Apparatus and method for detecting small distance changes between opposed surfaces using giant magneto resistance effect sensor

摘要

A device that can sense small changes in distance between opposed surfaces includes a ferromagnetic material and a giant magneto resistance effect sensor. A current source applies a current to the sensor to operate the sensor and read the magnetic field that impinges on the sensor from the ferromagnetic material. The magnetic field changes when the distance between the opposed surfaces changes. The device can be used in imaging apparatus to sense multifeeds and other conditions.