Patent ID: 7626380

Claim:
A sensor module for detecting a relative displacement of an object having a groove pattern with alternately formed projection and depression, comprising: a magnet for generating a magnetic field; a giant magneto resistance (GMR) sensor installed between the magnet and the object to detect a variation in the magnetic field and output an electric signal, wherein the GMR sensor includes first and second sub sensors, each includes first to fourth resistor devices, and wherein front two resistor devices of the first sub sensor, front two resistor devices of the second sub sensor, rear two resistor devices of the first sub sensor and rear two resistor devices of the second sub sensor are alternately disposed along a moving direction of the object and thus an output signal of the first sub sensor and an output signal of the second sub sensor are generated with a time difference when the object moves; a signal processing part for processing the output signal from the GMR sensor to output a square wave; and a housing for supporting the magnet, the GMR sensor and the signal processing part.