Hall Effect Sensing and Application

1 hall Effect Sensing AND Application . MICRO SWITCH Sensing and Control 7 DEOH RI &RQWHQWV. Chapter 1 hall Effect Sensing Introduction .. 1. hall Effect Sensors .. 1. Why use the hall Effect .. 2. Using this 2. Chapter 2 hall Effect Sensors Introduction .. 3. Theory of the hall Effect .. 3. Basic hall Effect sensors .. 4. analog output 5. Output vs. power supply characteristics .. 5. Transfer Function .. 6. digital output sensors .. 7. Transfer Function .. 7. Power Supply 8. Input Characteristics .. 8. Output 8. 8. Chapter 3 Magnetic Considerations Magnetic Fields .. 9. Magnetic materials and their specifications .. 9. Basic magnetic design 10. Magnetic materials 11. Magnetic 11. Unipolar head-on mode .. 12. Unipolar slide-by 12.

2 Bipolar slide-by mode .. 13. Bipolar slide by mode (ring magnet) .. 14. Systems with pole pieces .. 15. Systems with bias 16. Magnetic systems comparison .. 17. Ratiometric Linear hall Effect sensors .. 18. 18. For Application help: call 1-800-537-6945 Honeywell MICRO SWITCH Sensing and Control i Table of Contents Chapter 4 Electrical Considerations Introduction .. 19. digital output 19. Electrical specifications ..20. Specification 20. Absolute Maximum Ratings ..20. Rated Electrical Basic 21. Pull-up resistors .. 21. Logic gate Transistor interfaces ..22. Symbols for design calculations .. 24. analog Output Sensors .. 29. Electrical specifications ..30. Basic Interfaces to common components .. 31. 32. Chapter 5 hall -based Sensing Devices Introduction.

3 33. Vane-operated position 33. Principles of Operation ..33. sensor digital current 36. Principles of Operation ..37. sensor Linear current 38. Principles of Operation ..38. Loop Current Sensors .. 39. Principles of Operation ..39. Mechanically operated solid state switches .. 41. Principles of Operation ..41. Switch specifications .. 42. Gear Tooth Sensors .. 42. Principles of Operation ..43. Target 43. 44. Chapter 6 Applying hall - Effect Sensing Devices General Sensing device design .. 45. Design of hall Effect -based Sensing devices .. 47. System 48. Concept definition Discrete Sensing devices ..48. digital output hall Effect -based Sensing devices .. 49. Design approach Non-precision applications ..49. Design Approach Precision applications.

4 51. Linear output hall Effect -based Sensing devices .. 53. ii Honeywell MICRO SWITCH Sensing and Control For Application help: call 1-800-537-6945. Table of Contents Design approach Linear output sensors .. 53. Design approach Linear current sensors .. 55. sensor 57. Design approach Vane-operated sensors .. 58. Design approach digital output current 59. 60. Chapter 7 Application Examples Flow rate sensor ( digital ) .. 63. Sequencing sensors .. 63. Proximity sensors .. 64. Office machine sensors .. 64. Adjustable current 65. Linear feedback sensor .. 66. Multiple position sensor .. 66. Microprocessor controlled sensor .. 67. Anti-skid 67. Door interlock and ignition 67. Transmission mounted speed sensor .. 68. Crankshaft position or speed sensor .

5 68. Distributor mounted ignition sensor .. 68. Level/tilt measurement 69. Brushless DC motor sensors .. 69. RPM 70. Remote conveyor Sensing .. 70. Remote reading 71. Current 71. Flow rate sensor (linear output .. 72. Piston detection sensor .. 73. Temperature or pressure sensor .. 73. Magnetic card 74. Throttle angle 75. Automotive sensors .. 76. Appendix A Units and Conversion 77. Appendix B Magnet Application Data .. 79. Appendix C Magnetic Curves .. 89. Appendix D Use of Calibrated hall Device .. 99. Glossary .. 103. For Application help: call 1-800-537-6945 Honeywell MICRO SWITCH Sensing and Control iii Table of Contents iv Honeywell MICRO SWITCH Sensing and Control For Application help: call 1-800-537-6945. &KDSWHU.)

6 +DOO (IIHFW 6 HQVLQJ. Introduction The hall Effect has been known for over one hundred years, but has only been put to noticeable use in the last three dec- ades. The first practical Application (outside of laboratory experiments) was in the 1950s as a microwave power sensor . With the mass production of semiconductors, it became feasible to use the hall Effect in high volume products. MICRO. SWITCH Sensing and Control revolutionized the keyboard industry in 1968 by introducing the first solid state keyboard using the hall Effect . For the first time, a hall Effect Sensing element and its associated electronics were combined in a sin- gle integrated circuit. Today, hall Effect devices are included in many products, ranging from computers to sewing machines, automobiles to aircraft, and machine tools to medical equipment.)

7 Quantity to be sensed hall Effect sensors The hall Effect is an ideal Sensing technology. The hall element is constructed Input from a thin sheet of conductive material with output connections perpendicular to Interface Sensing the direction of current flow. When subjected to a magnetic field, it responds with Device an output voltage proportional to the magnetic field strength. The voltage output System is very small ( V) and requires additional electronics to achieve useful voltage Mathematic levels. When the hall element is combined with the associated electronics, it forms a hall Effect sensor . The heart of every MICRO SWITCH hall Effect de- hall vice is the integrated circuit chip that contains the hall element and the signal hall Effect Element conditioning electronics.

8 sensor Although the hall Effect sensor is a magnetic field sensor , it can be used as the principle component in many other types of Sensing devices (current, temperature, Output Interface pressure, position, etc.). hall Effect sensors can be applied in many types of Sensing devices. If the quantity Electrical (parameter) to be sensed incorporates or can incorporate a magnetic field, a hall Signal sensor will perform the task. Figure 1-1 shows a block diagram of a Sensing de- Figure 1-1 General sensor vice that uses the hall Effect . based on the hall Effect In this generalized Sensing device, the hall sensor senses the field produced by the magnetic system. The magnetic system responds to the physical quantity to be sensed (temperature, pressure, position, etc.)

9 Through the input interface. The output interface converts the electrical signal from the hall sensor to a signal that meets the requirements of the Application . The four blocks contained within the Sensing device (Figure 1-1) will be exam- ined in detail in the following chapters. For Application help: call 1-800-537-6945 Honeywell MICRO SWITCH Sensing and Control 1. Chapter 1 hall Effect Sensing Why use the hall Effect ? The reasons for using a particular technology or sensor vary according to the Application . Cost, performance and availabil- ity are always considerations. The features and benefits of a given technology are factors that should be weighed along with the specific requirements of the Application in making this decision.

10 General features of hall Effect based Sensing devices are: True solid state Long life (30 billion operations in a continuing keyboard module test program). High speed operation - over 100 kHz possible Operates with stationary input (zero speed). No moving parts Logic compatible input and output Broad temperature range (-40 to +150 C). Highly repeatable operation Using this manual This manual may be considered as two parts: Chapters 2 through 5 present the basic information needed to apply hall Effect devices. Chapter 6 brings this information together and relates it to the design and Application of the hall Effect Sensing systems. Chapter 2, hall Effect sensors. Introduces the theory of operation and relates it to the hall Effect sensors.