THCAD2 - HF start will kill it?

Hello!
I just bought a THCAD2 board.
As the manual says i have to connect a 2.9M resistor in series between INPUT+ and thorch. That's clear.
I have a parkside ppsk 40 a1 plasma cutter.

My question is where do I have to connect the Analog IN terminals, is it OK to connect to the cutter's output(torch and clamp terminals) or I have to search on the PCB for the rectifiers and solder wire after them?
I'm asking that becouse the cutter have HF ignition and i don't know does the board survive 25kV ignition voltage(I read that value somewhere on the forum).
Thank you!
 

The proper way would be to wire it to the rectifier output, and use 2 of 1.5Mohm resistors on each wire.
To answer your question, yes HF start can kill the THCAD, but... i have a THCAD10 wired through 2 of 1Mohm resistors at the plasma plugs, plasma is China made Kzubr 60A, it is HF start, it is in use for over 6 months i think, it did not die, yet.
Do this at your own risk, it is not recommended but it works.
Use 2 resistors, 1 on each wire, this is very important, short wires from plasma to resistors, no more than 20-30cm, keep those wires and resistors at least 10cm appart or mount the THCAD close to the source.
And, torch is not positive on plasma, it is negative, the clamp is positive.

If you are going to do this (I wouldn't) Make sure your divider resistors are rated for the voltage
and the power. This is difficult as 25KV times 5 mA = 125 W! (this is assuming a THCAD2 jumpered for
5V input and an external 5M resistor)

You can get away with a smaller watt rating because of the "peaky" nature of the HF signal
and it's short duration, but I would not skimp on the voltage rating. I would use  (5x) of
something like this as a minimum:

www.digikey.com/en/products/detail/visha...0001004FAC00/1994729

Because the voltage spikes are mainly in the negative lead,, I would put 4 resistors in the negative lead
and 1 in the positive lead. This combination will (with THCAD2 set for 5V) give a full scale voltage of 255V
 

Thank you guys, I connected before the choke coil, there are 3kV capacitors so the voltage can't be higher than that. I used HV resistors.

Now I'm stucked with the arc voltage.
I placed a 9V battery on the input with a potmeter to test it. I set and calibrrated everything, encoder.0.velocity net to arc-voltage-in, the value changes with the pot but the arc voltage on the GUI and arc-voltage-out signal does not change, stays zero. Tried different scale settings, no result.
How to get that voltage?