Patent ID: 7477080

Claim:
A system for isolating the input and output of a self-powered current loop including: input terminals for receiving an input loop current; output terminals for supplying an output loop signal; a voltage to frequency converter coupled to the input terminals for supplying a frequency output proportional to the input current applied to the input terminals; an optical isolator coupled to the output of the voltage to frequency converter for supplying an isolated frequency output therefrom; an output circuit having an input coupled to the output of the optical isolator and providing a signal on an output thereof coupled with the output terminals; and, a potentiometer coupled to the frequency to voltage converter for adjusting an offset between the input loops current applied to the input terminals and the signal obtained from the output terminals, and further including a coupling amplifier and a voltage to current converter connected in series with one another between the output of the frequency to voltage converter and the output terminals.