Comparison of the Josephson voltage standards of VNIIM and PTB

Comparisons of the 1 V Josephson array voltage standard (JAVS) of the "D.I. Mendeleyev Institute for Metrology" (VNIIM), Russia, with that of the Physikalisch-Technische Bundesanstalt (PTB), Germany, were carried out in St. Petersburg in June 1999. The results of the direct comparison agree within an overall standard uncertainty of less than 1 nV. The results also show that direct comparisons are useful for detecting voltage offsets of a few parts in 10/sup 10/.