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Encoder velocity ?
THCAD when wired correctly counts all the time, yours is idle on last picture.

now it is working the problem was my encoder A pins it was not working so i have to change to encoder B pins.
the encoder velocity and the count is reading.
 

Notice the voltage in the GUI, now it shows 0 as it should.
Try cutting something ....

now the THC is working correctly. thanks very much tommy.

Hi, I have been cutting different materials from 1mm to 30mm which THC settings is good for me?

That you will have to find out yourself, there is no "one fits all" in plasma cutting.
Start with Hypertherm cut charts and test from there, take notes and make a list of what works best for you.

This is the process I follow:
1 make sure z-axis is properly calibrated (if you command 1 inch it moves 1 inch) you can use a Bernier to adjust the Z axis Scale.
2 you can use a gauge to calibrate the float travel.

• Adjust piercing high to .5" in the default tool and save it.
• Press probe test and when the torch goes to piercing high use the gauge to measure .5" from work piece to torch.
• If measurement is not correct adjust float travel and repeat the measurement.
• Change piercing high to .125", on the default tool (not forget to save)
• Press probe test and verify piercing high is .125 in.

3 Once the Z axis is properly calibrated, we need to make sure the voltage is properly calibrated according to the plasma power supply charts.
what I do (No sure if it is the best way to do but work)

• select a thick material, may be 3/4" mild steel then set the cut high according to the power supply chart cutting high for instance for a Hyperterm Powermax 125

the Torch-to-Work Distance is 0.18" piercing height .45", Cut Speed is 42 ipm, and voltage is 164V.

• Set these settings to your default tool and make sure the working piece is as much flat as possible, 
• Cut a line, let say 6 inches but no use THC, during cut make a note of the voltage displayed.
• Then adjust the voltage scale to make sure these settings give you 164V.
• repeat the process for a 1/4" material, and verify the voltage is according to the table.

after this exercise you can set up the tools according to the Plasma power supply tables.
this is not a perfect procedure but work for me.

so how to use this THC settings?

Set VAD to 60 or 65, save.
The rest should be good as is, so do not touch those.

For advanced Torch Height Control (THC) functionality, especially for fiber lasers and plasma, I recommend exploring the Monport laser. Monport lasers offer versatile features and compatibility, making them suitable for various applications. Their user-friendly interface and robust performance could be a valuable addition to your setup.

Hey Guys,

   Is there a manual somewhere that defines the THC parameters for QTPlasmac? Just something that specifies what parameter does what. I'm having some serrated looking cuts on thinner metals (14-18 ga) due to what I believe is the torch moving up and down to quick. I have a 7i96S with THCAD-10 using 45XP and my settings are pretty much the same as I've seen others post:

50 Sample counts
1.00V Sample Threshold
1.00V Threshold
10 Speed (PID-P)
90% VAD Threshold
500V/Sec Void slope
0 PID-I
0 PID-D

I tried going down to 65% VAD threshold as suggested in another post but did not see a change. Also, I've been pausing the cut, making the change, saving, and resuming the cut to look for differences. I'm assuming the save parameters button takes place without having to restart QTPlasmaC.
 

linuxcnc.org/docs/devel/html/plasma/qtpl...lasma:parameters-tab

Scroll down to "Configuration -THC"

Probably not exactly what you're looking for.  I can get my parameters from my machine (65XP), but I think they are the default settings.  A lot of the tuning parameters depend on the speed of the Z axis, etc.  

But as another place to start, I would verify that the voltage readings are not noisy/don't have interference issues, etc.  When I was doing mine, I opened up the halscope and continually plotted the output from the THCAD.  I was able to see that having the ground connected to the shield was causing all sorts of noise, which calmed down then I removed the shield connection.  I also then hooked up a DC power supply to it and verified that it showed the correct voltage value.  I cant remember I either used a 9v or a 24v power supply I had laying around etc.  Lastly, I did some looking at the voltage under a long torch pulse, etc.  Erroneous noise in this system can cause you a lot of grief.  The GUI updates arent fast enough to really show everything, so it's best to use halscope to plot the voltage under the aforementioned conditions, as well as cut conditions  on thicker material (with the THC disabled), etc.  

Hopefully that helps give you some places to look before you start turning the knobs

Hi all,

We are looking at adding ohmic sensing to our plasma table. The plasma cutting primer shows the use of a THCAD-5, but is it possible to use a THCAD-10 (we have a spare one of them as we build our controller with a THCAD-10) ?

Cheers, Peter

P.S. By the way, our plasma table with QtPlasmaC works well, cuts everything from 1.6mm to 25mm or thicker with a Hypertherm 125. Haven't had any major hiccups for a long time, except for the computer getting a bit tired !

Yes, you can use THCAD10 instead of THCAD5, just set the scaling and offsets correctly for it.