in the present invention , a detection coil and a cancellation coil are closely provided and electrically connected in series to cancel induction noise . the cancellation coil may be disposed at a position not to sense the rotation . an axis of the cancellation coil may be provided in parallel to an axis of the detection coil . the numbers of turns for the cancellation coil may be the same as those for the detection coils . the cancellation coil may be disposed coaxial to the detection coils .