saultgeorge
Lifetime Supporting Member
Hey folks, I was looking through some previous logic that I wrote and I have a question about a PID instruction. I did many of these for some air handling processes (temp control by modulating a valve using a setpoint, fan speeds using a CFM setpoint, etc.). I never could get the valve control to fully work well; there were always swings.
Looking at this now, while working (not very busy; at a new place, which doesn't use ANY PID's), I was wondering about the integral feature. Although it doesn't show in the snip, I have the PID equation set to "Dependent". It seems to work fairly well that way and not so good in Independent. So as one can see by the snip, dependent changes the integral from 1/sec, which to me seems inverse of seconds selected, to min/repeat. Which seems a little non-intuitive to me. So with my setting of 0.016, does it repeat every sixteen thousandths of a minute? My update time is matched with a free running timer to the RPI. I think those are apples and oranges. I'm a little lost here. What would you enter for an integral setting on a dependent PID equation? Thanks for reading
Looking at this now, while working (not very busy; at a new place, which doesn't use ANY PID's), I was wondering about the integral feature. Although it doesn't show in the snip, I have the PID equation set to "Dependent". It seems to work fairly well that way and not so good in Independent. So as one can see by the snip, dependent changes the integral from 1/sec, which to me seems inverse of seconds selected, to min/repeat. Which seems a little non-intuitive to me. So with my setting of 0.016, does it repeat every sixteen thousandths of a minute? My update time is matched with a free running timer to the RPI. I think those are apples and oranges. I'm a little lost here. What would you enter for an integral setting on a dependent PID equation? Thanks for reading