[EricH]

Cv is a flow control spec when we're talking pneumatics. (MEs dealing with thermodynamics have another meaning for it.)

NPT port diameter is how big of a threaded connecter you can put in.

Taken together, it's how fast you can release air through a particular port size (and you can't use a larger port or faster release).

For calibrating the PRV, you'll need a gauge and the PRV attached to the robot. If you're already put together, you'll need to put a short across the pressure sensor, or disconnect it--anything to make the compressor run--and you'll need to be able to see the high-pressure gauge while you run the compressor. You run the compressor, but watch that pressure gauge. What it reads when the PRV hisses is the calibration setting. (If you hit 130, STOP and VENT immediately.)

If the PRV isn't set properly, you have to move it in or out. Move the small nut away from the end, then move the large end piece in or out on the threads. Check again. If you go the wrong way, go back the other way. Check again. Repeat until the PRV is calibrated properly. Lock the small nut against the large end piece.