| 摘要 |
The invention relates to an arrangement in connection with a feedback control system, the arrangement comprising a controllable device ( 10 ), a measuring device ( 7 ), a controlling device ( 9 ) and a user interface by which the controlling device ( 9 ) can be monitored by means of set values. The measuring device ( 7 ) is adapted to measure a measuring value ( 8 ) from a measuring point, which measuring value is dependent on the operation of the controllable device and the controlling device ( 9 ) is adapted to monitor the controllable device ( 10 ) on the basis of the measuring value and set values. To improve safety, the arrangement comprises means ( 15 a, 15 b, 15 c) adapted to feed a reference signal ( 16 ) to the measuring device ( 7 ) periodically. The controlling device ( 9 ) is adapted to compare a measuring value ( 18 ) obtained from the reference signal with the real reference value ( 17 ) of the reference signal and adapted to take a safety measure when the measuring value ( 18 ) and the real reference value ( 17 ) differ substantially from each other. |
