Influence of Sampling Voltmeter Parameters on RMS Measurements of Josephson Stepwise-Approximated Sine Waves

A binary Josephson-array voltage standard was used to investigate the influence of device settings on the reading of an 81/2-digit sampling voltmeter. This voltmeter is the heart of the primary standard for power at 50 Hz or 60 Hz at several National Metrology Institutes (NMIs). In this paper, we present results on the influence of the voltmeter synchronization and measurement parameters on the root-mean-square (RMS) measurements of Josephson stepwise-approximated sine waves for different frequencies. Our results show that for aperture times above 100 mus, the measured RMS voltage shows a large step in value with respect to shorter aperture times and is much more accurate. Furthermore, to obtain 0.2 muV/V accuracy, we show that for stepwise-approximated sine waves at 53 Hz, delay times higher than 10 mus are necessary. A slight delay time dependence limits the accuracy for frequencies above a few hundred hertz.