How can we wire the Gear Tooth sensor?

[Itamar]

There's a pole made out of aluminum and on it are a lot of screws at a constant distance. our "claw", the part of the robot that hold the tube, moves on that pole. the idea is that the sensor will rest on the claw and move with it, and that way we could count the response we get for every screw on the pole the claw passes, and thus knowing at what height the claw is located at.

When I try opening a Counter in LabVIEW it asks me for some kind of source, where do I get it from?
Edit: yeah, I just saw the "Dig Src" vi. is that what converts a digital input to the source needed?
and anyway, that makes me skeptic, because I tried using the sensor just with a regular digital input and it didn't work (always gave false value)

If I'm still using the digital input, why would it work now?