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 Measuremen t Standards (CMS), in the Republic of China (R.O.C.). To help evaluate its accuracy, we selected two Zener references that had been calibrat ed by means of this system over a three-month period and hand-carried them to four other national laboratories around the world for comparis on purposes. Over a four-week period in November and December, 1991, t hese two references were measured in turn at PTB (Germany), NPL (U.K.) , NIST (U.S.A.) and ETL (japan). The results of these international co mparisons at the 1-V level, using the Zener references as transfer sta ndards, showed good agreement to about 0.05 ppm between NML (R.O.C.) a nd the other national laboratories.