Patent ID: 7046000

Claim:
A rotation detecting sensor comprising: a detecting element for detecting rotation of a rotary body as a change in magnetic flux and outputting an output signal corresponding thereto; initializing means for effecting an initialization including at least a gain adjustment for obtaining a desired gain as an initial value based on variation in the output signal upon lapse of a predetermined number of rotations of said rotary body; means for amplifying said output signal together with said gain to provide an amplified signal; pulse generating means for generating a pulse corresponding to the rotation of said rotary body based variation in said amplified signal amplified based on said gain; and initial value evaluating means for evaluating whether said initial value obtained by said initialization is appropriate or not and subsequently causing said initializing means to effect a re-initialization to obtain a new initial value when said initial value is evaluated inappropriate, so that said sensor obtains a new amplified signal based on said new initial value.