Patent ID: 7290544

Claim:
An arrangement for a feedback control system connected to a medical apparatus, the arrangement comprising: a controllable device ( 10 ); a measuring device ( 7 ) adapted to measure a measuring value from a measuring point, which measuring value is dependent on the operation of the controllable device ( 10 ); a controlling device ( 9 ); a user interface by which the controlling device ( 9 ) can be monitored by means of set values; wherein the controlling device ( 9 ) is adapted to monitor the controllable device ( 10 ) on the basis of the measuring values and set values; and means ( 15 a , 15 b , 15 c ) for periodically feeding a reference signal ( 16 ) to the measuring device, the reference signal having a real, known reference value ( 17 ); wherein the controlling device ( 9 ) is programmed to compare the measuring value ( 18 ) obtained from the measuring device ( 7 ) based on the reference signal with the real, known reference value ( 17 ) of the reference signal; wherein the controlling device ( 9 ) is programmed to take a safety measure when the measuring value ( 18 ) obtained on the basis of the reference signal and the real, known reference value ( 17 ) differ substantially from each other.