Abstract
A reading head device for sensing an absolute position includes an encoding element and a reading element. The encoding element includes an absolute row track and an incremental row track. The absolute row track has a plurality of magnetic zone boundaries. The incremental row track has a plurality of magnetic pole boundaries. The distance between two adjacent magnetic pole boundaries is noted as P. The distance between two adjacent magnetic zone boundaries is noted as 2P. The reading element includes a first and a second magnetic flux sensing groups corresponding to the absolute row track, a third magnetic sensor corresponding to the incremental row track, and a fourth magnetic sensor corresponding to the incremental row track. The first magnetic sensor of the first magnetic sensing group and the second magnetic sensor of the second magnetic sensing group are staggered by a P distance. The third magnetic sensor is aligned with one of the first and second magnetic sensors. The distance between the third magnetic sensor and the fourth magnetic sensor is (N-0.5)*P, where N is a positive integer.