Help need on Level PID Control

[daba]

One doesn't just 'tune' a PID, one 'tunes' a system.

Sums it all up....

 

[Calistodwt]

Is this a real process or just a laboratory exercise?
If a real process then is it still in design or does it exist, as you imply that the control valve could be on the tank inlet or outlet?

 

[daba]

I prefer to always use SP-PV. In this case increasing the valve opening makes the water level lower so the controller gain is negative.

In Allen-Bradley PIDs, the controller gain has to be positive, and there's a configuration setting for SP-PV or PV-SP