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The value of the Planck constant h was determined in 2014 by means of the LNE watt balance experiment. The relative standard uncertainty was 31 parts in 10 8 . This first determination was performed in air with a 500 g mass standard made from XSH Alacrite. The main uncertainty components in air associated with the mass involve the calibration, the mass stability, the buoyancy correction and the magnetic interaction correction. The combined relative uncertainty due to the mass is 7.2 parts in 10 8 . The use in 2016 of a mass standard made from platinum iridium alloy significantly reduces the component of uncertainty arising from the mass standard for a Planck constant measurement either in air or under vacuum. The relative uncertainty due to this contribution is estimated to be about 3 parts in 10 8 in air and one part in 10 8 under vacuum. The future system for the dissemination of the mass unit using the LNE watt balance will be based on a primary realization with three 500 g mass standards made from platinum-iridium alloy, pure iridium and Udimet 720 respectively, coupled with a pool of kilograms made from different materials. Pure iridium and Udimet 720 are new materials to make reference mass standards proposed by CNAM and LNE respectively and have never been used by any NMI for manufacturing mass standards until now. Some new results concerning their surface behavior are given.
In order to demonstrate the equivalence in calibration of mass standards among National Metrology Institutes (NMIs) of EURAMET this key comparison (KC) on 1 kg stainless steel mass standards has been carried out under the auspices of EURAMET. The comparison was undertaken with reference to the International Prototype Kilogram (IPK) as the definition of the unit of mass. The overall result shows good consistency among the participants. 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 (CIPM MRA).
Main text The aim of this project was to compare results and method calibration of a 1000 L proving tank. Both gravimetric and volumetric method were used by several laboratories. This comparison allowed the participating laboratories to test the agreement of their results and uncertainties despite the different used equipment and different calibration methods. Another aim of the project was to determine long-term stability of the proving tank, since this tank was already used as a transfer standard in the intercomparison EURAMET 1157 in 2013. 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).
A measurement apparatus that uses an electrostatic force generator is being developed at LNE, toward the realization of small masses and forces in the International System of Units (SI). Two of the main parts are designed, i.e. a parallelogram balance mechanism, and two capacitance actuators. The balance mechanism is fully monolithic as well as the two adjustment systems of the electrostatic actuators. Special attention has been paid to the overall symmetry of the system and to cost efficiency.
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