This is an AC Adapter for the charge meter. It is based on an industrial clamp-on transducer. This current-regulates a supplied voltage according to the AC current in the wire passing through the sensor. It passes 4 MA for no current, and 20 MA for full-scale. This design makes it independent of the resistance of the connecting wires, and an open-circuit is detectable from zero current. It has full-scale values of 10, 20, and 50 amps, selected by jumpers. In this application I am using the 10-amp range. By putting 10 turns of 14-gage wire through the sensor, its sensitivity is increased to 1 AMP. A jumper in the Charge Meter connects up a counter-current for the 4MA base.