Absolute angle measurement using the earth-field-referenced hall effect sensors.
A miniaturized absolute angle sensor utilizing Hall generators referenced to the Earth's ambient magnetic field has been developed. The sensor has three-dimensional angular sensitivity which allows the output to be self-normalized resulting in high immunity to both B-field and temperature induced errors. The individual Hall generator elements were operated with a final sensitivity of 4.07 V G-1. The Earth's field, magnitude 0.486 G with a surface declination angle of 58.2 degrees (San Diego, California), was used as the excitation/reference field. Bandwidth limiting, low-noise design, and active/passive thermal compensation techniques were employed resulting in a sensor bandwidth of DC to 100 Hz with a maximum signal-to-noise ratio of 44.5 dB. The maximum angular resolution of the sensor was measured to be +/- 0.27 degrees. Temperature induced error was measured to be less than 2% from 25 degrees C to 40 degrees C. The measurement of shoulder joint rotation was used as the test case application for the sensor with excellent agreement between theoretical and experimental performance.
Kolen
P T
PT
Electrical and Computer Engineering Department, San Diego State University, CA 92182.
Rhode
J P
JP
Francis
P R
PR
D001703:Biophysics / Q000295:instrumentation*; D004581:Electronics / Q000295:instrumentation; D004867:Equipment Design; D006801:Humans; D008280:Magnetics; D008422:Materials Testing; D008954:Models, Biological; D008962:Models, Theoretical; D009068:Movement / Q000502:physiology*; D012399:Rotation; D012785:Shoulder Joint / Q000502:physiology; D014159:Transducers