Patent ID: 7694936

Claim:
A method for function-monitoring an actuator in a process engineering plant, said actuator comprising a valve and a pneumatic actuating drive for actuating said valve, and a positioner for setting a position of said valve, said positioner comprising a microprocessor, comprising the steps of: generating a predefined electrical activation test signal and applying it to said microprocessor to position said actuator into a predefined function condition; generating by said microprocessor an electrical output control signal for signalling an I/P transducer for said actuating drive in accordance with said electrical activation test signal; and directly sensing said electrical output control signal and monitoring it compared to a reference control signal which is independent of actual position of said actuating drive and valve; wherein said reference control signal is saved in a scope of operation initiated by said electrical activation test signal when said actuator correctly functions or is entered manually into a memory based on values gained from experience.