Electricity: measuring and testing – Magnetic – Displacement
Patent
1989-10-25
1990-07-03
Eisenzopf, Reinhard J.
Electricity: measuring and testing
Magnetic
Displacement
324252, 307309, 338 32R, 357 27, G01B 714, G01R 3302, H03K 1790, H01L 2722
Patent
active
049394568
ABSTRACT:
For increased sensitivity, an improved position sensor includes a magnetic circuit in which the stationary portion includes a permanent magnet whose width is optimally 1.5 times the tooth pitch of the exciter portion of the sensor and the magnet face proximate the exciter includes a thin layer of ferromagnetic material over which is centered a narrow magnetic sensing element, such as a magnetoresistor. The sensing element has a width typically less than the tooth width. The sensing element includes a thin film of a monocrystalline semiconductive material, preferably having only a moderate bulk mobility and a larger band gap, such as indium arsenide. Current carriers flow along the length of the thin film in a surface accumulation layer, effective to provide a significant apparent increase in mobility and conductivity of said semiconductive material, and an actual increase in magnetic sensitivity and temperature insensitivity. The flux density is typically applied by appropriate magnet thickness or choice of magnet material without the need of a flux guide.
REFERENCES:
S. Kataoka, "Recent Developments of Magnetoresistive Devices and Applications", Circulars of the Electrotechnical Laboratory No. 1982, Agency of Industrial Science and Technology, Tokyo (Dec. 1974).
H. H. Wieder, "Transport Coefficients of Indium Arsenide Epilayers", Applied Physics Letters, vol. 25, No. 4, pp. 206-208 (15 Aug. 1974).
G. Burns, Solid State Physics Sections 18-5 and 18-6, pp. 726-747, Academic Press, Inc., Harcourt Brace Jovanovich, Publishers, New York, 1985.
H. P. Baltes and R. S. Popovic, "Integrated Semiconductor Magnetic Field Sensors", Proceedings of the IEEE, vol. 74, No. 8, pp. 1107-1132 (Aug. 1986).
S. Kalem, J.-I. Chyi and H. Morkoc, "Growth and Transport Properties of InAs Epilayers on GaAs", Applied Physics Letters, vol. 53, No. 17, pp. 1647-1649 (24 Oct. 1988).
Green Louis
Heremans Joseph P.
Morelli Donald T.
Partin Dale L.
Thrush Christopher M.
Eisenzopf Reinhard J.
General Motors Corporation
Snow Walter E.
Wallace Robert J.
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