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Using a fixed range AC voltmeter with variable input [SOLVED]

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enut11:
I want to monitor the output voltage and current of a variac using a digital panel meter.
The meters available appear to work over a small voltage range (eg 80-200vAC)
My need is for (close to) zero and all the way up to 300vAC
Current will be around 2A max with a resolution of about 10mA

Has anyone modified one of the fixed range panel meters for variable input?
I guess the first step would be to isolate the meter power circuit from the voltage measurement circuit. Ideas?
enut11

https://www.ebay.com.au/itm/1x-LCD-Panel-Monitor-Current-Amplifier-AC-Combo-Meter-Voltage-Current-Accessory/193163573647?hash=item2cf972398f:m:mLZiHZlTM9LnQukgkhrbDFw

intabits:
Yes, they can be modified to do what you want.
As they sit, the input to the unit's internal power supply, and the voltage sensing input to the meter at connected together internally.
Separating them allows the unit to be powered from the 240V input to the variac, while measuring the variac output voltage via the meter voltage sense input.
Basically it involves disconnecting the large capacitor (or the resistor in series with it, whichever one it is) from the meter's input terminal and running it instead directly to the mains input.

I did exactly what you are looking at two years ago, and made a couple of videos about it:-



though I don't think I went into specific details on the mods required to the meter. I may have got them from this video, or one of several others out there covering the procedure:-
https://www.youtube.com/watch?v=wPFaEFEembc,

But your meter is a different model, so you'll need to nut it out for yourself, though I'm sure the essentials are the same. (I've got one of your type of meter on order, so I'll be looking into this again sometime also)

enut11:
Thanks @intabits, you have put me on the right track.

I ordered this meter and it has just arrived:
https://www.ebay.com.au/itm/AC-Digital-Multi-function-Meter-Power-Energy-Voltage-Current-V-A-W-KWh-Monitor/251878747833?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2648

Mods
I removed the back cover, snipped the input end of the 1uF cap and soldered a wire to it. Drilled a hole in the back cover to pass the wire through.
This (brown) wire goes straight to 240vAC to power the panel meter.

You can see the steps I took in the pix.
enut11

enut11:
More pix

enut11:
More pix

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