Hall-Effect Sensors

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
. Hall effect transducers
. transducer interfacing
. integrated Hall effect sensors and how to interface to them
. sensing techniques using Hall effect sensors
. application-specific sensor ICs
. relevant development and design tools

This second edition is expanded and updated to reflect the latest advances in Hall effect devices and applications!

Information about various sensor technologies is scarce, scattered and hard to locate. Most of it is either too theoretical for working engineers, or is manufacturer literature that can't be entirely trusted. Engineers and engineering managers need a comprehensive, up-to-date, and accurate reference to use when scoping out their designs incorporating Hall effect sensors.

* A comprehensive, up-to-date reference to use when crafting all kinds of designs with Hall effect sensors

*Replaces other information about sensors that is too theoretical, too biased toward one particular manufacturer, or too difficult to locate

*Highly respected and influential author in the burgeoning sensors community

1;Front Cover;1 2;Hall-Effect Sensors: Theory and Applications;4 3;Copyright Page;5 4;Contents;6 5;Chapter 1. Hall-Effect Physics;16 5.1;1.1 A Quantitative Examination;18 5.2;1.2 Hall Effect in Metals;20 5.3;1.3 The Hall Effect in Semiconductors;22 5.4;1.4 A Silicon Hall-Effect Transducer;24 6;Chapter 2. Practical Transducers;26 6.1;2.1 Key Transducer Characteristics;26 6.2;2.2 Bulk Transducers;31 6.3;2.3 Thin-Film Transducers;32 6.4;2.4 Integrated Hall Transducers;35 6.5;2.5 Transducer Geometry;41 6.6;2.6 The Quad Cell;42 6.7;2.7 Variations on the Basic Hall-Effect Transducer;45 6.8;2.8 Examples of Hall Effect Transducers;48 7;Chapter 3. Transducer Interfacing;50 7.1;3.1 An Electrical Transducer Model;51 7.2;3.2 A Model for Computer Simulation;53 7.3;3.3 Voltage-Mode Biasing;56 7.4;3.4 Current-Mode Biasing;60 7.5;3.5 Amplifiers;63 7.6;3.6 Amplifier Circuits;66 7.7;3.7 Analog Temperature Compensation;69 7.8;3.8 Offset Adjustment;72 7.9;3.9 Dynamic Offset Cancellation Technique;73 8;Chapter 4. Integrated Sensors: Linear and Digital Devices;76 8.1;4.1 Linear Sensors;77 8.2;4.2 Linear Transfer Curve;80 8.3;4.3 Drift;81 8.4;4.4 Ratiometry;82 8.5;4.5 Output Characteristics;83 8.6;4.6 Bandwidth;84 8.7;4.7 Noise;86 8.8;4.8 Power Supply Requirements for Linear Sensors;86 8.9;4.9 Temperature Range;87 8.10;4.10 Field-Programmable Linear Sensors;87 8.11;4.11 Typical Linear Devices;89 8.12;4.12 Switches and Latches;90 8.13;4.13 Definition of Switch vs. Latch;92 8.14;4.14 Switchpoint Stability;93 8.15;4.15 Bipolar Switches;93 8.16;4.16 Power Supply Requirements for Digital Sensors;94 8.17;4.17 Output Drivers;95 8.18;4.18 Typical Digital Devices;96 9;Chapter 5. Interfacing to IntegratedHall-Effect Devices;98 9.1;5.1 Interface IssuesLinear Output Sensors;98 9.2;5.2 Offset and Gain Adjustment;99 9.3;5.3 Output Thresholding;101 9.4;5.4 Interfacing to Switches and Latches;103 9.5;5.5 The Pull-Up Resistor;103 9.6;5.6 Interfacing to Standard Logic Devices;105 9.7;5.7 Discrete Logic;106
9.8;5.8 Driving Loads;108 9.9;5.9 LED Interfaces;108 9.10;5.10 Incandescent Lamps;109 9.11;5.11 Relays, Solenoids, and Inductive Loads;111 9.12;5.12 Wiring-Reduction Schemes;113 9.13;5.13 Encoding and Serialization;113 9.14;5.14 Digital-to-Analog Encoding;114 9.15;5.15 Mini-Networks;117 9.16;5.16 Voltage Regulation and Power Management;119 10;Chapter 6. Proximity-Sensing Techniques;122 10.1;6.1 Head-On Sensing;122 10.2;6.2 Slide-By Sensing;124 10.3;6.3 Magnet Null-Point Sensing;125 10.4;6.4 Float-Level Sensing;129 10.5;6.5 Linear Position Sensing;131 10.6;6.6 Rotary Position Sensing;133 10.7;6.7 Vane Switches;137 10.8;6.8 Some Thoughts on Designing Proximity Sensors;141 11;Chapter 7. Current-Sensing Techniques;146 11.1;7.1 Resistive Current Sensing;146 11.2;7.2 Free-Space Current Sensing;148 11.3;7.3 Free-Space Current Sensors II;151 11.4;7.4 Toroidal Current Sensors;155 11.5;7.5 Analysis of Slotted Toroid;157 11.6;7.6 Toroid Material Selection and Issues;158 11.7;7.7 Increasing Sensitivity with Multiple Turns;159 11.8;7.8 An Example Current Sensor;160 11.9;7.9 A Digital Current Sensor;161 11.10;7.10 Integrated Current Sensors;162 11.11;7.11 Closed-Loop Current Sensors;163 12;Chapter 8. Speed and Timing Sensors;166 12.1;8.1 Competitive Technologies;166 12.2;8.2 Magnetic Targets;168 12.3;8.3 Vane Switches;170 12.4;8.4 Geartooth Sensing;172 12.5;8.5 Geartooth Sensor Architecture;173 12.6;8.6 Single-Point Sensing;174 12.7;8.7 Single-Point/Fixed-Threshold Schemes;176 12.8;8.8 Single-Point/Dynamic-Threshold Schemes;178 12.9;8.9 Differential Geartooth Sensors;182 12.10;8.10 Differential Fixed-Threshold;184 12.11;8.11 Differential Variable-Threshold;185 12.12;8.12 Comparison of Hall-Effect Speed Sensing Methods;186 12.13;8.13 Speed and Direction Sensing;186 12.14;8.14 How Fast Do Speed Sensors Go?;188 13;Chapter 9. Application-Specific Sensors;192 13.1;9.1 Micropower Switches;192 13.2;9.2 Two-Wire Switches;195 13.3;9.3 Power Devices;197 13.4;9.4 Power + Brains = Smart Mot
or Control;198 14;Chapter 10. Development Tools;202 14.1;10.1 Electronic Bench Equipment;202 14.2;10.2 Magnetic Instrumentation;205 14.3;10.3 Mechanical Tools;211 14.4;10.4 Magnetic Simulation Software;214 15;Appendix A. A Brief Introduction;218 15.1;A.1 Where Magnetic Fields Come From;218 15.2;A.2 Magnetic Materials;220 15.3;A.3 Some Permanent Magnet Materials;225 16;Appendix B. Supplier List;226 17;Appendix C. Glossary of Common Terms;234 18;Appendix D. References and Bibliography;244 19;About the Author;246 20;Index;248