Measuring DC current >10a?

Gallery, Projects and General > How do I??

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vtsteam:
Here's lots more info on making shunts:

http://www.sentex.net/~mec1995/gadgets/shunts/shunts.html

And finally, last but not least -- the easiest way:

http://www.rcgroups.com/forums/showthread.php?t=393591

loply:
Hi folks,

Thanks for all the help! Really useful.

So basically if I split the current up so only a portion of it goes through my meter, but I know what percentage, I can measure it.

Is there any way I can measure the resistance of the multimeter's ammeter so that I can just buy/find an appropriate resistor, rather than working it out by finding something which draws exactly 10a?

Cheers,
Rich

loply:
Actually having read those links properly I think it would be easier to measure the voltage drop over a shunt instead.

BaronJ:
I've seen those cheap multimeters smoke with way less than ten amps going through the internal shunt.

But I agree with the posters suggesting that you measure the voltage across a suitable resistance, plus that is only what the meter is doing anyway.

John Hill:
You can approach the principle of the shunt from another angle..

Stretch a length of heavy gauge bare copper wire between two supports, maybe two nails driven into a plank a foot or two apart.

Put two alligator clips on your meter leads and clip these close together on the wire with the meter set on voltage, pass the current through the wire and move the clip leads apart until you get a convenient voltage reading. Switch off and measure the distance between the clips and calculate the current using the information on the wire gauge chart referenced by vsteam above.

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