Fundamental constants link seemingly different fields of physics and seemingly different quantities and measurement units. Consequently, they are of the utmost interest in metrology and it has been planned to redefine the kilogram by fixing the numerical value of the Planck constant. This paper summarises the methods to measure the ratio between the Planck constant and a mass and reviews the determination of the Avogadro constant by counting the atoms in a silicon crystal highly enriched by the Si-28 isotope

This report describes the results of a key comparison of hydraulic high-pressure standards at 16 national metrology institutes (NMIs: NMIJ/AIST, NPLI, CSIR-NML, NIS, KRISS, SCL, SPRING, NMIA, VMI, NML-SIRIM, KIM-LIPI, NSCL, PTB, NIMT, CMS/ITRI and NIM) was carried out during the period October 2002 to July 2004 within the framework of the Asia-Pacific Metrology Programme (APMP) in order to determine their degrees of equivalence at pressures in the range 10 MPa to 100 MPa for gauge mode. The pilot institute was the National Metrology Institute of Japan (NMIJ)/AIST. All participating institutes generally used hydraulic pressure balances as their pressure standards. High-precision pressure transducers were used as transfer standards. The sensing element of the transducer was a precision quartz crystal resonator. To ensure the reliability of the transfer standard, two pressure transducers were used on a transfer standard unit. Three nominally identical transfer packages were circulated independently to reduce the time required for the measurements. During this comparison, the three transfer standards were calibrated simultaneously at the pilot institute 11 times in total. From the calibration results, the behaviours of the transfer standards during the comparison period were well characterized and it was presented that the capabilities of the transfer standards to achieve this key comparison were sufficient. The degrees of equivalence of each national measurement standard were expressed quantitatively by two terms, deviations from the key comparison reference values and pair-wise differences of their deviations. The degrees of equivalence in this comparison were also transferred to the corresponding CCM key comparison, CCM.M.P-K7. The hydraulic pressure standards in the range 10 MPa to 100 MPa for gauge mode of the 16 participating NMIs were found to be equivalent within their claimed uncertainties.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 CCM, according to the provisions of the Mutual Recognition Arrangement (MRA).

This report summarizes the results of a regional key comparison (APMP-IC-2-97) under the aegis of the Asia Pacific Metrology Program (APMP) for pressure measurements in gas media and in gauge mode from 0.4 MPa to 4.0 MPa. The transfer standard was a pressure-balance with a piston-cylinder assembly with nominal effective area 8.4 mm2 (V-407) and was supplied by the National Metrology Institute of Japan [NMIJ]. Ten standard laboratories from the APMP region with one specially invited laboratory from the EUROMET region, namely Physikalisch-Technische Bundesanstalt (PTB), Germany, participated in this comparison. The comparison started in October 1998 and was completed in May 2001. The pilot laboratory prepared the calibration procedure [1] as per the guidelines of APMP and the International Bureau of Weights and Measures (BIPM) [2–4]. Detailed instructions for performing this key comparison were provided in the calibration protocol [1] and the required data were described in: (1) Annex 3 – characteristics of the laboratory standards, (2) Annex 4 – the effective area (A′p′/mm2) (the prime indicates values based on measured quantities) at 23°C of the travelling standard as a function of nominal pressure (p′/MPa) (five cycles both increasing and decreasing pressures at ten pre-determined pressure points) and (3) Annex 5 – the average effective area at 23°C (A′p′/mm2) obtained for each pressure p′/MPa with all uncertainty statements. The pilot laboratory processed the information and the data provided by the participants for these three annexes, starting with the information about the standards as provided in Annex 3. Based on this information, the participating laboratories are classified into two categories: (I) laboratories that are maintaining primary standards, and (II) laboratories that are maintaining standards loosely classified as secondary standards with a clear traceability as per norm of the BIPM. It is observed that out of these eleven laboratories, six laboratories have primary standards [Category (I)], the remaining five laboratories are placed in Category (II).The obtained data were compiled and processed under the same program as per the Consultative Committee for Mass and Related Quantities (CCM)/BIPM guidelines. From the data of Category (I), we evaluated the APMP reference value as a function of p′/MPa. Then, we estimated the relative difference of the A′p′ values with reference to the APMP reference value for all participating laboratories and we observed that they agree well within their expanded uncertainties. We further estimated the effective area at null pressure and at 23°C (A′0/mm2) and the pressure distortion coefficient (λ′/MPa-1) of the transfer standard for all the participating laboratories. We then estimated the relative deviation of the A′0/mm2 from the reference value for all eleven laboratories and compared this with their estimated expanded uncertainties. The result is once again extremely encouraging and all these eleven laboratories ar...

This report presents the results of a key comparison of liquid volume measurement conducted between ten participating institutes during the period July 2006 to August 2008 within the framework of the Asia Pacifica Metrology Program (APMP). The transfer standards comprised one 20 L volume measure and two 100 mL glass pycnometers. These transfer standards had been used in a similar CIPM key comparison CCM.FF-K4 in 2003 to 2005. The pilot institute was the National Measurement Institute, Australia (NMIA), which together with CENAM act as link laboratories to the CCM.FF-K4 comparison.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 CCM, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).