DVDdoug:
I guess you're trying to measure (or calculate) resistance?
[u]PWM[/u] is NOT analog and the Arduino (by itself) is NOT a current-source... It's a voltage-source and (as-usual) the current depends on resistance (and voltage).And this sounds like an industrial or production application... In general, measurement instruments in "serious applications" should be calibrated & verified. There's nothing wrong with using the Arduino in an industrial application but check with your QA department before using any "homemade" instrumentation.
ten years ago we used to build the devices. Now we just repair and calibrate them. Back then they were selling for $15,000. The only ones we see now are from universities. So i suspect this is a university lab project.
Paul