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Need some assistance with ammeter vehicle circuit

pityocamptes

Jul 26, 2012
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I picked one of these up from ebay, for my vehicle.

http://www.ebay.com/itm/0-100V-200A...083?pt=LH_DefaultDomain_0&hash=item418b8ffaab

I have an older vehicle with the stock ammeter and connected the shunt between the line coming into the old ammeter and the lines that were on the other side - basically I put the shunt in place of the old ammeter.

Now I am not sure how to hook up the digital ammeter/voltmeter? I see where it says it should be on the negative leg of the load, but this is not possible with it taking the place of the ammeter circuit as it goes into the fuse box.

I saw this schematic:

http://suns-power.en.alibaba.com/pr...tal_Ammeter_Digital_DC_Ammeter_72mA_100A.html

and that is basically how I have it hooked up with the load after the shunt.

the ammeter wires for the ammeter I got have a COM, IN+, and POWER+. I am not sure if the POWER+ wire go before the shunt and the IN+ after or vis vera. Also, is the COM a ground wire? Any help on this would be greatly appreciated. Thanks
 

Gryd3

Jun 25, 2014
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I can give you my observations... but I can't guarantee anything.
If you bought that meter from eBay, it looks to be divided into two distinct circuits.
The two thicker conductors (red/black) go to the shunt. It's important that the black wire is connected to ground, chassis or 0V. The red wire will measure the voltage across the shunt to determine current flow through it.
The other side of the meter (Yellow, Red, and Black) is for powering the device and getting a battery reading.
The Red/Black thinner wires will power the meter, the Yellow is for measuring the voltage on the battery.

So.. you have two setup options.
If one side of the shunt is connected to ground, 0V, chassis or negative on the battery (These should all be interconnected anyway) then you can power the meter off the car battery. Simply connect the black shunt wire to the shunt, and red wire to the shunt, then tie the thin red/yellow wires together and run to the battery (or other 12V source) and you are done. The last thin black wire can be left disconnected.
If the shunt is not connected to common (0V, chassis, ground, etc.) then you need a separate power supply for your meter. The yellow wire goes to the car battery to monitor voltage. The shunt wires go to the shunt... and the remaining red/black thin wire go to a secondary battery that appears to allow anywhere from 3.5V-10V

*Note that if your shunt does not have one of it's terminals tied to common, you could create an inadvertent current flow through the meter when you connect the second black wire to ground! (If you have a multi-meter, it's time to disconnect the battery, and measure resistance from the negative battery clamp to each end of the shunt. Please disconnect one end of the shunt first... as it's resistance will be vary low you may not be able to tell which side is actually connected to the battery negative clamp. Additionally, if the original ammeter was stock, you can look up a wire diagram)
 

pityocamptes

Jul 26, 2012
79
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Thanks. The two thin wires from what I am seeing power the voltmeter, and the three thicker wires power the ammeter - so I believe the ammeter has POWER+, COM, IN+ so I'm not sure if that changes what you said. Thanks.

OK, I do have two batteries on separate circuits. The one battery basically just powers my offroad lights, winch, etc. The other battery is the one that powers the ignition, etc. and what I have the shunt connected to.

Here is what I have so far. Not sure which ammeter leads to connect and where??

circuit.png
 
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Gryd3

Jun 25, 2014
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Thanks. The two thin wires from what I am seeing power the voltmeter, and the three thicker wires power the ammeter - so I believe the ammeter has POWER+, COM, IN+ so I'm not sure if that changes what you said. Thanks.
Perhaps the description on the eBay page was screwed.
I can certainly vouch for the fact that the black wires are tied together... which means that it would be ideal to have your shunt connected to the battery negative terminal.
Once you account for what the black wires do, the yellow will be a voltage sense wire (Sent to a 12V source)
The two remaining wires will measure the shunt, and power the device. I cannot say for certainty which is which... as the eBay description showed the group of 3 wires for voltage sense, and power. The other pair is for the ammeter.
Is there a label on the other side of the device?

Power+, COM, and In+ make sense, but I'm curious about the other side.
 

pityocamptes

Jul 26, 2012
79
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Thanks. I added a picture above

Thats the bad thing, I'm not going to be able to connect it to battery ground. Completely rewired the whole vehicle and going back to do this would be monumental... trying to work with the original analog ammeter circuit...

This pic shows the shunt on ground....

http://img.alibaba.com/img/pb/285/313/636/636313285_691.jpg

but it seems possible to do it to hot as well??

Here is some side pics of the same device from a different vendor...

http://www.aliexpress.com/item/Red-...meter-Voltage-Meter-Power-12V/1687073806.html


Here is a better schematic... but it still shows connecting inline with ground, I need to run this off the hot..

http://www.ebay.com/itm/Red-Blue-LE...383?pt=LH_DefaultDomain_0&hash=item5b0b302c4f


This pic, without shunt shows POWER+ before IN+, so is that measuring the differential? So in my case with the load AFTER (fuse box) would POWER+ go before or after the shunt? What exactly is the COM lead for? Is it a negative lead or does it measure the voltage differential to calculate the amps? Maybe the POWER+ just powers the unit? Thanks again!

http://i00.i.aliimg.com/img/pb/910/884/878/878884910_809.jpg


Does this youtube video help? He is doing it off of negative, not sure if there is a way to do it off positive..

 
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