[VAC] Re: Ammeter

["Dr. Gerald N. Johnson, electrical engineer" <geraldj@xxxxxxxx>]

Yes #2 is probably on the large side, but we don't like excess voltage
drops in 12 volt circuits. Another thing is that copper as a resistor is
fairly temperature sensitive and using say #8 (NEC for 40 amps) is
thermally limited and that means the shunt is guaranteed to change
temperature quite a lot and change the predicted meter reading for the
current. Better to use a longer and fatter wire to minimize the
temperature rise of the wire under load.

A brass bar or plate would be shorter than a copper plate because
brass's resistivity is significantly greater than copper. And brass is
easier to buy in say 3/4" wide by 1/16" thick by 12" long at the hobby
shop.