On Tuesday, January 1, 2013 8:19:55 PM UTC, wrote:
As part of another project, would like to take some High Current DC measurements.



I have a couple of multimeters ... but obviously not going to be
any good for around 80-100A

Ouch! That's a serious current.

Now going back to school physics lessons I could use a Shunt resistor ...
http://www.societyofrobots.com/robot...?topic=13900.0

The issue will be obtaining a suitable shunt ... assuming I use
a 1 ohm shunt, anybody made one of these ?

Ahem. Let's review those school physics lessons shall we?

Volts = Ohms x Amps

So 80A through 1 ohm will generate 80V. Further, the definition of
volts is:
Watts = Volts x Amp

So your shunt resistor is going to be dissipating
80 x 80 = 6400 W = 6.4 kW.

That's a serious amount of energy!

(Of course, what I expect will happen is that your shunt resistor
will have much higher resistance than the rest of the circuit,
and bring the current way down - or possibly kill it altogether.)

I suggest you need something more like 1 milli-ohm, which will produce
a voltage of 80 mV (perfectly within the range of digital volt meter),
and an energy output of 6.4W

http://uk.farnell.com/jsp/search/pro...=1292504&N=401
(for example) ?