Bilateral comparison of 1 V and 10 V standards between the NMISA (South Africa) and the BIPM April to June 2017 (part of the ongoing BIPM key comparison BIPM.EM-K11.a and b)

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As part of the ongoing BIPM key comparison BIPM.EM-K11.a and b, a comparison of the 1.018 V and 10 V voltage reference standards of the BIPM and the National Metrology Institute of South Africa, NMISA (South Africa), was carried out from April to June 2017. Two BIPM Zener diode-based travelling standards (Fluke 732B), BIPM_A (ZA) and BIPM_B (ZB), were transported by freight to NMISA and back to BIPM. In order to keep the Zeners powered during their transportation phase, a voltage stabilizer developed by BIPM was connected in parallel to the internal battery. It consists of a set of two batteries, electrically protected from surcharge-discharge, easy to recharge and is designed to power two transfer standards for ten consecutive days. At NMISA, the reference standard for DC voltage is a Josephson Voltage Standard. The output EMF (Electromotive Force) of each travelling standard was measured by direct comparison with the primary standard.At the BIPM, the travelling standards were calibrated, before and after the measurements at NMISA, with the Josephson Voltage Standard. Results of all measurements were corrected for the dependence of the output voltages of the Zener standards on internal temperature and atmospheric pressure.The final result of the comparison is presented as the difference between the values assigned to DC voltage standards by NMISA, at the level of 1.018 V and 10 V, at NMISA, U NMISA, and those assigned by the BIPM, at the BIPM, U BIPM, at the reference dates of the 19th and 18th of May 2017, respectively. U NMISA − U BIPM = + 0.07 μV; u c = 0.02 μV, at 1.018 V U NMISA − U BIPM = + 0.001 μV; u c = 0.34 μV, at 10 Vwhere u c is the combined standard uncertainty associated with the measured difference, including the uncertainty of the representation of the volt at the BIPM and at NMISA, based on K J-90, and the uncertainty related to the comparison.Main textTo 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 CCEM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).