Contactless angle detection using permalloy

An overview is given of measurements on angle detectors. The detectors consist of a pair of planar-Hall elements opposite to a rotatable magnet. The measurements are performed on a number of planar-Hall elements of different shape and size, and show good agreement with a previously described theoretical mode. To increase the accuracy of the angle detector, three modifications of the original concept of the planar-Hall elements are treated: a ring-shaped element having increased output voltage; an optimized configuration of a pair of planar-Hall elements and a permanent magnet, to cancel out the effects of magnetic anisotropy in the permalloy on the accuracy of the angle detector; and an annealing step at 500 degrees C applied to the permalloy to create a magnetically isotropic film. The results of measurements on planar-Hall elements as suggested in modifications are presented and show good agreement with theory.