1 Data Acquisition ............................................. 1
1.1 Sensors, Signals, and Systems ........................... 1
1.2 Sensor Classification ................................... 1
1.3 Units of Measurements .................................. 11
References .................................................. 12
2 Sensor Characteristics ...................................... 13
2.1 Transfer Function ...................................... 13
2.1.1 Mathematical Model .............................. 14
2.1.2 Functional Approximations ....................... 15
2.1.3 Polynomial Approximations ....................... 16
2.1.4 Sensitivity ..................................... 17
2.1.5 Linear Piecewise Approximation .................. 18
2.1.6 Spline Interpolation ............................ 19
2.1.7 Multidimensional Transfer Functions ............. 19
2.2 Calibration ............................................ 20
2.2.1 Computation of Transfer Function Parameters ..... 22
2.2.2 Linear Regression ............................... 25
2.3 Computation of Stimulus ................................ 26
2.3.1 Computation from Linear Piecewise
Approximation ................................... 26
2.3.2 Iterative Computation of Stimulus (Newton
Method) ......................................... 28
2.4 Span (Full-Scale Full Scale Input) ..................... 30
2.5 Full-Scale Output ...................................... 31
2.6 Accuracy ............................................... 31
2.7 Calibration Error ...................................... 34
2.8 Hysteresis ............................................. 35
2.9 Nonlinearity ........................................... 36
2.10 Saturation ............................................. 37
2.11 Repeatability .......................................... 38
2.12 Dead Band .............................................. 38
2.13 Resolution ............................................. 38
2.14 Special Properties ..................................... 39
2.15 Output Impedance ....................................... 40
2.16 Output Format .......................................... 40
2.17 Excitation ............................................. 41
2.18 Dynamic Characteristics ................................ 41
2.19 Environmental Factors .................................. 45
2.20 Reliability ............................................ 47
2.21 Application Characteristics ............................ 49
2.22 Uncertainty ............................................ 50
References .................................................. 52
3 Physical Principles of Sensing .............................. 53
3.1 Electric Charges, Fields, and Potentials ............... 54
3.2 Capacitance ............................................ 60
3.2.1 Capacitor ....................................... 62
3.2.2 Dielectric Constant ............................. 63
3.3 Magnetism .............................................. 67
3.3.1 Faraday Law ..................................... 69
3.3.2 Solenoid ........................................ 71
3.3.3 Toroid .......................................... 72
3.3.4 Permanent Magnets ............................... 72
3.4 Induction .............................................. 73
3.5 Resistance ............................................. 77
3.5.1 Specific Resistivity ............................ 79
3.5.2 Temperature Sensitivity ......................... 80
3.5.3 Strain Sensitivity .............................. 84
3.5.4 Moisture Sensitivity ............................ 85
3.6 Piezoelectric Effect ................................... 86
3.6.1 Ceramic Piezoelectric Materials ................. 89
3.6.2 Polymer Piezoelectric Films ..................... 93
3.7 Pyroelectric Effect .................................... 96
3.8 Hall Effect ........................................... 103
3.9 Thermoelectric Effects ................................ 106
3.9.1 Seebeck Effect ................................. 106
3.9.2 Peltier Effect ................................. 111
3.10 Soundwaves ............................................ 113
3.11 Temperature and Thermal Properties of Materials ....... 116
3.11.1 Temperature Scales ............................. 117
3.11.2 Thermal Expansion .............................. 118
3.11.3 Heat Capacity .................................. 120
3.12 Heat Transfer ......................................... 121
3.12.1 Thermal Conduction ............................. 122
3.12.2 Thermal Convection ............................. 125
3.12.3 Thermal Radiation .............................. 126
3.13 Light ................................................. 135
3.13.1 Light Polarization ............................. 136
3.13.2 Light Scattering ............................... 137
3.14 Dynamic Models of Sensor Elements ..................... 138
3.14.1 Mechanical Elements ............................ 139
3.14.2 Thermal Elements ............................... 141
3.14.3 Electrical Elements ............................ 142
3.14.4 Analogies ...................................... 143
References ............................................ 144
4 Optical Components of Sensors .............................. 147
4.1 Radiometry ............................................ 149
4.2 Photometry ............................................ 154
4.3 Windows ............................................... 157
4.4 Mirrors ............................................... 158
4.5 Lenses ................................................ 161
4.6 Fresnel Lenses ........................................ 163
4.7 Fiber Optics and Waveguides ........................... 165
4.8 Concentrators ......................................... 169
4.9 Coatings for Thermal Absorption ....................... 170
4.10 Nano-optics ........................................... 172
References ................................................. 172
5 Interface Electronic Circuits .............................. 173
5.1 Input Characteristics of Interface Circuits ........... 173
5.2 Amplifiers ............................................ 178
5.2.1 Operational Amplifiers ......................... 178
5.2.2 Voltage Follower ............................... 181
5.2.3 Instrumentation Amplifier ...................... 182
5.2.4 Charge Amplifiers .............................. 183
5.3 Light-to-Voltage Converters ........................... 186
5.4 Excitation Circuits ................................... 188
5.4.1 Current Generators ............................. 188
5.4.2 Voltage References ............................. 192
5.4.3 Oscillators .................................... 192
5.4.4 Drivers ........................................ 194
5.4.5 Optical Drivers ................................ 196
5.5 Analog-to-Digital Converters .......................... 196
5.5.1 Basic Concepts ................................. 196
5.5.2 V/F Converters ................................. 198
5.5.3 Dual-Slope Converters .......................... 203
5.5.4 Successive Approximation Converter ............. 203
5.5.5 Resolution Extension ........................... 205
5.6 Direct Digitization ................................... 207
5.7 Capacitance-to-Voltage Converters ..................... 208
5.8 Integrated Interfaces ................................. 210
5.9 Ratiometric Circuits .................................. 211
5.10 Differential Circuits ................................. 214
5.11 Bridge Circuits ....................................... 215
5.11.1 General Concept ................................ 215
5.11.2 Disbalanced Bridge ............................. 216
5.11.3 Null-Balanced Bridge ........................... 218
5.11.4 Bridge Amplifiers .............................. 218
5.12 Data Transmission ..................................... 220
5.12.1 Two-Wire Transmission .......................... 220
5.12.2 Four-Wire Sensing .............................. 221
5.12.3 Six-Wire Sensing ............................... 222
5.13 Noise in Sensors and Circuits ......................... 223
5.13.1 Inherent Noise ................................. 223
5.13.2 Transmitted Noise .............................. 227
5.13.3 Electric Shielding ............................. 231
5.13.4 Bypass Capacitors .............................. 234
5.13.5 Magnetic Shielding ............................. 235
5.13.6 Mechanical Noise ............................... 237
5.13.7 Ground Planes .................................. 237
5.13.8 Ground Loops and Ground Isolation .............. 238
5.13.9 Seebeck Noise .................................. 240
5.14 Calibration ........................................... 242
5.15 Batteries for Low-Power Sensors ....................... 243
5.15.1 Primary Cells .................................. 244
5.15.2 Secondary Cells ................................ 245
References ................................................. 246
6 Occupancy and Motion Detectors ............................. 247
6.1 Ultrasonic Detectors .................................. 249
6.2 Microwave Motion Detectors ............................ 249
6.3 Capacitive Occupancy Detectors ........................ 254
6.4 Triboelectric Detectors ............................... 258
6.5 Optoelectronic Motion Detectors ....................... 260
6.5.1 Sensor Structures .............................. 261
6.5.2 Visible and Near IR Light Motion Detectors ..... 264
6.5.3 Far-Infrared Motion Detectors .................. 267
6.6 Optical Presence Sensors .............................. 274
6.7 Pressure-Gradient Sensors ............................. 276
References ................................................. 278
7 Position, Displacement, and Level .......................... 279
7.1 Potentiometrie Sensors ................................ 280
7.2 Capacitive Sensors .................................... 284
7.3 Inductive and Magnetic Sensors ........................ 288
7.3.1 LVDT and RVDT .................................. 288
7.3.2 Eddy Current Sensors ........................... 290
7.3.3 Transverse Inductive Sensor .................... 292
7.3.4 Hall Effect Sensors ............................ 293
7.3.5 Magnetoresistive Sensors ....................... 297
7.3.6 Magnetostrictive Detector ...................... 300
7.4 Optical Sensors ....................................... 302
7.4.1 Optical Bridge ................................. 302
7.4.2 Proximity Detector with Polarized Light ........ 303
7.4.3 Fiber-Optic Sensors ............................ 304
7.4.4 Fabry-Perot Sensors ............................ 306
7.4.5 Grating Sensors ................................ 308
7.4.6 Linear Optical Sensors ......................... 310
7.5 Ultrasonic Sensors .................................... 314
7.6 Radar Sensors ......................................... 316
7.6.1 Micropower Impulse Radar ....................... 316
7.6.2 Ground Penetrating Radars ...................... 318
7.7 Thickness and Level Sensors ........................... 320
7.7.1 Ablation Sensors ............................... 320
7.7.2 Thin Film Sensors .............................. 322
7.7.3 Liquid Level Sensors ........................... 323
7.8 Pointing Devices ...................................... 324
7.8.1 Optical Pointing Devices ....................... 324
7.8.2 Magnetic Pickup ................................ 325
7.8.3 Inertial and Gyroscopic Mice ................... 325
References ................................................. 325
8 Velocity and Acceleration .................................. 327
8.1 Accelerometer Characteristics ......................... 329
8.2 Capacitive Accelerometers ............................. 332
8.3 Piezoresistive Accelerometers ......................... 334
8.4 Piezoelectric Accelerometers .......................... 335
8.5 Thermal Accelerometers ................................ 336
8.5.1 Heated Plate Accelerometer ..................... 336
8.5.2 Heated Gas Accelerometer ....................... 337
8.6 Gyroscopes ............................................ 339
8.6.1 Rotor Gyroscope ................................ 340
8.6.2 Monolithic Silicon Gyroscopes .................. 341
8.6.3 Optical (Laser) Gyroscopes ..................... 344
8.7 Piezoelectric Cables .................................. 346
8.8 Gravitational Sensors ................................. 348
References ................................................. 351
9 Force, Strain, and Tactile Sensors ......................... 353
9.1 Strain Gauges ......................................... 355
9.2 Tactile Sensors ....................................... 357
9.2.1 Switch Sensors ................................. 358
9.2.2 Piezoelectric Sensors .......................... 359
9.2.3 Piezoresistive Sensors ......................... 362
9.2.4 MEMS Sensors ................................... 564
9.2.5 Capacitive Touch Sensors ....................... 365
9.2.6 Acoustic Touch Sensors ......................... 309
9.2.7 Optical Sensors ................................ 309
9.3 Piezoelectric Force Sensors ........................... 370
References ............................................ 372
10 Pressure Sensors ........................................... 375
10.1 Concepts of Pressure .................................. 375
10.2 Units of Pressure ..................................... 377
10.3 Mercury Pressure Sensor ............................... 378
10.4 Bellows, Membranes, and Thin plates ................... 379
10.5 Piezoresistive Sensors ................................ 381
10.6 Capacitive Sensors .................................... 387
10.7 VRP Sensors ........................................... 388
10.8 Optoelectronic Pressure Sensors ....................... 390
10.9 Indirect Pressure Sensor .............................. 591
10.10 Vacuum Sensors ....................................... 393
10.10.1 Pirani Gauge .................................. 393
10.10.2 Ionization Gauges ............................. 395
10.10.3 Gas Drag Gauge ................................ 396
10.10.4 Membrane Vacuum Sensors ....................... 396
References ................................................. 397
11 Flow Sensors ............................................... 399
11.1 Basics of Flow Dynamics ............................... 399
11.2 Pressure Gradient Technique ........................... 402
11.3 Thermal Transport Sensors ............................. 404
11.3.1 Hot-Wire Anemometers ........................... 405
11.3.2 Three-Part Thermoanemometer .................... 409
11.3.3 Two-Part Thermoanemometer ...................... 411
11.3.4 Microflow Thermal Transport Sensors ............ 414
11.4 Ultrasonic Sensors .................................... 416
11.5 Electromagnetic Sensors ............................... 418
11.6 Breeze Sensor ......................................... 420
11.7 Coriolis Mass Flow Sensors ............................ 422
11.8 Drag Force Sensors .................................... 423
11.9 Dust and Smoke Detectors .............................. 424
11.9.1 Ionization Detector ............................ 424
11.9.2 Optical Detector ............................... 426
References ................................................. 428
12 Acoustic Sensors ........................................... 431
12.1 Resistive Microphones ................................. 432
12.2 Condenser Microphones ................................. 432
12.3 Fiber-Optic Microphone ................................ 434
12.4 Piezoelectric Microphones ............................. 435
12.5 Electret Microphones .................................. 437
12.6 Dynamic Microphones ................................... 439
12.7 Solid-State Acoustic Detectors ........................ 440
References ................................................. 443
13 Humidity and Moisture Sensors .............................. 445
13.1 Concept of Humidity ................................... 445
13.2 Capacitive Sensors .................................... 448
13.3 Electrical Conductivity Sensors ....................... 452
13.4 Thermal Conductivity Sensor ........................... 455
13.5 Optical Hygrometer .................................... 456
13.6 Oscillating Hygrometer ................................ 458
References ................................................. 459
14 Light Detectors ............................................ 461
14.1 Introduction .......................................... 461
14.2 Photodiodes ........................................... 465
14.3 Phototransistor ....................................... 471
14.4 Photoresistors ........................................ 472
14.5 Cooled Detectors ...................................... 475
14.6 Image Sensors ......................................... 478
14.6.1 CCD Sensor ..................................... 479
14.6.2 CMOS-Imaging Sensors ........................... 480
14.7 Thermal Detectors ..................................... 481
14.7.1 Golay Cells .................................... 482
14.7.2 Thermopile Sensors ............................. 483
14.7.3 Pyroelectric Sensors ........................... 487
14.7.4 Bolometers ..................................... 491
14.7.5 Active Far-Infrared Sensors .................... 494
14.8 Optical Design ........................................ 497
14.9 Gas Flame Detectors ................................... 498
References ................................................. 500
15 Radiation Detectors ........................................ 503
15.1 Scintillating Detectors ............................... 504
15.2 Ionization Detectors .................................. 507
15.2.1 Ionization Chambers ................................. 508
15.2.2 Proportional Chambers ............................... 509
15.2.3 Geiger-Mьller Counters .............................. 510
15.2.4 Semiconductor Detectors ............................. 512
15.3 Cloud and Bubble Chambers ............................. 516
References ................................................. 518
16 Temperature Sensors ........................................ 519
16.1 Coupling with Object .................................. 519
16.2 Temperature Reference Points .......................... 526
16.3 Thermoresistive Sensors ............................... 528
16.3.1 Resistance Temperature Detectors ............... 528
16.3.2 Silicon Resistive PTC Sensors .................. 529
16.3.3 Thermistors .................................... 532
16.4 Thermoelectric Contact Sensors ........................ 549
16.4.1 Thermoelectric Laws ............................ 550
16.4.2 Thermocouple Circuits .......................... 552
16.4.3 Thermocouple Assemblies ........................ 554
16.5 Semiconductor pn-Junction Sensors ..................... 556
16.6 Optical Temperature Sensors ........................... 560
16.6.1 Fluoroptic Sensors ............................. 561
16.6.2 Interferometric Sensors ........................ 562
16.6.3 Thermochromic Solution Sensor .................. 563
16.7 Acoustic Temperature Sensor ........................... 564
16.8 Piezoelectric Temperature Sensors ..................... 565
References ................................................. 566
17 Chemical Sensors ........................................... 569
17.1 Overview .............................................. 570
17.2 History ............................................... 570
17.3 Chemical Sensor Characteristics ....................... 571
17.4 Classes of Chemical Sensors ........................... 572
17.4.1 Electrical and Electrochemical Transducers ..... 572
17.4.2 Elastomer Chemiresistors ....................... 581
17.4.3 Photoionization Detector ....................... 585
17.4.4 Physical Transducers ........................... 586
17.4.5 Optical Transducers ............................ 595
17.5 Biochemical Sensors ................................... 597
17.5.1 Enzyme Sensors ................................. 597
17.6 Multisensor Arrays .................................... 598
17.7 Electronic Noses and Tongues .......................... 599
17.8 Specific Difficulties ................................. 602
References ................................................. 603
18 Sensor Materials and Technologies .......................... 607
18.1 Materials ............................................. 607
18.1.1 Silicon as Sensing Material .................... 607
18.1.3 Metals ......................................... 615
18.1.4 Ceramics ....................................... 617
18.1.5 Glasses ........................................ 617
18.1.6 Optical Glasses ................................ 618
18.1.7 Nanomaterials .................................. 620
18.2 Surface Processing .................................... 621
18.2.1 Deposition of Thin and Thick Films ............. 621
18.2.2 Spin Casting ................................... 621
18.2.3 Vacuum Deposition .............................. 622
18.2.4 Sputtering ..................................... 623
18.2.5 Chemical Vapor Deposition ...................... 624
18.2.6 Electroplating ................................. 625
18.3 Microtechnology ....................................... 626
18.3.1 Photolithography ............................... 627
18.3.2 Silicon Micromachining ......................... 628
References ................................................. 635
Appendix ...................................................... 637
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