Rotating magnetic object motion sensor with unbalanced bias

Abstract

A magnetic object motion sensor which can operate with high accuracy not only when a magnetic object moves at high speeds but also even when it moves at low speeds, which can be produced with a greater production tolerance and a greater dimensional tolerance. The magnetic object motion sensor includes: magnetoelectric transducer elements disposed opposite protrusions of a moving magnetic object; a magnet for generating bias magnetic flux toward the magnetoelectric transducer elements; unbalanced bias producing means for producing imbalance in the magnetic field sensitivity between the magnetoelectric transducer elements; a differential amplifier for amplifying in a differential fashion the electric signals output by the magnetoelectric transducer elements; a waveform shaping circuit for converting the differential signal output by the differential amplifier to a pulse signal corresponding to the edges of the magnetic material protrusion; the unbalanced bias producing means producing a difference in the amplitude of the magnetic flux density between that applied to one element of the pair of magnetoelectric transducer elements and that applied to the other element so that the difference in the electric signal level corresponding to the difference in the amplitude of the magnetic flux density becomes greater than the hysteresis of the waveform shaping circuit, thereby, in effect, introducing imbalance in the sensitivity between the magnetoelectric transducer elements.