An Energy Measurement Frontend With Integrated Adaptive Background Accuracy Monitoring of the Full System Including the Current and Voltage Sensors

This article presents an ac energy measurement frontend on 0.18 μ CMOS with integrated, condition-based monitoring capability that can continuously monitor and report on the accuracy of the full measurement system, including the external current and voltage sensors, without interruption of the measurement used for billing. This is achieved using a highly stable, digitally controlled, adaptive background accuracy monitoring (ABAM) system, which injects a small, known signal into the sensors and extracts it using digital signal processing, in the background while normal measurement is ongoing. The realized system is an energy metering frontend that can be used for utility metering applications capable of measuring rms current to 0.1% accuracy over a 1000:1 dynamic range and active energy to 0.25% accuracy over a 5000:1 dynamic range over the full supply and temperature range, while continuously monitoring the system accuracy in the background. The ABAM signal references and drivers used for monitoring the current and voltage channels independently achieve an absolute accuracy in the order of 0.1%, and the full ABAM system has been shown to track the relative accuracy of the full meter when subjected to interference and when trialed in the field to 0.1%.