| 摘要 |
The rotor disc (1) is provided with at least one reflector (11) with asymmetrically varying reflection properties in at least one direction on one side. A control unit sends out a detection signal when it receives a signal from the reflected light sensor (5) significantly in excess of a stored reference value corresponding to the asymmetrically varying reflection properties. The meter contains a radiation source (4) for directing electromagnetic radiation against the rotor disc, a sensor for detecting the radiation reflected by the disc, and a control unit coupled to the radiation source and sensor. |
