Comparison of quantum Hall effect resistance standards of the BNM/LCIE and the BIPM

Abstract

The comparison procedure was to measure these three resistance ratios first with the BIPM’s QHE standard, then with that of the BNMLCIE and again with that of the BIPM, all within three hours. By performing the measurements so quickly, scatter in the comparison results is greatly reduced. The BNMLCIE bridge operates at dc using a cryogenic current comparator (CCC). The BIPM transportable ac resistanceratio bridge operates at 1 Hz and at room temperature. At 1 Hz, variations in the quantized Hall resistance with frequency [3] are undetectable. However, for the standards we used, the difference between values of resistance measured at 1 Hz and at dc are small but not negligible and so they must be determined accurately. Before the comparison the BIPM used the ac bridge at 1 Hz and its CCC bridge [4], operating at dc, to measure the three standard resistors in terms of the QHR. The measured differences are a few parts in 10’ or less for the 100 R and 10 kR standards and I part in 10’ for the 1 R standard. For the purposes of the present comparison, these differences are applied as corrections to results of the BIPM measurements carried out at 1 Hi when comparing them with the corresponding results of dc measurements performed with the BNMLCIE’s CCC. This procedure has the effect of using the ac bridge as a transfer instrument referenced to the BIPM’s CCC. This method is preferable to transporting the BIPM CCC bridge itself since the ac bridge is a more rugged instrument, easily transportable, simple to operate, and virtually insensitive to electromagnetic interference and to fluctuations in ambient temperature. Furthermore, it provides resolution and reproducibility that are comparable with those