Comparison of the Josephson voltage standards of the MSL and the BIPM (part of the ongoing BIPM key comparison BIPM.EM-K10.b)

Abstract

A comparison of the 10 V Josephson array voltage standard of the Bureau International des Poids et Mesures (BIPM) was made with that of the Measurement Standards Laboratory (MSL), New Zealand, in April 2011. For this exercise, option B of the BIPM.EM-K10.b comparison protocol was applied. This option required the BIPM to provide a reference voltage for measurement by the MSL using its Josephson standard with its own measuring device. The BIPM array is kept floating from ground.The final results are in very good agreement within the combined relative standard uncertainty of 4.0 parts in 1010 for the nominal voltage of 10 V.Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCEM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Direct comparison of two NIST PJVS systems at 10 V

“…Compared with configurations A and B, configuration C permitted identification of voltage noise of several hundred nanovolts peak to peak. In configurations A and B, the noise at the input of the digital nanovoltmeter was rectified such that it generated a proportional dc offset when the polarity of the signals provided to the detector was reversed [21]. The amplitude of the noise measured by the analogue detector remained small if it was directly connected at the output of each of the PJVS standing alone, but rose dramatically when the two PJVS systems were connected in series-opposition.…”

BIPM direct on-site Josephson voltage standard comparisons: 20 years of results

“…In particular cases a junction can show a lower than expected value for its critical current. The direct consequence will be shorter voltage steps and instability of the output voltage in the dynamic mode [13]. This is often the case when arrays are temperature cycled.…”

“…Both frequency counters (in all cases either EIP model 578 or 578B) were referred to a common standard frequency for all comparisons so that, unlike the normal calibration situation, the accuracy of the reference frequency did not contribute to the uncertainty. In some cases the internal 10 MHz frequency reference of the counter was used to eliminate the clock ground potential which is transferred to the counter through the BNC connector [29]. The use of a dedicated isolation transformer is also a suitable method to achieve insulation.…”

“…Filipski and Boecker [32] observed problems which they attributed to a common-mode effect related to a noise compensation system. Whenever possible, it is recommended that different DVMs are tested to evaluate their effect on the measurement loop [13].…”