How do I specify if the PID object is direct or reverse acting?

[Pat Westlake]

I have a process that requires a reverse acting controller - eg if the PV is above the setpoint, I need to increase the controller output to lower the PV. Where in the PID object configuration do I specify this?

[Roli]

Pat,

I think - you can achieve a "reverse acting" PID controller by setting the Gain value negative. However, if you manipulate the PID parameters you should know what effect it will have on your system. If you want to be sure you should simulate the parameter before you apply them to the "real" world. In addition you could verify the -Gain setting with the formula (position/velocity control equations) given in the Lookout online help of the PID control object.

Hope this helps
Roland
PS: I always keep in mind what my control profssor told us once - "just a minus sign (sign change) in contol theory could mean a lot"