Automated comparator for accurate AC-DC difference measurements at the BNM-LCIE

This paper describes the new automated comparator system developed at the BNM-LCIE for the calibration of voltage thermal converters used as national AC-DC transfer standards. The system achieves Type A standard uncertainties of a few parts in 10/sup 7/ in the frequency range from 10 Hz to 1 MHz (100 kHz for voltages above 100 V). Type B standard uncertainties, depending on the type of converters to be compared and on the measurement voltage level, are between a few parts in 10/sup 7/ and a few parts in 10/sup 6/.