Fundamentals of Industrial Instrumentation and Process Control
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������������ Want to learn more? We hope you enjoy this McGraw-Hill eBook! If you’d like more information about this book, its author, or related books and websites, please click here. Fundamentals of Industrial Instrumentation and Process Control William C. Dunn McGraw-Hill New York Chicago San Francisco Lisbon London Madrid Mexico City Milan New Delhi San Juan Seoul Singapore Sydney Toronto Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved. Manufactured in the United States of America. Except as permitted under the United States Copyright Act of 1976, no part of this publication may be reproduced or distributed in any form or by any means, or stored in a database or retrieval system, without the prior written permission of the publisher. 0-07-146693-2 The material in this eBook also appears in the print version of this title: 0-07-145735-6. All trademarks are trademarks of their respective owners. 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DOI: 10.1036/0071466932 To my wife Nadine for her patience, understanding, and many helpful suggestions during the writing of this text For more information about this title, click here Contents Preface xiii Chapter 1. Introduction and Review 1 Chapter Objectives 1 1.1 Introduction 1 1.2 Process Control 2 1.3 Definitions of the Elements in a Control Loop 3 1.4 Process Facility Considerations 6 1.5 Units and Standards 7 1.6 Instrument Parameters 9 Summary 13 Problems 13 Chapter 2. Basic Electrical Components 15 Chapter Objectives 15 2.1 Introduction 15 2.2 Resistance 16 2.2.1 Resistor formulas 17 2.2.2 Resistor combinations 19 2.2.3 Resistive sensors 23 2.3 Capacitance 24 2.3.1 Capacitor formulas 24 2.3.2 Capacitor combinations 25 2.4 Inductance 26 2.4.1 Inductor formulas 26 2.4.2 Inductor combinations 27 Summary 27 Problems 28 Chapter 3. AC Electricity 31 Chapter Objectives 31 3.1 Introduction 31 3.2 Circuits with R, L, and C 32 v vi Contents 3.2.1 Voltage step 32 3.2.2 Time constants 33 3.2.3 Phase change 35 3.3 RC Filters 38 3.4 AC Bridges 39 3.5 Magnetic Forces 40 3.5.1 Magnetic fields 40 3.5.2 Analog meter 42 3.5.3 Electromechanical devices 43 Summary 44 Problems 45 Chapter 4. Electronics 47 Chapter Objectives 47 4.1 Introduction 48 4.2 Analog Circuits 48 4.2.1 Discrete amplifiers 48 4.2.2 Operational amplifiers 49 4.2.3 Current amplifiers 53 4.2.4 Differential amplifiers 54 4.2.5 Buffer amplifiers 55 4.2.6 Nonlinear amplifiers 56 4.2.7 Instrument amplifier 56 4.2.8 Amplifier applications 57 4.3 Digital Circuits 58 4.3.1 Digital signals 58 4.3.2 Binary numbers 58 4.3.3 Logic circuits 60 4.3.4 Analog-to-digital conversion 61 4.4 Circuit Considerations 63 Summary 63 Problems 64 Chapter 5. Pressure 67 Chapter Objectives 67 5.1 Introduction 67 5.2 Basic Terms 68 5.3 Pressure Measurement 69 5.4 Pressure Formulas 70 5.5 Measuring Instruments 73 5.5.1 Manometers 73 5.5.2 Diaphragms, capsules, and bellows 75 5.5.3 Bourdon tubes 77 5.5.4 Other pressure sensors 79 5.5.5 Vacuum instruments 79 5.6 Application Considerations 80 5.6.1 Selection 80 5.6.2 Installation 80 5.6.3 Calibration 81 Summary 81 Problems 82 Contents vii Chapter 6. Level 85 Chapter Objectives 85 6.1 Introduction 85 6.2 Level Formulas 86 6.3 Level Sensing Devices 87 6.3.1 Direct level sensing 88 6.3.2 Indirect level sensing 92 6.4 Application Considerations 95 Summary 97 Problems 97 Chapter 7. Flow 99 Chapter Objectives 99 7.1 Introduction 99 7.2 Basic Terms 100 7.3 Flow Formulas 102 7.3.1 Continuity equation 102 7.3.2 Bernoulli equation 103 7.3.3 Flow losses 105 7.4 Flow Measurement Instruments 107 7.4.1 Flow rate 107 7.4.2 Total flow 111 7.4.3 Mass flow 112 7.4.4 Dry particulate flow rate 113 7.4.5 Open channel flow 113 7.5 Application Considerations 114 7.5.1 Selection 114 7.5.2 Installation 115 7.5.3 Calibration 115 Summary 115 Problems 116 Chapter 8. Temperature and Heat 119 Chapter Objectives 119 8.1 Introduction 119 8.2 Basic Terms 120 8.2.1 Temperature definitions 120 8.2.2 Heat definitions 121 8.2.3 Thermal expansion definitions 123 8.3 Temperature and Heat Formulas 124 8.3.1 Temperature 124 8.3.2 Heat transfer 124 8.3.3 Thermal expansion 126 8.4 Temperature Measuring Devices 127 8.4.1 Thermometers 127 8.4.2 Pressure-spring thermometers 129 8.4.3 Resistance temperature devices 130 8.4.4 Thermistors 131 8.4.5 Thermocouples 131 8.4.6 Semiconductors 133 viii Contents 8.5 Application Considerations 134 8.5.1 Selection 134 8.5.2 Range and accuracy 134 8.5.3 Thermal time constant 134 8.5.4 Installation 137 8.5.5 Calibration 137 8.5.6 Protection 137 Summary 138 Problems 138 Chapter 9. Humidity, Density, Viscosity, and pH 141 Chapter Objectives 141 9.1 Introduction 141 9.2 Humidity 142 9.2.1 Humidity definitions 142 9.2.2 Humidity measuring devices 146 9.3 Density and Specific Gravity 149 9.3.1 Basic terms 149 9.3.2 Density measuring devices 150 9.3.3 Density application considerations 153 9.4 Viscosity 153 9.4.1 Basic terms 153 9.4.2 Viscosity measuring instruments 154 9.5 pH Measurements 155 9.5.1 Basic terms 155 9.5.2 pH measuring devices 156 9.5.3 pH application considerations 156 Summary 157 Problems 158 Chapter 10. Other Sensors 161 Chapter Objectives 161 10.1 Introduction 161 10.2 Position and Motion Sensing 161 10.2.1 Basic position definitions 161 10.2.2 Position and motion measuring devices 163 10.2.3 Position application consideration 166 10.3 Force, Torque, and Load Cells 166 10.3.1 Basic definitions of force and torque 166 10.3.2 Force and torque measuring devices 167 10.3.3 Force and torque application considerations 170 10.4 Smoke and Chemical Sensors 170 10.4.1 Smoke and chemical measuring devices 171 10.4.2 Smoke and chemical application consideration 171 10.5 Sound and Light 171 10.5.1 Sound and light formulas 171 10.5.2 Sound and light measuring devices 173 10.5.3 Light sources 174 10.5.4 Sound and light application considerations 174 Summary 176 Problems 176 Contents ix Chapter 11. Actuators and Control 179 Chapter Objectives 179 11.1 Introduction 179 11.2 Pressure Controllers 180 11.2.1 Regulators 180 11.2.2 Safety valves 182 11.2.3 Level regulators 182 11.3 Flow Control Actuators 183 11.3.1 Globe valve 183 11.3.2 Butterfly valve 185 11.3.3 Other valve types 185 11.3.4 Valve characteristics 186 11.3.5 Valve fail safe 187 11.4 Power Control 188 11.4.1 Electronic devices 188 11.4.2 Magnetic control devices 193 11.5 Motors 195 11.5.1 Servo motors 195 11.5.2 Stepper motors 195 11.5.3 Valve position feedback 196 11.5.4 Pneumatic feedback 196 11.6 Application Considerations 196 11.6.1 Valves 196 11.6.2 Power devices 197 Summary 198 Problems 198 Chapter 12.