Simple PID Controller Help.....

[Jmc006]

Hello, I need to maintain a cooling tower system at 50PSI, and will have a pressure transmitter (0-5 or 4-20) reading the pressure in the in the pipe, and need it to have a proportional 4-20mA out to control a valve.  Basically the 50 psi will be my setpoint, the pressure guage will be my process variable, and the 4-20 valve control is my output correct?  I tried modifying an example(attached) where I have a setpoint, and just put a slider for what represents my pressure transmitter, but it does not seem to be working......can anyone help me modify this program?

[Jmc006]

If you can't open the above just see the example called General PID Simulator

[nathand]

I don't have the PID Toolkit installed at the moment so I haven't actually tested your VI, but it looks like you need to move your slider control inside the while loop.  Right now you're only reading the value from the slider once before the loop starts, so changing it while the VI is running won't change your input.

[seVEMes]

Did you get it working from the previous suggestion? You said that you are trying to use the slider as the setpoint? That's interesting because there is already a slider to set the setpoint. But if you wanted to use the slider as an indicator of the actual preasure it is better to first, change it to an indicator and second, put it inside the loop as suggested; probably as the output of the plant VI.