Position sensor including a thin film indium arsenide magnetoresistor on a permanent magnet

US4939456A · kind A · utility

Assignee

• General Motors LLC · US

Inventors

• Donald T. Morelli · White Lake, US
• Joseph P. Heremans · Troy, US
• Dale L. Partin · Sterling Heights, US
• Christopher M. Thrush · Muskegon, US
• Louis A. Green · Fountain Hills, US

Key dates

• Filing date: Oct 25, 1989
• Grant date: Jul 3, 1990
• Expiry date: Oct 25, 2009

Classification

• Technology area (CPC G): Physics
• CPC primary: G01D5/147
• WIPO field: Measurement
• WIPO sector: Instruments

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.