A resource on position sensor technology, including background, operational theory, design and applications
This book explains the theory and applications of the technologies used in the measurement of linear and angular/rotary position sensors. The first three chapters provide readers with the necessary background information on sensors. These chapters review: the working definitions and conventions used in sensing technology; the specifications of linear position transducers and sensors and how they affect performance; and sensor output types and communication protocols. The remaining chapters discuss each separate sensor technology in detail. These include resistive sensors, cable extension transducers, capacitive sensors, inductive sensors, LVDT and RVDT sensors, distributed impedance sensors, Hall Effect sensors, magnetoresistive sensors, magnetostrictive sensors, linear and rotary encoders, and optical triangulation position sensors.
- Discusses sensor specification, theory of operation, sensor design, and application criteria
- Reviews the background history of the linear and angular/rotary position sensors as well as the underlying engineering techniques
- Includes end-of-chapter exercises
Position Sensors is written for electrical, mechanical, and material engineers as well as engineering students who are interested in understanding sensor technologies.
Table of Contents
About the Author xv
Preface xvii
Trademarks xix
About the Companion Website xxi
1 Sensor Definitions and Conventions 1
1.1 Is it a Sensor or a Transducer? 1
1.2 Position versus Displacement 5
1.3 Absolute or Incremental Reading 6
1.4 Contact or Contactless Sensing and Actuation 7
1.5 Linear/Angular Configuration 10
1.6 Position Velocity and Acceleration 11
1.7 Application versus Sensor Technology 13
1.8 Operational Lifetime 13
1.9 Questions for Review 14
References 16
2 Specifications 17
2.1 About Position Sensor Specifications 17
2.2 Measuring Range 18
2.3 Zero Span and Full Scale 18
2.4 Repeatability 21
2.5 Nonlinearity 22
2.6 Hysteresis 28
2.7 Calibrated Accuracy 31
2.8 Drift 33
2.9 What does all this Accuracy Stuff Mean to Me? 34
2.10 Temperature Effects 36
2.11 Response Time 40
2.12 Damping 42
2.13 Cross Sensitivity 44
2.14 Shock and Vibration 45
2.15 Electromagnetic Compatibility 48
2.16 High Voltage Pulse Protection 50
2.17 Power Requirements 52
2.18 Intrinsic Safety Explosion Proofing and Purging 54
2.19 Reliability 62
2.20 Questions for Review 66
3 Output Types and Communication Protocols 69
3.1 Analog Output Types 69
3.2 Digital Output Types 73
3.3 SSI 73
3.4 CANbus 80
3.5 PROFIBUS 104
3.6 HART 106
3.7 Questions for Review 117
4 Resistive/Potentiometric Sensing 119
4.1 Resistive Position Sensors 119
4.2 Resistance 120
4.3 History of Resistors and Resistive Position Sensors 122
4.4 Position Sensor Design 124
4.5 The Resistive Element 127
4.6 The Wiper 129
4.7 Linear and Rotary Mechanics 130
4.8 Signal Conditioning 131
4.9 Advantages/Disadvantages 132
4.10 Typical Performance Parameters 132
4.11 Specifications and Application 135
4.12 Manufacturers 136
4.13 Questions for Review 136
5 Cable Extension Transducers 139
5.1 Cable Extension Transducer History 139
5.2 Cable Extension Transducer Construction 140
5.3 Signal Conditioning 144
5.4 Application 144
5.5 Advantages/Disadvantages 148
5.6 Typical Performance Specifications 148
5.7 Manufacturers 149
5.8 Questions for Review 150
6 Capacitive Sensing 153
6.1 Capacitive Position Sensors 153
6.2 Capacitance 154
6.3 Dielectric Constant 157
6.4 History of Capacitive Position Sensors 158
6.5 Capacitive Position Sensor Design 159
6.6 Electronic Circuits for Capacitive Sensors 163
6.7 Guard Electrodes 169
6.8 EMI/RFI 170
6.9 Typical Performance Specifications and Application 172
6.10 Manufacturers 173
6.11 Questions for Review 173
7 Inductive Sensing 175
7.1 Inductive Position Sensors 175
7.2 Inductance 177
7.3 Permeability 182
7.4 History of Inductive Position Sensors 183
7.5 Inductive Position Sensor Design 184
7.6 The Coil and Bobbin 185
7.7 Core 188
7.8 Signal Conditioning 189
7.9 Advantages 192
7.10 Typical Application and Performance Specifications 192
7.11 Manufacturers 194
7.12 Questions for Review 194
8 The LVDT and RVDT 197
8.1 LVDT and RVDT Position Sensors 197
8.2 History of the LVDT and RVDT 198
8.3 LVDT and RVDT Position Sensor Design 199
8.4 Coils 200
8.5 Core 202
8.6 Carrier Frequency 206
8.7 Demodulation 207
8.8 Signal Conditioning 211
8.9 Synchronization 217
8.10 Calibration 219
8.11 Advantages 221
8.12 Typical Performance Specifications and Application 222
8.13 Manufacturers 224
8.14 Questions for Review 225
References 226
9 Distributed Impedance 227
9.1 Distributed Impedance Position Sensors 227
9.2 History 229
9.3 Operational Theory 229
9.4 The Distributed Impedance Sensing Element as a Transmission Line 234
9.5 Periodic Structures 235
9.6 Hybrid Waves 235
9.7 Distributed Impedance Sensor Design 236
9.8 Electronics 237
9.9 Advantages 239
9.10 Typical Performance Specifications and Applications 239
9.11 Infinite Resolution? 241
9.12 Calibration 241
9.13 Manufacturers 243
9.14 Questions for Review 243
10 The Hall Effect 247
10.1 Hall Effect Sensors 247
10.2 The Hall Effect 248
10.3 History of the Hall Effect 250
10.4 Hall Effect Position Sensor Design 251
10.5 The Hall Effect Element 254
10.6 Electronics 254
10.7 Linear Arrays 257
10.8 Advantages 258
10.9 Typical Performance Specifications and Applications 259
10.10 Manufacturers 260
10.11 Questions for Review 261
11 Magnetoresistive Sensing 263
11.1 Magnetoresistive Sensors 263
11.2 Magnetoresistance 264
11.3 History of Magnetoresistive Sensors 271
11.4 Magnetoresistive Position Sensor Design 273
11.5 The Magnetoresistive Element 275
11.6 Linear Arrays 276
11.7 Electronics 276
11.8 Advantages of Magnetoresistive Sensors 278
11.9 Typical Performance Specifications and Applications 278
11.10 Manufacturers 281
11.11 Questions for Review 281
12 Magnetostrictive Sensing 285
12.1 Magnetostrictive Sensors 285
12.2 Magnetostriction 286
12.3 History of Magnetostriction 288
12.4 Magnetostrictive Position Sensor Design 289
12.5 Waveguide 291
12.6 Position Magnet 295
12.7 Pickup Devices 299
12.8 Damp 301
12.9 Waveguide Suspension 302
12.10 Electronics 303
12.11 Angular/Rotary Magnetostrictive Sensors 307
12.12 Advantages 308
12.13 Typical Performance Specifications 309
12.14 Application 311
12.15 Manufacturers 313
12.16 Questions for Review 313
13 Encoders 315
13.1 Linear and Rotary 315
13.2 History of Encoders 315
13.3 Construction 317
13.4 Absolute versus Incremental Encoders 319
13.5 Optical Encoders 320
13.6 Magnetic Encoders 321
13.7 Quadrature 323
13.8 Binary versus Gray Code 325
13.9 Electronics 326
13.10 Advantages 328
13.11 Typical Performance Specifications and Applications 329
13.12 Manufacturers 331
13.13 Questions for Review 331
14 Optical Triangulation 335
14.1 Linear Sensing 335
14.2 History 336
14.3 Construction 337
14.4 Light Sensor 340
14.5 Electronics 343
14.6 Laser 347
14.7 Advantages 349
14.8 Typical Performance Specifications and Applications 350
14.9 Manufacturers 350
14.10 Questions for Review 351
Bibliography 353
Glossary of Sensor Terminology 355
Index 363
