Touch / Continuity Sensing

[sbaum]

Looking for some ideas on sensing contact between 2 metal parts.

The application is a part gauge fixture. The gauge and part are both conductive metals. There is an aluminum test tool that is isolated from the rest of the gauge. We need to sense if that tool comes in contact with the part and turn on a light.

We have been using Omron D5C-1DA0 touch sensors for this. Works reasonably well, although can be a bit sensitive to set up. These sensors are now being discontinued so we're looking for another solution.

The toolmaker's suggestion has been to use a 5vdc source to a relay coil. Could connect the 0vdc to the fixture chassis and run the 0vdc of the relay coil to the isolated tool. Of course this would work but in my view this is a shock hazard for the operator when loading the part. Unless there's a way to limit the current to <1mA. (Still don't know what my electrical inspector would say)

Seems there must be a solution on the market for this but I've search several industrial sensor suppliers and so far no success.