CMOS digital wattmeter design

This paper describes the design of an electronic wattmetric instrument whose operation is dependent on digital techniques. The prototype is built from MSI and LSI CMOS circuits that consume few microwatts. The method of measurement adopted is that of digital integration, which involves the instantaneous sampling of both voltage and current signals. These samples are converted simultaneously by the appropriate type of analogue-to-digital conversion system to be delivered to a digital multiplier. The output of this digital multiplier is accumulated over at least one cycle of voltage waveform. The output of the accumulator is a representative of electrical power that may be converted to a decimal equivalent for readout purposes.