Good Day,
I have recently replaced one of my D4-450 CPU's with a new D4-454 CPU. I downloaded the backup program onto it, and it all worked perfect.
After almost a month, the PID control stopped working. Right now I have to control my valves by placing the controller in manual, and adjusting the output myself. As soon as I put the controller into Auto mode, the output changes to 5 milliamps and stays there. Even if the controller shows 4095 in the output, the milliamp output on the analog output card does not change. Only If I put the controller in Manual, and and adjust the output to 100%, does the analog output card give me 20 milliamps. This has now suddenly happened on all 8 of my loops.
I trend my PV, SP and OUTPUT in the PID setup, and the controller clearly increases the output to 100% (4095). When I test my milliamp output, I only get 5 milliamps. When I put my controller in Manual mode and adjust the output to 100%, then I measure 20 milliamps on my output card.
It's weird... but now the plant operator has to control these loops in manual, so i'm desperate to find the problem quickly.
Topic: PID Controller Stopped Working (Read 7029 times)