Hall-Effect Sensors: Theory and Application

Front Matter......Page 2
About the Author......Page 0
Table of Contents......Page 4
About the Author......Page 9
Introduction......Page 10
1. Hall-Effect Physics......Page 13
1.1 A Quantitative Examination......Page 15
1.2 Hall Effect in Metals......Page 17
1.3 The Hall Effect in Semiconductors......Page 19
1.4 A Silicon Hall-Effect Transducer......Page 21
2.1.1 Sensitivity......Page 23
2.1.2 Temperature Coefficient of Sensitivity......Page 24
2.1.3 Ohmic Offset......Page 25
2.1.6 Input and Output Resistances......Page 26
2.1.8 Noise......Page 27
2.2 Bulk Transducers......Page 28
2.3 Thin-Film Transducers......Page 29
2.4 Integrated Hall Transducers......Page 32
2.5 Transducer Geometry......Page 38
2.6 The Quad Cell......Page 39
2.7 Variations on the Basic Hall-Effect Transducer......Page 42
2.8 Examples of Hall Effect Transducers......Page 45
3. Transducer Interfacing......Page 46
3.1 An Electrical Transducer Model......Page 47
3.2 A Model for Computer Simulation......Page 49
3.3 Voltage-Mode Biasing......Page 52
3.4 Current-Mode Biasing......Page 56
3.5 Amplifiers......Page 59
3.6 Amplifier Circuits......Page 62
3.7 Analog Temperature Compensation......Page 65
3.8 Offset Adjustment......Page 68
3.9 Dynamic Offset Cancellation Technique......Page 69
4. Integrated Sensors: Linear and Digital Devices......Page 72
4.1 Linear Sensors......Page 73
4.2 Linear Transfer Curve......Page 76
4.3 Drift......Page 77
4.4 Ratiometry......Page 78
4.5 Output Characteristics......Page 79
4.6 Bandwidth......Page 80
4.8 Power Supply Requirements for Linear Sensors......Page 82
4.10 Field-Programmable Linear Sensors......Page 83
4.11 Typical Linear Devices......Page 85
4.12 Switches and Latches......Page 86
4.13 Definition of Switch vs. Latch......Page 88
4.15 Bipolar Switches......Page 89
4.16 Power Supply Requirements for Digital Sensors......Page 90
4.17 Output Drivers......Page 91
4.18 Typical Digital Devices......Page 92
5.1 Interface Issues - Linear Output Sensors......Page 94
5.2 Offset and Gain Adjustment......Page 95
5.3 Output Thresholding......Page 97
5.5 The Pull-up Resistor......Page 99
5.6 Interfacing to Standard Logic Devices......Page 101
5.7 Discrete Logic......Page 102
5.7.1 Logic NOT Output......Page 103
5.9 LED Interfaces......Page 104
5.10 Incandescent Lamps......Page 105
5.11 Relays, Solenoids, and Inductive Loads......Page 107
5.13 Encoding and Serialization......Page 109
5.14 Digital-to-Analog Encoding......Page 110
5.15 Mini-Networks......Page 113
5.16 Voltage Regulation and Power Management......Page 115
6.1 Head-On Sensing......Page 118
6.2 Slide-By Sensing......Page 120
6.3 Magnet Null-Point Sensing......Page 121
6.4 Float-Level Sensing......Page 125
6.5 Linear Position Sensing......Page 127
6.6 Rotary Position Sensing......Page 129
6.7 Vane Switches......Page 133
6.8 Some Thoughts on Designing Proximity Sensors......Page 137
7.1 Resistive Current Sensing......Page 142
7.2 Free-Space Current Sensing......Page 144
7.3 Free-Space Current Sensors II......Page 147
7.4 Toroidal Current Sensors......Page 151
7.5 Analysis of Slotted Toroid......Page 153
7.6 Toroid Material Selection and Issues......Page 154
7.7 Increasing Sensitivity with Multiple Turns......Page 155
7.8 An Example Current Sensor......Page 156
7.9 A Digital Current Sensor......Page 157
7.10 Integrated Current Sensors......Page 158
7.11 Closed-Loop Current Sensors......Page 159
8.1 Competitive Technologies......Page 162
8.2 Magnetic Targets......Page 164
8.3 Vane Switches......Page 166
8.4 Geartooth Sensing......Page 168
8.5 Geartooth Sensor Architecture......Page 169
8.6 Single-Point Sensing......Page 170
8.7 Single-Point/Fixed-Threshold Schemes......Page 172
8.8 Single-Point/Dynamic-Threshold Schemes......Page 174
8.9 Differential Geartooth Sensors......Page 178
8.10 Differential Fixed-Threshold......Page 180
8.11 Differential Variable-Threshold......Page 181
8.13 Speed and Direction Sensing......Page 182
8.14 How Fast Do Speed Sensors Go?......Page 184
9.1 Micropower Switches......Page 187
9.2 Two-Wire Switches......Page 190
9.3 Power Devices......Page 192
9.4 Power + Brains = Smart Motor Control......Page 193
10.1.1 Power Supplies......Page 196
10.1.2 Voltmeters and DMMs......Page 197
10.1.5 Clamp-On Current Probes......Page 198
10.2.1 Gaussmeter......Page 199
10.2.2 Fluxmeter......Page 200
10.2.4 Polarity Probe......Page 201
10.2.6 Magnetizers and Magnet Conditioners......Page 202
10.2.7 Helmholtz Coil......Page 204
10.3.2 Linear Positioning Slides......Page 205
10.3.4 Calipers and Micrometers......Page 206
10.3.5 Machine Tools......Page 207
10.4 Magnetic Simulation Software......Page 208
A.1 Where Magnetic Fields Come From......Page 212
A.2 Magnetic Materials......Page 214
A.3 Some Permanent Magnet Materials......Page 219
Appendix B: Supplier List......Page 220
Appendix C: Glossary of Common Terms......Page 227
Appendix D: References and Bibliography......Page 237
A......Page 239
B......Page 242
C......Page 244
D......Page 249
E......Page 252
F......Page 255
G......Page 257
H......Page 259
I......Page 263
L......Page 265
M......Page 268
N......Page 273
O......Page 274
P......Page 277
R......Page 280
S......Page 282
T......Page 290
V......Page 294
Z......Page 296