Winston wrote:
For A.C. operation, I'd expect that a current transformer
would give you much better isolation and signal - to - noise ratio.

For D.C. (or A.C.) operation, I'd expect that a Hall Effect
Current Sensor would be a better choice, for the same reason.

I've used the Allegro ACS756 in some extremely low impedance
applications where a sense resistor caused power supply
instability.
http://www.allegromicro.com/en/Produ...0756/index.asp

Highly recommended, though you will need to normalize it's
output. (I did that automatically with DAQ gear.)

For seven bucks, it is a great value.

http://search.digikey.com/scripts/DkSearch/dksus.dll?lang=en&site=US&WT.z_homepage_link=hp_go _button&KeyWords=ACS756&x=0&y=0

Ooh, and up to 100 amps, I like that. Curious as to what you mean by
"normalize it's output", though; is this referring to the "typical
application" diagram given in the datasheet (sorry I'm rather dense on some
things).

Jon