New Project with Mesa 7I96 and THCAD-05

The 24V power supply should only over see a few mA current from the plasma supply even with a direct plasma voltage short to the shield. Without a leakage path, there should be 0 current from shield to ground when the plasma source is off. It may be that the diodes prevent full torch voltage causing increased current and increased electrolysis.

Also, the OHMIC THCAD will read above full voltage while the torch is on during a cut, when it is not shorted, and not touching the metal.

That is expected. You are seeing the arc voltage and the THCAD should go to full scale. The arc-on pin should also be true under these conditions.

Ohmic3 is an experimental component which was written becasue several people had bought the hardware and could not it work on their water table right at the beginning.
From the feedback, it  probably should stay that way.
If you have to add additional isolating relays,  it makes no sense to use it as it just pushes the costs higher. The original intent was to remove all of the additional components.

I would have thought that if the voltage got up around a 22 volt threshold, a relay would trip too. The ones I tested at the time came on at around 8-11 volts and off at about 5 volts. The original Ohmic.comp (and ohmic3.comp) allowed this threshold to be set much higher. (18-22 volts). The thought was that we could use the component to increase the hysteresis over a relay and were using on at 18 volts and off at 1 volt would increase reliability.

I follow this thread with great interest.

So if i want to use a water table.

Do you recommend ohmic sensing?
If yes which one Thcad or relay?

Whatever your preference is, both seem to work.

Can I turn it on and off at any time?

What is the latest recommendation for the resistor?

Creative25 wrote:

Do you recommend ohmic sensing?

Make the machine work properly with floating head/switch, later you can have a go at ohmic sensing as it does require more reading and editing and wiring and testing.
Also requires plasma torch with a separate shield.