Recent developments in BIPM voltage standard comparisons

The Bureau International des Poids et Measures (BIPM) carries out a number of comparisons of dc voltage standards with National Metrology Institutes (NMIs). These take the form of on-site comparisons of Josephson standards or bilateral comparisons using traveling standards based on Zener diodes. This paper describes some of the new procedures used in both types of comparison and presents some results of five recent BIPM key comparisons.