A magnetic sensor is provided with a carrier that has a cavity shaped to receive a magnet in sliding association therein. Ribs are provided to guide the movement of the magnet into the cavity and a deformable rib is used to hold the magnet at a precise position determined by an active calibration process....http://www.google.com/patents/US5488294?utm_source=gb-gplus-sharePatent US5488294 - Magnetic sensor with means for retaining a magnet at a precise calibrated position
