Patent ID: 7135858

Claim:
A speed measuring system for determining a speed of a measuring body rotating relative to a speed sensor, the speed measuring system comprising: a plurality of one of electric and magnetic discontinuities located on a periphery of the rotating measuring body, a distance measuring surface located on the periphery of the rotating measuring body, and the speed sensor located at an air gap distance from the periphery of the rotating measuring body, wherein the speed sensor is reactive to the plurality of one of electric and magnetic discontinuities, during rotation of the rotating measuring body, to provide a speed output signal representing rotation of the plurality of one of electric and magnetic discontinuities past the speed sensor and having an amplitude dependent upon an air gap distance between the speed sensor and the periphery of the rotating measuring body, a distance sensor located next to the speed sensor for scanning the distance measuring surface and providing a distance output signal representing the air gap distance between the distance sensor and the distance measuring surface on the periphery of the rotating measuring body, and an evaluation device for compensating for any variation in the air gap distance when the amplitude of the speed output signal is one of greater than an upper release threshold and smaller than a lower release threshold; and the upper and the lower release thresholds are adjusted by the distance output signal so that the upper and the lower release thresholds are a function of the air gap distance.