New algorithm for measuring 50/60 Hz AC values based on the usage of slow A/D converters

Today digital measuring of utilities AC values is based on application of very fast (flash) A/D converters, along with powerful processors required by such digital processing. This paper presents a new approach based on the use of very slow, high-precision, and inexpensive dual-slope A/D converters. Measurements of voltage and current are performed more than once in a period, so the measured value is reconstructed after n periods. The presented algorithm is of an adaptive type in accordance with the harmonic content of the input signal with modest hardware demands. The assumed stationarity of the electric utilities is validated with an experimental setup, consisting of a fast, high-precision sigma-delta ADC. The necessary synchronization is secured by software measurements of the frequency of the measured signal, Measurements performed in electric utilities in Yugoslavia indicate that the voltage waveform remains unchanged while the required accuracy is maintained.