Low voltage AC-DC transfer standards at LNE
This paper describes the method used to establish the traceability of LNE AC-DC transfer standards in the mV-range to the 1 V multijunction converter, which serves as the primary AC-DC standard. Main uncertainty components are listed and final uncertainty given for the different voltage levels. An independent method was developed for the calibration of thermal converters at 0.3 V and 0.2 V. The agreement between this method and the step-down is within the standard uncertainty.
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/.
Thermal current converters for accurate AC current measurement
A new 14-range set of thermal current converters consisting of shunted thermoelements has been constructed to measure ac-dc difference and ac current from 10 mA to 20 A at 20 Hz to 50 kHz. The ac-dc difference corrections for all ranges can be determined relative to two ranges by a 7-step intercomparison of certain adjacent ranges.