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Mystery IC

jsmith725

Oct 14, 2018
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I recently bought a small DC voltmeter to use in a power supply and it turns out it only measures down to ~7 volts as it displays the voltage it's powered by. I believe I can cut a trace and add a wire to this IC to measure to 0 volts, but I can't find any information anywhere.

IMG_2136.JPG IMG_2136.JPG
 

Bluejets

Oct 5, 2014
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Some small voltmeters can be modified to read down to 0 volt by cutting a link and providing the meter first with the voltage needed to drive the meter, and then another lead to measure the voltage in question. The link is usually in the area of a couple of voltage divider resistors on the input.
With this arrangement it uses a common negative.

Edit...I did one just the other day to read 0-1v but sadly could not use it as I required a floating input.

Do you have a link to your particular meter?
 

jsmith725

Oct 14, 2018
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I could not find a datasheet or for it but it is pretty common from resellers if you search for it

The model is PZEM-051
 

Bluejets

Oct 5, 2014
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I'm not about to go searching all over for something you may or may not have bought.

However, here is a link to a 4 wire meter that will read down to 0 volts.
Note it requires a separate supply battery from the measuring supply.
Most digital metering you will find requires similar approach.
Notes on connections are below the details on the web page.

https://www.ebay.com.au/itm/DC-0-20...h=item236d445cff:g:llgAAOSwXeJXfMLm:rk:5:pf:0
 

jsmith725

Oct 14, 2018
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Ok. I’ll try to use a separate supply voltage instead. I don’t really want to ship something from eBAy.

Thanks for the help.
 

kellys_eye

Jun 25, 2010
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You should look for the onboard regulator for the meter and cut the trace to its input and make your three wire meter a four wire meter.
 
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