I have a PID that I am using for an oxygen valve that regulates the pressure. Often when the header pressure is too low, the output will reach 123%. My CV High Limit is set to 100%. Why would this exceed the limit?
Based on those screen shots, it appears that your .CV is scaled 0 to 1000, corresponding to 0 to 100% output. So a CV value of 123 will be 12.3% output of the loop.
Based on those screen shots, it appears that your .CV is scaled 0 to 1000, corresponding to 0 to 100% output. So a CV value of 123 will be 12.3% output of the loop.
According to the Allen-Bradley documentation (see attached), output limiting is the last thing to happen before conversion to CV. I don't have a good explanation unless external logic is writing to .OUT and the PID is not being scanned.
I think I've figured out my issue. I was retrieving the Setpoint from the Rosemount valve via an OF8H. For whatever reason the extra 23% is only the feedback from the valve. Ive since changed it to the PID output. Thanks for the help.