Patent ID: 8239161

Claim:
Shaft encoder device for sampling a shaft, comprising a magnetic sensor device designed to detect the magnetic field of a magnetic field generating device stationary with respect to the shaft; a light source; an optical sensor device designed to detect light emitted from the light source and reflected or transmitted by an encoder disk stationary with respect to the shaft; signal processing means designed to receive first data from the magnetic sensor means and second data from the optical sensor means, and to determine the angle of rotation of the shaft from the received first data, and/or to determine the angle of rotation of the shaft from the received second data; selection means designed to cause the signal processing means to detect the angle of rotation of the shaft selectively from the received first data and/or the received second data; and operational conditions determining means designed to obtain operational conditions data by which the selection means can be controlled; wherein the operational conditions determining means is designed such that it obtains the operational conditions data from a comparison of the angle of rotation determined from the first data and the angle of rotation determined from the second data.