This report presents the results of a comparison of measurements on four electronic DC reference standards performed by national metrology institutes in the EUROMET region and BIPM. The results of the comparison, in terms of degrees of equivalence, show that there is a good agreement between the measurement results of the participants. The results also show that the time-dependent fluctuations in the output voltages of the travelling standards provide one of the main sources of uncertainty. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the EUROMET, comparison identifier EUROMET.EM.BIPM-K11, according to the provisions of the Mutual Recognition Arrangement (MRA).

Three 1 V binary Josephson arrays developed by the NIST, the PTB and the VTT and using respectively SNS (superconductor-normal-superconductor), SINIS (superconductor-insulator-normal-insulator-superconductor) and externally shunted SIS (superconductor-insulator-superconductor) junctions have been tested at BNM-LNE. Preliminary results of direct comparisons with conventional SIS arrays globally show a good agreement of less than 0.5 nV, at any nominal voltages between 41 mV and 1.3 V.

Various operational parameters of two different I-V binary programmable Josephson arrays are evaluated and compared within different Josephson array voltage standard (JAVS) set-ups at microwave frequencies around 70 GHz. For this purpose, the investigation of the electrical characteristics of a SINIS-type Josephson array and of an externally shunted SIS-type Josephson array is under way at ten national metrology institutes. The results of the measurements are presented and discussed.

In anticipation of the start of a European comparison of 10 V Josephson array voltage standards (EUROMET project 429 led by NMi VSL), the BIPM and the BNM-LCIE Josephson standards have been compared by means of Zener travelling references. An overall spread of 5 parts in 10/sup 9/ has been found with a standard uncertainty of 6 parts in 10/sup 9/. These results show that the performance of the Zener references could be the main cause of uncertainty in such a comparison.

An indirect comparison between the 10 V Josephson array voltage standards of the BNM/LCIE and the BIPM has been carried out using Zener-diode based voltage references as transfer standards. The results show an agreement of 5 parts in 10/sup 9/ with an uncertainty (1/spl sigma/) of 3 parts in 10/sup 9/, mainly due to instability of the Zener references. A direct comparison is to be carried out early in 1994 to avoid this limitation.< >

An international voltage standard comparison has been carried out by six metrological laboratories using a Zener diode as the travelling voltage standard. The results show agreement within the uncertainty of the measurements: this is limited only by the stability of the Zener, which shows a very linear drift. The data present a residual standard deviation of 0,047 μV from the linear regression fit for the 1,018 V output. This makes it possible to confirm the performance of the new 1V TPYCEA Josephson voltage standard.

We have carried out a direct comparison between the BIPM and the BNM/LCIE Josephson junction arrays driving them with a single microwave source. The mean difference observed at the 1,018 V level is, 1,2 parts in 10(10) with a total uncertainty. below 1,7 parts in 10(10). By removing uncertainties due to frequency instability, the technique allows closer examination of the other limiting factors in these measurements. In this case we studied the resolution of different detectors.

Subharmonic voltage steps have been observed on the current-voltage (I-V) characteristic of a 1 V Josephson array used at the BNM/LCIE. A direct comparison of the 1,018 V output of this array biased on half-integer steps with that of an array biased on integer steps shows agreement within 3 parts in 1010 with a combined (1 σ) uncertainty of 3 parts in 1010.