Precision measurement of AC voltage below 20 Hz at IEN

A new system for ac voltage measurements at low frequencies has been built at the Istituto Elettrotecnico Nazionale (IEN). The system uses a sampling voltmeter working as an integrating analog to digital converter and software programs for data acquisition and processing. An algorithm for the reconstruction of the input voltage based on a model of the converter allows the precise evaluation of the signal parameters. Comparisons at 20 Hz and 40 Hz with measurements made using the thermal converters of the national standard have shown differences lower than a few parts in 10/sup 6/.