THCAD-300 Jumper

Kale, more info, please.
To what you are connecting the THCAD ?
If to a Mesa card, then 1/32 is the best option regarding noise immunity and resolution.
If to a parallel port, that will greatly depend on how good the latency of that PC is.
Also, be very careful where you wire the THCAD inside the plasma source, there is only one place inside it that the THCAD can be safely wired, otherwise it is very likely to mess up the card.
Pictures of the insides of the plasma source would help to pinpoint the location.
Or maybe your plasma has an output for THC with full voltage scale (no divider), so that is easy.

Kale wrote:

The left screw terminal is the wire for the ground clamp. The middle with the red wire is labeled 500v.

I really hope Hypertherm did not put that terminal there, that is a 16A/500V terminal, hence that is not a label for anything except the terminal block. The left wires (you said go to the clamp) should be yanked from that terminal strip and put on a 60A to 100A terminal.

Kale wrote:

The SanRex part is the rectifier for 600V/60A, so you can attach the THCAD inputs to the + and - terminals on that rectifier, not on the ~ terminals. Use proper plugs for that and tighten the screws properly.

Yes.