Not that it matters at this point, but aren't those units repeat/minute?
Nope, they're definitely minutes/repeat. I didn't grab a picture of the tuning page, but lowering the number definitely increases the integral action, and the math instruction that calculates the integral term based on the value input from the HMI and put into the control word for the PID instruction also says "min/repeat."
I'll attach some of the pictures I have of the trend here.
The name of each picture is pretty descriptive, but I'll expand on them a little bit. Also note that not all of the trends are displayed at the same time scale, note the "Time range" at the top left of the window for each.
"PV noise in manual 50 percent": This is the fluctuation we experienced on the PV with the controller set to manual at 50% controller output (or Control Variable/CV). I'm aware that in this particular trend, it looks like a consistent oscillation, but that's just a coincidence.
"Change to auto": This is the trend after we changed the loop to auto with a setpoint of 200. The extreme noise on the PV at the beginning is what I was referring to in a previous post about the PV being very oscillatory/noisy until the CV hit ~12.5%. After that point it gets relatively smooth.
Note, at the start of this trend, the integral term was 3min/repeat, but where the CV (blue/teal line) slope changes at around 1/4 into the trend, I had changed this to 1min/repeat, hence the change in slope of the CV.
"Reaching SP": This is where the loop finally approaches and reaches setpoint (200), it looks a bit smoother here, but again the time scale here is shorter (0.07 hours or 4.2 minutes). This is actually the loop responding to a disturbance, the water (for test purposes) that we were pumping out of a small vessel had run out so the PV dropped until we refilled. The reason all of the trends are so short is that I had to keep exiting the trend screen to silence/acknowledge alarms or change other things and the trend isn't persistent when it's not open.
"Decreased SP": Setpoint changed to 31, which is the first programmed setpoint for the batch process.
"Decreased SP 2": This is where it approximately reaches the new setpoint. Here you can see the oscillations above setpoint I was referring to. At the moment the picture was taken, the PV was 25.2335, but it was clearly bouncing between 30 and approximately 45. Again, this doesn't look
too bad, but again note the time scale of the trend - 0.57 hours or 34 minutes, so we're at just under a half hour of actual trending in this photo. I could deal with oscillations like this if it didn't also take so long to get to this point.
EDIT: Not sure why my pictures uploaded rotated, sorry about that