A survey of Josephson comparisons

In 2007 the CCEM proposed changes in the SI electrical units (Recommendation E-1), which has refocused attention on the validity and accuracy of the Josephson effect. We review comparisons of Josephson effect voltage standards and summarize the results as they pertain to the accuracy of the Josephson relationship between voltage and frequency. We also report a list of possible influence parameters and the range and accuracy over which they have been evaluated.