PID control for a temperature and humidity sensor

[RonCarter1952 0]

I am trying to develop an air washer program using Automation Direct Productivity P2000 plc. The inputs will be a temperature and humidity sensor input that combined will control I/P’s ( current to pressure transducer) this will control dampers and chill water valves. The response time needs to be slow but adjustable. As the system senses a rise in temperature it will begin to go to a zero output so the dampers will close.

it seems the set point is what is giving me the fits the Pid has locked up on me a few times. I have tried several pods and scaling functions but nothing seems to work smoothly enough for me that I could trust in application. I am using a signal generator to represent the 0-20 ma signal.

Any help would be appreciated.

[DanW 41]

Testing with a manually controlled signal generator is not a good test for PID because your signal generator is not responding like the process would respond to the PID output changes.

If the output is wired to the I/Ps and the I/P's are connected to the damper and valve, then a signal generator can prove the control direction is correct with rise or fall of the input.

It would not surprise me if "PID has locked up" means that the output is stuck at either 100% output or 0% output when the input does not reflect the output change.