Hello, I am working on a PI controller for a pump system, and I am trying to figure out how to relate the gain and integration time to the physical system. The system set point is 60 psi. If the system is in manual mode, sitting at 40 psi, and I give a step input of 20 psi, it takes about 15 seconds to reach the set point of 60 psi. As I remember from controls class way back when, the 15 seconds represent four time constants for the system. And so the system time constant is around 3.67 seconds. How do I use this information to set the integration time? And, what is the integration time with respect to the physical system? I would assume that I could set the gain to 1 and adjust in the field. Is there a method of system testing which would give me an initial ball park estimate for gain?

thanks for your help.

Andy