Proximity detector employing magneto resistive sensor in the central magnetic field null of a toroidal magnet

摘要

The present invention is a proximity sensor employing a magneto resistive structure. This proximity sensor includes a toroidal magnet having a central aperture, an inner circumference and an outer circumference. This toroidal magnet has a first magnetic pole at the inner circumference and a second magnetic pole at the outer circumference thereby creating a magnetic field null at a center portion of the central aperture. A magneto resistive structure is disposed at the magnetic field null in the central aperture of the toroidal magnetic. This magneto resistive structure has a resistance dependent upon magnetic flux. The proximity of a magnetically permeable target to the toroidal magnet shifts the position of the magnetic null, thereby causing a large change in the magnetic flux through the magneto resistive structure. An electrical detection circuit detects changes in this resistance for indication of the proximity of the magnetically permeable target.