Did you get that to work? I tried for about 2 weeks, using all kinds of bits from cheapo to expensive ($35). I did the height map.I do height mapping on my CNC3018 when milling copper laminate for making PCBs.
You just need to bridge the sense input to ground.
Since my spindle motor is mounted in a plastic bracket and insulated from ground, I connect a wire from the motor frame to the sense input. When the tip of the cutting tool touches a grounded copper laminate or a thin piece of grounded metal foil, zero height is sensed. This is only done during a mapping procedure or Z=0 probing where Z probing is done very slowly.
I never got it this to work. The depth of cut (and hence the width) varied wildly as it went across the board. With the original spindle it would crash the software if the cut got anywhere deep. Tried snubbing network to no avail. Tried replacing spindle with a line powered Dremel with much higher RPM, and never got anything close to reasonable results.
Moderator edit: New thread created from this.