Automation of Direct Josephson Voltage Standard Comparison and an Application

A direct comparison between two Josephson voltage standard (JVS) systems has been used in the Bureau International des Poids et Mesures key comparisons or regional supplementary comparisons to ensure the uniformity of the representation of the volt based on K_{J - 90} with a relative uncertainty of a few parts in 10¹⁰ at a nominal voltage of 10 V. Most direct JVS comparisons are manually operated. Hardware and protocol for an automatic direct JVS comparison have been developed to verify the performance of a JVS while retaining the same level of uncertainty attained by a manual comparison. The automatic JVS direct comparison significantly improves the efficiency of the data acquisition. A case study examining the offset related to the digital voltmeter polarity in an automatic direct JVS comparison is presented.