Setting up THCAD-5 with 7i96

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09 Feb 2021 16:48 - 09 Feb 2021 20:35 #198161 by razplaz
I'm setting up the THCAD-5 with plasmac and under the THCAD calibration calculator I entered the figures located on the back of my THCAD-5. I have Hypertherm 45xp on 50-1 voltage divider, and the THCAD-5 jumper on 32. Since under the calculator I don't see an option for the THCAD-5 I just divided the THCAD-10 results by 2 to get the scale for my THCAD-5. However, when I punch the calculated scale/offset into my Plasmac config the resulting voltage shown at torch idle is 83. If I pulse fire the torch, the reading is 240V. If I play with the scale settings I can manipulate it towards zero but not sure if this is an acceptable way to "manually" correct whatever my issue is? I don't think so, because if I pulse the torch after reducing the scale it only says 1v. The calculator gives me 0.0096*** but I have to bump it down to 0.000058 to make it go from 83v to 0v while the torch is idle.

FWIW, I also have a THCAD-10 that I'm also having the same issue with i.e. after entering my THCAD-10 frequencies into the calculator and then changing my config settings to reflect the newly calculated numbers, my torch at idle is reading about double what the THCAD 5 is. In either case, if I drop the "arc ok" parameter to above the idle reading then I get an "arc ok" signal. I'm lost as to what I'm doing wrong?? Thanks for any help.
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Last edit: 09 Feb 2021 20:35 by razplaz.

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09 Feb 2021 21:34 - 09 Feb 2021 21:46 #198201 by AgentWD40
Funny story: After I hit submit to save that calculator I realized I didn't have the option there for THCAD-5 and for the life of me I couldn't figure out how to login to edit the calculator.

Here are the formulas used in that calculator:
scale = thcad_model_voltage * frequency_divider * plasma_divider_ratio / (max_voltage_frequency - zero_voltage_frequency)
offset = zero_voltage_frequency / frequency_divider

So simply dividing the scale value by 2 should have been sufficient.

If someone doesn't spot an obvious error you've made you could always disconnect the plasma and attach a LV DC power supply and verify readings/calibration against a multimeter...
Last edit: 09 Feb 2021 21:46 by AgentWD40.
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09 Feb 2021 21:34 #198202 by phillc54
What are the figures you are entering for Voltage Scale and Voltage Offset, and what are the figures on the THCAD calibration sticker.

Have you tried manual calculations as shown in the user guide:

Scale calculation:
Divider_Ratio / ((THCAD_Full_Scale_Frequency - THCAD_0V_Frequency) / THCAD_Frequency_Divider / THCAD_Full_Scale_Voltage)

Offset calculation:
THCAD_0V_Frequency / THCAD_Frequency_Divider
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09 Feb 2021 22:33 - 09 Feb 2021 23:11 #198209 by razplaz
The THCAD-5 figures on back sticker are
0v = 137.3
5v = 966.8

I'm entering scale of .0096 and offset of 4290.625 in the config after running the calc for THCAD-10 and then dividing the given scale (0.01929803) by 2 to reflect the THCAD-5...hoping I did it right...my math is a bit shaky so was scared to try it manual yet lol

If I try the offset manually I get
137.3 / 32 = 4.290625

If I put that in config panel, that bumps my readout value down to 42V...if I pulse the torch my readout goes to +/- 200v.
Last edit: 09 Feb 2021 23:11 by razplaz.

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10 Feb 2021 00:16 #198227 by phillc54
You need the full number so it would be 137300/32 = 4290.625

Scale should be 0.00964436

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10 Feb 2021 00:39 #198229 by razplaz
Okay so I gave scale 0.00964436 and offset 4290.625 a try and my idle voltage is 42v now..pulsing the torch over a piece of 3/16" sheet my the arc-ok indicator comes on and the voltage shows 160v-170v.

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10 Feb 2021 00:49 - 10 Feb 2021 00:50 #198230 by razplaz

If someone doesn't spot an obvious error you've made you could always disconnect the plasma and attach a LV DC power supply and verify readings/calibration against a multimeter...


So if I understand correctly you're suggesting to hook up a known voltage such as from my 24v power supply, in place of where the voltage divider is located, then I can adjust the scale to reflect the 24v on the readout?
Last edit: 10 Feb 2021 00:50 by razplaz.

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10 Feb 2021 00:55 #198231 by phillc54
You need to get the zero voltage correct first. Are you 100% sure it is set to 50:1

What if you try -4290.625

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10 Feb 2021 01:31 #198235 by razplaz
I just now after reading your post realized that the - sign was missing from the scale. Okay the problem is fixed now I believe, as I have 0v now that it's changed. When torch is fired it shows around 120v. I will go see if I can cut some things now, thank you!

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10 Feb 2021 17:19 #198300 by AgentWD40
Do what now? :huh:

Just for my own edification what's going on here? I wouldn't think either the scale as raz mentioned, or the offset as phill mentioned, should be negative. Since FFS > FZERO then the scale should be positive. And since FZERO > 0 then the offset should be positive.

Does it have to do with hal config settings?

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