Direct comparison between the NIST 10 V Conventional Josephson Voltage Standard and 2.5 V Programmable Josephson Voltage Standard

In the present paper, the intercomparison results of the NIST 10 V Conventional Josephson Voltage Standard (NIST10) and 2.5 V Programmable Josephson Voltage Standard (PJVS) Systems have been discussed. The two systems were directly intercompared at 1.018 V and 2.511 V from September 2006 to February 2007. The differences between the two systems (i.e. NIST10 — PJVS) at 1.018 V and 2.511 V were 0.21 nV and −0.95 nV respectively. The intercomparison results reveal that the noise of digital voltmeter (DVM) affects the measurement results significantly. Even with DVM of the same model, their noise rejection capability may be different when accuracy of a few nanovolt (nV) is required, although for Zener reference standard measurement, it is sufficient because the measurement uncertainty is dominated by the noise and non-linear drift of Zener reference standard.