Hi,
Mach3 is not a feedback controller, the communication delays and particularly the motion buffer delay, preclude any useful closed loop performance.
If you wish to use the LVDT as a feedback device and use it in manner not dissimilar to Torch Height Control, familiar to plasma table
enthusiasts, then you will need an external motion controller that can close the loop. Mach3 can supervise the but cannot close the loop
itself.
The two best known feedback capable controllers are the Hicon Integra or the CSMIO/A at $1200 (with the required activations) and 600 Euro
respectively.
If your feedback requirement is very low bandwidth, say of the order of seconds, then using a Mach3 Brain would work.
Mach4 has a similar feature called PMC but is nearly two orders of magnitude faster and so might be used to make a feedback loop
of 10Hz or so. Indeed NFS has released a THC feature that uses this technique, while not the high bandwidth you would expect from
a realtime controller, its still adequate for THC with modest dynamic requirements.
Craig