Patent ID: 7714738

Claim:
A method for detecting rotational movement, comprising the steps of arranging at an end of a rotation axle of a rotating object and at a distance from the rotation axle a sensor, arranging external to the end of the rotation axle of the rotating object a detector in such a manner that the distance between the sensor and detector changes as the object rotates around its rotation axle, transmitting a poll from the detector to the sensor, receiving the poll with the sensor and in response to receiving the poll transmitting a reply from the sensor to the detector, determining a signaling power, and detecting rotational movement on the basis of a change in the signaling power, wherein the method also comprises steps in which the detector transmits the poll at regular intervals and a transmit power of the poll transmitted by the detector is changed in response to the reply transmitted by the sensor in such a manner that if a reply is received from the sensor, the transmit power of the next poll is decreased, and if the reply is not received from the sensor, the transmit power of the next poll is increased, in which case the power being determined is the transmit power of the detector.