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HOWTO: Make your own amp meter shunt from 10 AWG wire (Read 5471 times)
electron
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Re: HOWTO: Make your own amp meter shunt from 10 AWG wire
Reply #1 - Jan 26th, 2014 at 5:44pm
 
Here's a PDF someone made that shows the lengths of a lot of size wires.

BEWARE: As you can see the real world is different from these calculations, read my previous post, I have #10 wire as 10 and 3/16 inches and they show it as about 12 inches so you must calibrate this against a good meter.

May depend on the copper used to make the wire.

Thanks goes to YouTube user "Willy IV" for finding this.

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electron
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HOWTO: Make your own amp meter shunt from 10 AWG wire
May 17th, 2011 at 10:42am
 
I needed to read several different circuits for amps and had some of these cheap little DVM meters laying around so I built my own shunts.

The little meters go to 10A and can be pushed to 15A but the built in shunts lose too much power through them for my taste.

I used #10 AWG stranded wire. The attached photo shows how one looked when it was done, I coiled it so it was shorter, you can do whatever you want, it doesn't matter.

Most professional shunts are just a short piece of mostly copper, but with a few other alloys mixed in to make them more accurate over a wide range (see below references).

I am not looking for perfection, just something close enough so I know I am getting about 8A or 12A or whatever some solar panels may be putting out.

This is easy to build and inexpensive, plus you can use left over wire you may have lying around. You should have a good meter around to confirm it's accuracy, but I don't see why it wouldn't be close if you just make one exactly to the length I used for mine.

The most important thing you need to measure is the length between the places you solder the sense wires. I used normal small zip cord speaker wire for the sense wires. Your sense wire doesn't have to be large gauge and can be long. I made them about 5 ft and it's working fine. That wire is probably #26.

The distance between the sense connections on the #10 wire is 10 and 3/16 inches.

Try not to get solder between the sense wire connections, it will throw off the reading and you will have to adjust for that. You would be making that section of wire a little thicker when you think about it.

To solder this I used a soldering gun since it has higher wattage and makes it easy to work with thicker wire. To adjust the readings you simply slide the wire connections while they are hot, closer or farther depending on what change you need.

I measured up to 15A against a good digital amp meter and it's pretty close all the way up the scale, within .2 or .3 amps. Good enough for me.

Just hook the sense wires to a digital meter that reads in millivolts and it should read 15mV for 15A. I use the 200mV scale on my meters.

Remember, you are reading VOLTS to get a measurement of AMPS going THROUGH the shunt.

And at 15A you are only losing 15mV across the shunt wire.

You could build a bigger one to measure higher amps if you used thicker wire but I don't see why this wouldn't be good to at least 50A with a loss of only 50mV.

Have fun measuring!

References:

"Manganin is a trademarked name for an alloy of typically 86% copper, 12% manganese, and 2% nickel. It was first developed by Edward Weston in 1892, improving upon his Constantan (1887). It is used in the manufacture of resistors, particularly ammeter shunts, because of its virtually zero temperature coefficient of resistance value and long term stability"
http://en.wikipedia.org/wiki/Manganin
http://en.wikipedia.org/wiki/Shunt_(electrical)
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« Last Edit: May 17th, 2011 at 10:49am by electron »  

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