Establishing a Josephson-array voltage standard system at NML, ROC

A 1-V Josephson-array voltage standard system has been operational at the National Measurement Laboratory (NML) of the Center for Measurement Standards (CMS) in the Republic of China (ROC). To help evaluate its accuracy, the authors selected two Zener references that had been calibrated by means of this system over a three-month period and hand-carried them to four other national laboratories around the world for comparison purposes. Over a four-week period in November and December, 1991, these two references were measured in turn at PTB (Germany), NPL (UK), NIST (USA), and ETL (Japan). The results of these international comparisons at the 1-V level, using the Zener references as transfer standards, shows good agreement to about 0.05 ppm between NML (ROC) and the other national laboratories