Report on the APMP key comparison of hydrometer calibrations APMP.M.D-K4

Abstract

Main text This report describes the APMP key comparison on the hydrometer calibrations, APMP.M.D-K4. This comparison is an APMP regional key comparison of CIPM key comparison CCM.D-K4. Three hydrometers in the density range from 640 kg m-3 and 1 320 kg m-3 were used as travelling standards. Each hydrometer has a nominal density range of 20 kg m-3 with a scale division of 0.2 kg m-3. Eleven laboratories participated in this comparison. All laboratories except NMISA are from APMP. NMISA from AFRIMETS is also an APMP associate member. Each participant reported the results of hydrometer calibration using Cuckow's method. The reference temperature for the hydrometer calibration was 20 °C and the surface tension of the reference liquid was given in the protocol for this comparison. KRISS and NMIJ acted as pilot and coordinating laboratories. The measurement was performed between July 2008 and April 2010. The report from participants was completed in February 2012. The results of this comparison were linked to CCM.D-K4 through the results of KRISS, NMIJ, and NMIA. NPLI, SNSU-BSN, and NMISA withdrew their results while preparing Draft A report of this comparison. The results of two participants, MSL and NIM, were inconsistent. However, because it has been more than 10 years since the measurements were completed, it is difficult to determine that the results reflect the current measurement capabilities of the two participants. 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 https://www.bipm.org/kcdb/. The final report has been peer-reviewed and approved for publication by the CCM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).