>1. Use a 1:1 transformer to isolate the voltage across
>the low-ohm resistor (current sensor), from the
>interfacing analog circuitry. On the secondary side,
>the voltage can be referenced to ground, making it
>quite easy to get reasonable accuracy out of an
>inverting op-amp circuit with .1% resistors.
> This will work, since I am only concerned with AC
>current. The problem is finding a 1:1 transformer with
>truly accurate winding ratios (within 1%). Or else, I
>will have to perform some type of testing in each unit
>during manufacturing and come up with a normalization
>look-up table in software.

Use a Bifilar wound transformer. I would also put the resistor on the
secondary, but that decision would also depend on getting a transformer with
suitable core and windings.

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