Angle detection based on the resistance anisotropy of permalloy

A newly developed type of angle detector is described. The device consists of a ferromagnetic film opposite to a rotatable permanent magnet. When choosing a film with magnetization-dependent resistance anisotropy, the direction of the in-plane field of the permanent magnet can be measured electronically. Theory and experiment prove that detectors with an accuracy of the order of 0.1 degree can be produced. A model based on the resistance anisotropy effect and the Stoner-Wohlfarth model for single domains explains the behaviour of the device accurately. Two phenomena are responsible for eventual errors in the detector output: the magnetic anisotropy of the film material and the unbalance of the elements used in the detector. Both of them are described by the model with high accuracy. Methods have been developed to reduce their influence to a minimum. The detector output is synchro-resolver compatible.