In article ,
www.GymRatZ.co.uk wrote:
On 02/01/2013 16:55, harry wrote:

So if it's measuring milivolts, the internal resistance will be
miliohms. And the shunt will be smaller resistance still. Micro ohms.
So, a futile pursuit trying to make one.

Not futile in the slightest.
As long as the shunt is capable of carrying the maximum drawn current
it's just a matter of trial and error with a know load.
Very simple actually. You could probably make one from a bit of
automotive jump-lead or car battery earth strap etc. Hammered flat 15mm
copper pipe (or several lengths in parallel) perhaps?

Presumably anything DIY measuring 100 amps isn't going to be matter of
extreme accuracy so a margin of error of a few % should be perfectly
acceptable and easy to achieve.

In practice I found it pretty difficult. Best thing to do is check Ebay to
see if a ready made one is available. You'd need to know the exact
parameters of the material you are using and make it by measuring size -
measuring the actual resistance at 0.00001 ohms or whatever isn't easy.

--
*What hair colour do they put on the driver's license of a bald man? *

Dave Plowman London SW
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