IEC class 0.5 electronic watt-hour meter implemented with first-order sigma-delta converters

This paper presents a design of a precise electronic watt-hour meter implemented with first-order sigma-delta analog-to-digital converters. An efficient digital signal-processing circuit is introduced into the design where the whole signal processing is performed directly on an oversampled signal, eliminating the necessity for a decimation filter. It is shown that Gaussian noise, added to the input signal of sigma-delta modulators, decorrelates quantization error of first-order sigma-delta modulators and thus substantially reduces measurement error at low-signal amplitudes. The effect of added noise is analyzed by extensive behavioral simulations for various input signal amplitudes and for various input noise levels. The results show that IEC accuracy class 0.5 can be achieved with first-order sigma-delta converters and digital signal processing in the sigma-delta domain.