On Jan 2, 6:01*pm, "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.



So how are you going to calibrate it?