Enhancements of NMC'S Josephson array voltage standard system

A series of system enhancements for the Josephson array voltage standard (JAVS) have been implemented to improve the efficiency and quality of dc voltage dissemination in the National Metrology Centre, A*STAR. Periodic direct comparison between two JAVS systems has been adopted as a quality assurance procedure to ensure accurate reproduction of the volt for calibration of secondary standards. A miniature millimeter-wave synthesizer is employed for better control of microwave power and locking frequency. Low thermal terminal reversing switches are introduced to minimize zero-offset measurement uncertainty. Monte Carlo method and ANOVA method are implemented in the data analysis and reporting.