Towards a BIPM On-Site Comparison Program for AC Voltages Based on the Differential Sampling Technique

BIPM has conducted a few pilot studies to investigate the possibility of extending the protocol of the BIPM program of on-site DC Josephson Voltage Standard comparisons (BIPM.EM-KI0.b) to AC voltages. On-site indirect comparisons have been performed for AC low frequency sinewaves, at 1 V and 6.5 V rrns, using the new BIPM Programmable Josephson Voltage Standard and the differential sampling method. A relative agreement within a few parts in 10⁷ can typically be achieved using a commercial calibrator as a transfer standard. The noise of the phase locking process appears to be the limiting factor. We have been investigating other AC generators as possible candidates for an accurate transfer standard.