Control way

[Tom749 0]

As the attachment, I should control the pressure from 1st to 2nd step by step. The 1st Pressure Purpose Value and then stable time. And 2nd Pressure Purpose Value(the final purpose valve). In this case what kind of the control solution is good for this control? Just use the two PID functions one by one? Thanks for your help in advance. Edited 30 Jul 2013 by Tom749

[PLCMentor.com 60]

Looks like to me you just have 2 pressure setpoints with alarm points set +/- around the active setpiont. Generally the characteristics of the system are similar so the PID constants at both setpoints will suffice. I would not suggest 2 PID blocks in either case. Edited 30 Jul 2013 by PLCMentor.com