For not breaking the wire (assuming you can still insert it though a loop!) try something like this 100mA Flux Gate ([1]http://www.lemusa.com/docs/products/ct_e.pdf). If you CAN interrupt the wire, then there are many feed through chips that have the whole current flowing through them to bring it a precise distance away from a Hall effect sensor, that is then linearly amplified to an output voltage (powered by separate power lines) proportional to current passing through like this ([2]http://www.allegromicro.com/en/Products/Part_Numbers/0712/0712.pdf) Or, you could just the high and low sense lines to the inputs of a J-FET OpAmp. As the current changes direction, the inputs will swing from being + over - to being - over +, which should give a rail to rail output swing from the opamp without any measurable current drain from the circuit. Mike -- Burn the Land, Boil the Sea, You can't take the SKY from me!
References 1. http://www.lemusa.com/docs/products/ct_e.pdf 2. http://www.allegromicro.com/en/Products/Part_Numbers/0712/0712.pdf
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