World Metrology Day Research Articles

METROLOGY WITHOUT BORDERS 2023

The content of the International Metrology Forum dedicated to the next World Metrology Day and the accompanying exhibition is briefly described. The main topics of the business program were the improvement of the level of metrological measurements, the development of standardization systems and product certification. The exhibition demonstrated modern metrological measuring instruments and product certification produced by leading enterprises of the industry.

Metrology in the Digital Era

Abstract The World Metrology Day Team has confirmed that the theme for World Metrology Day 2022 is “Metrology in the Digital Era”.

News from the BIPM laboratories—2020

In order to fulfil its mission to ensure and promote the global comparability of measurements, the BIPM operates laboratories in the fields of physical metrology, time, ionizing radiation and chemistry. These laboratories act as centres for scientific and technical collaboration between member states providing capabilities for international measurement comparisons on a shared cost basis. They coordinate international comparisons of national measurement standards agreed to be of the highest priority, and they establish and maintain appropriate reference standards for use as the basis of key international comparisons at the highest level and provide selected calibrations from them. The BIPM sustained all of its key activities throughout the periods of confinement resulting from the global pandemic in 2020 including: the publication of Circular T each month, the annual World Metrology Day celebrations and the launch of the new key comparison database (KCDB 2.0). Several activities were brought forward in the work programme including the automation of data handling in the International Reference System (SIR) for radionuclide metrology and on-line technical exchanges and capacity building initiatives. The BIPM has also worked to understand how best to support the National Metrology Institutes (NMIs) as a ‘new normal’ emerges. As a first step, the NMI ‘COVID action’ repository was implemented and two pilot studies were launched by the CCQM on the measurement of SARS-CoV-2 and SARS-CoV-2 antibodies. New ways have been developed to support the International Committee for Weights and Measures (CIPM) consultative committees on-line. For example, during 2020 a total of 70 video meetings were held for the CCQM, with similar trends for other CCs. In the following sections, we provide highlights of the work the laboratories have undertaken during 2020.

Journey of Kilogram from Physical Constant to Universal Physical Constant (h) via Artefact: A Brief Review

The redefinition of mass adopted in November 2018 and implemented from 20 May 2019, i.e. World Metrology Day, eliminated the artefact-based approach dependent upon the International Prototype of the Kilogram (IPK), in favour of realizing the kilogram in terms of the Planck constant h by fixing its value as 6.62607015 × 10−34 J s. In this paper, the authors present a general outline of the circumstances and related developments that paved the way for the new definition that replaced the IPK after a period of 130 years since it was formally sanctioned to define the kilogram in 1889. The new definition opens up fascinating developments in mass metrology which include different realization techniques, realizing the unit at values other than 1 kg, numerous sources for traceability can be envisaged etc.

Basic Metrology for 2020.

2019 was a big year for metrology. The international system of units was revised on World Metrology Day, May 20 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup> , that year [1]. What will 2020 bring? In this article we discuss five promising advances that we have on a watchlist for 2020. First, we describe the measurement of volume and gas pressure using electromagnetic waves. These measurements rely on the fixed value of the speed of light in vacuum c <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> . We then pivot to the Planck constant h. SI traceable measurements of mass and force can be obtained from h. Interesting developments are coming in mass metrology since the definition changed from the mass of the international prototype of the kilogram to the value of the Planck constant. Adding the elementary charge e to h gives access to resistance and impedance measurements via the quantum Hall effect. This has been a very interesting field for some time, since the discovery of graphene in 2004. The last section explains how the noise across a resistor can be used to measure thermodynamic temperature. As will be shown, the temperature can be linked to the quotient of the Boltzmann constant k <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B</sub> and the Planck constant.

Measurements for Global Trade

Abstract May 20 is World Metrology Day, commemorating the anniversary of the signing of the Metre Convention in 1875. This treaty provides the basis for a worldwide coherent measurement system that underpins scientific discovery and innovation, industrial manufacturing and international trade, as well as the improvement of the quality of life and the protection of the global environment.

Redefined SI Units and Their Implications

Metrology plays the key role as the engine of industrial revolution and growth of any country. It promotes global competence and confidence. With the advent of better quality products through metrological advancement, our industries can compete internationally and to overcome trade barriers/constraints and finally to achieve exports targets. This translates into growth of industries through rapid industrialization, economic growth and societal upliftment. The metrology requires continued and sustained efforts to cater the stakeholders’ demands for advancements in measurement technologies, standards and measurement techniques for more and more precise, reliable, reproducible and accurate measurements with improved measurement uncertainties. In this context, the recent revolutionary changes in redefinition of SI units based on fundamental constants were unanimously voted for adoption by world community during November 16, 2018, at Versailles, France, and implemented world over from May 20, 2019—the World Metrology Day. Therefore, it was considered appropriate to compile a brief status report and apprise the readers about these historical events. The present paper touches glimpse of some of these activities and describes the implications of these changes in our daily life.

Editorial

Dear reader, This year is full of events, anniversaries and milestones. Not only does HTHP celebrate its 50th anniversary, but also the Periodic Table of Elements has its 150th birthday. In 1869 Dimitri Mendeleyev and Lothar Meyer discovered and presented this table. In order to commemorate this breakthrough, UNESCO has declared 2019 as the “International Year of the Periodic Table of Chemical Elements”. In addition, another important event takes place in May 2019. The Conférence Générale des Poids et Mesures will put into effect the new SI system of units on May 20, 2019, the “World Metrology Day”. The introduction of this new system marks a change in paradigm: the new system relates all units to fundamental constants, rather than artefacts. The most prominent example is the definition of the new kilogram, which is now linked to the Planck constant, h. Of course, all of this has an impact on thermophysical property measurements. Therefore, we have asked Dr. Matthieu Thomas from the Laboratoire National de Métrologie et d’Essais (LNE), France, to explain shortly how this new definition works and how it was implemented. Dr. Thomas is involved in the Kibble balance project of LNE, a key element in the realisation of the new kilogram. You find his article in this issue of HTHP. The editors thank Dr. Thomas for his cooperation; we hope you will enjoy reading his article as well as the rest of this issue.

Highlights of Physics

Highlights of Physics

Why have international metrology Heads called the New SI “fundamentally better” and could it be even better?

In November 2018, the 26th General Conference on Weights and Measures (CGPM) adopted the changes to the In­ternational System of Units (SI), which got the conventional name “the New SI”. These changes came into force on May 20, 2019, on World Metrology Day. International metrology Heads have called it “fundamentally better”. This article is devoted to discussing such an assessment.The article shows that the whole history of metrology development is the search for optimal physical quantities and units of measurement, as well as such stable phenomena and objects of nature that could be the basis for the reproduction of these units and creation of the measurement standards.It took almost 150 years of searching and taking certain steps before the ideas of scientists were put into practice in the New SI — quantum SI. The base of this system is fundamental physical constants (FPCs) — standards of nature, micro objects have become the carriers of the sizes of units, and methods of their connection with the macrocosm — quantum phenomena and effects.The article shows that in all measurement fields where quantum methods and definitions of units were implemented through FPCs, there was a significant — by 2–3 orders of magnitude — increase in the accuracy and reliability of the realization of units.The 26th CGPM made the final decision on the new definitions of the base units. The article contains an excerpt from Resolution 1 of the 26th CGPM 2018, as well as its Annexes.An analysis of new definitions of the base units is given. It is shown that the new definitions of second, metre and candela are relevant to their definitions in the previous version of SI and differ only in wording. The definition of kilogram is fundamentally new and is based on the fixed value of Planck’s constant. Significantly new definition is also obtained by the unit of electric current. This means the recognition of quantum methods in electrical measurements, which have in practice confirmed their outstanding metrological capabilities. Definition of kelvin through the Boltzmann constant, experts believe, will contribute to the development of primary thermometry and thermodynamics as a whole.The article also highlights the fundamental advantages of the New SI and outlines the prospective tasks of metrology.

Guest editorial: The revised international system of units (SI)

A major revision to the SI was unanimously approved by delegates to the General Conference on Weights and Measures (CGPM) on November 16, 2018, to take effect on the following World Metrology Day: May 20, 2019. The revised SI has arrived but was a long time in coming.

The units for mass, voltage, resistance, and electrical current in the SI

On May 20, World Metrology Day 2019, the international system of units (SI) underwent a momentous change. The philosophy behind the unit system was altered by replacing the former definitions that rely on seven base units with seven defining physical constants to be used as a basis for realizations of the units. Supported by results from decades of precise measurements, four new definitions and four fixed numerical values were assigned. In this article, we discuss the significance of this change for the unit of mass the kilogram and the electrical units ampere, volt, and ohm.

The end of artefacts

Bill Phillips celebrates a beautiful reformation of the metric system, by which scientists measure the physical world, coming into effect on World Metrology Day, 20 May 2019.

The Design and Development of a Tabletop Kibble Balance at NIST

On November 16, 2018, the 26th General Conference on Weights and Measures voted unanimously to revise the International System of Units from a system built on seven base units to one built on seven defining constants and will officially become effective on May 20, 2019, or World Metrology Day. More specifically, the unit of mass, the kilogram, will be realized via a fixed value of the Planck constant $h$ and a Kibble balance (KB) serves as one method of achieving this. Over the past few decades, national metrology institutes around the world have developed KBs, the majority aimed at realizing the unit of mass at the 1-kg level with uncertainties on the order of a few parts in $10^{8}$ . However, upon fixing the Planck constant, mass can be directly realized at any level, deeming the kilogram only a historically unique benchmark. At the National Institute of Standards and Technology, a tabletop-sized Kibble balance (KIBB-g1) designed to operate at the gram-level range with uncertainties on the order of a few parts in $10^{6}$ is currently under development.

Silicon spheres for the future realization of the kilogram and the mole

New definitions of the units for amount of substance – the mole – and for mass – the kilogram – will presumably come into force on the World Metrology Day 2019. In the revised SI, the mole will be defined by a fixed value of the Avogadro constant and the kilogram by a fixed value of the Planck constant. The X-ray-crystal-density (XRCD) method has been used for the determination of these fundamental constants by counting the number of atoms in 28Si-enriched spheres. Thus, silicon spheres will – after the redefinition – be used to realize the definitions of the mole and the kilogram. This is possible by SI-traceable measurements of lattice parameter, isotopic composition, volume, and surface properties, yielding a relative standard uncertainty below 2⋅10−8. Whereas this high accuracy is only reached with isotopically enriched silicon, it is also planned to use natural silicon spheres on a slightly lower level of accuracy. The future definitions will allow also new realization methods using silicon, in particular for small mass values. De nouvelles définitions des unités de quantité de matière (la mole) et de masse (le kilogramme) entreront vraisemblablement en vigueur lors de la Journée mondiale de la métrologie de 2019. Dans le Système international révisé, la mole sera définie par une valeur fixe de la constante d'Avogadro et le kilogramme par une valeur fixe de la constante de Planck. La méthode de mesure de densité par cristallographie aux rayons X (XRCD – X-ray crystal density) a été utilisée pour déterminer ces constantes fondamentales par comptage du nombre d'atomes dans des sphères de silicium enrichi en silicium 28. Après la redéfinition, les définitions de la mole et du kilogramme seront ainsi réalisées à l'aide de sphères de silicium. Ceci est possible en effectuant des mesures des paramètres de réseau, de la composition isotopique, du volume et des propriétés de surface traçables au SI. On obtient alors une incertitude-type relative inférieure à 2⋅10−8. Alors qu'une telle précision ne peut être atteinte qu'avec du silicium enrichi isotopiquement, il est également prévu d'utiliser des sphères de silicium naturel avec un niveau de précision légèrement inférieur. Les futures définitions permettront également de mettre en oeuvre de nouvelles méthodes de réalisation faisant appel au silicium, en particulier pour de faibles valeurs de masses.

The Boltzmann Constant for the Definition and Realization of the Kelvin

AbstractIn November 2018, the four base units, kilogram, ampere, kelvin, and mole, of the International System of Units (SI) are redefined in terms of fundamental physical constants. The redefinition comes into force on World Metrology Day, 20 May 2019. The kelvin, the base unit of thermodynamic temperature, from then is to be founded on a fixed numerical value of the Boltzmann constant. Herein, the change in the definition of the kelvin and the consequences for practical temperature measurement are explained. The primary thermometry methods applied to determine the numerical value of the Boltzmann constant for the redefinition are reviewed. The prospects for the future application of these methods are outlined.

New definitions for kilogram and mole

It doesn’t happen too often, but after a vote that took place Nov. 16 near Paris, science textbooks really will have to be rewritten. At the Congress Chamber in the Palace of Versailles, metrologists from over 50 countries voted to redefine four fundamental units of measure in the International System of Units (SI): the ampere, kelvin, kilogram, and mole. These units will join the meter, candela, and second in being defined not in reference to physical artifacts, but in reference to fundamental physical constants. Scientists say redefining these units to be based on physical constants will make measurements more accurate and stable. The redefined units, which will take effect May 20, 2019, World Metrology Day, are the result of years of work, discussion, and competition to measure the fundamental constants of nature to an incredible degree of certainty. Although most people will not notice the change, the increased precision will

The European Metrology Programme for Innovation and Research project: Implementing the new kelvin 2 (InK2)

The International System of Units (SI) is to be redefined with implementation set to be on World Metrology Day (20th May 2019). Under the auspices of the Consultative Committee of Thermometry (CCT) the world thermometry community has been working together to ensure a smooth and effective redefinition of the kelvin. A large part of that activity has been coordinated through the European Metrology Programme for Innovation and Research: “Implementing the new kelvin” projects. This paper describes the InK2 project contribution.

Quantity Calculus, Fundamental Constants, and SI Units.

A revised International System of Units (SI) is expected to be established by the 26th General Conference on Weights and Measures when it convenes in November 2018 and to be put into practice starting on 20 May 2019, World Metrology Day. In consequence, the article published in this journal in 2011, "The Current SI Seen from the Perspective of the Proposed New SI," is updated in this paper, which provides an opportunity to again demonstrate the usefulness of the quantity calculus in dealing with quantities and units. The quantity calculus and the seven defining constants of the current and revised SI are reviewed, and expressions for the seven current and revised SI base units are given. Relationships between the magnitudes of revised and current SI units and expressions for the numerical values of current SI defining constants expressed in revised SI units are also obtained using the quantity calculus.

World Metrology Day, 20 May 2018

Abstract The theme for World Metrology Day 2018 is Constant evolution of the International System of Units. This theme was chosen because in November 2018, the General Conference on Weights and Measures is expected to agree one of the largest changes to the International System of Units (the SI) since its inception. The proposed changes are based on the results of research into new measurement methods that have used quantum phenomena as the basis for standards that are fundamental. The SI will be based on a set of definitions each linked to the laws of physics and have the advantage of being able to embrace further improvements in measurement science and technology to meet the needs of future users for many years to come.