Direct Comparison of Josephson Voltage Standards at 10 V Between BIPM and CENAM

摘要

A direct comparison of Josephson voltage standards at 10 V between the Bureau International des Poids et Mesures (BIPM) and the Centro Nacional de Metrología (CENAM), México, was carried out in September 2011. This comparison is part of the BIPM key comparisons (BIPM.EM-K10.b) and took place in the new DC Voltage Laboratory of CENAM. Both systems were very stable during the comparison, and the type “A” uncertainty was very low. The relative voltage difference between the two quantum standards was $-$6 parts in $10^{11}$ ( $-$0.6 nV), with a combined uncertainty of 7 parts in $10^{11}$ (0.7 nV).