A metering module (12) for use in a power circuit monitoring system including a circuit monitor (10) having a processor for processing data related to power signals, said metering module comprising at least one sensor for sensing a predetermined property of a power signal and for producing a corresponding sensor signal, and a modular metering circuit monitor, wherein said metering module (12) is selectively detachable and replaceable relative to said circuit monitor (10) to permit one or more of testing, calibration and repair of said metering module thereby minimizing any interruption in operation of said circuit monitor.
