How do i measure plasma raw voltage with a meter.

Ross

Ross
Like it says, having problems with not blowing up meters.

Before I went on holidays I successfully measured the raw voltage with a meter.

But now I have destroyed two and don't wish to waste more money replacing them.
  1. Where to set the dial on the meter,
  2. if the meter can handle the power

The type of meter I am trying plus plasma is shown in the photo attached.

"JASIC CUT 100" "UNI-T ut33b+" meter.

Thanks if you can help on this one, From Ross.
 

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breezy

Arie
Staff member
Ross,

A good rule of thumb is to select the highest range and test, if the measured voltage is lower than the next range then move down. Now most digital meters have an over-range indication so if you select a range lower than the actual voltage you should not damage the meter. Old analog meters you could overdrive the needle into the endstop and upset the calibration. (Bend the needle).

The only reason I can think of, that would destroy a digital meter is that you have connected it incorrectly. To measure the plasma voltage you connect across the output and ground connections. Not inline!!! Selecting DC voltage when you are measuring AC voltage shouldn't cause problems.

Looking at the meter it is fused to 10 Amps max at 250 Volts on the Amp connection point and 200 mAmps at 600 Volts on the Voltage/Ohms connection. As long as your plasma is not outputting more that 600V you should be OK with that meter. Most meters have a high impedance resistor on the Voltage input so it shouldn't draw more than a couple of mAmps at 600V.

Regards,

Arie.
 

clover

clover
@ross

Plasma voltages are DC (Direct Current) usually with a voltage of somewhere between 200v and 400v.

When using a multimeter with an unknown voltage one works down from the highest voltage range the meter is capable of, in your case that is the 600v range. Switch the meter as indicated in the attached photo and it will read up to 600v DC. The next lower range is 200v so if the voltage you are measuring is 200v or less you can switch down to that setting. For your purposes though the 600v range should be sufficient.

Note also where the coloured leads are to be inserted inserted. The probe (loose) ends of the leads will need to be connected Red (positive) to the workpiece and Black (negative) to the source of the Plasma voltage.

If you follow this you will not 'blow-up' your meter. However if you select other than the DC voltage ranges you will more than likely have to replace your meter. Hope this helps, Patrick
 

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clover

clover
The only reason I can think of, that would destroy a digital meter is that you have connected it incorrectly.

Actually, the easiest way to destroy the meter is to try and measure voltage on either the Current ranges and the Ohms ranges. This of course assumes a low source impedance which the Plasma supply is. So Ross don't switch the meter to anything but the voltage ranges. They are the ones between about 2 and 3 o'clock on the dial.
 

Ross

Ross
Thanks Arie and Patrick,

Where Patrick shows the dial is where I had it set, but maybe my leads were back to front.

Red to + Black to - on the Proma raw voltage.

Ok the thing I didn't state in the question and was just curious about peoples knowledge on the subject, is I found last night on the internet was when the arc is struck there is a very high voltage and it is on a timer then drops back to cut voltage, How long I don't know, but that might be the reason as well.

Can try a long cut and use the meter half way along the cut, hopefully no "BOOM"

I will try and be brave and try it again tomorrow, Ps if it fails can I sent you both my bank details so you can reimburse me. Is that OK? ;)

Thanks again from Ross.
 

breezy

Arie
Staff member
Quote from Ross on April 1, 2019, 10:29 am

Thanks Arie and Patrick,

I will try and be brave and try it again tomorrow, Ps if it fails can I sent you both my bank details so you can reimburse me. Is that OK?
?


Thanks again from Ross.

Haha! I like that.

Just double check your settings before you stick the probes in.

Regards,

Arie.
 

clover

clover
Where Patrick shows the dial is where I had it set, but maybe my leads were back to front.

No Ross that wouldn't cause your meter to go BOOM
I found last night on the internet was when the arc is struck there is a very high voltage

That is correct, it is a very high frequency, high voltage - about 5000 v. AC (alternating current) used to strike the plasma arc. Now, that more than likely would damage your meter if it were connected during this initial phase. Wait a bit till the plasma has struck before measuring is the safest thing to do. Good luck, Patrick
 

Ross

Ross
Looks like I won't be needing your bank details.

I waited for the pierce then cut to start before connecting the meter leads and it worked.

I got a reading of 91volts from the meter, now to figure out the Proma configuration.

Will try again tomorrow with the Proma, but not having much luck!

Thanks Patrick and Arie, I owe you both a coffee if you come over to where I live. "Yep nice coffee at Surin Plaza!" From Ross.

 

clover

clover
Excellent @ross, good luck with the Proma config.
I owe you both a coffee if you come over to where I live. "Yep nice coffee at Surin Plaza!"

Ross you have a date if I ever get to exotic Thailand, a long way to travel from Australia for a coffee though! Cheers Patrick
 
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