non ARC height sensor

[sunmix]

Usually THC reads arc voltage of a plasma machine and adjusts the height of the Z Axis motor for cutting. I've seen a couple of oxy height sensing products in the net such as Hypertherm OHC ( Oxy Height Sensor ) and Rutex r9812 Oxy Complete Kit that suits my application, but the spirit of building your own kit by yourself is not there. Anyone here can provide some information or if even possible, circuit schematic designs regarding this height sensor? I'm using Mach3 by the way.

[sunmix]

Okay, i did some research , and another name of calling this system is : Capactive Height Control.

It's used to provide a means of regulating the work distance between the torch and the plate surface during the cutting process, and a constant distance is accurately maintained.