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Panel-mount Volt/Amp Meter Sourcing
Can't find appropriate volt/amp meters for high voltage applications. What are my options?

I am developing a power supply unit which has two high voltage outputs, one AC 0-500V 0-2.4A, the other DC 0-700V 0-3.4 A. I am having a significant amount of trouble finding dedicated panel meters which can handle these voltages.

I need to be able to view the voltage and amperage of both outputs, which will be on simultaneously.

Is there a company which manufactures parts of this description I'm not finding? Are there any companies which take custom orders for panel meters? Could it be possible to find a programmable meter which handles these values?

I have a preference for digital display, but if that can't be found, analog would work fine.

Thanks,
Sam

By Curt Wuollet on 22 March, 2018 - 11:18 am

The way I've done this is to get the widely available digital panel meters that let you program the decimal point. Then you simply use 1% or better resistors to make a voltage divider 10:1 or 100:1. Then simply adjust the decimal point to correct.

Works fine and lets you use commodity panel meters.

Regards
cww

Curt,

This looks like the best option so far, thanks for the advice. In calculating resistor values, will I need to know the total resistance of the meter in order to place it in parallel with the second resistor? In addition, how could I use this system to measure amperage?

For current meters look for a meter that reads millivolts and either buy a shunt that puts out 1 or 10 millivolts per Amp (0 or 1 decimal).

If you are not worried about super accuracy take a foot of 12 gauge copper wire and bare the insulation at two points 7.7 inches apart. Solder small wires to the bare spots and run those to the meter. This will give you 1 millivolt per Amp, Because the current in the meter wires is so low you can run them as far as you like.

Make the main current connection at the ends of the 12 gauge wire away from the meter taps.

For the same mV/A you can use 4.5" of 14 gauge or 2.9" of 16 gauge. If you want one decimal place just multiply the lengths by 10.

Copper is not as good as the metal normally used for shunts, because the resistance goes up more with temperature but ok for most purposes.

First off, 600VAC is not an unusual voltage for a meter. I don't know where you are looking, maybe hobby sites? But any INDUSTRIAL meter supplier will have 600VAC meters.

700VDC is more problematic, because that's not a standard voltage; 600VDC is typically the limit, then the next level is 1000VDC, and that takes special wiring etc. When you search though, don't search for 700VDC, search for 1000VDC.

So if you cannot find a meter that accepts your voltage directly, the proper and accepted way to do this is to get a TRANSDUCER that takes the line voltage and produces a SAFE low energy alternative signal that is proportional to your line voltage. So for example a transducer that will take in 0-1000VDC and give you an output that is 0-10VDC, then you get a meter that is scaled to display at a 10:1 ratio.

Current is different. At values less than 5A (AC or DC), you can just get a DIRECT reading ammeter with a scale that reads 0-5A. Those are very common. It only gets more complex when you want to read HIGHER current values, because you need a Current Transformer to change the current DOWN to a level that is 5A or less fro AC, or a DC Shunt that creates a proportional signal that you feed to a DC Volt meter with a scale that reads in amps. You don't need that here though.

If you want digital meters, look at people like Precision Digital, Yokagawa, Simpson, Red Lion, more industrial focused companies like that.