Hi, I have a problem with my regulated waterpump with a pressuretransducer. It's work fine. Quick response and so on BUT after a few seconds a small interference develop on the signal. Like a squarewave almost. The amplitude is about 10% of the total pressure (i.e I want 3 bar and gets 2.8-3.2 bar). That interference (about 1-0.5 Hz) must come from the PID regulator loop but what do I make wrong? I checked and tried everything. Tested different P and I, made the loop slower and so on...nothing helps.
I tried the filter at input but the freq. of the interference is too low.
A hardware regulator had not this interference.
regards
