Knight Posted November 21, 2022 Report Share Posted November 21, 2022 Hi all, I'm new with Unitronics PID and struggling a bit so please help. I'm having some trouble with PID auto tune for a pumping application trying to achieve a set point pressure. I have V700 and 2x IO-AI4-AO2, a 0-10bar (4-20mA) pressure transducer as my process feedback and 4-20mA output to a VFD scaled to 0-50Hz, using 4x pumps of varying size so introduce the next size up if duty pump cant reach SP, therefore using 4x PID loops writing to 4x analogue output channels. When starting auto tune I'm getting -4 status fairly quickly and also -11 often so auto tune not completing. Being verticle multistage pumps, once the VFD is given run enable, the VFD is internally set up to ramp quickly to 30Hz min speed before following the mA speed ref, which appears to be 50Hz anyway from the PID control output. Is this integral error -4 due to forcing the VFD to 30Hz outside of the PID control on start up?. Can anyone suggest why I'm getting this -4, do I need to force the integral error to zero? Your help will be greatly appreciated. Quote Link to comment Share on other sites More sharing options...
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