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Pressure & Temperature Measurement & Temperature Pressure WIKA Handbook WIKA Handbook U.S. Edition Pressure & Temperature Measurement U.S. Edition WIKA Instrument Corporation 1000 Wiegand Boulevard Lawrenceville, GA 30043 Toll Free 1-888-WIKA-USA (945-2872) Tel (770) 513-8200 Fax (770) 338-5118 [email protected] • www.wika.com HB001 - 1000 8/08 ©2008, by WIKA Instrument Corporation. All rights reserved. WIKA-Handbook · Pressure and Temperature Measurement U.S. Edition I 15494_INTRO.P65 1 7/18/01, 18:28 II 15494_INTRO.P65 2 7/18/01, 18:28 WIKA-Handbook Pressure and Temperature Measurement U.S. Edition I WIKA Instrument Corporation 1000 Wiegand Boulevard Lawrenceville, GA 30043-5868 USA A wholly owned subsidiary of: WIKA Alexander Wiegand GmbH & Co. Alexander Wiegand Straße 63911 Klingenberg Germany Original Authors: Beckerath, Alexander von Eberlein, Anselm Julien, Hermann Kersten, Peter Kreutzer, Jochem Scientific advisers: Prof. Dr. Fritz Aldinger Johannes Dürr Editor for U.S. Edition: Cameron Reebals Printing: Corporate Printers, Cumming, GA 2008 ©1998 WIKA Instrument Corporation. All rights reserved. No part of this book may be reproduced or transmitted in any form, by any means (electronic, photocopying, recording, or otherwise) without the prior written permission of the publisher. Printed in the United States of America IV Foreword For more than fifty years WIKA has been a leading manufacturer of pressure and temperature measurement instruments. Today, the name WIKA stands for a broad product range of industrial pressure and temperature measurement instrumentation. The more than 300 million measuring instruments made by WIKA so far not only prove the quality of our products, but have also enabled us to gain an extensive knowledge of practical applications requiring the measurement of pressure and temperature. The present new edition of the WIKA handbook is intended to provide a reference book for our worldwide customers, dealing not only with the fundamentals, but also important practical aspects of industrial pressure and temperature measurement. Additionally, all new developments concerning mechanical and electronic pressure and temperature measurement are considered. Alexander Wiegand V 15494_INTRO.P65 5 7/18/01, 18:28 Introduction Industrial development now faces challenges and opportunities of unprecedented magnitude and diversity. Economical manufacturing processes for existing or new products, new technology trends, the internationalization of markets and conditions of competition, new research developments and questions of safety for man and his environment call for innovative and visionary solutions. In many cases the optimum utilization of energy and raw materials, the reproducibility of product quality and the operational reliability of plants and equipment depend essentially on being able to control fundamental operations and parameters. Parameters of central importance in this respect are pressure and temperature. Their simple and exact measurement and control are becoming more and more important for many fields of technology and daily life. Indeed, they are already indispensable in heating, air conditioning, energy and vacuum systems, in chemical processing, petrochemicals, paper manufacturing, the food industry and biotechnology, and in automotive, mechanical, apparatus and plant engineering. The same appplies to measurement and testing laboratories and to the equipment needed to conduct experiments for research in the natural sciences and technology. The success of measurement and control in the above mentioned fields depends greatly on the availability of useful measurement methods and test facilities. The WIKA Handbook sets out to present all the measurement methods and equipment now in use in the technical field. In addition to reviewing the classical mechanical and electrical methods of measuring pressure and temperature, the book also takes a detailed look at modern electronic sensor principles. The measurement ranges of the instruments described extend from fractions of a millibar to 105 x atmospheric pressure, with greatly varying demands on precision. As for temperature measurements, the book describes methods for measuring the entire range from just above absolute zero to several thousand degrees Fahrenheit. In addition to describing the actual measurement methods and equipment the reader will also find detailed information about the physical fundamentals of pressure and temperature metrology, measurement transducers, influencing variables and the demands placed on pressure and temperature instruments by process engineering. National and international standards and regulations are also covered extensively. In its comprehensive treatment of all pressure and temperature measurement aspects this handbook is without equal. Details are presented in sufficient depth to grasp even complex subjects. Attention is drawn to specialized literature and relevant handbooks on physics and metrology where additional reading is required to answer further questions. The WIKA Handbook will not only prove extremely useful for WIKA customers but will certainly also find its way into many measurement and testing laboratories. Prof. Dr. Fritz Aldinger Scientific Member and Director of the Max-Planck-Institute for Metal Research and Full Professor at Stuttgart University VI 15494_INTRO.P65 6 7/18/01, 18:28 Contents 1 Pressure measurement 1 1.1 Pressure and its units of measurement 1 1.1.1 Common units 1.1.1 Pressure of gases 1 1.1.2 Pressure of liquids 2 1.2 Types of pressure 3 1.2.1 Absolute pressure 3 1.2.2 Atmospheric air pressure 3 1.2.3 Pressure difference, differential pressure 3 1.2.4 Atmospheric pressure difference, overpressure 4 1.3 Common methods for measuring pressure 5 1.3.1 Direct pressure measuring instruments 5 1.3.1.1 Pressure measuring instruments with liquid column 5 • U-tube manometer 6 • lnclined-tube manometer 6 • Multiple liquid manometer 7 • Float-type manometer 7 1.3.1.2 Pressure balances with liquid separation 7 1.3.1.3 Piston-type pressure measuring instruments 9 • Piston-type pressure measuring instruments • with spring-loaded piston 9 • Dead-weight pressure measuring instruments 9 1.3.2 Indirect pressure measurement instruments 11 1.3.2.1 Pressure measuring instruments with flexible elements 11 1.3.2.2 Electrical pressure sensors and pressure measuring instruments 13 • Sensor types with strain gauges 13 • Strain gauge transmission principles 21 • Diaphragm conversion 21 • Sensor principles with displacement measurement 22 • Other sensor principles 25 • Sensor principles for inspection and calibration systems 26 1.4 Pressure measuring instruments with flexible measuring elements 30 1.4.1 Flexible measuring elements 31 1.4.1.1 Bourdon tubes 31 1.4.1.2 Diaphragm measuring elements 41 • Diaphragms 42 • Capsules 46 VII 15494_INTRO.P65 7 7/18/01, 18:28 1.4.1.3 Bellows 48 1.4.2 Movements 48 1.4.3 Dials and pointers 52 1.4.4 The case 54 1.4.4.1 Connection positions 54 1.4.4.2 Design types 55 • Modular design of commercial pressure measuring instruments 55 • Modular design for industrial measuring instruments 56 • Forged cases for liquid filling 57 1.4.4.3 Vibration damping by liquid filling 58 • Resonant frequencies and amplitudes 58 • Resistance to resonance 59 • Investigation of various instrument types 60 1.4.4.4 Safety of pressure measuring instruments 63 1.4.5 Electrical and pneumatic accessories 66 1.4.5.1 Alarm contacts 66 • Direct contacts 66 • Indirect contacts 68 1.4.5.2 Transmitters 69 • Potentiometric transmitter 69 • Capacitive transmitters 69 1.4.6 Special flexible element pressure measuring instruments 72 1.4.6.1 Pressure measuring instruments for absolute and differential pressure 72 • Differential pressure measuring instrument with diaphragm 73 • Absolute pressure measuring instrument with diaphragm 73 • Absolute pressure measuring instrument with capsule 74 1.4.6.2 Pressure measuring instruments with high overload capability 75 1.4.6.3 Pressure measuring instruments and pressure transducers for ultrapure gases 76 1.4.6.4 Gas density monitors for SF6 systems 77 1.4.7 Special designs and optional accessories 79 1.4.7.1 Pressure measuring instruments for oxygen and acetylene 79 1.4.7.2 Calibration with other pressure media 79 1.4.7.3 Bourdon tube with tip bleed 79 1.4.7.4 Bourdon tube with filling 80 1.4.7.5 Extension of the lower scale range (retard scale) 80 1.4.7.6 Dual scales 80 1.4.7.7 Scales for direct measurement of force 80 1.4.7.8 Temperature scale 81 1.4.7.9 Scales with compensation for difference in levels 82 1.4.7.10 Luminous dials 83 1.4.7.11 Mark pointers 83 1.4.7.12 Drag pointers 83 1.4.7.13 Suppressed zero 83 1.4.7.14 Extended pointer shaft 84 1.4.7.15 Safety glass 84 1.4.7.16 Special protection during shipment 84 1.4.8 Measurement data and standards concerning applications 84 1.4.8.1 Full scale range and maximum operating range 84 VIII 15494_INTRO.P65 8 7/18/01, 18:28 1.4.8.2 Accuracy of the indication 85 1.4.8.3 Process fluids 86 1.4.8.4 Environmental conditions 87 1.5 Pressure transducers, pressure measuring converters and pressure transmitters with analog and digital circuits 90 1.5.1 Definition of a pressure transducer 90 1.5.1.1 Pressure transducers and their specifications 92 1.5.1.2 Pressure measuring converters 92 1.5.1.3 Technical data and their definition 93 • Measuring range / measuring span 93 • Overload pressure range 93 • Burst pressure 93 • Power supply 93 • Output signal (analog, digital) 94 • Response time 94 • Accuracy and conformity error 95 •
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