Yep, makes sense to me - get 5 volts, an earth and something that can read the output signal. Stick a pipe on the end of the vacum nipple and suck/blow to see which pin gives a variable reading? Id do that with a crappy old one first so I had an idea of what range I expected to see. Is there a worry that it might blow it if you put the 5volts in the wrong one?

RW