>Trying to figure out the best way to measure current
>in a car (12V neg gnd system).  The current path to
>be measured is that going into/out of the battery.
>For now, I'll use a "safe" figure of 100A, although
>the current drain/alternator charge current should
>not be anywhere near that.

Try using a "DC Current transformer" in the shape of a hall effect sensor. I
am currently about to try some from LEM http://www.lem.com/ and go to
sensors. These are a ferrite core with a hall effect sensor in a gap, and an
op amp to give a voltage output. Some of them go to the sort of current
level you are looking for. Worst problem may be supplying +/-15V for the
sensor output, although some versions will accept single supply 5V, but not
sure if they are available in the rating you want.

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