How do I wire up those 100 volt 10 amp multimeters from ebay?

Thread Starter

uraniumhexoflorite

Joined Oct 23, 2016
216
I bought one of those red and blue LED multimeters off ebay for a project I'm building (a basic LM317 power supply). I already accidentally fried one due to a lack of instructions from the manufacturer. This time, I decided to do the smart thing and do some research. Unfortunately, there are a couple different ways that people say to wire these things up and I'm not sure which is correct and I don't want to risk destroying another multimeter. Is this wiring correct?
Small red and black: Voltage supply + and - respectively
Thick red and black: Measured voltage + and - respectively
Thick yellow: + for the load (load - is attached to the thick black wire)
Here is a link to the ebay page for the one I bought (the 100 volt 10 amp red and blue)
https://www.ebay.ca/itm/272963482961
Thanks in advance for the help.
 

jpanhalt

Joined Jan 18, 2008
11,087
It does not appear in your link that the 100 V version has a yellow wire. The 200V version has the yellow wire. The odd wire in the 100 V version is blue. Do you have the right version?

How did you connect the one you destroyed? I have found with similar stuff from China that some listings have instructions and others do not. (Accepting that they may all be the same one or two real sellers.) Try to find a similar device from a seller/lister that has instructions.
 

BobTPH

Joined Jun 5, 2013
8,922
Here

Select from the pictures below the one diplayed. There is one wiring diagram for use with a single supply and one for use with a separate supply for the meter.

Bob
 

MisterBill2

Joined Jan 23, 2018
18,414
I don't find any wiring diagrams, and the ebay post was less useful than the verbal description. Often the digital meters need a separate power supply, which is very reasonable although it may be less convenient. and often that separate supply is 5 volts.
 
On another thread I posted a diagram of how this meter is wired internally. I do NOT show the required 5volt power supply.

In my limited experience the Chinese have excelent circuit designers, pretty good assembly staff and no tech writers at all. If you get any information it will be difficult to understand. If you get a diagram, it will be a so-called "pictorial" which will be hard to follow but usually accurate.

If you want to run this meter self-powered search e-bay for diagrams (they do exist) and follow the proper one. Draw it out, melding my diagram and theirs till you get something that looks right.

dualmeter.jpg
 

Tonyr1084

Joined Sep 24, 2015
7,886
Mine (don't recall the voltages) has 5 wires. Red and black wires and its own plug. I'm assuming it's for power to the unit. Mine should take 4.5 volts to 30 volts as a source of power for the meter. The other three wires are Blue, Green and Yellow. (B,G,Y) They're on their own plug. This is the best diagram I've come up with for mine, though I haven't used it yet. Maybe one day. So I can't say "This works" And like I said, I don't think mine is good for 200 volts. According to the paperwork I've found it should be 100 volts. But maybe I'm wrong. Anyway:
 

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Tonyr1084

Joined Sep 24, 2015
7,886
A quick bench test: Red ( + ) & Black ( - ) powers the unit. When I short the blue wire to the incoming power it reads 5.09 volts (because I'm powering it from a 5 volt source.

When I tap the green wire to ( + ) the unit blanks out. Likely a short circuit. When I touch the yellow wire to ( + ) it displays a current of 100 amps. So likely green and yellow are a part of the current sensing circuit. Does so by calculating the voltage across a shunt. So many volts (or whatever it's measuring) is calculated as amps. In the case of my test, a full 5 volts on the yellow wire is translated as 100 amps.

According to the drawing I posted, you're supposed to leave the black wire unconnected. When I disconnect the black wire from ( - ) the unit still operates. And again, touching the yellow wire to ( + ) I get the full 100 amp readout.

Well, that's what I got on mine.
 
If the meter is the one I think it is and for which I drew a diagram, it has an internal shunt. If it does require an external shunt the images you posted are undoubtedly what the T.S. needs.
 

Thread Starter

uraniumhexoflorite

Joined Oct 23, 2016
216
Out of curiosity, I pulled out a 100 volt model that I had, but thought was dead on arrival. I wired it up identical to diagram 2 and it worked. The ones I have all have built in shunts thankfully. I will try and replicate the working wiring on the 200 volt model.
 

Tonyr1084

Joined Sep 24, 2015
7,886
Also of note: With the diagram I posted, the negative side of the circuit is where the shunt goes. IF I were to put it on the positive side then my reading would be 100 amps minus the current draw. In other words, if I were drawing 2 amps then my reading would be 98 amps. That's why it goes on the negative side.

[edit] I have a 100 amp shunt. Meaning it gets put in-circuit and the meter measures the voltage across the shunt.
 

Thread Starter

uraniumhexoflorite

Joined Oct 23, 2016
216
Just tested out wiring diagram 2 on the 200 volt model. It works just fine. Thanks for helping me figure out how to wire up these multimeters.

Edit: Turns out all 3 of the multimeters I ordered are working. I'm definitely not complaining. :)
 
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Tonyr1084

Joined Sep 24, 2015
7,886
With the external shunt I can customize the sensitivity. A 100 amp shunt isn't going to be very accurate with a load of around 1 amp. But if I use a 10 amp shunt then that would amplify the sensitivity by ten. 1 amp would read as 10 amps, but I'd have to calculate in my mind that it's actually 1.0 amps. If it read 9.9 amps then it's 0.99 amps. Simple division. Move the decimal one place in my head.
 
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