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...http://www.google.com/patents/US4939456?utm_source=gb-gplus-sharePatent US4939456 - Position sensor including a thin film indium arsenide magnetoresistor on a permanent magnet
