a percent of span or number temperature control. The I of PID. membership organization focused on of digits. See “integral.” the expansion of the Internet. interchangeability The ability to interchange system components with minimum effect on system accuracy.

198 Glossary , 199 ® , ® . ® . are registered ® ® An electrical circuit and HAI-KP The measure of a material's and HAI-KP ® ® and HAI-KN Kilovoltampere or 1,000 A thermocouple alloy made of A thermocouple alloy The amount of time delay between Lead Adaptor. Watlow's patented A thermocouple alloy made of 90 A thermocouple alloy ® KN two percent 95 percent nickel, manganese aluminum, two percent that is used in and one percent silicon of ASTM Type the negative conductor Manufacturer K thermocouples. include Alumel trademarks for KN trademarks of Harrison Alloys Company. L LA method for adding a variety of options for leads and lead protection to stock heaters. ladder logic diagram schematic style that arranges the positive and negative sides of the power input as the two main beams of a vertical ladder, and arranges the connections between them as the rungs of the ladder. lag two related parts of a process or system. HAI-KN KP 10 percent percent nickel and chromium that is used in the positive conductors of ASTM Type E and K thermocouples. Manufacturer trademarks for KP include Chromel kVA voltamperes (VA). One unit of apparent power equals 1VA. k-value thermal conductivity coefficient or its ability to conduct heat. Copper conducts better than plastic; copper has a higher k value. The k-value is expressed in W/cmK (watt per centimeter Kelvin) or in Btu/hft.F (Btu per hour per ft. degree Fahrenheit). The k-value is the reciprocal of the R- value, thermal resistance. Nial Tophel (JIS) A are registered ® are registered trademarks of (kWh) Unit of electrical ® The point where two A lightweight organic (kW) Unit of electrical power and Alumel A basic unit of heat energy, ¨ (k) An absolute temperature ® A set of operating conditions for a A set of operating and Tophel (k) A prefix meaning thousand. ® dissimilar metal conductors join to form a thermocouple. Japanese agency that establishes and Japanese agency for equipment maintains standards Also known as JISC and components. Standards (Japanese Industrial Committee), its function is similar to Germany’s Deutsche Industrial Norm (DIN). Joule equal to the work done when a current of one ampere is passed through a resistance of one ohm for one second. junction job stored and process that can be memory. recalled in a controller’s Also called a recipe. Joint Industrial Standards Carpenter Technology (Car Tech). Chromel Nial Kapton K trademarks of Hoskins Manufacturing Company. polymer film that is a versatile dielectric material because of its tensile strength, dimensional stability A and low emission of gas in vacuums. registered trademark of the E.I. duPont de Nemours & Company. Kelvin scale. Zero Kelvin is absolute zero. No degree symbol (°) is used with the Kelvin scale. (0°C = 273.15K, 100°C = 373.15K). kilo kilowatt equal to 1,000 watts or 3,412 Btus per hour when the power factor equals 1.0. kilowatt hour energy, or work, expended by one kilowatt in one hour. Also expressed as 1,000 watt hours. W A T L O W O L T A W A form of A process, volume or area International Practical Electrical separation of The outer covering on a wire or International Temperature Scale Joint Development Agreement. The positive conductor in ASTM See “Instrument Society of See “Joint Industrial Standards.” One of two primary protocols that One of two primary jacket cable. It may provide electrical insulation and/or resistance to chemicals, abrasion and moisture. JDA Specifies what role each party agrees to when developing a new product. JIS J internet hosts use. IP describes the internet hosts use. or message packet (datagrams format. IP is segment of messages) defined by the network layer protocol “TCP/IP.” IETF. See “TCP” and IPTS48, 68 Type J thermocouples. ISA America.” isolation junction Glossary IP of 1948 and 1968. Temperature Scales superseded by These have been ITS90. See “ITS90.” iron thermocouple probe construction in which the measuring junction is fully enclosed in a protective sheath and electrically isolated from it. Commonly called an ungrounded junction. isolation sensor from high-voltage circuitry. Allows use of grounded or ungrounded sensing element. isothermal that maintains a constant temperature. ITS90 of 1990. The standard scale made of fixed points that closely approximate thermodynamic temperatures. All temperatures between the fixed points are derived by interpolation using the assigned interpolation instrument. Adopted in late 1993, this scale replaces both IPTS48 and 68. Glossary LAN Local Area Network. A computer linear input A process input that low reading An input level network in a single physical location. represents a straight line function. corresponding to the low process LANs can be connected together in a linearity The deviation in response value. For linear inputs, the low Wide Area Network (WAN). from an expected or theoretical reading is a percentage of the full scale input range. For pulse inputs, the latent heat of fusion (HF) The amount straight line value for instruments and of heat energy, expressed in Btu/lb or transducers. Also called linearity error. low reading is expressed in cycles per second, Hertz (Hz). Joule/gram, required to change a solid linearization, input See to a liquid without an increase in “linearization” and “square root.” temperature. linearization, square root The M latent heat of vaporization (HV) The extraction of a linear signal from a manual mode A selectable mode amount of heat energy, expressed in nonlinear signal corresponding to the Btu/lb or Joule/gram, required to without automatic control. The operator measured flow from a flow transmitter. sets output levels. Same as open loop change a liquid to a vapor without an Also called square root extraction. increase in temperature. control. liquid crystal display (LCD) A type of manual reset 1) A feature on a limit lava cone Low temperature silicate- digital display made of a material that based insulator used between control that requires human changes reflectance or transmittance intervention to return the limit to electrically conductive and non- when an electrical field is applied to it. conductive casings or tubes. normal operation after a limit condition load The electrical demand of a has occurred. 2) The adjustment of LCP Liquid Crystal Polymer. A process, expressed in power (watts), a proportional control to raise the high-temperature thermoplastic with current (amps) or resistance (ohms). proportional band to compensate good impact strength. The item or substance that is to be for droop. heated or cooled. LED See “light emitting diode.” mass flow rate The amount of a local set point The primary set point. leg One connection in an electric substance that flows past a given circuit. loop See “control loop.” cross-section area of a conduit in a given unit of time. light emitting diode (LED) loop alarm Any alarm system that A solid-state electronic device that includes high and low process, master A device that transmits a set glows when electric current passes deviation band, dead band, digital point signal to other controlling through it. outputs, and auxiliary control outputs. devices, called remotes. limit of error A tolerance band of the loop resistance The total resistance maximum load impedance The thermal electric response of of the conducting materials in a largest load that the output device can thermocouple wire, expressed as a thermocouple circuit. operate. Usually specified in ohms. percentage or a specific degree value low deviation alarm Warns that the maximum operating temperature in defined temperature ranges, defined process is below the set point by the The highest temperature at which a by the ASTM specification MC96.1 low deviation value or move process device can operate safely, or with (1982). variable. It can be used as either an expected normal service life. limit or limit controller A highly alarm or control function. maximum power rating The reliable, discrete safety device low process alarm Warns that the maximum operating power at which a (redundant to the primary controller) process is below a set value. It can be device can operate safely or with that monitors and limits the used as either an alarm or control expected normal operating life. temperature of the process, or a point function. MCDA Mutual Confidential Disclosure in the process. When temperature low process variable See “process Agreement. A legal document that exceeds or falls below the limit set variable.” spells out mutual provisions for both point, the limit controller interrupts parties, and the conditions and power through the load circuit. A limit circumstances in which confidential controller can protect equipment and information can be shared by both people when it is correctly installed parties, and the remedies required for with its own power supply, power lines, violations. switch and sensor.

200 Glossary 201 is a (NBS) ® (NEC) A set (NPT) The A hybrid circuit (NEMA) A United States (NIST) A United States An alloy made of nickel and An alloy made of nickel Terephtalate (polyester) film. A ¨ ¨ Monel N National Bureau of Standards Now called the National Institute of Standards Technology (NIST). National Electrical Code of specifications devised for the safe application and use of electric power and devices in the United States. National Electrical Manufacturers Association association that establishes specifications and ratings for electrical components and apparatuses. Conformance by manufacturers is voluntary. National Institute of Standards and Technology government agency responsible for establishing scientific and technical standards. Formerly the National Bureau of Standards. National Pipe Thread taper pipe thread standard used in North America. registered trademark of the E.I. duPont de Nemours & Company. copper sensor sheath that is used to copper sensor sheath It exhibits make sensor sheaths. to sea water; to excellent resistance and hydrochloric hydrofluoric, sulfuric alkalis. Monel acids; and to most registered trademark of the Special registered trademark (formally Inco). Metals Corporation multilayer hybrid conductive constructed of alternating and insulating layers. The multilayer structure combines very dense packaging of electronics with good ability to remove generated heat. Multilayers are typically built through repeated firings as layers are added and are typically constructed with gold, silver-palladium or copper conductors. Mylar A See A -3 of a volt The smallest (thousandth) -6 The relative -3 meters. -6 A machined groove (mA) One 10 protocol driver (µV) One 10 ª (mV) One 10 A unit of length. One micron is A unit of length. One informal; Male (external) A silicate material used primarily A silicate material Magnesium Oxide. The One thousandth of an inch, or One thousandth of thousandth) of an ampere. as an electrical and heat insulator. as an electrical and micron equivalent to 10 mica millivolt software program subroutine that converts programming language- or operating system-specific instructions to the MODBUS™ protocol for a MODBUS™ device. moisture resistance ability to resist permeation by water. microvolt load current required to ensure proper operation of an output switching device. minimum output impedance of a volt. mineral insulated thermocouple thermocouple probe constructed by loading a metal sheath with thermocouple conductors and a mineral-based dielectric material, then compacting the entire assembly. minimum load current “offstate impedance.” MNPT National Pipe Thread. MO powdered chemical compound used in heater manufacturing to insulate the resistance wire from the metal sheath. This high grade material also contributes to the long life of Watlow heaters. MODBUS (one millionth in the US). (one millionth in the mil form. 0.001 inches in decimal milled groove milled into a part to accept a heater shaped to fit the groove. milliampere ( 6 binder. W A T L O W O L T A W ® . An optional ® watts or 6 See “junction.” The 1x10 The temperature at A breakdown in metal Mineral Insulated leads. A A list of options from which the (M) A prefix that means one 10 (M) A prefix that means See “relay, mercury Mica Glass Teflon Management Information Base A (one million in the US). (one million in the megawatt (MW) measuring junction that is affixed to thermocouple junction material being or inserted into the hot junction. measured. Also called mega Glossary MDR displacement.” measuring junction strength caused by mechanical action. For example, when sheath and conductor materials have different linear expansion coefficients, heating and cooling cause mechanical movement that induces strain. Metal fatigue shortens the life of the heater and the thermocouple. MGT operator can select the tasks to be done. mercury displacement relay (MDR) A power switching device in which mercury, displaced by a plunger, completes the electric circuit across contacts. metal fatigue 1,000,000 (one million) watts. melting point which a substance changes from a as solid to liquid state. This is the same the freezing point of pure materials. menu heater lead wire covering, used with several Watlow heater lines, made with mica, fiberglass and a Teflon MI leads Watlow LA (Lead Adaptor) termination option for cartridge heaters that handles both high temperatures up to 815°C (1,500°F) and contamination, such as moisture, gases, oils, plastic drool, solvents and water. MIB database of defined properties of objects that can be monitored or manipulated by a network administrator via an SNMP agent. Glossary NBS See “National Bureau of nisil A thermocouple alloy that is NSF 1) National Sanitation Standards.” made of 95.6 percent nickel and Foundation; 2) National Science NEC See “National Electrical Code.” 4.4 percent silicon. It is used in the Foundation. negative conductor of an ASTM negative temperature coefficient A NUWARMTH¨ A Watlow wholly- Type N thermocouple. decrease in electrical resistance that owned subsidiary that produces and occurs with a temperature increase. NIST See “National Institute of markets consumer-focused See “thermistor.” Standards and Technology.” thermopolymer products primarily for the home and automotive industries. NEMA See “National Electrical no key reset A method for resetting Manufacturers Association.” the controller's memory (for instance, nylon A thermoplastic that is after an EPROM change). commonly used as an insulation NEMA 4X A NEMA specification for because it exhibits excellent abrasion determining resistance to moisture noble metal thermocouple The and good chemical resistance. infiltration and corrosion resistance. general designation for thermocouples This rating certifies the controller as with conductors made of platinum washable and corrosion resistant. and/or platinum alloys (ASTM Types B, R and S). They are used in high- O neoprene A synthetic rubber, also temperature or corrosive applications. referred to as polychloroprene, that O.D. Outside diameter. exhibits good resistance to oil, node A connection point on a offset Synonym for “droop.” In a chemicals and flame. computer network for one computer or stable thermal system, the difference other addressable device, such as a NetBios Network Basic Input Output between the process set point and the printer. System. An application programming process actual temperature. An offset interface (API) that adds special no-heat The part of a Watlow heater variable can be introduced network functions to a computer’s intentionally designed as unheated, or intentionally into the system by some basic operating system. as an unheated extension, outside the controllers to compensate for sensor resistance wire (heater coil) area. The placement. In PID control, integral Network Layer (OSI Layer 3) The no-heat area has a lower temperature (reset) will eliminate droop. third layer of the seven-layer OSI due to heat losses of various types: (Open System Interconnection) offstate impedance The minimum radiation; conduction; or convection. protocol model that handles switching, electrical resistance of the output routing, and packet sequencing noise Unwanted electrical signals that device in the off, or de-energized, between nodes on a network. The usually produce signal interference in state. It is based on the frequency of Network Layer resides between the sensors and sensor circuits. See the load supply current plus internal Transport Layer and the Data Link “electromagnetic interference (EMI).” and/or external noise suppression Layer. noise suppression The use of devices. Nial¨ A thermocouple alloy made of components to reduce electrical OFHC Oxygen-free, high conductivity 95 percent nickel, two percent interference that is caused by making copper. The pure copper used in the aluminum, two percent manganese or breaking electrical contact, or by positive conductor of a an ASTM and one percent silicon that is used in inductors. Type T thermocouple. the negative conductor of ASTM Nomex¨ A temperature-resistant, ohm (Ω) The unit of electric Type K thermocouples. Nial® is a flame retardant nylon compound that is resistance. The resistance value registered trademark of Carpenter used as a wire insulation. A registered through which one volt will maintain Technology. trademark of E.I. duPont de Nemours a current of one ampere. See “Ohm’s nicrosil A thermocouple alloy that is & Company. Law.” made of 84.6 percent nickel, 14.0 NPT See “National Pipe Thread.” Ohm’s Law Current in a circuit is percent chromium and 1.4 percent NPT American National Standard directly proportional to the voltage, silicon. It is used in the positive Taper Pipe Thread as defined by ANSI and inversely proportional to conductor of an ASTM Type N B1.20.1. resistance; stated as: E = IR, I = E/R, thermocouple. R = E/I, P = EI where 1 = current in amperes, E = EMF in volts, R = resistance in ohlms and P = power in watts.

202 Glossary 203 The Open-loop Restriction of A mode of power Inverse of Seebeck .” Proportioning control with ® The time-based relationship Chemical abbreviation Chemical abbreviation for See “polyetherimide.” Proportional, Integral, Derivative. representing a perfluoroalkyl group. See “Teflon control with output power set at a control with output particular level. percent power limit predetermined level. output power to a PET polyethylene terephthalate. PFA PEI Peltier Effect effect, used in thermoelectric “Seebeck” effect. applications. See percent power control first and lowest layer of the seven-layer OSI (Open System Interconnection) protocol model where bits of information move through the physical medium or space. The Physical Layer includes the hardware means of moving the information. The Physical Layer resides below the Data Link Layer. PI control integral (automatic reset) action. PID A control mode with three functions: proportional action dampens the system response, integral corrects for droop, and derivative prevents overshoot and undershoot. phase between alternating current cycles and it a fixed reference point. In electricity, is usually expressed in angular degrees, with a complete cycle equal to 360˚. It describes the relationships of voltage and current of two or more alternating waveforms. phase-angle firing control in silicon controlled rectifiers (SCRs). Phase-angle firing varies the point at which the SCR switches voltage inside the AC sine wave. Physical Layer (OSI Layer 1) A component A circuit configuration Proportional derivative The form of PID control A process for treating Proportioning control with The amount by which a The amount by which A feature that prevents 1. A variable that is given a Proportioning control. The control signal that affects The control signal See “polycarbonate.” output the and process value. output type proportioning, output, such as time serial digital- distributed zero crossing, or analog. Also the to-analog converter electrical hardware description of the output. that makes up the overshoot the set point process variable exceeds before it stabilizes. P P control panel lock operation of the front panel. parallel circuit in which the same voltage is applied to in which the same voltage is applied all components, with current divided among the components according to their respective resistances or impedances. parameter constant value for a specific application or process. 2. A value that determines the response of an electronic controller to given inputs. passivation stainless steel surfaces, usually with dilute nitric acid to remove contaminants, and to apply a passive film protecting the fresh metal surface. passive component whose properties do not change with changes in the applied signal. Resistors, capacitors and inductors are passive components. PC PD control derivative (rate) action. PDR control control with manual reset, used in fast responding systems where the reset causes instabilities. With PDR control, an operator can enter a manual reset value that eliminates droop in the system. entifier. W A T L O W O L T A W (Open System bject ID A temperature Two electronic The menus A control system with no Occupational Safety and A method of control that turns A method of control ("oh-eye-dee") O Glossary OID Interconnection, ISO/IEC 7498-1) A seven-layered model for developing and implementing communication among systems. Control passes from one layer to the next and back again, beginning at the application layer in the system that initiates the communication. The reference model provides a common basis for the coordination of standards development for the purpose of systems interconnection from ISO/IEC 7498-1. accessible from the front panel of a controller. These menus allow operators to set or change various control actions or features. optical isolation networks that are connected through an LED (light emitting diode) and a photoelectric receiver. There is no electrical continuity between the two networks. OSHA Health Act. Also the Occupational Safety and Health Agency, the United States governmental agency that establishes and enforces safety standards in the workplace. OSI Reference Model sensory feedback. See “manual mode.” operator menus In the NAFEM (National Association of In the NAFEM (National Food Equipment Manufacturers) form an context, Object Identifiers of a supplier's index of attributes in a data programmable objects identifiers protocol model. Object standard. derive from the SNMP on-off set point is the output full on until reached, and then off until the process error exceeds the hysteresis. on-off controller controller that operates in either full-on or full-off state. open loop Glossary ping Packet Internet groper. A polarity The electrical quality of potting The sealing of components computer utility used to troubleshoot having two opposite poles, one and associated conductors with a Internet connections. Ping verifies that positive and one negative. Polarity compound to exclude moisture and a specific IP address is available. determines the direction in which a contaminants. plastic Natural and synthetic current tends to flow. power factor (PF) The ratio of real polymeric substances, excluding poll engine A software application power (PR) to apparent power (PA). rubbers, that flow under heat and/or dedicated to continuously requesting power loss alarm Associated with pressure. See http://www. data from connected devices on a latching limit controls, the limit control plasticstechnology.com/materials/ network. recognizes a power outage as a limit index.html for an extensive materials polycarbonate (PC) A thermoplastic condition. Manual reset is required to database, including abbreviations, that offers high strength and re-energize the output after power is properties, features, etc. toughness. restored. Platinel¨ A nonstandard platinum polyester A broad class of polymers PPS See “polyphenylene sulfide.” alloy with thermoelectric possessing good moisture resistance pre-aging A process by which a characteristics that closely match and electrical properties. thermocouple is subjected to ASTM Type K thermocouples at polyetherimide (PEI) A high- application conditions that cause most temperatures above 800°C (1440°F). temperature thermoplastic with of any electromagnetic force shift Platinel® is a registered trademark of excellent strength and chemical (decalibration). When it is installed and Englehard Industries. resistance. calibrated to an instrument, a pre-aged platinum (Pt 2) A noble metal that is polyethylene (PE) A thermoplastic thermocouple will produce reliable more ductile than silver, gold or that exhibits excellent dielectric readings. copper, and has excellent chemical characteristics. preferential oxidation Commonly and heat resistant characteristics. It is called green rot. A phenomenon used in the negative conductor in polymer Any substance made of many repeating chemical molecules. peculiar to nickel-based ASTM Types R and S thermocouples. thermocouples, most often ASTM Type platinum 10 percent rhodium The Often used in place of plastic, rubber or elastomer. K, when oxygen is limited. The limited platinum-rhodium thermocouple alloy oxygen reacts with the more active that forms the positive conductor on polyphenylene sulfide (PPS) A high- chromium in the conductor alloy, which ASTM Type S thermocouples. temperature thermoplastic with good changes to chromium oxide and platinum 13 percent rhodium The solvent resistance and flame creates a green scale. An increasing platinum-rhodium thermocouple alloy retardation. nickel skin is left behind, causing that forms the positive conductor on polypropylene A thermoplastic that is decalibration. Decalibration is caused ASTM Type R thermocouples. similar to polyethylene, but has a when the negative thermoelement is platinum 30 percent rhodium The higher softening point (temperature). paired against a nickel skin and not platinum-rhodium thermocouple alloy polysulfone (PSU) A thermoplastic the original homogeneous nickel- that forms the positive conductor on with excellent water and similar fluid chromium alloy. Preferential oxidation ASTM Type B thermocouples. resistance. will not occur when there is an platinum 6 percent rhodium The polyurethane (PUR) A broad class of abundant supply or a total absence of platinum-rhodium thermocouple alloy polymers that has good abrasion and oxygen. that forms the negative conductor on chemical resistance. presentation layer (OSI Layer 6) The ASTM Type B thermocouples. polyvinyl chloride (PVC) A sixth layer of the seven-layer OSI platinum 67 An NIST platinum thermoplastic with excellent dielectric (Open System Interconnection) standard. Platinum 67 is used to strength and flexibility. protocol model where syntax, interpolate the temperature scale compatibility, and encryption issues between 630.74 and 1064.43°C positive temperature coefficient are resolved. The Presentation Layer (1167.33 and 1947.97°F). Replacing (PTC) An increase in resistance that resides between the Application Layer platinum 27, platinum 67 (IPTS68) is occurs with an increase in and the Session Layer. nine microvolts negative to temperature. See “resistance platinum 27. temperature detector” and “thermistor.”

204 Glossary A 205 A ) to ® (RTI) A long- The known Energy from the A range in which the rate See “job.” The area between two limits in The area between A programmed increase in the A programmed increase A method by which the controller Anticipatory action that is based Anticipatory action A switching device. term heat aging test used by Underwriter’s Laboratories (UL control feature that automatically corrects the reading from a sensor. reflective energy background that causes an error when an infrared sensor measures the radiant energy of a specific object. refractory metal thermocouple thermocouple made from materials such as tungsten and rhenium, which melt above 1935°C (3515°F). These are non-ASTM types C, D and G. relative thermal index ramp point system. temperature of a set range value is measured. which a quantity or in terms of lower It is usually described and upper limits. rate change, on the rate of temperature to minimize and compensates overshoot and undershoot. See “derivative.” rate band function of a controller is active. Expressed in multiples of the proportional band. See “PID.” ratio measures the flow of an uncontrolled variable and uses a portion of it to control the flow of a second variable. recipe reference junction temperature point at which a thermocouple or its extension wire connects to a temperature measurement instrument or controller. To prevent an error from introducing itself at this point, some instruments will add a compensation value to the signal. Also called the “cold junction.” reflection compensation mode determine the maximum application temperature for plastics. relay ” ® (RFI) An enclosure that A tube that protects a A tube that protects Digital pulse signals from Radiant energy emitted in Thermodynamic term that Chemical abbreviation for See “polysulfone.” Pounds per square inch gauge. Pounds per square inch Pounds per square See “polyvinyl chloride.” protection head connections of protects the electrical probes. heaters or sensor protection tube RTD or sensor (thermocouple, environmental thermistor) from harsh or process conditions. psia expressed in terms absolute. Pressure value with of its actual or absolute = reference to a perfect vacuum. psia psig + 14.7 psi (1 atmosphere). See “psig.” psig Pressure expressed in terms of a value read directly from installed gauges. psig = psia -14.7 psi (1 atmosphere). See “psia.” PSU PTFE polytetrafluoroethylene. See “Teflon R radiation the form of waves or particles. See “emissivity” and “infrared.” radio frequency interference Electromagnetic waves between the frequencies of 10kHz and 300gHz that can affect susceptible systems by conduction through sensor or power input lines, and by radiation through space. Q quality indicates the relative amount of liquid present in saturated steam as a percent of the total weight. The quality of steam is 100 percent minus the percent of liquid. Dry saturated steam has a quality of 100 percent. and “TFE.” pulse input devices, such as optical encoders. PVC Displayed W A T L O W O L T A W A control using (PB) A range in An instrument that The parameter that Warns that process The difference Output effort A symbol or message A temperature sensor. A probe A temperature sensor. meets conditions required by the meets conditions required Scale International Temperature (ITS90). probe RTD, may contain a thermocouple, circuit (IC) thermistor or integrated sensor. process alarm the process alarm values are outside range. A fixed value independent of the set point. process error between the set point and the actual process value. process variable is controlled or measured. Typical examples are temperature, relative humidity, pressure, flow, fluid level, events, etc. The high process variable is the highest value of the process range, expressed in engineering units. The low process variable is the lowest value of the process range. programmed display data information that gives the operator the as intended process information, such intended set point, intended alarm limit, etc., corresponding to temperature or other engineering units. prompt displayed by the computer or controller that requests input from the user. proportional proportional to the error from set point. For example, if the proportional band is 20° and the process is 10° below set point, the heat proportioned effort is 50 percent. The lower the PB value, the higher the gain. proportional band Glossary primary standard which the proportioning function of the control is active. Expressed in units, degrees or percent of span. See “PID.” proportional control only the P (proportional) value of PID control. Glossary remote A controller that receives its resolution An expression of the RTD See “resistance temperature set point signal from another device smallest input change unit detectable detector.” called the master. at a system output. RTI See “relative thermal index.” remote set point A signal from response time (time constant) 1) The rubber insulation A general another device that indicates the set time required by a sensor to reach designation for thermosetting point for the process. 63.2 percent of a temperature step elastomers, such as natural and repeatability The ability to provide the change under a specified set of synthetic rubbers, neoprene, same output or reading under conditions. Five time constants are Hypalon®, and butyl rubber. They are repeated, identical conditions. See required for the sensor to stabilize at used to insulate wire conductors. “stability.” 100 percent of the step change value. Hypalon® is a registered trademark of 2) With infrared temperature sensing, reset Control action that automatically the E.I. duPont de Nemours & the time required for a sensor to reach eliminates offset, or droop, between Company. 95 percent of a step change. This is set point and actual process known as the time constant times temperature. Also see “integral.” three. The overall system response S reset windup inhibit See “anti-reset time is the sum of the time constants of wind-up.” each component. SAE See “Society of Automotive Engineers.” resistance Opposition to the flow of retransmit output An analog output electric current, measured in ohms. signal that may be scaled to represent safety limit An automatic limit See “ohms.” the process value or set point value. intended for use in applications where an over-temperature fault may cause a resistance temperature reverse action An output control fire or pose other safety concerns. characteristic The characteristic action in which an increase in the change in a sensor’s resistance when process variable causes a decrease in SAMA See “Scientific Apparatus exposed to a change in temperature. the output. Heating applications Makers Association.” See “positive temperature coefficient” usually use reverse action. saturation pressure The pressure on and “negative temperature coefficient.” RFI See “radio frequency a liquid when it boils at a given resistance temperature detector interference.” temperature. Both the saturated liquid (RTD) A sensor that uses the and saturated vapor phases can exist rhenium (Re) A metallic element that, resistance temperature characteristic at this time. when added to tungsten, forms an to measure temperature. There are two alloy with better ductility and higher saturation temperature The boiling basic types of RTDs: the wire RTD, temperature strength than tungsten temperature of a liquid at its existing which is usually made of platinum, and alone. pressure. the thermistor, which is made of a scfm Standard volumetric flow rate in semiconductor material. The wire RTD rhodium (Rh) A metallic element cubic feet per minute. A measure of is a positive temperature coefficient inside the platinum group that, when the flow rate of gases and vapors sensor only, while the thermistor can added to pure platinum, forms an alloy under standard conditions of 15°C have either a negative or positive with reduced ductility and better high (60°F) and standard atmospheric temperature coefficient. temperature strength than platinum alone. pressure. resistive loads All loads that limit the Scientific Apparatus Makers flow of electric current. With pure router A device that connects one Association (SAMA) An association resistive loads, voltage and current are computer local area network (LAN) to that sets standards for platinum, nickel in phase. another using ICMP (Internet Control Message Protocol), part of IP (Internet and copper resistance elements Protocol), to communicate with other (RTDs). routers, and to determine optimum SCR See “silicon controlled rectifier.” data paths.

206 Glossary 207 (SCR) A The relative A method of The area of a Rubber that is made A thermosetting elastomer A tetravalend nonmetallic Any electrical transmittance Simple Mail Transfer Protocol. In an electrical circuit, a low In an electrical circuit, Systems Internationale. The system shield effectiveness to screen ability of a shield material effectiveness is interference. Shield shield percentage. often confused with shield percentage is covered by a circuit or cable that expressed as a shielding material, percentage. shunt between two resistance connection points that forms an alternate path for some of the current. Dielectric materials lose resistance at temperatures above their operating range. This condition can cause shunting of the sensor’s signal, causing an error in the reading. SI of standard metric units. signal that conveys information. silicon element. silicon controlled rectifier solid-state device, or thyristor, with no moving parts, that is used in pairs to control ac voltages within one cycle. SCRs control voltage from a power source to the load by burst firing (also called zero-cross firing) or phase angle firing. See “burst fire.” silicone that is made of silicone and oxygen, and noted for high heat resistance. silicone rubber from silicone elastomers and noted for its retention of flexibility, resilience and tensile strength. slidewire feedback controlling the position of a valve. using a potentiometer. The resistance indicates the valve position. SMTP A protocol that enables e-mail servers and clients to send e-mail. A mineral- Closeness between See “shield (OSI Layer 5) The fifth (OSI Layer 5) The The amount of energy a The desired value A potentiometer used to adjust A metallic foil or braided wire Standard flow velocity in feet Standard flow velocity in feet the value established by an input device, such as a dial, and the desired value. Usually expressed as a percent of span or number of digits. SFPM per minute. For gas flow, it is evaluated using the SCFM (standard cubic feet per minute) divided by the flow area. sfpm controller set point temperature. setting accuracy per minute. Gas flow is calculated using scfm divided by the flow area. shape factor Session Layer OSI (Open layer of the seven-layer protocol System Interconnection) stops and manages model that starts, applications. connections between resides between The Session Layer and the the Presentation Layer Transport Layer. set point a controller. For programmed into example, the temperature at which a system is to be maintained. setpot target object receives, relative to the size of the heater and its distance from the object. sheath thermocouple percentage.” insulated thermocouple that has an outer metal sheath. It is usually made from mineral-insulated thermocouple cable. shield layer surrounding conductors that is designed to prevent electrostatic or electromagnetic interference from external sources. shield coverage W A T L O W O L T A W A method of A measurement The rate of A printing method Any material that When a circuit is The net thermal A circuit configuration The process by which A device or computer on a Glossary screen printing that uses a photographic process to that uses a photographic a fine screen, and create an image on image to another then transfers that forcing ink or surface with a squeegee through the other viscous material Watlow uses mesh of the screen. both traditional screen printing in in thick film product labeling and manufacturing. secondary standard device that refers to a primary standard. Seebeck coefficient change (derivative) of thermal EMF (voltage) with respect to temperature. Expressed as millivolts per degree. Seebeck effect formed with a junction of two dissimilar metals and the junctions at each end are held at different temperatures, a current will flow in the circuit. Seebeck EMF electromotive force (EMF) in a thermocouple under conditions of zero current. semiconductor exhibits a degree of electrical conductivity that falls between that of conductors and dielectrics. serial communications transmitting information between devices by sending all bits serially over a single communication channel. series circuit in which a single current path is arranged among all components. server network that serves or delivers network resources, such as a file server, database server, print server or web server. serving metallic or nonmetallic filaments or fibers are woven around a wire conductor to produce electrical insulation, shielding or improved abrasion resistance. See “braid.” Glossary SNMP Simple Network Management span The difference between the standard wire error The level of Protocol. Protocols for managing lower and upper limits of a range deviation from established standards. complex networks. SNMP exists at the expressed in the same units as the Usually expressed in terms of ±°C or Presentation (Layer 6) and Application range. See “range.” percent. Also known as standard (Layer 7) layers of the seven-layer spark test A high voltage, low tolerances. Open System Interconnection (OSI) amperage test that detects insulation subnet Part of a TCP/IP network that model, from standard ISO/IEC defects in wire and cable. shares the same IP address prefix. (International Organization for specific gravity (sp. gr.) Density Networks are divided into subnets to Standardization/International relative to the density of water, which is increase performance and security. Electrotechnical Commission) 7498-1. given the arbitrary value of one at 0°C. superheat Heating of a gas or vapor SNMP agent A means for a network See “density.” to a temperature well above its dry administrator to communicate with an specific heat capacity The quantity of saturation temperature. This term will object within a specific device on a heat (in joules or Btus) necessary to be encountered frequently when network. raise the temperature of one kilogram working with steam. These SNMP manager A network (or pound) of substance through 1 temperatures, coupled with the administrator’s interface for performing Kelvin. In most materials, specific heat tabulated enthalpy values, provide a network management tasks on a capacity varies with changes in simple means of calculating the power network’s Simple Network temperature and material state. needed for superheating. Management Protocol layers. specific volume The inverse of surge current A short duration rush of soaking In heat treating, the practice density, expressed in units of cubic current that occurs when power is first of immersing an object in a heated feet per pound or cubic meters per applied to capacitive, inductive or environment so it can complete a kilogram. temperature dependent resistive desired metallurgical change at a loads, such as tungsten or silicon spectral filter A filter that restricts the specific temperature. carbide heating elements. It also electromagnetic spectrum to a specific occurs when inductive loads are de- Society of Automotive Engineers bandwidth, such as four to eight energized. Surge currents usually last (SAE) A society that establishes microns infrared radiation. standards for the transportation no more than several cycles. spectral response band The region industries (automotive, marine and swage Uniform compaction process of the infrared portion of the aviation), including the system of that decreases the diameter and electromagnetic spectrum over which English units (pounds, feet, gallons, increases the length of a cylinder. This an infrared sensor processes a signal. etc.). compaction process used in cartridge Infrared sensors that operate at shorter heater and sensor manufacturing, soft start A method of using phase- wavelengths are designed for higher creates higher thermal conductivity angle SCR control to gradually temperatures. increase the output power over a (better heat transfer) and greater spot size See “field of view.” period of several seconds. Soft starts dielectric strength (longer life). The unit are used for heaters that have a low spread In heat/cool applications, the can be swaged multiple times, known electrical resistance when they are difference between heat and cool. Also as double swaging. cold, or for limiting in-rush current to known as process dead band. See switch 1) A device, either electrical or inductive loads. “dead band.” mechanical, used to open or close an software Instructions that enable a SSR See “solid state relay.” electrical circuit. 2) A computer computing device 1) to function, as in stability The ability of a device to programming technique that will an operating system , or 2) to perform maintain a constant output with the change a selection from one state to specific tasks, as in applications. application of a constant input. another. 3) A telephone interface that connects callers. 4) A network routing These instructions are typically stored standard A set value or reference device that provides numbered nodes, in some type of memory media. point from which measurements or one for each connected device. solid-state relay (SSR) A switching calibrations are made. device with no moving parts that switching differential See completes or interrupts a circuit “hysteresis.” electrically.

208 Glossary 209 The A pair (T/C) A temperature A temperature sensing thermistor semiconductor device made of a a large change in material that exhibits change in resistance for a small usually have temperature. Thermistors coefficients, negative temperature also available with although they are coefficients. positive temperature thermocouple by joining two sensing device made dissimilar metals. This junction produces an electrical voltage in proportion to the difference in temperature between the hot junction (sensing junction) and the lead wire connection to the instrument (cold junction). thermocouple aging or aging range A positive shift in electromotive force (EMF) in nickel-based thermocouple alloys that is caused by a temperature gradient along the thermocouple elements. Factors that cause EMF shift are the measured temperature, the previous thermal history of the element, the amount of time spent at the aging temperature and the amount of the element subjected to the aging temperature. Different thermocouple types age differently under different application conditions. thermocouple break protection ability of a control to detect a break in the thermocouple circuit and take a predetermined action. thermocouple extension wire of wires connecting a thermocouple sensor to its reference junction or instrumentation. The electromotive force (EMF) characteristics of the extension wire must be similar to the EMF characteristics of the thermocouple. . ® (one 12 The The quantity of , An increase in the The distribution of A regulated PTFE A condition in which The ability of a The delay in the (T) A prefix meaning 10 (T) A prefix meaning A common short hand temperature, ambient air or other medium temperature of the components of a that surrounds the thermal system. tera trillion in the US). TFE abbreviation for polytetrafluoroethylene, or Teflon polytetrafluoroethylene, the mass of the sensor absorbs a portion of the heat being measured, which results in an erroneous reading. thermal system environment that consists of a heat source, heat transfer medium or load, sensing device and a control instrument. distribution of heat energy throughout a system. Thermal lag can cause process temperature instability. thermal shunt heat transmitted by conduction through a body per unit area, per unit time, per unit thickness for a temperature difference of 1 Kelvin. in This value changes with temperature most materials and must be evaluated for conditions given. Expressed in Btu/hr-ft-°F or Watts/meter-°C. thermal EMF thermocouple to produce a voltage that increases or decreases in proportion to its change in temperature. thermal expansion size of a material that is caused by an as increase in temperature. Expressed the number of inches/inch/°F or cm/cm/°C per reference length. thermal gradient differential temperatures through a body or across a surface. thermal lag thermal conductivity A W A T L O W O L T A W Factory (SI) The In on-off is a registered ® (TIA) A trade group that A registered trademark of E.I. (ETFE) Fluoropolymer material, Transmission Control ¨ ¨ Transmission Control Protocol. Timed derivative. The derivative T TCP One of two primary protocols that distinct Internet hosts use to establish a connection and exchange data while ensuring that data packets are received in the same order as they were sent. TCP is a session-based transport layer protocol defined by the IETF. See “IP” and “TCP/IP.” TCP/IP Protocol/Internet Protocol. The two primary protocols used to connect hosts and exchange data on the Internet. TD function. Teflon Glossary switching sensitivity control, the temperature change control, the temperature the output from necessary to change “hysteresis.” full on to full off. See Systems Internationale metric units. system of standard ethylene tetrafluoroethylene, with excellent mechanical properties, particularly important in wire and cable applications. Tefzel duPont de Nemours & Company, covering a family of fluorocarbon materials that includes FEP, PFA and PTFE. Tefzel trademark of the E.I. duPont de Nemours & Company. Telecommunication Industry Association sets standards for the telecommunications industries. temperature calibration point temperature at which the output of a sensor is compared against a standard. temperature limit switch Mutual (FM) Standard 3545. See “limit control.” Glossary thermocouple junction The point thermowell A tube with a closed end Transport Layer (OSI Layer 4) The where the two dissimilar metal that is designed to protect temperature fourth layer of the seven-layer OSI conductors join. In a typical sensors from hostile environments. See (Open System Interconnection) thermocouple circuit, there is a “protection tube.” protocol model that handles data measuring junction and a reference Thompson Effect When a current transfer, flow control and error junction. See “junction,” “measuring flows through a conductor within a recovery between communicating junction” and “reference junction.” thermal gradient, a reversible hosts. The Transport Layer resides thermocouple pre-aging See absorption or evolution of heat occurs between the Session Layer and the “pre-aging.” in the conductor at the gradient Network Layer. thermocouple type A particular boundaries. triac A solid-state device that combination of metallic elements three-mode control Proportioning switches alternating current. and/or alloys that make up the control with integral (reset) and tribology The science or study of conductors of a thermocouple, and derivative (rate). Also see “PID.” surface friction. defines their EMF output relative to TI Integral term. triple point A thermodynamic state in absolute temperature. ASTM TIA See “Telecommunications which the gas, liquid and solid phases designated types include: B, E, J, K, Industry Association.” all occur in equilibrium. For water, the N, R, S and T. Non-ASTM types triple point is 0.01°C at standard time proportioning control A method include: C, D and G (tungsten based atmospheric pressure. thermocouples) and Pt 2. of controlling power by varying the on- off duty cycle of an output. This tungsten (W) An element that is used thermocouple, heat treating A variance is proportional to the as the positive conductor in a Type G thermocouple that is appropriate for difference between the set point and thermocouple, which is made of the temperature range and the actual process temperature. tungsten/tungsten 26 percent rhenium atmospheres used in heat treating. (W/W26Re). Type G is not an ASTM Tophel¨ A thermocouple alloy that is Heat treating is a process that alters symbol. the physical properties of a metal by made of 90 percent nickel and 10 tungsten 25 percent rhenium The heating and cooling at specific rate percent chromium. It is used in the thermocouple alloy that is used as the changes, and by introducing chemical positive conductors of ASTM Type E negative conductor in a Type D atmospheres. and K thermocouples. Tophel® is a registered trademark of Carpenter thermocouple, which is made of thermopile An arrangement of Technology. tungsten 3 percent rhenium/tungsten thermocouples in a series with 25 percent rhenium thermocouple transducer A device that receives alternate junctions at the measuring (W3Re/W25Re). Type D is not an energy in one form and retransmits it in temperature and the reference ASTM symbol. temperature. This arrangement another form. For example, a tungsten 26 percent rhenium The amplifies the thermoelectric voltage. thermocouple transforms heat energy thermocouple alloy that is used as the Thermopiles are usually used in input into a voltage output. negative conductor in both the Type G infrared detectors in radiation transient A surge in electrical current, thermocouple, which is made of pyrometry. usually of short duration. Transients tungsten/tungsten 26 percent rhenium can damage or interfere with the thermopolymer technology The (W/W26Re), and the Type C proper operation of electronic technology that applies heated thermocouple, which is made of temperature and power controllers. plastics to applications. tungsten 5 percent/tungsten 26 thermoset A material that undergoes transmitter A device that transmits percent rhenium (W5Re/W26Re). a chemical reaction and is cured or set temperature data from either a Types G and C are not ASTM symbols. thermocouple or a resistance when subjected to heat. An example is tungsten 3 percent rhenium The temperature detector (RTD) by way of bakelite. Thermosetting also applies to thermocouple alloy that is used as the a two-wire loop. The loop has an vulcanizing, as with rubber and positive conductor in a Type D external power supply. The transmitter neoprene. thermocouple, which is made of acts as a variable resistor with respect tungsten 3 percent rhenium/tungsten to its input signal. Transmitters are 25 percent rhenium (W3Re/W25Re). desirable when long lead or extension Type D is not an ASTM symbol. wires produce unacceptable signal degradation. 210 Glossary 211 A measurement of The difference in electrical The resistance of fluid to The resistance of The unit of measure for 1) Volatile Organic viscosity High viscosity sheering forces (flow). for a fluid to flow indicates a tendency viscosity of fluids or move slowly. The temperatures decreases as their gases will increase increase. Heating their absolute viscosity. VOC organic Compound(s). Carbon-based compounds that evaporate quickly. Watlow's thick film heaters do not contain harmful volatile organic compounds, such as hydrocarbons, or ammonia fluorine, hydrogen sulfide sulfur dioxide. 2) Voice of the Customer; APICS (The Educational Society for Resource Management). volt (V) electrical potential, voltage or electromotive force (EMF). See “voltage.” volt amperes (VA) apparent power. The product of voltage and current in a reactive I circuit. V I = VA, where V is volts and is is current in amperes. The term watt used for real power. voltage (V) potential between two points in a circuit. It’s the push or pressure behind current flow through a circuit. One volt (V) is the difference in potential required to move one coulomb of charge between two points in a circuit, consuming one joule of energy. In other words, one volt (V) is equal to one ampere of current (I) flowing through one ohm of resistance (R), or V = IR. A form of See “isolated A process to join Without thermal The amount by which a The amount by which The portion of the A pipe fitting that joins The quantitative measure of a Universal Serial Bus. An external Abbreviation for Verband insulation; without electrical insulation (bare wire). union extension pipes, without regard to their thread orientation. upscale break protection break detection for burned-out thermocouples. It signals the operator that the thermocouple has burned out. USB bus standard for connecting as many as 127 peripheral devices to computers with data transfer rates of up to 12 Mbps (million bits per second). USB is likely to supercede its serial and parallel ports because of speed and "hot swappable" (unplug and plug in with power on) feature. junction.” uninsulated process variable falls below the set process variable falls point before it stabilizes. ungrounded junction electromagnetic spectrum that is just electromagnetic spectrum in the visible beyond the violet light can degrade spectrum. Ultraviolet many insulation materials. undershoot ultraviolet V vacuum braze metals or alloys with heat in the absence of atmosphere, in a vacuum chamber or furnace, for example. value Deutscher Elektrotechniler, an independent German testing and certification institute concerned with the safety of electrical products. Authorizes use of the VDE Mark. signal or variable. VDE The W A T L O W O L T A W The technology used Two insulated A selling feature describing a User Datagram Protocol. A The registered trademark and ¨ UDP connectionless protocol that runs on top of IP networks as UDP/IP. Hosts can broadcast messages via UDP/IP without establishing connections with the receivers. Datagrams are packets, pieces of messages. UDP is a sessionless transport layer protocol defined by the IETF. UL U complete and ready to use system, one similar to simply turning the door key of a ready-to-live-in home. Watlow offers turnkey solutions with cast-in and thick film heaters. twisted pair thermocouple alloy that is used as the thermocouple alloy in a Type C positive conductor is made of thermocouple, which 26 tungsten percent rhenium/tungsten Type percent rhenium (W5Re/W26Re). symbol. C is not an ASTM tungsten lamp light by the standard incandescent 1911, with a bulb, in place since by tungsten metal filament surrounded an inert gas or a vacuum. Tungsten has a 16:1 hot to cold resistance ratio, that is, the filament has 16 time higher resistance at its hot operating temperature than at cooler ambient. turnkey conductors that are twisted together. An effective method of duplexing and reducing electromagnetic interference (EMI). Glossary rhenium tungsten 5 percent abbreviation for the Underwriter’s Laboratories, Inc. An independent testing laboratory that establishes commercial and industrial standards, and tests and certifies products in the United States. Glossary W - X Z watt (W) A measurement of real zero cross Action that provides power. The product of voltage and output switching only at or near the current in a resistive circuit. VI = P, zero-voltage crossing points of the where V is volts, I is current in amperes AC sine wave. See “burst fire.” and P is power in watts. zero switching See “zero cross.” watt density The watts of power produced per unit of surface area of a heater. Watt density indicates the potential for a surface to transmit heat energy and is expressed in W/in2 or W/cm2. This value is used to express heating element ratings and surface heat loss factors. WCADª A computer-based version of a power calculations tool published by Watlow Polymer Technologies. web server A device with an IP address and running server software to make it capable of serving web pages to a network or to the Internet. A web server may also have a domain name. wire size The specification and use of proper wire gauge for the load size and its distance from the control. Wire sizing is of prime importance to output wiring. Refer to the National Electrical Code (NEC) and local codes for wire sizing guidelines. See “American Wire Gauge” and “B & S Gauge.” working standard A measurement device that refers to a secondary standard. WPT Watlow Polymer Technologies. A Watlow division that manufactures heated plastics. XML eXtensible Markup Language. A document markup language defined by the Worldwide Web Consortium (WC3) as a subset of SGML (Standard Generalized Markup Language), and a web-friendly document description tool. XML provides for customized tags that enable data sharing between systems, applications and organizations.

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