Patent ID: 8582257

Claim:
A ground fault circuit interrupter (GFCI) device for sensing a leakage current between line and return conductors, the device comprising: a current transformer having a core, a portion of the line and return conductors wrapped at least once around the core, the current transformer providing a fault signal induced by the leakage current; a fault-sensing circuit coupled to the current transformer to process the fault signal, the fault-sensing circuit comparing the fault signal to a reference fault threshold to determine whether to generate a protection signal; and a protective trigger coupled to the fault-sensing circuit for disconnecting the line conductor upon receiving the protection signal, wherein the portion of the line and return conductors are secured in a stable position with respect to the core, wherein the fault-sensing circuit includes an amplifier with an adjustable gain for amplifying the fault signal, the adjustable gain set so that when a leakage current threshold is exceeded the amplified fault signal exceeds the reference fault threshold, the amplifier comprises an op-amp and the adjustable gain comprises a potentiometer, the op-amp is in a negative feedback configuration and the potentiometer adjusts gain of the amplifier by changing a feedback ratio of the negative feedback configuration, and wherein the fault-sensing circuit comprises a full wave rectifier AC-to-DC converter to rectify the amplified fault signal.