DIY Arc voltage divider

I am trying to build a circuit for university project that I have which would scale and isolate the arc voltage from a hypertherm powermax 85. The arc voltage would be obtained from the in-built voltage divider, manufactured from hypertherm, then it would go to an isolation circuit, scaling, filtering and impedance isolation. In order to do this, I would require the maximum and minimum arc voltage that can be supplied by the powermax 85 in order to choose the right components so as not to exceed their limits or the intended analog input limit which would be 0-5VDC.

So far I've found out that the powermax 85 has 143VDC "output voltage" and 305VDC "open circuit voltage", which I have found within the 860270 leaflet titled as "Powermax mechanized applications - cutting and gouging". I would assume that the "output voltage" is the arc starting voltage and the "open circuit voltage" is the worst case scenario voltage which would be applied in case where the arc would be hard to start due to bad consumables.

In addition, I have found out in the powermax 85 operator manual that the hypertherm voltage divider could supply max of 18VDC. I found this confusing because it did not clarify whether this max voltage would be supplied with a 50:1, 30:1, 21.1:1 or 20:1 setup. If I divide the 305VDC open circuit voltage with a 50:1 ratio I would get a maximum of 6.1VDC, which is far from the designated 18VDC in the operator manual.

I don't know if I am interpreting the manuals correctly or if I am missing something therefore I was hoping if someone could provide the exact details for the minimum and maximum voltage that could be obtained from 50:1 voltage divider on a powermax 85.I can't see myself designing the circuit if I don't know them because I could damage the circuit if they turn out to be higher than I thought.

look at the cutting chart, there are the common working voltages. I would say 75v to 225v range is okay

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Originally Posted by fdoncevski

I am trying to build a circuit for university project that I have which would scale and isolate the arc voltage from a hypertherm powermax 85. The arc voltage would be obtained from the in-built voltage divider, manufactured from hypertherm, then it would go to an isolation circuit, scaling, filtering and impedance isolation. In order to do this, I would require the maximum and minimum arc voltage that can be supplied by the powermax 85 in order to choose the right components so as not to exceed their limits or the intended analog input limit which would be 0-5VDC.

So far I've found out that the powermax 85 has 143VDC "output voltage" and 305VDC "open circuit voltage", which I have found within the 860270 leaflet titled as "Powermax mechanized applications - cutting and gouging". I would assume that the "output voltage" is the arc starting voltage and the "open circuit voltage" is the worst case scenario voltage which would be applied in case where the arc would be hard to start due to bad consumables.

In addition, I have found out in the powermax 85 operator manual that the hypertherm voltage divider could supply max of 18VDC. I found this confusing because it did not clarify whether this max voltage would be supplied with a 50:1, 30:1, 21.1:1 or 20:1 setup. If I divide the 305VDC open circuit voltage with a 50:1 ratio I would get a maximum of 6.1VDC, which is far from the designated 18VDC in the operator manual.

I don't know if I am interpreting the manuals correctly or if I am missing something therefore I was hoping if someone could provide the exact details for the minimum and maximum voltage that could be obtained from 50:1 voltage divider on a powermax 85.I can't see myself designing the circuit if I don't know them because I could damage the circuit if they turn out to be higher than I thought.

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Have you been able to get any solution or answers to your problems?