June 2019
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98 Reads
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20 Citations
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Publications (48)
February 2019
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851 Reads
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170 Citations
On 16 November 2018 a revision of the International System of Units (the SI) was agreed by the General Conference on Weights and Measures. The definitions of the base units were presented in a new format that highlighted the link between each unit and a defined value of an associated constant. The physical concepts underlying the definitions of the kilogram, the ampere, the kelvin and the mole have been changed. The new definition of the kilogram is of particular importance because it eliminated the last definition referring to an artefact. In this way, the new definitions use the rules of nature to create the rules of measurement and tie measurements at the atomic and quantum scales to those at the macroscopic level. The new definitions do not prescribe particular realization methods and hence will allow the development of new and more accurate measurement techniques.
January 2018
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319 Reads
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236 Citations
Sufficient progress towards redefining the International System of Units (SI) in terms of exact values of fundamental constants has been achieved. Exact values of the Planck constant h, elementary charge e, Boltzmann constant k, and Avogadro constant N A from the CODATA 2017 Special Adjustment of the Fundamental Constants are presented here. These values are recommended to the 26th General Conference on Weights and Measures to form the foundation of the revised SI.
October 2017
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595 Reads
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28 Citations
The new definition of the kilogram, which is expected to be adopted by the General Conference on Weights and Measures in 2018, will bring some major changes to mass metrology. The most fundamental change will be the replacement of the present artefact-based definition with a universal definition, enabling in principle any National Metrology Institute (NMI) to realize the kilogram. The principles for the realization and dissemination of the kilogram in the revised SI are described in the mise en pratique of the definition of the kilogram. This paper provides some additional information and explains how traceability can be obtained by NMIs that do not operate a primary experiment to realize the definition of the kilogram.
September 2016
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75 Reads
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22 Citations
In 2014 the Bureau International des Poids et Mesures (BIPM) carried out a calibration campaign using the international prototype of the kilogram (IPK). This is the second part in a series of publications describing the results of that campaign. As reported (Metrologia 52 310–6), following the comparisons between the IPK and its official copies, it was found that the BIPM ‘as-maintained mass unit’ was offset by 35 μg from the mass of the IPK in 2014. We report here the results of an investigation into this offset that has considered all data available from internal BIPM mass comparisons carried out between 1992 and 2014. This has enabled us to model the evolution of the offset in the as-maintained mass unit and to identify some possible reasons why it has developed. We also report how the model has been used to estimate corrections to all 1 kg mass calibration certificates issued by the BIPM during this period.
June 2016
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39 Reads
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7 Citations
This paper reports the latest advances made on the BIPM watt balance experiment. The improved apparatus is now fully assembled. The new, open support structure allows convenient access to all key components of the apparatus. This, together with the alignment mechanism will allow to improve significantly the alignment accuracy. The magnetic circuit was aligned to better than 10 μrad with an uncertainty of 20 μrad. A new interferometer based on space-heterodyning techniques has been integrated.
September 2014
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21 Reads
This paper reports the latest progress made on the BIPM watt balance project. The type A uncertainty of the Planck constant measurements was reduced from 1.4 parts in 106 to about 5 parts in 107. The new magnet was successively fabricated and assembled with an expected high uniformity of the flux density of several parts in 104. Several new components are being introduced into the apparatus which we expect to reduce the type B measurement uncertainty significantly.
March 2014
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40 Reads
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9 Citations
The BIPM has built an experimental setup dedicated to the study of the physical behaviour of a superconducting coil during the dynamic phase of a watt balance experiment. We have compared it with the behaviour of a normal conducting coil. First experimental results are presented and preliminary conclusions are drawn.
January 2014
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13 Reads
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3 Citations
June 2013
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35 Reads
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25 Citations
IEEE Transactions on Instrumentation and Measurement
This paper presents the progress made to improve and develop the Bureau International des Poids et Mesures (BIPM) watt balance during the last two years. A reduction by a factor of five of the type A uncertainty was achieved by refining the velocity measurement. The BIPM simultaneous weighing and moving approach was experimentally compared to a bifilar coil technique. The relative difference to the Planck constant determination between the two approaches is 2 ×10-7 with a type A uncertainty of 3 × 10-7. A vacuum enclosure located in a dedicated laboratory with better thermal and vibrational isolation is ready to receive the present apparatus for further improvement.
Citations (30)
... With knowledge of the molar polarizability, it is possible to realize (or assess) the molar density of gas and, by also measuring its temperature, its pressure [1][2][3][4][5][6][7][8][9][10][11]. By this, FP refractometry provides possibilities to realize these entities in terms of primary standards [12,13]. ...
- Citing Article
- Full-text available
June 2019
... With knowledge of the molar polarizability, it is possible to realize (or assess) the molar density of gas and, by also measuring its temperature, its pressure [1][2][3][4][5][6][7][8][9][10][11]. By this, FP refractometry provides possibilities to realize these entities in terms of primary standards [12,13]. ...
- Citing Article
- Full-text available
February 2019
... Since 1885, the fixed number of entities in one mole has been measured (with uncertainty) through various experiments, materials, and methods in which the mole is quantified by mass, Becker (2001), Mohr et al (2018), Newell et al (2018). The mass of one atom of carbon-12 is fixed. ...
- Citing Article
- Full-text available
January 2018
... Despite the scales have been re-defined later via physical constants (e.g. [49]), the same principle of traceability of mass measurement results to the same/commonly stated reference is used continuously. In turn, it results in a hierarchy of calibrators on the mass scale. ...
- Citing Article
- Full-text available
October 2017
... The mass of the 1 kg stainless steel standard was determined beforehand based on platinum-iridium standards No. 94 and E59 [35], which were calibrated with a standard uncertainty of 3.5 µg in the second phase of the Extraordinary Calibration conducted at the Bureau International des Poids et Mesures (BIPM, France) in 2015 [36,37] and are traceable to the International Prototype of the Kilogram. ...
- Citing Article
- Full-text available
September 2016
... This significantly increases the heating of the system NPL, UK, is now working on a single-mode two-phase Kibble balance(Robinson 2012; Stock 2012) NIST, USA The initial results from NIST's Kibble balances were published in 1989 To date, they have developed four full-fledged Kibble balances The latest Kibble balance called NIST-4 uses Sm 2 Co 17 as a permanent magnet and low-carbon steel as a yoke It works in a vacuum, with a relative uncertainty of 1.3 Â 10 À8 , published in 2017 (Haddad et al. 2017) NIST has also developed a Lego Kibbe balance for 10 g and achieved uncertainty of the order of 10 À2 (Chao et al. 2015) One of the recent activities taken up by NIST is developing a tabletop Kibble balance called "KIBB-g1 Kibble balance" for mass up to 10 g with targeted uncertainty of 10 À6 (Chao et al. 2020; Chao et al. 2019) NRC, Canada The Kibble balance project started in 2009When the MARK-II of NPL, UK, was sent to NRC Canada NRC successfully identified and corrected a systematic error relating to the effect of the test mass's weight on the equipment's construction(Wood et al. 2017) The relative uncertainty reported in 2017 is 9.1 Â 10 À9 , which is the smallest in the world(Wood et al. 2017) BIPM, FranceThe Kibble balance project started in 2005 It operates in one-mode two-measurement scheme technique It operates in a vacuum and uses a bifilar coil The relative uncertainty of 1 kg Pt/Ir artifact published by BIPM in 2020 is 49 μg. Details of the BIPM Kibble balance can be read in(Fang et al. 2016(Fang et al. , 2020 KRISS, KoreaThe Kibble balance project started in 2012 Out of four different permanent magnet configurations widely used by different NMIs, KRISS uses closed cylindrical permanent magnet system(Kim et al. 2014(Kim et al. , 2017Choi et al. 2016) ...
- Citing Conference Paper
June 2016
... При разработке киббл-весов требуется участие предприятий (по-видимому, Минпромторга), специализирующихся в разработке прецизионных механических систем для высокоточного перемещения катушки ФУНДАМЕНТАЛЬНАЯ МЕТРОЛОГИЯ в магнитном поле, разработка магнита -постоянного или сверхпроводящего (см., например, [21]), создающего поле высокой степени однородности на пути движения катушки. Системы на основе эффекта Джозефсона и квантового эффекта Холла, прослеживаемые к СИ, для измерений с киббл-весами могут быть созданы во ВНИИМ им. ...
- Citing Article
- Publisher preview available
March 2014
... Furthermore, superconducting wire will behave differently in weighting phase and velocity phase in watt balance or mutual inductance phase in joule balance because of the diamagnetic (Meissner effect) of superconducting wire. In [18], a similar phenomenon has been also observed. Thus, Meissner effect should be investigated further when the superconducting coil is used in both watt balance and joule balance. ...
- Citing Conference Paper
July 2012
CPEM Digest (Conference on Precision Electromagnetic Measurements)
... In reference to the consistency argument, one must distinguish the physical quantity from a unit used to measure it [53]. In this context, the 'ultimate test of the consistency of physics is made by the measurement of dimensionless constants' [54]. However, all base quantities are dimensional and 'it is in our best interest to choose some dimensional fundamental constants as the basis of our SI by fixing their numerical values because to test the consistency of physics precisely we need units which are intrinsically stable and universally accessible' [54]. ...
- Citing Article
- Publisher preview available
January 2014
... The revised SI started to come into effect on May 20th, 2019, in which, for example, the kilogram is redefined by fixing the numerical value of the Planck constant [2]. The Kibble balance [3][4][5][6][7][8][9][10] and x-ray crystal density (XRCD) methods [11] are the two mainstream methods adopted by the majority of national metrology institutes (NMIs) across the globe to establish the relationship between the kilogram and the Planck constant h. The Kibble balance compares electrical power with mechanical power through two measurement phases: a weighing phase and a moving phase [3]. ...
- Citing Article
June 2013
IEEE Transactions on Instrumentation and Measurement