Make – Encyclopedia of Electronic Components Sensors – VOL. 3

Make – Encyclopedia of Electronic Components Sensors – VOL. 3
Charles Platt and Fredrik Jansson
Location n Presence n Proximity n Orientation n
Oscillation n Force n Load n Human Input n Liquid and
Gas Properties n Light n Heat n Sound n Electricity
Location , Presence , Proximity , Orientation , Oscillation , Force , Load , Human Input , Liquid and Gas Properties , Light , Heat , Sound , Electricity
Table of Contents
Preface . xix

1. GPS . 1
   What It Does 1
   Schematic Symbol 1
   GPS Segments 1
   How It Works . 2
   Variants . 2
   Values 3
   How to Use It . 3
   Pulse per Second Output . 4
   What Can Go Wrong 4
   Electrostatic Discharge 4
   Failure to Ground Properly 4
   Cold Joints . 4
   Restricted Availability . 4
   Inability to Detect Satellites . 4
   Exceeding Maximum Velocity or Altitude 4
2. magnetometer 5
   What It Does 5
   Schematic Symbol 5
   IMU 5
   Applications 6
   How It Works . 6
   Magnetic Fields . 6
   Earth’s Axes . 7
   Coil Magnetometer . 8
   Hall Effect and Magnetoresistance 8
   Variants . 9
   vHow to Use It . 9
   What Can Go Wrong 9
   Bias 9
   Mounting Errors . 10
3. object presence sensor 11
   What It Does . 11
   Schematic Symbol . 12
   Variants . 12
   Optical Detection 12
   Transmissive Optical Sensors . 13
   Retroreflective Optical Sensors . 15
   Magnetic Sensors 16
   Reed Switch . 17
   Reed Switch Variants 17
   Reed Switch Values 18
   How to Use a Reed Switch . 18
   Hall-Effect Sensor 18
   How a Hall-Effect Sensor Works 19
   Hall-Effect Sensor Variants . 19
   Other Applications 20
   Values . 20
   How to Use a Hall-Effect Sensor 20
   Configuration of Object Presence Sensors 21
   Linear Motion . 21
   Sensing by Interruption 21
   Angular Motion . 21
   Sensor Comparisons . 22
   Advantages of Optical Presence Sensors . 22
   Disadvantages of Optical Presence Sensors . 22
   Advantages of a Reed Switch 22
   Disadvantages of a Reed Switch 22
   Advantages of a Hall Effect Sensor . 22
   What Can Go Wrong . 23
   Optical Sensor Issues 23
   Reed Switch Issues 23
4. passive infrared sensor 25
   What It Does . 25
   Schematic Symbols 25
   Applications . 25
   How It Works 26
   Pyroelectric Detector 26
   Elements 26
   Lenses 27
   Variants . 29
   vi Encyclopedia of Electronic Components Volume 3What Can Go Wrong . 30
   Temperature Sensitivity 30
   Detector Window Vulnerability 30
   Moisture Vulnerability . 30
5. proximity sensor . 31
   What It Does . 31
   Schematic Symbols 31
   Applications . 32
   Variants . 32
   Ultrasound 32
   Infrared . 32
   Relative Advantages . 33
   Ultrasonic Examples . 33
   Imports . 33
   Individual Elements . 34
   Infrared Examples 34
   Trends in Infrared Proximity Sensing . 35
   Capacitive Displacement Sensor 36
   Applications . 37
   How It Works 37
   Sources of Error . 37
   Values . 38
   What Can Go Wrong with Optical and Ultrasound Proximity Sensors . 38
   Object Too Close 38
   Multiple Signals . 38
   Inappropriate Surfaces 38
   Environmental Factors . 38
   Deterioration of LEDs 38
6. linear position sensor 39
   What It Does . 39
   Applications . 39
   Schematic Symbol . 39
   How It Works 39
   Linear Potentiometer 40
   Magnetic Linear Encoders . 41
   Optical Linear Encoders 41
   Linear Encoder Applications . 42
   Linear Variable Differential Transformers . 42
   What Can Go Wrong . 43
   Mechanical Issues . 43
   LED Longevity . 43
7. rotary position sensor 45
   What It Does . 45
   viiTable of ContentsApplications . 45
   Schematic Symbol . 46
   Potentiometers 46
   Arc-Segment Rotary Potentiometer 46
   End Stops . 46
   Multiturn Rotary Potentiometer 46
   Magnetic Rotary Position Sensor . 47
   Rotary Position Sensing Chips . 48
   Rotary Encoders . 48
   Optical Rotary Encoders . 48
   Optical Products . 49
   Computer Mouse Principles 50
   Rotational Speed 50
   Absolute Position 51
   The Gray Code 51
   Magnetic Rotary Encoders . 52
   How to Use It 53
   What Can Go Wrong . 53
   Wiring Errors 53
   Coding Errors . 53
   Ambiguous Terminology 54
8. tilt sensor 55
   What It Does . 55
   Schematic Symbol . 56
   How It Works 56
   Simplified Version . 57
   Applications . 57
   Variants . 58
   Mercury Switches . 58
   Pendulum Switch 58
   Magnetization . 59
   Tilt Sensors 59
   Two-Axis Tilt Sensors 59
   Values . 60
   How to Use It 61
   What Can Go Wrong . 61
   Contact Erosion . 61
   Random Signals . 61
   Environmental Hazard . 61
   Requirement for Gravity . 61
   Requirement for Stability 62
9. gyroscope 63
   What It Does . 63
   Schematic Symbol . 63
   viii Encyclopedia of Electronic Components Volume 3IMU . 63
   Applications . 63
   How It Works 64
   Vibrating Gyroscope . 64
   Variants . 66
   IMUs 66
   Values . 67
   How to Use It 67
   What Can Go Wrong . 67
   Temperature Drift . 67
   Mechanical Stress . 68
   Vibration 68
   Placement 68
10. accelerometer 69
    What It Does . 69
    IMU . 69
    Schematic Symbols 70
    Applications . 70
    How It Works 70
    Gravity and Free Fall . 71
    Rotation 71
    Calculation 72
    Variants . 72
    Values . 73
    What Can Go Wrong . 74
    Mechanical Stress . 74
    Other Problems . 74
11. vibration sensor 75
    What It Does . 75
    Schematic Symbols 75
    Variants . 75
    Pin-and-Spring 76
    Piezoelectric Strip . 76
    Chip-Based Piezoelectric . 77
    “Mousetrap” Type . 77
    Magnetic 77
    Mercury . 78
    Values . 78
    Primary Variables 78
    Dynamic Attributes 79
    How to Use It 79
    What Can Go Wrong . 79
    Long Cable Runs 79
    Interference . 79
    ixTable of ContentsCorrect Grounding 80
    Fatigue Failure 80
12. force sensor 81
    What It Does . 81
    Applications . 81
    Schematic Symbol . 82
    How It Works 82
    Strain Gauge 82
    Wheatstone Bridge Circuits 83
    Wheatstone Bridge Errors 84
    Strain-Gauge Amplification 84
    Other Strain-Gauge Modules 85
    Plastic-Film Force Sensors 85
    How to Use It 86
    Values . 87
    Film-Based Force Sensors for User Input 87
    Specifications for Film-Based Force Sensors 87
    Strain Gauges . 88
    What Can Go Wrong . 88
    Soldering Damage 88
    Bad Load Distribution . 88
    Water Damage 88
    Temperature Sensitivity 88
    Leads Too Long 88
13. single touch sensor 89
    What It Does . 89
    Applications . 90
    Schematic Symbols 90
    How It Works 90
    How to Use It 91
    Obtaining Touch Pads . 91
    Individual Touch Pad 91
    Wheels and Strips . 92
    Design Considerations . 92
    What Can Go Wrong . 93
    Insensitive to Gloves . 93
    Stylus Issues . 93
    Conductive Ink 93
14. touch screen . 95
    What It Does . 95
    Schematic Symbol . 95
    Variants . 95
    Resistive Sensing 95
    x Encyclopedia of Electronic Components Volume 3Capacitive Sensing 96
    Screens Available as Components 97
15. liquid level sensor 99
    What It Does . 99
    Schematic Symbols 99
    Applications . 99
    How It Works . 100
    Binary-Output Float Sensor . 100
    Analog-Output Float Sensor 101
    Incremental-Output Float Sensor . 101
    Displacement Level Sensors 102
    Ultrasonic Level Sensors 102
    Reservoir Weight . 103
    Pressure Sensing . 103
    What Can Go Wrong 104
    Turbulence . 104
    Tilting . 104
16. liquid flow rate sensor 105
    What It Does . 105
    Schematic Symbols 105
    Paddlewheel Liquid Flow Rate Sensors 105
    Turbine Flow Rate Sensors 106
    Limitations of Paddlewheels and Turbines 107
    Thermal Mass Liquid Flow Rate Sensor 107
    Sliding Sleeve Liquid Flow Switch . 108
    Sliding Plunger Liquid Flow Switch 108
    Ultrasonic Liquid Flow Rate Sensor 108
    Magnetic Liquid Flow Sensor 108
    Differential Pressure Liquid Flow Meter 109
    What Can Go Wrong 109
    Vulnerability to Dirt and Corrosive Materials . 109
17. gas/liquid pressure sensor . 111
    What It Does . 111
    Schematic Symbols 111
    Applications . 111
    Design Considerations . 112
    Units . 112
    How It Works . 112
    Basic Sensing Elements . 112
    Relative Measurement 113
    Variants 114
    Ambient Air Pressure . 114
    Altitude 114
    xiTable of ContentsGas Pressure . 115
    What Can Go Wrong 116
    Vulnerability to Dirt, Moisture, and Corrosive Materials 116
    Light Sensitivity 116
18. gas concentration sensor . 117
    What It Does . 117
    Schematic Symbol . 117
    Semiconductor Gas Sensors . 117
    Oxygen Sensors 119
    Humidity Sensors . 119
    Dew-Point Sensor 120
    Absolute Humidity Sensors . 120
    Relative Humidity Sensors 120
    Humidity Sensor Output 121
    Analog Humidity Sensor 121
    Design Considerations . 122
    Digital Humidity Sensor 122
    What Can Go Wrong 122
    Contamination . 122
    Recalibration . 123
    Soldering 123
19. gas flow rate sensor 125
    What It Does . 125
    Applications . 125
    Schematic Symbol . 125
    How It Works . 126
    Anemometer . 126
    Mass Flow Rate Sensing 127
    Applications . 128
    Units . 128
    Measuring Higher Volumes . 128
    Output . 128
    What Can Go Wrong 129
20. photoresistor . 131
    What It Does . 131
    Schematic Symbol . 131
    How It Works . 132
    Construction . 132
    Variants 132
    Photoresistors in Optical Isolators . 132
    Values 133
    Comparisons with a Phototransistor 133
    How to Use It . 133
    xii Encyclopedia of Electronic Components Volume 3Choosing a Series Resistor 134
    What Can Go Wrong 134
    Overload . 134
    Excessive Voltage 134
    Confusion Among Components 134
21. photodiode 135
    What It Does . 135
    Schematic Symbols 135
    Applications . 135
    How It Works . 135
    Variants 136
    PIN Photodiodes . 136
    Avalanche Diodes 136
    Packages . 136
    Wavelength Range . 137
    Photodiode Arrays . 137
    Output Options 137
    Specific Variants 137
    Values 138
    How to Use It . 139
    What Can Go Wrong 140
22. phototransistor . 141
    What It Does . 141
    Schematic Symbols 141
    Applications . 142
    How It Works . 142
    Variants 142
    Optional Base Connection 142
    Photodarlington . 142
    PhotoFET 142
    Values 143
    Behavior Compared to Other Light Sensors . 143
    Binning 144
    How to Use It . 144
    Output Calculation . 145
    What Can Go Wrong 145
    Visual Classification Errors 145
    Output Out of Range . 145
23. NTC thermistor . 147
    What It Does . 147
    Schematic Symbols 147
    Applications . 148
    How an NTC Thermistor Works 148
    xiiiTable of ContentsOutput Conversion for Temperature Sensing 149
    Choosing a Series Resistor 149
    Wheatstone Bridge Circuit 150
    Deriving the Temperature Value 150
    Inrush Current Limiter 150
    Restart . 151
    Thermistor Values 152
    Time and Temperature . 152
    Resistance and Response . 152
    Kilohms and Kelvin . 152
    Reference Temperature . 152
    Reference Resistance . 152
    Dissipation Constant . 152
    Temperature Coefficient 152
    Thermal Time Constant . 152
    Tolerance 153
    Temperature Range 153
    Switching Current 153
    Power Limitations 153
    Interchangeability 153
    What Can Go Wrong 153
    Self-Heating . 153
    Heat Dissipation . 153
    Lack of Heat 153
    Addendum: Comparison of Temperature Sensors 153
    NTC Thermistor 154
    PTC Thermistor . 154
    Thermocouple . 154
    Resistance Temperature Detector . 154
    Semiconductor Temperature Sensor 155
24. PTC thermistor . 157
    What It Does . 157
    Schematic Symbols 157
    PTC Overview 158
    Silistor for Temperature Measurement . 158
    RTDs . 159
    Nonlinear PTC Thermistors 159
    Over-Temperature Protection . 159
    Over-Current Protection 160
    PTC Inrush Current Limiting 161
    PTC Thermistor for Lighting Ballast 162
    PTC Thermistor as a Heating Element . 162
    What Can Go Wrong 163
    Self-Heating . 163
    Heating Other Components 163
    xiv Encyclopedia of Electronic Components Volume 325. thermocouple . 165
    What It Does . 165
    Schematic Symbol . 166
    Thermocouple Applications . 166
    How a Thermocouple Works 167
    Thermocouple Details 168
    How to Use It . 168
    Types of Thermocouples . 169
    Seebeck Coefficients . 169
    Chips for Output Conversion . 170
    Thermopile . 171
    What Can Go Wrong 171
    Polarity 171
    Electrical Interference 171
    Metal Fatigue and Oxidation 171
    Using the Wrong Type 171
    Heat Damage from Creating a Thermocouple . 172
25. RTD (resistance temperature detector) . 173
    What It Does . 173
    RTD Attributes 173
    Schematic Symbol . 174
    Applications . 174
    How It Works . 174
    Variants 175
    Wiring . 175
    RTD Probe . 176
    Signal Conditioning 176
    What Can Go Wrong 176
    Self-Heating . 176
    Insulation Affected by Heat . 176
    Incompatible Sensing Element . 176
26. semiconductor temperature sensor . 177
    What It Does . 177
    Semiconductor Temperature Sensor Applications . 178
    Schematic Symbol . 178
    Attributes 178
    How It Works . 179
    CMOS Sensors . 179
    Multiple Transistors 179
    PTAT and the Brokaw Cell . 180
    Variants 180
    Analog Voltage Output . 181
    Analog Current Output . 182
    Digital Output . 183
    xvTable of ContentsCMOS Semiconductor Temperature Sensors . 185
    What Can Go Wrong 185
    Different Temperature Scales . 185
    Interference in Cable Runs 185
    Latency 186
    Processing Time 186
27. infrared temperature sensor 187
    What It Does . 187
    Applications . 188
    Schematic Symbol . 188
    How It Works . 188
    Thermopile 189
    Temperature Measurement . 190
    Variants 190
    Surface-Mount Specifications . 191
    Sensor Arrays 191
    Values 191
    Temperature Range 191
    Field of View . 192
    What Can Go Wrong 192
    Inappropriate Field of View . 192
    Reflective Objects 192
    Glass Obstruction 192
    Multiple Heat Sources 192
    Thermal Gradients . 192
28. microphone . 193
    What It Does . 193
    Schematic Symbol . 193
    How It Works . 194
    Carbon Microphone 194
    Moving-Coil Microphone . 194
    Condenser Microphone 194
    Electret Microphone 195
    MEMS Microphone . 195
    Piezoelectric Microphone . 196
    Values 196
    Sensitivity 196
    Directionality 197
    Frequency Response . 197
    Impedance . 198
    Total Harmonic Distortion 198
    Signal-to-Noise Ratio . 198
    What Can Go Wrong 198
    Cable Sensitivity . 198
    xvi Encyclopedia of Electronic Components Volume 3Noisy Power Supply 198
29. current sensor 199
    What It Does . 199
    Applications . 199
    Ammeter . 199
    Schematic Symbol . 200
    Ammeter Wiring . 200
    Series Resistor 200
    Current-Sense Resistors 201
    Voltage Measurement 202
    Hall-Effect Current Sensing 202
    What Can Go Wrong 203
    Confusing AC with DC 203
    Magnetic Interference 203
    Incorrect Meter Wiring . 203
    Current Out of Range . 203
30. voltage sensor 205
    What It Does . 205
    Applications . 205
    Volt Meter 205
    Schematic Symbol . 206
    Volt Meter Wiring 206
    How It Works . 206
    Load-Related Inaccuracy . 207
    Bar Graph 207
    What Can Go Wrong 208
    Confusing AC with DC 208
    High Circuit Impedance 208
    Voltage Out of Range . 208
    Voltage Relative to Ground . 208
    Appendix A. Sensor Output . 209
    Glossary . 217
    Index . 221
    Index
    A
    absolute humidity, 119, 120
    absolute magnetic encoder, 41
    absolute pressure, 113
    accelerometer
    and gyroscope, 72
    applications, 70
    free fall, 71
    gravity, 71
    how it works, 70
    IMU, 5, 63, 66, 69
    Newton’s Second Law, 72
    rotation, 71
    schematic symbol, 70
    spring, 70
    values, 73
    variants, 72
    what can go wrong, 74
    what it does, 69
    ADC, 210, 217
    air pressure, 114
    alcohol vapor sensor (see gas concentration sensor, alcohol)
    altimeter, 114
    ammeter (see current sensor)
    analog-to-digital conversion, 210,
    217
    anemometer, 125, 126
    angle sensor (see rotary position
    sensor)
    angular motion, 21
    angular position sensor (see rotary
    position sensor)
    Arduino-compatible
    gas flow rate sensor, 127
    gyroscope, 67
    IMU, 67
    magnetometer, 9
    pressure sensor, 114
    proximity sensor, 34
    temperature sensor, 184, 185
    touch screen, 97
    touch sensor, 91
    avalanche diode, 136
    axis of the earth, 7
    B
    bandgap temperature sensor (see
    semiconductor temperature
    sensor)
    barometer, 114
    barometric pressure, 114
    Beidou positioning system, 3
    bin switch, 57
    black-body radiation, 25
    Bourdon tube, 112
    breakout board, 217
    breakover switch (see tilt sensor)
    Brokaw cell, 180
    C
    capacitive displacement sensor,
    36
    capacitive proximity sensor (see
    touch sensor)
    capacitive touch screen, 96
    capacitive touch sensor, 90
    carbon microphone, 194
    chip-based temperature sensor
    (see semiconductor temperature sensor)
    clinometer, 55
    coil magnetometer, 8
    communications satellites, 1
    compass, 6, 8
    condenser microphone, 194
    contact bounce, 18, 23
    contents
    volume 1, xxi
    volume 2, xxii
    volume 3, xxii
    crystal microphone, 196
    current sensor
    ammeter, 199-200
    applications, 199
    Hall effect, 202
    how it works, 199
    microcontroller, 201
    panel meter, 199
    schematic, 200
    schematic symbol, 200
    221series resistor, 200
    voltage drop, 200
    what can go wrong, 203
    what it does, 199
    current-sense resistor, 201
    D
    debouncing, 18, 48, 61, 217
    decibels, 196, 217
    declination, 7
    detection sensor (see presence
    sensor)
    dew point, 119
    dielectric, 90, 218
    differential pressure, 113
    diode temperature sensor (see
    semiconductor temperature
    sensor)
    distance sensor (see proximity
    sensor)
    dual slope converter, 211
    dynamic pressure, 111
    E
    electret microphone, 195
    encoder
    linear, 41
    magnetic, 41
    rotary, 48
    errata, xxv
    F
    feedback to and from authors, xxv
    flash converter, 211
    float sensor, 100
    float switch, 57
    flux density, 6
    flux, magnetic, 6
    force sensor
    applications, 81
    deformative, 86
    how it works, 82
    how to use it, 86
    piezoelectric, 82
    plastic film, 82, 85-87
    resistive, 82, 86
    schematic symbol, 82
    strain gauge, 82, 83, 85, 88
    units of measurement, 82
    values, 87
    what can go wrong, 88
    what it does, 81
    wheatstone bridge, 83
    four-wire touch screen, 96
    frequency response, 197
    fresnel lens, 27
    G
    Galileo positioning system, 3
    gas concentration sensor
    alcohol, 118
    breakout board, 119
    cross-sensitivity, 118
    how it works, 117
    humidity, 117, 119
    oxygen, 119
    propane, 118
    schematic symbol, 117
    semiconductor-based, 117
    what can go wrong, 122
    what it does, 117
    gas flow rate sensor
    anemometer, 125, 126
    applications, 128
    data output, 128
    schematic symbol, 125
    thermal mass, 127
    thermopile, 127
    units of measurement, 128
    what can go wrong, 129
    what it does, 125
    gas pressure sensor (see pressure
    sensor)
    gas sensor (see gas concentration
    sensor)
    gauge pressure, 113
    geographical meridians, 7
    Global Positioning System (see
    GPS)
    GLONASS positioning system, 3
    GPS
    antenna, 2
    definitions, 1
    frequencies, 2
    how to use it, 3
    NMEA protocol, 3
    satellites, 1
    schematic symbol, 1
    time-keeping, 4
    tracker, 2
    values, 3
    what can go wrong, 4
    what it does, 1
    gray code, 51
    gyroscope
    and accelerometer, 72
    applications, 63
    axes, 64
    how it works, 64
    how to use it, 67
    IMU, 5, 63, 66, 69
    resonator (see gyroscope,
    vibrating)
    schematic symbol, 63
    values, 67
    variants, 66
    vibrating, 64
    what can go wrong, 67
    what it does, 63
    H
    Hall effect
    current sensor, 202
    Hall effect sensor
    advantages, 22
    applications, xx, 52
    float sensor, 100
    how it works, 18
    how to use, 20
    magnetometer, 8
    rotary position sensor, 48
    variants, 19
    hard-iron bias, 9
    heading, navigational, 5
    humidity sensor (see gas concentration sensor, humidity)
    hygrometer, 120
    hysteresis
    222 Indexfloat sensor, 101, 218
    reed switch, 17, 218
    I
    I2C, 214, 218
    IC temperature sensor (see semiconductor temperature sensor)
    IMU, 5, 63, 66, 69, 218
    inclination, 7
    inclinometer, 55
    inertial measurement unit (see
    IMU)
    infrared proximity sensor, 32-34
    infrared radiation, 188
    infrared temperature sensor
    advantages, 187
    applications, 188
    array, 191
    compared with other temperature sensors, 153
    how it works, 188
    limitations, 188
    schematic symbol, 188
    thermopile, 189
    values, 191
    variants, 190
    what can go wrong, 192
    what it does, 187
    inrush current limiter, 150, 161
    interintegrated circuit bus (see
    I2C)
    K
    Kelvin temperature scale, 218
    L
    light meter, 137
    light-dependent resistor (see photoresistor)
    linear displacement sensor (see
    linear position sensor)
    linear feedback shift register, 2
    linear position sensor
    absolute, 41
    applications, 39, 42
    how it works, 39
    incremental, 41
    linear potentiometer, 40
    magnetic linear encoder, 41
    optical linear encoder, 41
    quadrature, 41, 218
    schematic symbols, 39
    what can go wrong, 43
    what it does, 39
    linear potentiometer, 40
    linear variable differential transformer, 42
    liquid displacement sensor, 102
    liquid flow rate sensor
    differential pressure, 109
    magnetic, 108
    paddlewheel, 105
    reed switch, 105
    rotor, 105
    schematic symbols, 105
    thermal mass, 107
    turbine, 106
    ultrasonic, 108
    what can go wrong, 109
    what it does, 105
    liquid flow switch, 108
    liquid level sensor
    displacement, 102
    float, 100
    float switch, 57
    how it works, 100
    incremental output, 101
    potentiometer, 101
    pressure of liquid, 103
    schematic symbols, 99
    tilting, 104
    turbulence, 104
    ultrasonic, 102
    weight of reservor, 103
    what can go wrong, 104
    what it does, 99
    liquid pressure sensor (see pressure sensor)
    load cell (see load sensor)
    load sensor, 81
    (see also force sensor)
    applications, 82
    deformative, 86
    liquid level measurement, 103
    schematic symbol, 82
    strain gauge, 83, 85, 88
    values, 87
    what can go wrong, 88
    what it does, 81
    LVDT (see linear variable differential transformer)
    M
    magnetic
    axis, 7
    ball in tilt sensor, 59
    declination, 7
    encoder, 41, 52
    field, 6
    flux, 6
    liquid flow rate sensor, 108
    meridians, 7
    presence sensors, 16
    rotary position sensor, 47
    magnetic, linear encoder, 41
    magnetometer
    breakout board, 6, 9
    coil, 8
    hard-iron bias, 9
    heading, 5
    how it works, 6
    how to use it, 9
    IMU, 5, 63, 69
    magnetoresistance, 8
    meridians, 7
    placement, 10
    scalar, 5
    schematic symbol, 5
    soft-iron bias, 9
    vector, 5
    what can go wrong, 9
    what it does, 5
    magnetoresistance, 8
    mass flow rate sensor (see gas
    flow rate sensor)
    mathematical syntax, xxiv
    membrane switch, 89
    MEMS, xix, 218
    MEMS microphone, 195
    mercury switch, 58, 61, 78
    223Indexmeridians, 7
    metric system, xxiv
    microelectromechanical devices
    (see MEMS)
    microphone
    carbon, 194
    condenser, 194
    crystal, 196
    directionality, 197
    dynamic, 194
    electret, 195
    frequency response, 197
    how it works, 194
    impedance, 198
    MEMS, 195
    moving coil, 194
    piezoelectric, 196
    rolloff, 197
    schematic symbols, 193
    sensitivity, 196
    signal-to-noise ratio, 198
    total harmonic distortion, 198
    units of measurement, 196
    what can go wrong, 198
    what it does, 193
    motion sensor (see PIR)
    mouse, 50
    moving coil microphone, 194
    N
    navigational heading, 5
    newton unit of force, 218
    Newton’s Second Law, 72
    NMEA protocol, 3
    north pole, 7
    NTC thermistor (see thermistor,
    NTC)
    O
    object detector (see presence sensor)
    object presence sensor (see presence sensor)
    open collector output, 218
    opt-pass sensor, 15
    optical
    linear encoder, 41
    optical isolator, 132
    optical presence sensor, 12
    optical rotary encoder, 48, 53
    optical switch, 13, 15, 50
    optocoupler, 142
    optointerrupter, 21
    orthogonal, 218
    output
    analog current conversion, 213
    analog voltage conversion, 210,
    217
    analog-to-binary conversion,
    210
    analog-to-digital conversion,
    210
    binary, 209, 210, 213, 217
    digital, 209
    dual slope converter, 211
    flash converter, 211
    frequency conversion, 214
    I2C, 214, 218
    open collector, 212, 218
    options, 209
    pullup resistor, 213, 218
    PWM conversion, 209, 213
    resistance-to-voltage conversion, 211
    scaling, 211
    SPI, 215
    successive approximation converter, 211
    voltage divider, 210
    voltage-to-frequency converter, 211
    over-current protection, 160
    over-temperature protection, 159
    oxygen sensor (see gas concentration sensor, oxygen)
    P
    paddlewheel flow rate sensor, 105
    panel meter, 199, 205
    pascal unit of pressure, 218
    passive infrared motion sensor
    (see PIR)
    pendulum switch, 58
    photocell (see photoresistor)
    photoconductive cell (see photoresistor)
    photodarlington, 142
    photodiode
    applications, 135
    array, 137
    avalanche diode, 136
    band gap, 137
    color sensing, 137
    dark current, 135
    how it works, 135
    how to use it, 139
    light meter, 137
    photoconductive mode, 135
    phototransistor comparison,
    143
    photovoltaic mode, 135
    PIN type, 136
    reverse bias, 135
    schematic symbols, 135
    ultraviolet, 137
    values, 138
    variants, 136-137
    wavelength range, 137
    what can go wrong, 140
    what it does, 135
    photointerruptor, 13
    photomicrosensor, 15
    photoresistor
    availability, 131
    how it works, 132
    how to use it, 133
    optical isolator, 132
    phototransistor comparison,
    133
    schematic symbols, 131
    sizes, 132
    voltage divider, 134
    wavelengths of sensitivity, 134
    what can go wrong, 134
    what it does, 131
    phototransistor
    applications, 142
    base connection, 142
    binning, 144
    FET, 142
    how it works, 142
    how to use it, 144
    224 Indexoptocoupler, 142
    output current calculation, 145
    photodarlington, 142
    photodiode comparison, 143
    photoresistor comparison, 133
    schematic symbols, 141
    values, 143
    what can go wrong, 145
    what it does, 141
    photovoltaic effect, 135
    piezoelectric
    force sensor, 82
    heat detector, 26
    microphone, 196
    ultrasonic transducer, 32
    vibration sensor, 76
    PIN photodiode, 136
    pin-and-spring vibration sensor,
    76
    PIR
    applications, 25
    fresnel lens, 27
    how it works, 26
    schematic symbols, 25
    variants, 29
    what can go wrong, 30
    what it does, 25
    potentiometer
    arc segment, 46
    end stops, 46
    float sensor, 101
    logarithmic, 46
    multiturn, 46
    rotary position, 46
    presence sensor
    angular motion, 21
    configuration, 21
    linear motion, 21
    magnetic, 16
    optical, 12, 22, 23
    optointerrupter, 21
    reflective, 12
    retroreflective, 12, 15
    schematic symbol, 12
    transmissive, 12-13
    what can go wrong, 23
    what it does, 11
    pressure sensor
    absolute pressure, 113
    altitude, 114
    ambient air, 114
    applications, 111
    barometric, 114
    Bourdon tube, 112
    diaphragm, 112
    differential pressure, 113
    dynamic, 111
    gas and liquid behavior, 112
    gases, 115
    gauge pressure, 113
    how it works, 112
    schematic symbols, 111
    sensing elements, 112
    static, 111
    units of measurement, 112
    what can go wrong, 116
    what it does, 111
    propane sensor (see gas concentration sensor, propane)
    proximity sensor
    applications, 32
    capacitive displacement, 36
    infrared, 32-34
    schematic symbols, 31
    triangulation, 32
    ultrasound, 32-33
    what can go wrong, 38
    what it does, 31
    PTC thermistor (see thermistor,
    PTC)
    pullup resistor, 213, 218
    pulse-width modulation (see
    PWM)
    PWM, 209, 213
    pyroelectric detector, 26
    Q
    quadrature, 41, 49, 218
    R
    range finder (see proximity sensor)
    reed switch
    advantages, 22
    alarm system, 17
    float sensor, 100
    how it works, 17
    how to use it, 18
    hysteresis, 17
    liquid flow rate sensor, 105
    values, 18
    variants, 17
    what can go wrong, 23
    reference sources, xxvii
    reference temperature, 218
    reflective interrupter, 15
    reflective object sensor, 15
    reflective optical sensor, 15
    reflective photointerrupter, 15
    register, 218
    relative humidity, 119, 120
    resistance temperature detector
    (see RTD temperature sensor)
    resistance-to-voltage conversion,
    211
    resistive force sensor, 82, 86
    resistive temperature device (see
    RTD temperature sensor)
    resistive touch screen, 95
    retroreflective presence sensor,
    12, 15
    rotary encoder, 48, 52-53
    rotary position sensor
    absolute, 51
    accelerometer, 71
    applications, 45
    gray code, 51
    Hall Effect sensor, 48
    incremental, 49
    magnetic, 47
    mouse, 50
    optical encoder, 48
    potentiometer, 46
    quadrature, 49, 218
    reflective optical, 48
    rotary encoder, 48
    schematic symbols, 46
    sensing chips, 48
    transmissive optical, 48
    what can go wrong, 53
    what it does, 45
    rotary sensor (see rotary position
    sensor)
    rotating coil magnetometer, 8
    225Indexrotation sensor (see rotary position sensor)
    rotational encoder (see rotary
    encoder)
    rotational position sensor (see
    rotary position sensor)
    RTD temperature sensor
    applications, 174
    attributes, 173
    compared with other temperature sensors, 153
    how it works, 174
    output conversion, 176
    probe enclosure, 176
    schematic symbol, 174
    three-wire variant, 175
    variants, 175
    what can go wrong, 176
    what it does, 173
    S
    Safari Books Online, xxvi
    satellites, 1
    scalar magnetometer, 5
    schematic conventions, xxiv
    schematic symbol
    accelerometer, 70
    current sensor, 200
    force sensor, 82
    gas concentration sensor, 117
    gas flow rate sensor, 125
    GPS, 1
    gyroscope, 63
    infrared temperature sensor,
    188
    linear position sensor, 39
    liquid flow rate sensor, 105
    liquid level sensor, 99
    load sensor, 82
    magnetometer, 5
    microphone, 193
    photodiode, 135
    photoresistor, 131
    phototransistor, 141
    PIR, 25
    presence sensor, 12
    pressure sensor, 111
    proximity sensor, 31
    rotary position sensor, 46
    RTD temperature sensor, 174
    semiconductor temperature
    sensor, 178
    thermistor, NTC, 147
    thermistor, PTC, 157
    thermocouple, 166
    tilt sensor, 56
    touch screen, 95
    touch sensor, 90
    vibration sensor, 75
    voltage sensor, 206
    Seebeck effect, 167
    semiconductor temperature sensor
    analog current output, 182
    analog voltage output, 181
    applications, 178
    attributes, 178
    Brokaw cell, 180
    CMOS type, 185
    compared with other temperature sensors, 153
    digital output, 183
    how it works, 179
    multiple transistors, 179
    schematic symbol, 178
    variants, 180
    what can go wrong, 185
    what it does, 177
    sensor
    categories, xx
    chip-based, 217
    multifunction, xx
    output options, 209
    suppliers, xxv
    serial peripherals interface (see
    SPI)
    shift register, 2
    silistor, 158
    slider potentiometer, 40
    soft-iron bias, 9
    solar panel, 135
    sound pressure, 196
    sources, xxvii
    south pole, 7
    speed sensor, 45
    SPI, 215
    static pressure, 111
    stomp box, 133
    strain gauge, 82-83, 85, 88
    successive approximation converter, 211
    suppliers, xxv
    surge limiter (see inrush current
    limiter)
    T
    tactile switch, 89
    target, 218
    temperature coefficient, 147, 152,
    218
    temperature sensor
    comparison of types, 153
    infrared (see infrared temperature sensor)
    noncontact type, 187
    RTD (see RTD temperature sensor)
    semiconductor (see semiconductor temperature sensor)
    thermistor, NTC (see thermistor,
    NTC)
    thermistor, PTC (see thermistor,
    PTC)
    thermocouple (see thermocouple)
    thermal mass flow rate sensor (see
    gas flow rate sensor)
    thermal mass liquid flow rate sensor, 107
    thermistor, NTC
    applications, 148
    compared with other temperature sensors, 153
    datasheet terminology, 152
    how it works, 148
    inrush current limiter, 150
    output conversion, 149
    schematic symbols, 147
    values, 152
    what can go wrong, 153
    what it does, 147
    wheatstone bridge, 150
    thermistor, PTC
    226 Indexcompared with other temperature sensors, 153
    externally heated, 159
    heating element, 162
    inrush current limiter, 161
    lighting ballast, 162
    linear, 158
    nonlinear, 158, 159
    over-current protection, 160
    over-temperature protection,
    159
    schematic symbols, 157
    silistor, 158
    starting current, 162
    what can go wrong, 163
    what it does, 157
    thermocouple
    applications, 166
    compared with other temperature sensors, 153
    how it works, 167
    how to use it, 168
    identifiers, 169
    measurement junction, 168
    output conversion, 170
    reference junction, 168
    schematic symbol, 166
    Seebeck coefficients, 169
    Seebeck effect, 167
    thermopile, 171
    what can go wrong, 171
    what it does, 165
    thermopile
    gas flow rate sensor, 127
    infrared temperature sensor,
    189
    overview, 171
    tilt sensor
    applications, 57
    bin switch, 57
    breakout board, 59
    float switch, 57
    how it works, 56
    how to use it, 61
    magnetic ball, 59
    mercury switch, 58, 61
    miniaturized, 59
    pendulum switch, 58
    schematic symbol, 56
    two-axis, 59
    values, 60
    what can go wrong, 61
    what it does, 55
    tilt switch (see tilt sensor)
    tip sensor (see tilt sensor)
    tipover switch (see tilt sensor)
    touch pad (see touch sensor)
    touch screen
    Arduino-compatible, 97
    capacitive, 96
    four-wire, 96
    resistive, 95
    schematic symbol, 95
    variants, 95, 97
    what it does, 95
    touch sensor
    applications, 90
    breakout boards, 91
    capacitive, 90
    design considerations, 92
    how it works, 90
    how to use it, 91
    schematic symbols, 90
    tactile feedback, 90
    touch pad availability, 91
    what can go wrong, 93
    what it does, 89
    wheels and strips, 92
    touch strip, 92
    touch wheel, 92
    triangulation, 32
    turbine flow rate sensor, 106
    U
    ultrasonic anemometer, 126
    ultrasonic flow rate sensor, 108
    ultrasonic liquid level sensor, 102
    ultrasonic proximity sensor, 32-33
    units of measurement, xxiv
    V
    Vactrol, 132
    vapor sensor (see gas concentration sensor)
    vector magnetometer, 5
    vibrating gyroscope, 64
    vibration sensor
    how to use it, 79
    magnetic, 77
    mercury switch, 78
    mousetrap type, 77
    piezoelectric, 76
    pin-and-spring, 76
    schematic symbols, 75
    values, 78
    variables, 78
    variants, 75
    what can go wrong, 79
    what it does, 75
    vibration switch (see vibration
    sensor)
    video display, 95
    volt meter (see voltage sensor)
    voltage divider, 210
    voltage sensor
    accuracy, 207
    bar graph, 207
    how it works, 206
    panel meter, 205
    schematic, 206
    schematic symbol, 206
    volt meter, 205
    what can go wrong, 208
    what it does, 205
    voltage-to-frequency converter, 211
    W
    wheatstone bridge, 83, 150, 160, 219

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