To add to that, the unit would thus be that of the parameter you are controlling with the PID VI. You can refer to the detailed help for this function to find out more information on it. This can be accessed by going to Context Help (click on the question mark in top right of the VI), hovering the mouse over this function and then clicking on the Detailed Help link in the Context Help window.
Vivek Nath
National Instruments
Applications Engineer
Machine Vision