Monitoring industrial voltage standards by transporting Zener references calibrated by ETL Josephson standard

Industrial voltage standards were monitored for 2 years by transporting Zener references calibrated by ETL Josephson standard. Standards of two participants maintained by using Zener's 10-V output agreed with the ETL standard within 0.4 ppm. A standard of one participant maintained by using standard cells agreed within 1.2 ppm. Voltage transfer capability of Zener's 10-V output was 0.1 ppm, 1.018-V outputs was 0.4 ppm.<>