Patent ID: 7637020

Claim:
A sensor for determining the absolute angular position of a body that can rotate through a plurality of rotations, the sensor comprising: first and second code wheels each having a magnet, wherein each code wheel is connected to the body to rotate as the body rotates, wherein the code wheels are driven at a different gear ratio such that the code wheels rotate at a faster rate than the body and such that the code wheels rotate at different rates from one another; and first and second magnetic sensor elements for respectively monitoring the rotational angle positions of the magnets of the code wheels to determine the rotational angle positions of the code wheels, wherein the difference between rotational angle positions of the code wheels is a beat angle; wherein the different gear ratio is selected such that more than one beat angle period is in an angular measuring range of the sensor and the absolute angular positions of the code wheels in the beat angle periods is different; wherein the absolute angular positions of the code wheels in successive beat angle periods is offset by the nth part of the measuring range of one of the magnetic sensor elements, where n represents the number of beat angle periods within the angular measuring range of the sensor.