Absolute multi-revolution encoder

摘要

Magnetic field detection elements and detect a magnetic material member formed at a rotary disc. An A pulse generation portion and a B pulse generation portion generate an A pulse a and a B pulse b which phases differ by 90 degrees to each other. The B pulse generation portion is supplied with the power from a backup power supply for a predetermined time period necessary for detecting the level of the B pulse from a time point of the edge of the A pulse.