Improvements of the 10 V CENAM Josephson Voltage Standard to reach a standard uncertainty at 1 nV level

The CENAM Josephson Voltage Standard (JVS) was purchased in 1994. During its 18 years of use, several improvements have allowed to reduce noise immunity, measurements dispersion and uncertainty. During this period we participated in several international comparisons, the results show the improvements of the JVS. The current combined uncertainty of the CENAM JVS is 1.3 nV as a DC voltage measurement system. The difference between the CENAM JVS and the BIPM JVS during the direct on-site comparison [1] was found to be equal to - 0.6 nV. The uncertainty of the difference is under evaluation.