Patent ID: 7479787

Claim:
A level measurement system, said level measurement system being powered by a two wire loop, said level measurement system comprising: (a) a transducer for emitting energy pulses and detecting reflected energy pulses; (b) a controller having a component for controlling said transducer, and a component for determining a level measurement based on the time of flight of said reflected energy pulse; (c) a power supply having an input port for receiving power from the loop, and a circuit for producing an output voltage; (d) a protection circuit, said protection circuit being coupled to the two wire loop and including one or more protection diodes and a current regulator circuit, said current regulator circuit generating a constant current output for the two wire loop, and including a detector circuit coupled to said one or more protection diodes for detecting a leakage signal corresponding to leakage current flowing in said one or more protection diodes, and said current regulator including a compensator circuit, said compensator circuit having an input for receiving said signal and a circuit for generating a variable current signal based on said signal, said variable current having a magnitude for maintaining said constant current output.