PID behavior

[Felipe Sagui]

Originally Posted by Manoel

Felipe,

Are you manually increasing the process variable value?


We can discuss this in Portuguese if you'd like.

yes, I'm increasing manually the process variable value.

What I mean is that when is only P it is ok the behavior: the output starts high and while the PV is increasing the output starts to decrease until 0. This we understand.

The problem is now, when we put P and I: the output starts on 0 e it starts do raise slowly and not like when is only P, that starts directly high.
After, when is running, we start to increase the process variable value, the output came down but after it begin to increase again coming back to the value before ("like an inverse pulse").

When the PV = SP the output starts to be constant but not 0. We guess that it has something with the I term and with the reinitialize boolean on PID .VI

Now we ask: why output doesn't decrease until 0? What we can make to do it in the better way that is possible?