Fundamentals of industrial instrumentation and process control

337 Pages·2005·3.286 MB·English

by  William Dunn

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Fundamentals of
Industrial Instrumentation
and Process Control
William C. Dunn
McGraw-Hill
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Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved. Manufactured in the
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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
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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 RCFilters 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. Signal Conditioning 201
Chapter Objectives 201
12.1 Introduction 201
12.2 Conditioning 202
12.2.1 Characteristics 202
12.2.2 Linearization 204
12.2.3 Temperature correction 205
12.3 Pneumatic Signal Conditioning 205
12.4 Visual Display Conditioning 206
12.4.1 Direct reading sensors 206
12.5 Electrical Signal Conditioning 207
12.5.1 Linear sensors 208
12.5.2 Float sensors 208
12.5.3 Strain gauge sensors 211
12.5.4 Capacitive sensors 212
12.5.5 Resistance sensors 213
12.5.6 Magnetic sensors 214
12.5.7 Thermocouple sensors 215
12.5.8 Other sensors 215
12.6 A-D Conversion 216
Summary 216
Problems 216