Arc voltage question from Everlast 82i to THCAD-2

Hello,

  I have an Everlast 82i with a 7i96s and a THCAD-2. I'm very new to linuxcnc but I'm slowly catching on and enjoying learning everything. I have a few questions about the THC that I haven't been able to find the answers to:

So, a lot of what I have read says the best way to get voltage from an everlast is to connect directly to the ground and the torch inside the machine, which I have done. I have a little bit of confusion on which side goes where on the THCAD-2. My thought is that I go from the ground clamp side to a HV resistor 2.4m and then to the Negative side of the analog in on the THCAD-2. Then just connect the side from the torch to the positive. Is this correct? 

Second question is if I leave the frequency divide ratio jumper on the 1 if I am using the raw voltage through the resistor?

Finally I do see that if I'm using the raw voltage I should've purchased the THCAD-300. At the time of my purchase I thought I would be using the 50:1 divided voltage. Right now I am waiting on the resistor to run the raw voltage and just wondering if the 50:1 is worth trying and the main question that has already kept me from trying is what would I put the jumper for the frequency divide ratio on? 

Thanks for any help.

The 2.4M resistor should be on the negative input (the plasma voltage)
Ground is positive on plasma machines.

The division ratio can be specified in the setup (/32 suggested)

Ah, that makes a lot more sense on why I was confused. Thanks for clearing that up.

The Everlast has a voltage divider builtin. Why reinvent the wheel?
The only issue is that with a THCAD, the internal resistors are seen by the thcad so what the THCAD sees is distorted.
Set yout THCAD to use a 10 volt range, no resistor and use the 16:1 range on the everlast.
The divider seen will be 24:1 (not 16:1). This will give you a full scale reading of 240 volts.
Just calibrate your software to 24:1 instead of 16:1
Do not ground the HV side of the thcad as that will allow a mains 50/60 Hz ripple show up.
You must use a RFI filter on the control panel mains power entry. 

By don't ground the HV side do you mean to just leave the star ground off the thcad-2 that I see on some of the wiring diagrams? Thanks for the reply I will give that a try.

fmj435 wrote:

By don't ground the HV side do you mean to just leave the star ground off the thcad-2 that I see on some of the wiring diagrams? Thanks for the reply I will give that a try.

I don't know about the star ground but I was thinking frame ground of your control box (which I guess will also be attached to the star ground).
I did not bother running a sepreate lead from the enclosure to the star ground as both were bolted to the table.
I had copper ground points in my enclosure so I used them. Also the mains ground and motor cable shields were attached to these.
Also run seperate ground wires back from the motors to yuor star. This helped to quieten noise. Every bit helps.

I will say the Everlast voltage is quite noisy compared with the Thermal Dynamics I had after it. But Linuxcnc handled it.
 

I have my machine running and everything with it seems to be running well. The one problem I have is the tips on the torch keep getting ruined and then the plasma arc seems to come out at different angles. I had thought maybe it was water in the air lines but I'm pretty confident that I have dried the air and it still happens. A 10 minute cut with a couple dozen pierces and I need to replace the cup. When the tip is new it cuts very straight and cleanly.

I have a 1.2 tip in the everlast 82i with it set to 45 amps and 80 IPM for 10 gauge steel. I have tried increasing the voltage more to the max rating for the tip but that didn't seem to change anything. I run the torch around .06 off the material with it on auto volts and it seems to keep that height pretty well with the THC. Wondering what I should focus on to get it tuned in. Is there anything out there in the way of a tuning guide for the THCAD? Thanks for any help.

I would say water. I had to ad da refrigerated air drier and it fixed everything.