When PID is reinitialized, it stays low

Question

I am using a PID to control a power supply which alters its output in response to a current signal.  I am writing the output of the PID to the power supply via a compact field point, and reading the current produced by the power supply with a current transducer, which becomes the process variable.  It all works fine until I reinitialize the PID, or sometimes when it is first enabled.  Often what happens is that the PID will only put out the lowest possible output even though the set point is clearly higher than the process variable.  If I then alter one of the PID gains, the signal will jump, then begin to behave normally until I reinitialize it again, at which time it will often end up stuck low again.
I wrote a VI that simulates the response of the power supply, and the PID displays the same behavior.  Is this normal?  No matter how I set the gains it behaves the same, it always ends up stuck putting out 4mA no matter what I set the target to.
~Jo-Jo

Answer 1

Fellas,
Thanks for the responses.
Here are the two VIs I was using to test the PID.  The Payne Sim simulates the response from the power supply we are using which uses an input  which ranges from 4-20mA.  It should work with the current default values for all the controls.  If "reinitialize the PID" is pressed, the signal from the PID goes to 4, and stays there until one of the PID gains is changed, which changes the integrated error in the PID.
~Jo-Jo
Attachments:
PID Test.vi ‏29 KB
Payne Simulator2.vi ‏15 KB