Abstract: An automatic dynamic error compensator for compensating the position error arising within a servo drive system includes a measuring head which is operative to measure the relative indicated position of two or more measuring vanes on the movable member. The measuring head, together with a feedback transducer, that measures indicated movable member position, are coupled to a feedback system. The feedback system determines the indicated movable member position from the feedback transducer reading and then compares the indicated movable member position to the known vane position upon occurrence of a vane crossing to yield a compensating value.