Without sensors most electronic applications would not exist-sensors perform a vital function, namely providing an interface to the real world. Hall effect sensors, based on a magnetic phenomena, are one of the most commonly used sensing technologies today. In the 1970s it became possible to build Hall effect sensors on integrated circuits with onboard signal processing circuitry, vastly reducing the cost and enabling widespread practical use. One of the first major applications was in computer keyboards, replacing mechanical contacts. Hundreds of millions of these devices are now manufactured each year for use in a great variety of applications, including automobiles, computers, industrial control systems, cell phones, and many others. The importance of these sensors, however, contrasts with the limited information available. Many recent advances in miniaturization, smart sensor configurations, and networkable sensor technology have led to design changes and a need for reliable information. Most of the technical information on Hall effect sensors is supplied by sensor manufacturers and is slanted toward a particular product line. System design and control engineers need an independent, readable source of practical design information and technical details that is not product- or manufacturer-specific and that shows how Hall effect sensors work, how to interface to them, and how to apply them in a variety of uses. This book covers: . the physics behind Hall effect sensors .
Author(s): Edward Ramsden
Edition: 2
Publisher: Newnes
Year: 2006
Language: English
Pages: 296
Front Matter......Page 1
About the Author......Page 0
Table of Contents......Page 3
About the Author......Page 8
Introduction......Page 9
1. Hall-Effect Physics......Page 12
1.1 A Quantitative Examination......Page 14
1.2 Hall Effect in Metals......Page 16
1.3 The Hall Effect in Semiconductors......Page 18
1.4 A Silicon Hall-Effect Transducer......Page 20
2.1.1 Sensitivity......Page 22
2.1.2 Temperature Coefficient of Sensitivity......Page 23
2.1.3 Ohmic Offset......Page 24
2.1.6 Input and Output Resistances......Page 25
2.1.8 Noise......Page 26
2.2 Bulk Transducers......Page 27
2.3 Thin-Film Transducers......Page 28
2.4 Integrated Hall Transducers......Page 31
2.5 Transducer Geometry......Page 37
2.6 The Quad Cell......Page 38
2.7 Variations on the Basic Hall-Effect Transducer......Page 41
2.8 Examples of Hall Effect Transducers......Page 44
3. Transducer Interfacing......Page 45
3.1 An Electrical Transducer Model......Page 46
3.2 A Model for Computer Simulation......Page 48
3.3 Voltage-Mode Biasing......Page 51
3.4 Current-Mode Biasing......Page 55
3.5 Amplifiers......Page 58
3.6 Amplifier Circuits......Page 61
3.7 Analog Temperature Compensation......Page 64
3.8 Offset Adjustment......Page 67
3.9 Dynamic Offset Cancellation Technique......Page 68
4. Integrated Sensors: Linear and Digital Devices......Page 71
4.1 Linear Sensors......Page 72
4.2 Linear Transfer Curve......Page 75
4.3 Drift......Page 76
4.4 Ratiometry......Page 77
4.5 Output Characteristics......Page 78
4.6 Bandwidth......Page 79
4.8 Power Supply Requirements for Linear Sensors......Page 81
4.10 Field-Programmable Linear Sensors......Page 82
4.11 Typical Linear Devices......Page 84
4.12 Switches and Latches......Page 85
4.13 Definition of Switch vs. Latch......Page 87
4.15 Bipolar Switches......Page 88
4.16 Power Supply Requirements for Digital Sensors......Page 89
4.17 Output Drivers......Page 90
4.18 Typical Digital Devices......Page 91
5.1 Interface Issues - Linear Output Sensors......Page 93
5.2 Offset and Gain Adjustment......Page 94
5.3 Output Thresholding......Page 96
5.5 The Pull-up Resistor......Page 98
5.6 Interfacing to Standard Logic Devices......Page 100
5.7 Discrete Logic......Page 101
5.7.1 Logic NOT Output......Page 102
5.9 LED Interfaces......Page 103
5.10 Incandescent Lamps......Page 104
5.11 Relays, Solenoids, and Inductive Loads......Page 106
5.13 Encoding and Serialization......Page 108
5.14 Digital-to-Analog Encoding......Page 109
5.15 Mini-Networks......Page 112
5.16 Voltage Regulation and Power Management......Page 114
6.1 Head-On Sensing......Page 117
6.2 Slide-By Sensing......Page 119
6.3 Magnet Null-Point Sensing......Page 120
6.4 Float-Level Sensing......Page 124
6.5 Linear Position Sensing......Page 126
6.6 Rotary Position Sensing......Page 128
6.7 Vane Switches......Page 132
6.8 Some Thoughts on Designing Proximity Sensors......Page 136
7.1 Resistive Current Sensing......Page 141
7.2 Free-Space Current Sensing......Page 143
7.3 Free-Space Current Sensors II......Page 146
7.4 Toroidal Current Sensors......Page 150
7.5 Analysis of Slotted Toroid......Page 152
7.6 Toroid Material Selection and Issues......Page 153
7.7 Increasing Sensitivity with Multiple Turns......Page 154
7.8 An Example Current Sensor......Page 155
7.9 A Digital Current Sensor......Page 156
7.10 Integrated Current Sensors......Page 157
7.11 Closed-Loop Current Sensors......Page 158
8.1 Competitive Technologies......Page 161
8.2 Magnetic Targets......Page 163
8.3 Vane Switches......Page 165
8.4 Geartooth Sensing......Page 167
8.5 Geartooth Sensor Architecture......Page 168
8.6 Single-Point Sensing......Page 169
8.7 Single-Point/Fixed-Threshold Schemes......Page 171
8.8 Single-Point/Dynamic-Threshold Schemes......Page 173
8.9 Differential Geartooth Sensors......Page 177
8.10 Differential Fixed-Threshold......Page 179
8.11 Differential Variable-Threshold......Page 180
8.13 Speed and Direction Sensing......Page 181
8.14 How Fast Do Speed Sensors Go?......Page 183
9.1 Micropower Switches......Page 186
9.2 Two-Wire Switches......Page 189
9.3 Power Devices......Page 191
9.4 Power + Brains = Smart Motor Control......Page 192
10.1.1 Power Supplies......Page 195
10.1.2 Voltmeters and DMMs......Page 196
10.1.5 Clamp-On Current Probes......Page 197
10.2.1 Gaussmeter......Page 198
10.2.2 Fluxmeter......Page 199
10.2.4 Polarity Probe......Page 200
10.2.6 Magnetizers and Magnet Conditioners......Page 201
10.2.7 Helmholtz Coil......Page 203
10.3.2 Linear Positioning Slides......Page 204
10.3.4 Calipers and Micrometers......Page 205
10.3.5 Machine Tools......Page 206
10.4 Magnetic Simulation Software......Page 207
A.1 Where Magnetic Fields Come From......Page 211
A.2 Magnetic Materials......Page 213
A.3 Some Permanent Magnet Materials......Page 218
Appendix B: Supplier List......Page 219
Appendix C: Glossary of Common Terms......Page 226
Appendix D: References and Bibliography......Page 236
A......Page 238
B......Page 241
C......Page 243
D......Page 248
E......Page 251
F......Page 254
G......Page 256
H......Page 258
I......Page 262
L......Page 264
M......Page 267
N......Page 272
O......Page 273
P......Page 276
R......Page 279
S......Page 281
T......Page 289
V......Page 293
Z......Page 295
