Comparison of Josephson Impedance Bridges

The first two impedance bridges based on pulse-driven Josephson voltage standards show the lowest uncertainties among digital bridges even comparable with state-of-the-art bridges using inductive voltage divider. In this paper, we will present the world’s first comparison between these bridges. The observed difference between both systems measuring impedance ratios (C:C and R:R) is 6 nF/F and 6 nΩ/Ω at 1233.15 Hz. Up to 50 kHz, the measurements from both bridges agree within uncertainties, which are still below one part in 10
⁶
and dominated by cable effects.