THCAD-10

The other detail not mentioned about arc voltage scaling is the plasma supplies
divider ratio, unless the arc voltage scaling is right none of the THC setpoint numbers will makes sense either.

I apologize for my ignorance in this situation...My lack of knowledge sticks out like a sore thumb...I did find some information on just how others have gone about obtaining a voltage reading through the THCAD-10...Rick G. suggests the following method:

"Can you disconnect the voltage input to the THCAD from your plasma power supply and apply a know voltage such as a battery to the THCAD and confirm that the thc voltage in hal is correct?"
Rick G

Rodw used a different method which appears from his pictures and written description to go through his plasma power supply and voltage divider with 96volts

forum.linuxcnc.org/show-your-stuff/32029...tter-build?start=190

Using Rick G's method we applied 9.45 volts input (from a battery) and the HAL meter indicated 3.46 volts...I don't know if I am correct but I am assuming this ratio between these values must be factored in so that the THCAD-10 input and output are equal and this is done by changing the scaling...

As we are using a PM45, it has a voltage divider of 50:1...How does the torch power supply fit in to the overall scheme of things, if in fact it does, and what method is used to obtain measurements?...We would prefer not to have to break into the plasma power box if at all possible, but will do so if necessary...Then how are the results used to make calculations?...
thanks in advance

Mike

If you have a 50:1 divider, this means that the full scale reading should be close to 500V (and should read 450V if a 9V source is connected directly to the THCAD-10)
It should also read close to 0V if the THCAD analog input is disconnected

If you have a 50 to 1 voltage divider this piece of electronic will scale 50 to 1.

If your plasma inverter has a raw arc of 300 volts dc. The same piece of electronic will do 50 to 1 of 300 volt's.

If a mesa input card is 0 to 10 volt input. It's okey. It can be used for analog input.
If a mesa input plasma card is 0 to 500 volt dc input, they have to tell you, because, then you know your scaling.

Rodw used a different method which appears from his pictures and written description to go through his plasma power supply and voltage divider with 96volts

forum.linuxcnc.org/show-your-stuff/32029...tter-build?start=190

The only reason for this approach was I was getting strange things. It seemed the documented divider ratio in my plasma differed from the published 16:1 ratio for that machine. So I was testing the internal plasma voltage divider circuit, not the THCAD-10.

Unexpectedly, I found by using a voltage near what we cut at was that the resistor network in the plasma itself was counted by the THCAD-10 as being part of scaling resistor network resulting in additional voltage division that I had not allowed for.

But I did this test after I had confirmed with low voltage as Peter suggests that the THCAD was working.

So do the battery test, then use Halscope, to capture a plot of the torch voltage when cutting and compare that with the published cut chart data to make sure you are in the ball park.

UPDATE: IT WORKS!!...A Giant thanks to all that have contributed their information to our project...That information finally sank in...Although everyones input was instructing me properly, it was not sinking in...I was not understanding how the information fit in...I read and re-read the thc-pid manual, the Mesa thcad-10, and hypertherm manuals numbers of times and pored over all the postings in this forum, I just did not grasp the relationships of the info sufficient to be able to plug it in and be usable...
Yesterday as I read PCW's post something clicked and thought I was beginning to grasp what had to be done and place the proper numbers in the right boxes...
Today when I got to my brother's shop, it took about 1/2 hour starting with a battery and multimeter then applied the numbers based on what I thought I was understanding, and voila!, IT WORKS properly...
We made some test cuts...My brother then cut two parts he need for his work out of 20 ga. S/S...The THC follows the tool path adjusting elevation as necessary...We know we will have to do some tweaking on the correction velocity...But I now know what needs to be changed and why and the effects...I also realize that there is more to learn so I am sure I will be asking questions in the future...
Thanks to all for the help...I apologize if it seemed I was being a pest...

Mike