Abstract: Two magnetically sensitive field plates are provided in a caliper to determine the distance between a movable leg and a stationary leg. The field plates are located on the movable leg adjacent grooves in a portion of the caliper which is magnetic and along which the movable leg is moved. Each plate magnetically senses each groove and produces an electrical signal in response thereto. The field plates are arranged relative to each other so that the signals produced therefrom are out of phase with each other, the phase difference between the two signals indicating the direction of travel of the movable leg and the number of signals indicating the magnitude of the movement of the movable leg. Depending on the direction of travel, the number of signals are added or subtracted to determine the distance between the legs.