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I’ve confirmed that I am setup as a direct-acting process (E = PV – SP).
I’ve been tinkering with the set points on one of the fermenters and the behavior I’m seeing does not reflect my understanding of the PIDE.
The set point is at 75. The current temperature (PV) is at 71.7. The cooling water valve position (CV) is 0%.
If I change the SP to 74. The PV is the same. The CV immediately begins to increase! How can that be? The value of E is less than 0.
If I move the SP back to 75, the CV returns to 0.
I’ve attached a trend that shows the behavior.
What am I missing here?