I'm not native English speaker. I hope I can be clear enough. Sorry.
My scenario is me trying to convert a 3D printer into a CNC PCB mill and as the bed and I need to use the drill as a probe to work as Z axis endstop. So the printer circuit has a pin with a pullup resistor (12v) and it being driven to ground marks the z=0 height. So I connect the PCB to ground and the drill to that pin and that's it.
But I observed electrical arcs between the drill and the PCB and I think that reduces the precission. And I need that precission. I think the board is "sensed" before actual contact is made. 0.05 mm is enough error to reduce que quality of the result as I am milling 0.16 mm with a cone drill.
So, Is there a simple way to prevent that arc? My first thought was to put a resistor but there is already one there, the pullup, so I think it might be useless.