learner
Lifetime Supporting Member
Urgent, Commissioning deadline.
I am using CONT_C in a function block. I call the FB in a Cyclic Program (OB32). when the PID is in manual I can change the Block CV by entering a manual value of 0-100%. The problem is starts when I put the loop in Automatic. It is a simple Flow control loop. As soon as I put the loop in Automatic, the loop becomes very unstable. Proportional gain is 0.1, Ti is 0 ms, PV_FAC=1. Derivative is also 0. SP=1100, PV (0-1800).
My Question: Why is this loop become so unstable with such a very small gain? Is this because my SP and PV can only be between (-100 to 100 %)? Does it have anything to do with PV_FAC?
Thank you in advance
I am using CONT_C in a function block. I call the FB in a Cyclic Program (OB32). when the PID is in manual I can change the Block CV by entering a manual value of 0-100%. The problem is starts when I put the loop in Automatic. It is a simple Flow control loop. As soon as I put the loop in Automatic, the loop becomes very unstable. Proportional gain is 0.1, Ti is 0 ms, PV_FAC=1. Derivative is also 0. SP=1100, PV (0-1800).
My Question: Why is this loop become so unstable with such a very small gain? Is this because my SP and PV can only be between (-100 to 100 %)? Does it have anything to do with PV_FAC?
Thank you in advance