PWM/frequency signal as input to Mesa card

7i84 should also have 4 analog inputs that can do up to VCC, so yes you can use it to measure 9V, but at low resolution and at low speeds.
Although speed might not be much of an issue for slow cutting with plasma, the resolution is as it will cause big jumps when correcting.
Buy a THCAD.
Or make a THC using a "voltage to frequency converter" chip, plenty of those around and quite cheap, until you figure out you need high voltage isolation and care with wiring and stuff, so it really does not pay off to build one, given the price of THCAD is really low for what you get.

One big issue with reading the plasma voltage is that the GND connection
will have large (possibly 50V or more) high frequency transients when the
torch fires. This makes is very easy to damage connected devices. This is why
the THCAD is fully isolated and has only a few pF of capacitance between the
plasma side and the control side.

Funny aside: We had to change the name of the THCAD on a invoice for a
shipment to Brazil as anything with the letters THC gets held up in customs...

PCW wrote:

Funny aside: We had to change the name of the THCAD on a invoice for a
shipment to Brazil as anything with the letters THC gets held up in customs...

I wonder why, they should check for stuff containing THC LEAVING the country!

You remember the episode lol, I was the one who bought thcad, and I had them held up in customs. Thank you very much for doing your best to get the plates to me.

We have a very rich and beautiful country, but we still have a lot to develop,

A quick revival of this thread.

The analog inputs of the 7i84 card in mode 1 are working great. I'm using it to monitor the load of my spindle servo and it shows load correctly in Probe Basic.

However the update frequency is quite high and the spindle load bar in Probe Basic jumps around quite a bit during heavy operations.

What would be simplest/best way to smoothen/filter the value so it doesn't jump around so much?

I looked through all the HAL components and noticed that the lowpass component might have some potential.