The Republic of Azerbaijan acceded to the Metre Convention and became a Member State of the BIPM on 17 August 2026, strengthening its participation in the international measurement system.

Prior to this, Azerbaijan participated in BIPM activities as an Associate.

Full membership will allow Azerbaijan to take an active role in the governance of the BIPM, through voting and representation at the General Conference on Weights and Measures (CGPM), and to contribute to the scientific and technical work coordinated through the BIPM.

Azerbaijan’s engagement with the BIPM

After becoming an Associate on 1 January 2015, Azerbaijan Institute of Metrology (AzMI), joined the CIPM Mutual Recognition Arrangement (CIPM MRA) on 28 January.

Since 2015, AzMI has actively contributed to the realization of the CIPM MRA by:

• building a steadily growing portfolio of Calibration and Measurement Capabilities (CMCs). As of today, AzMI has declared 35 CMCs in the CIPM MRA database (KCDB).
• active engagement in international comparisons, evidenced by participation in 11 key and supplementary comparisons.

AzMI participates in the CIPM MRA as a member of the Euro-Asian Cooperation of National Metrological Institutions (COOMET), the Regional Metrology Organization recognized by the CIPM.

Learn more about Azerbaijan’s participation

The Republic of Albania acceded to the Metre Convention and became a Member State of the BIPM on 4 June 2026, strengthening its participation in the international measurement system.

Prior to this, Albania participated in BIPM activities as an Associate.

Full membership will allow Albania to take an active role in the governance of the BIPM, through voting and representation at the General Conference on Weights and Measures (CGPM), and to contribute to the scientific and technical work coordinated through the BIPM.

Albania’s engagement with the BIPM

After becoming an Associate on 10 September 2007, the General Directorate of Metrology and Calibration of Albania (DPM), joined the CIPM Mutual Recognition Arrangement (CIPM MRA) on 14 November.

Since 2007, DPM has actively contributed to the realization of the CIPM MRA by:

• building a steadily growing, portfolio of Calibration and Measurement Capabilities (CMCs). As of today, DPM has declared 10 CMCs in the CIPM MRA database (KCDB).
• active engagement in international comparisons, evidenced by participation in 11 key and supplementary comparisons.

Albania is a member of the Regional Metrology Organization: European Association of National Metrology Institutes (EURAMET).

Learn more about Albania’s participation

Regional metrology experts from around the world exchanged practical experience and lessons learned during the 2026 Summer School for Regional Metrology Organization (RMO) Technical Committee and Working Group (TC/WG) Chairs, helping strengthen the consistent implementation of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Held at the BIPM Headquarters in Sèvres from 30 June to 2 July 2026, the Summer School brought together 27 current, newly appointed and prospective TC/WG Chairs and Vice-Chairs representing all RMOs.

Caption: Participants in the 2026 Summer School for RMO TC/WG Chairs.

Sharing experience across the RMOs

One of the defining features of this year's programme was the extensive exchange of experience between the RMOs. The discussions helped participants identify common approaches while learning from differences in regional implementation of the CIPM MRA.

Participants shared practical approaches on topics including:

• Calibration and Measurement Capability (CMC) reviews and reviewer training;
• comparison coordination;
• Technical Committee and Working Group management;
• mentoring and support for countries and economies with emerging metrology systems;
• maintaining reviewer continuity and institutional knowledge.

Continuing collaboration

Finally, the discussions contributed to the development of a practical good-practice guide for RMO TC/WG Chairs intended to support the day-to-day operation of TC/WGs, promote greater consistency across RMOs and continue evolving as experience and good practice develop.

The Republic of Peru acceded to the Metre Convention and became a Member State of the BIPM on 11 August 2026, strengthening its participation in the international measurement system.

Prior to this, Peru participated in BIPM activities as an Associate.

Full membership will allow Peru to take an active role in the governance of the BIPM, through voting and representation at the General Conference on Weights and Measures (CGPM), and to contribute to the scientific and technical work coordinated through the BIPM.

Peru's engagement with the BIPM

After becoming an Associate on 28 May 2009, the National Institute for Quality of Peru (INACAL), joined the CIPM Mutual Recognition Arrangement (CIPM MRA) on 17 November.

Since 2009, INACAL has actively contributed to the realization of the CIPM MRA by:

• building a portfolio of Calibration and Measurement Capabilities (CMCs). As of today, INACAL has declared 1492 CMCs in the CIPM MRA database (KCDB).
• active engagement in international comparisons, evidenced by participation in 111 key and supplementary comparisons.

INACAL participates in the CIPM MRA as a member of the Inter-American Metrology System (SIM), subregion ANDIMET, the Regional Metrology Organization recognized by the CIPM.

Learn more about Peru’s participation

As metrology continues its digital transformation, ensuring that the International System of Units (SI) can be understood and used consistently by both people and machines has become increasingly important.

Held on 20 July 2026, a webinar Introducing the SI Reference Point (SIRP) explored how the SI Reference Point provides a machine-actionable knowledge model of the SI Brochure, supporting the consistent use of the SI in digital applications, data exchange and emerging digital metrology services.

Speakers include Dr Cornelia Denz (PTB), Dr Frédéric Meynadier (BIPM), Dr Jean-Laurent Hippolyte (NPL), and moderation and Q&A hosted by Cristhian Paredes (BIPM)

Learn more about Version 1.0.0 of the SI Reference Point

The SI Reference Point is a digital representation of the SI Brochure, which defines the International System of Units (SI), the world’s only internationally agreed system of units. By making core SI reference information available in machine-actionable-format, the SI Reference Point helps ensure that the SI can be used consistently in digital applications and data exchange.

Supporting digital metrology

The first stable release of the SI Reference Point marks an important milestone in the digital transformation of the international metrology system. It provides a common digital reference for representing SI units in a machine-actionable-format.

The SI Reference Point provides a machine-actionable representation of the SI units that can be accessed and reused across digital environments. This helps support:

• the interoperability and reuse of measurement information;
• digital metrological traceability;
• the harmonization of digital calibration certificates and digital reference material certificates;
• consistent communication between measurement devices and sensor networks;
• anchoring other systems for digital representation of units of measurement.

The SI Reference Point was developed by an international group of experts working through the CIPM Forum on Metrology and Digitalization (FORUM-MD) and its associated working groups.

As metrology continues its digital transformation, ensuring that the International System of Units (SI) can be understood and used consistently by both people and machines has become increasingly important.

Held on 20 July 2026, a webinar Introducing the SI Reference Point (SIRP) explored how the SI Reference Point provides a machine-actionable knowledge model of the SI Brochure, supporting the consistent use of the SI in digital applications, data exchange and emerging digital metrology services.

Speakers include Dr Cornelia Denz (PTB), Dr Frédéric Meynadier (BIPM), Dr Jean-Laurent Hippolyte (NPL), and moderation and Q&A hosted by Cristhian Paredes (BIPM)

Learn more about Version 1.0.0 of the SI Reference Point

The SI Reference Point is a digital representation of the SI Brochure, which defines the International System of Units (SI), the world’s only internationally agreed system of units. By making core SI reference information available in machine-actionable-format, the SI Reference Point helps ensure that the SI can be used consistently in digital applications and data exchange.

Supporting digital metrology

The first stable release of the SI Reference Point marks an important milestone in the digital transformation of the international metrology system. It provides a common digital reference for representing SI units in a machine-actionable-format.

The SI Reference Point provides a machine-actionable representation of the SI units that can be accessed and reused across digital environments. This helps support:

• the interoperability and reuse of measurement information;
• digital metrological traceability;
• the harmonization of digital calibration certificates and digital reference material certificates;
• consistent communication between measurement devices and sensor networks;
• anchoring other systems for digital representation of units of measurement.

The SI Reference Point was developed by an international group of experts working through the CIPM Forum on Metrology and Digitalization (FORUM-MD) and its associated working groups.

The Bureau International des Poids et Mesures (BIPM) and IOP Publishing (IOPP) will convert Metrologia, the leading international journal in pure and applied metrology, to a fully open access (OA) publishing model.

The move reflects the growing global demand for open science and underscores both BIPM’s and IOPP’s commitment to making universal access to research a reality. It also aligns with funder mandates that require publicly funded research to be published in OA journals.

From 1 January 2026, all articles published in Metrologia will be freely accessible to readers worldwide, removing barriers to knowledge and significantly enhancing the visibility and impact of the journal’s content.

IOPP, which has co-published Metrologia with the BIPM since 2003, has successfully supported similar transitions to fully OA for the American Astronomical Society, the International Atomic Energy Agency, and the Japan Society of Applied Physics.

“Open access is a natural evolution for Metrologia, ensuring that the journal continues to serve the global metrology community while supporting the principles of transparency, accessibility, and equity in science,” says Dr Martin Milton, Director of the BIPM.

“We’re proud to support BIPM in making Metrologia more accessible to researchers and readers around the world. This transition reflects our shared commitment to open science and to supporting our publishing partners through sustainable and inclusive open access models,” adds Violeta Ribarska, Head of Partner Publishing and Engagement at IOP Publishing.

To support the transition, any articles submitted after 18 August 2025 will be processed as open access submissions. Metrologia will be included in IOPP’s transformative agreements, allowing authors affiliated with participating institutions to publish OA without incurring direct costs.

For more information visit: https://iopscience.iop.org/journal/0026-1394

On 27 July 2026, the Director of the Dominican Republic’s National Metrology Institute (NMI) signed the CIPM Mutual Recognition Arrangement (CIPM MRA).

As a signatory to the CIPM MRA, the Institute is now able to participate in international scientific comparisons, develop Calibration and Measurement Capabilities (CMCs), and publish them in the CIPM MRA database (the KCDB).

The Dominican Republic participates in the CIPM MRA through its National Metrology Institute (NMI), Instituto Dominicano para la Calidad (INDOCAL), which is a member of the Inter-American Metrology System (SIM), the Regional Metrology Organization (RMO) recognized by the CIPM.

Learn more about the CIPM Mutual Recognition Arrangement (CIPM MRA)

Together, Member State status and participation in the CIPM MRA enable the Dominican Republic to contribute fully to, and benefit from, the international measurement system.

Published 30 July 2026

Published on 30 July 2026

More than 200 participants gained new insights into how quality management systems (QMS) are reviewed across the CIPM Mutual Recognition Arrangement (CIPM MRA) during a BIPM Capacity Building and Knowledge Transfer (CBKT) Technical Exchange held on 17 June 2026.

The session introduced QMS as a new topic within the CBKT Technical Exchange programme and provided an opportunity to better understand how confidence is established and maintained across the CIPM MRA framework.

Why this matters

Quality management systems are a core element of the CIPM MRA. They help ensure that Calibration and Measurement Capabilities (CMCs) are supported by robust technical and quality processes, providing confidence in the international recognition of measurement results.

While review processes are well established, these types of technical exchanges provide further opportunities for quality system specialists, technical committee members, and representatives from National Metrology Institutes (NMIs) and Designated Institutes (DIs) to explore and compare the differing approaches applied by Regional Metrology Organizations (RMOs) around the world. As a result, these sessions also help participants better understand how confidence is established and maintained across the international metrology system in general.

Sharing regional approaches

Caption: Speakers contributing to the CBKT Technical Exchange on quality management systems held on 17 June 2026.

A particular highlight of the session was the contribution of the Technical Committees for Quality Systems Chairs from all six RMOs: AFRIMETS, APMP, COOMET, EURAMET, GULFMET and SIM.

Participants heard directly from each region about their approaches to quality system reviews and the processes used to support mutual recognition under the CIPM MRA.

By bringing together these regional perspectives in a single forum, the session highlighted how quality management systems are reviewed and how confidence is maintained across different regions.

In feedback following the event, Prof. Dr Noha Khaled of NIS, representing AFRIMETS, and Dr Enver Sadikoglu of TÜBİTAK UME highlighted the value of comparing how different RMOs approach QMS reviews, while also identifying common principles and useful practices that could help strengthen work in other regions.

The positive response from participants highlighted the value of creating opportunities to share experience and strengthen understanding across the CIPM MRA community. Presentation slides and additional resources from the session are now available to support ongoing learning and engagement.

Version 1.0.0 of the SI Reference Point has been officially released.

The SI Reference Point is a digital representation of the SI Brochure, which defines the International System of Units (SI), the world’s only internationally agreed system of units. By making core SI reference information available in machine-readable form, the SI Reference Point helps ensure that the SI can be used consistently in digital applications and data exchange. .

Learn more →

Supporting digital metrology

The first stable release of the SI Reference Point marks an important milestone in the digital transformation of the international metrology system. It provides a common digital reference for representing SI units in machine-readable form.

The SI Reference Point provides a machine-actionable representation of the SI units that can be accessed and reused across digital environments. This helps support:

• the interoperability and reuse of measurement information;
• digital metrological traceability;
• the harmonization of digital calibration certificates and digital reference material certificates;
• consistent communication between measurement devices and sensor networks.

The SI Reference Point was developed by an international group of experts working through the CIPM Forum on Metrology and Digitalization (FORUM-MD) and its associated working groups.

The Consultative Committee for Electricity and Magnetism (CCEM) has published a new guide supporting the characterization and reliable use of graphene-based quantum Hall devices for measurements of the quantized Hall resistance.

Published in Metrologia as a “Guide, Standard and Convention”, the document provides practical guidance for laboratories working with graphene-based devices and is expected to become an important reference for the electrical metrology community.

Background

Graphene-based quantum Hall devices have attracted increasing interest because they can operate at lower magnetic fields and higher temperatures than traditional gallium arsenide (GaAs)-based devices. These operating conditions facilitate the use of more compact cryomagnet systems and are expected to support wider deployment of primary resistance standards based on the quantum Hall effect.

The new guide builds on the CCEM’s long-established technical guidelines for reliable measurements of the quantized Hall resistance, adapting them to the specific characteristics of epitaxial graphene devices. It provides guidance on device characterization, performance verification and measurement considerations, to support reliable and consistent use.

Version 4.01 of the 9th edition of the SI Brochure has now been published.

The SI Brochure is the authoritative document describing the International System of Units (SI), the world's only internationally agreed system of units. The new version introduces revisions to the section on non-SI units and updates the presentation of informative notes throughout the publication.

Clarifying the role of non-SI units

The revised section on non-SI units responds to feedback received from stakeholders and clarifies how non-SI units are presented within the SI Brochure.

For the first time since the SI was formalized, the SI Brochure now makes explicit that non-SI units do not hold any special status within the SI. The revision also introduces a more inclusive list of non-SI units together with their conversion coefficients to SI units.

To help explain their inclusion, the listed units are organized into four indicative categories:

• Long-standing units of time and angle;
• Historical names for decimal multiples and submultiples of SI units;
• Internationally recognized units that are not decimal multiples or submultiples of SI units;
• Units used in specialized technical disciplines.

Supporting the digitalization of the SI

The update also incorporates the informative notes that previously appeared in the margins of the SI Brochure into the main body of the text.

This change supports the continued digitalization of the SI Brochure and improves the presentation of information across digital formats.

As 2025 — and our celebrations marking the 150th Anniversary of the Metre Convention, and the BIPM itself — come to a close, we look back on a milestone year that honoured our history while advancing scientific work across time, chemistry, ionizing radiation and mass/physical metrology. From major collaborations to technical breakthroughs and capacity-building efforts, here are ten of the most significant news stories that shaped this anniversary year.

1. Celebrating 150 Years of the Metre Convention — A Global Milestone

2025 saw the global metrology community come together to mark 150 years since the signing of the Metre Convention. Flagship events including international gatherings, public webinars, and scientific sessions reminded us why measurement science matters worldwide — and created lasting digital resources of talks, videos and educational material.

Get the details: A Celebration of 150 Years of the Metre Convention  |  End of Year Highlights

2. Summer Schools Expand Training Opportunities for UTC Laboratories

Training in Coordinated Universal Time (UTC) remains one of the most valuable ways to strengthen technical understanding and support global participation in timekeeping. In 2025, BIPM delivered UTC Summer Schools both at its headquarters in Sèvres and through a regional programme in Mexico — giving participants practical guidance from experts and building global collaboration.

Get the details: UTC Summer School at the BIPM  |  UTC Summer School in Mexico

3. Latest Updates from the 2025 CCTF Meeting — Shaping the Future of Timekeeping

The 2025 meeting of the Consultative Committee for Time and Frequency (CCTF) marked an important moment for international timekeeping. Discussions advanced work toward a future redefinition of the second, examined options for a more resilient and continuous Coordinated Universal Time (UTC), and explored emerging topics such as lunar timekeeping. Together, these updates reflect how time metrology is evolving to meet scientific, technological and societal needs.

Get the details: Latest Updates from the 2025 CCTF Meeting

4. Metrologia Transitions to Full Open Access

In a major step forward for open science in measurement, Metrologia — the leading international journal in metrology — became fully open access in 2025. This transition enables researchers worldwide to access high-quality metrology research without paywalls, supporting global collaboration and equity in science.

Get the details: Metrologia to Fully Open Access

5. Sharing Practical Expertise: 2025 Kibble Balance Technical Meeting

Held at the BIPM in November, the 2025 Kibble Balance Technical Meeting brought together the international mass metrology community to exchange progress on realizing the kilogram and expanding applications of precision mass measurement. A special knowledge-transfer session introduced early-career researchers and new entrants to core Kibble balance concepts, reinforcing the meeting’s role as a practical forum for sustaining expertise across generations.

Get the details: 2025 Kibble Balance Technical Meeting

6. CCRI Workshop on the Evolution of Ionizing Radiation Metrology

In 2025, the BIPM’s Ionizing Radiation Department marked its 65th anniversary — a milestone reflected in a dedicated CCRI workshop held at the BIPM in November. The meeting brought together international experts to review the evolution of ionizing radiation metrology, from the development of core radiation units and global measurement networks to current and emerging priorities in medicine, environmental monitoring and fusion research. Together, the discussions highlighted both the continuity of international cooperation and the innovation shaping the future of the field.

Get the details: CCRI Workshop Explores the Past and Future of Ionizing Radiation Metrology

7. Metrology in the Digital Age — The Critical Role of Trustworthy Data and AI

As digital transformation advances, 2025 saw BIPM placing renewed emphasis on trustworthy data practices, FAIR data principles, and the role of measurement science in supporting reliable data and AI-driven systems — a reflection of metrology’s evolving role in a data-centric world.

Get the details: Metrology in the Digital Age

8. Measuring Accurately for Clean Air and Blue Skies — Environmental Metrology for the Planet

Environmental measurement remained a key priority in 2025, with major progress in ozone and air-quality metrology, gas standards, and collaborations to strengthen global environmental monitoring. These advances will help inform policy, public health, and climate science worldwide.

Get the details: Measuring Accurately for Clean Air and Blue Skies | A Global Thank You to the Ozone Measurement Community

9. BIPM150: Nine Standout Scientific Posters Announced — Showcasing Global Metrology Innovation

As part of the 150th anniversary, BIPM released a collection of scientific posters submitted by National Metrology Institutes and Designated Institutes worldwide. These posters highlight cutting-edge research and emerging innovations across multiple metrology fields, from fundamental measurement science to applied areas like digital data and environmental metrology.

Get the details: BIPM150 Scientific Posters

10. BIPM Director Martin Milton Concludes His Term

Director Martin Milton ended his term in December 2025 after leading the BIPM through a period of significant growth and reflection, including the landmark 150th anniversary of the Metre Convention. With Director-Designate Dr Annette Koo set to take up office in 2026, the BIPM enters its next phase with continuity in leadership and purpose.

Get the details: Director Martin Milton – Farewell Message 

Looking Ahead to 2026 and Beyond

With the 150th anniversary celebrations now behind us, the BIPM is looking forward — guided by a renewed strategy and a clear vision for the future. The priorities set in 2025, together with global collaboration, open science, capacity building and scientific innovation, will shape the next chapter of international metrology under the upcoming 28th CGPM in 2026.

Background

World Metrology Day is celebrated annually on 20 May to commemorate the signing of the Metre Convention in 1875, which established international cooperation in measurement science and created the framework for the BIPM.

UNESCO first celebrated World Metrology Day in 2024 following a decision of its 42nd General Conference in 2023. This reflects the growing recognition of the importance of accurate, internationally recognized measurements in addressing global challenges, including sustainable development, public health and technological innovation.

The BIPM works with Member States, National Metrology Institutes and international partners to ensure the global comparability of measurements and to support the International System of Units (SI).

This year’s joint webinar contributes to the International Decade of Sciences for Sustainable Development (2024–2033).

Published 1 April 2026

Six keynote presentations from the third Forum on Metrology and Digitalization (FORUM-MD), held at the BIPM in Sèvres, France, are now available on the BIPM’s official YouTube channel.

The recordings provide direct insight into key topics discussed during the Forum, including machine-actionable data, Digital Calibration Certificates (DCCs), and the role of metrology in supporting trustworthy artificial intelligence (AI), which forms part of the Forum’s ongoing work on digital transformation.

Presentations were delivered by Martina Paul (ISO/IEC JTC 1/SC 42 JWG 6) on conformity assessment schemes for AI systems; Thomas Doms (AIQI, TÜV Austria) on the test and certification of safety-relevant AI applications; Rania Wazir (NoLeFa, leiwand.ai) on metrics and data for testing of AI systems; Rodolfo Souza (INMETRO, Brazil) on Smart Documents Vision; Dong-Hun Ryu (KTL, Korea) on the development of a calibration certificate application with AI; and Jeff Gust (Fluke, USA) on the application of AI in metrology.

​​​

Caption: Participants at the third Forum on Metrology and Digitalization (FORUM-MD), held at the BIPM headquarters in Sèvres, France.

What happens next

Looking ahead, FORUM-MD will continue to address key challenges identified during the meeting, including the interpretation of metrological information by AI systems, the development of machine-actionable quality infrastructure within the CIPM Mutual Recognition Arrangement (CIPM MRA), and the wider dissemination of digitalization practices across the international metrology community.

Progress on these topics will be reviewed at the next FORUM-MD meeting at the BIPM in February 2027.

The official poster for World Metrology Day 2026 is now available, highlighting this year’s theme: Metrology: Building Trust in Policy Making.

The poster was designed in association with A*STAR NMC, to support communication and outreach activities ahead of 20 May.

​Download the poster

Supporting communication on metrology and policy

National Metrology Institutes (NMIs), legal metrology authorities, regulators, academic institutions and international partners are encouraged to use the poster in their World Metrology Day activities.

It can be displayed at events, shared on social media, or incorporated into outreach and educational materials to:

• illustrate how measurement supports evidence-based policy making
• highlight the role of the International System of Units (SI) in ensuring coherence and comparability of data
• raise awareness of metrology’s contribution to public trust, safety, sustainability and economic stability

The poster is available in multiple formats, including Adobe® Photoshop® and PDF, and may be customized with organizational logos or translated for local use.

Organizations are also invited to share translated versions and details of their activities via the World Metrology Day website, helping to showcase global engagement with this year’s theme.

Learn more and download the poster in English and French here.

To support institutes developing biological metrology programme capabilities, and to help the wider metrology community strengthen their understanding of infectious disease diagnostics, the CCQM Task Group on Infectious Disease Diagnostics and Metrology for Pandemic Preparedness has developed a targeted e-learning course. Comprised of multiple short modules, the course focuses on strengthening technical understanding of infectious disease diagnostics in pandemic response.

New eLearning course supports wider knowledge transfer

In this new self-study course participants will explore why measurement standards and reference materials are essential for reliable infectious disease diagnostics.

The course examines:

• The critical balance between speed and accuracy, detailing how uncalibrated diagnostic tests can lead to false results, wasted resources, and inappropriate public health decision-making.
• The foundational concepts of metrology, including the definition of reference materials, metrological traceability, and commutability.
• How the international metrology community utilizes rapid "fire drills" to quickly establish measurement baselines during novel outbreaks.
• And finally, practical guidance on:
  • test validation
  • proper material handling
  • avoiding matrix effects
  • troubleshooting discordant lab results.

The course is available on the BIPM eLearning site to National Metrology Institutes (NMIs) and Designated Institutes (DIs) from BIPM Member States and Associates.

Background

The CCQM Task Group on Infectious Disease Diagnostics and Metrology for Pandemic Preparedness was established to oversee implementation of recommendations identified by the measurement community, global policy and the wider healthcare sector, in the CCQM Roadmap to Metrology Readiness for Infectious Disease Pandemic Response.

In response to needs identified in this roadmap, the first molecular biology ‘fire-drill’ exercise has already been completed, and the second protein exercise is currently underway.

In parrel, in collaboration with the WHO, further efforts have also established metrological consideration in several relevant infectious disease Target Product Profiles (TPPs).

This most recent capacity-building activity aims to support institutes developing biological metrology capabilities and to help the wider metrology community strengthen their understanding of infectious disease diagnostics in pandemic response.

The CIPM MRA Comparison Reports are now available directly on the BIPM website.

As part of our continued efforts to strengthen accessibility and digital integration across the CIPM MRA framework, all new CIPM MRA Comparison Reports submitted from 1 December 2025 are being hosted on bipm.org.

You can now find them at: https://www.bipm.org/comparison-reports

or by following the steps below from bipm.org

Screenshot caption: Route to the page through website navigation: Publications & Events - Publications - CIPM MRA Comparison reports

Screenshot caption: Route to the page through website navigation: Coordination - CIPM MRA - CIPM MRA Comparison reports

All previously published reports remain available in the Metrologia Technical Supplement and all reports continue to be accessible via the BIPM’s Key Comparison Database (KCDB).

Hosting the new CIPM MRA Comparison Reports to bipm.org will:

• provide direct and central access through the BIPM’s own platform,
• ensure faster updates and publication workflows, and
• enhance discoverability and usability alongside other CIPM MRA resources.

We encourage the international metrology community to update bookmarks and begin accessing new Comparison Reports directly via bipm.org.

UPDATE

We are pleased to announce the successful completion of the 7th BIPM–TÜBİTAK UME project placements, marking another milestone in our Capacity Building and Knowledge Transfer Programme.

In this cycle, ten young metrologists from ten National Metrology Institutes (NMIs) spent 1-3 months conducting research in TÜBİTAK UME’s world-class laboratories, working on projects that contribute to the advancement of precision measurements worldwide. Their research spanned key scientific areas, including:

• Advancing precision in healthcare measurements
• Developing a Digital Twin of a Quantum Voltage Standard
• Producing and characterizing a wastewater reference material
• Exploring atomic clocks for modern applications
• Strengthening techniques in mass, torque, ultrasound and thermometry

In addition to their research, participants took part in a CIPM MRA seminar, designed to reinforce their understanding of the international metrology system and strengthen global collaboration in scientific measurement.

Feedback from Cycle 7 participants highlights the significant impact of this initiative in fostering knowledge exchange, strengthening scientific collaboration and enhancing global measurement capabilities.

Photo depicts: ten young metrologists stand together with three programme coordinators from BIPM and TÜBİTAK UME (in the centre), to mark the successful completion of Cycle 7 of the BIPM–TÜBİTAK UME Project Placements.

This International Day of Women and Girls in Science, the BIPM is shining a light on some incredible women working in international metrology today.

From redefining the second and enabling space navigation, to supporting climate monitoring, personalized medicine and scientific literacy — watch this selection of speeches and presentations from BIPM's "Women Shaping Metrology" YouTube playlist to see some of the faces driving measurement science and to learn about the exciting initiatives they are championing in 2026. 

Featured videos

Access the full YouTube playlist here, and be sure to share it with your colleagues to raise awreness for these important areas of work.

Dr Annette Koo takes up her role as Director of the Bureau International des Poids et Mesures (BIPM) in January 2026. With a career spanning national and international metrology, Dr Koo brings deep scientific expertise and long-standing experience within the global metrology community.

This week, amid a very busy schedule, she kindly took the time to sit down with our communications team so that we could have a chance to get to know her better - and share a little more of her story with you all. From her journey into measurement science and what motivates her as a metrologist, to the values she sees as fundamental to the work of the BIPM, and the international system it serves, follow our conversation below.

Interview with Annette Koo  |  26 January 2026

In the months ahead, Dr Annette Koo will continue to engage with the community the BIPM exists to serve, building on a shared commitment to trusted measurement, cooperation across borders, and the quiet work that enables progress worldwide.

If you are interested in the work that follows, you can follow Dr Koo on LinkedIn. For all updates related to the BIPM and our community, you can follow our Official LinkedIn account here register to receive the BIPM’s monthly eNewsletter here.

Published on 6 August 2025

Published 6 August 2025

Published 14 March 2025

In 2025, a quiet but consequential shift took place across environmental monitoring networks worldwide. Scientists, laboratories and monitoring stations began implementing a new ultraviolet ozone absorption cross-section value for ground-level ozone measurements — a change that strengthens the accuracy and comparability of air-quality data used every day by researchers, regulators and policymakers.

As the year draws to a close, the Bureau International des Poids et Mesures (BIPM) would like to recognise and thank the many scientists and institutions who made this transition possible. Their collective effort — spanning national metrology institutes (NMIs), atmospheric observatories, calibration laboratories and more — reflects years of collaboration and shared commitment to improving how ozone is measured, understood and reported around the world.

Watch the wrap-up video:

Why this transition matters

The newly implemented absorption cross-section value, CCQM.O3.2019, significantly reduces measurement uncertainty and improves consistency across global ozone monitoring networks. By strengthening comparability across sites and over time, the update enables more reliable trend analysis, research and evidence-based decision-making.

As Damian Smeulders, Director Reference Gases at National Measurement Institute, Australia noted during during the 2025 Gas Analysis Working Group:

“Air pollution and greenhouse gas emissions remain amongst the biggest environmental and health challenges of our time. Yet without consistent measurement standards, countries cannot fairly compare data, assess progress or coordinate responses. This initiative helps bridge that gap by strengthening global metrology for air quality.”

A shared effort, grounded in expertise

The transition to the new cross-section value reflects sustained technical work across the international metrology community, coordinated through the Consultative Committee for Amount of Substance: Metrology in Chemistry and Biology (CCQM), its Gas Analysis Working Group (GAWG) and the Task Group on Ozone Cross-Section Change Management, with coordination support from the BIPM.

For those implementing the change at monitoring sites and laboratories, the benefits are practical as well as scientific. As Dr. Andrew M Crotwell, from the Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder explained:

“This will improve comparability across sites and over time and reduce uncertainty. In turn, it allows trend analysis, research and health-related decisions to be based on more reliable measurements.”

Javis Nwaboh, Research Scientist at PTB Germany, highlighted how this work connects local measurements to global observing systems:

“Looking ahead, the focus is on scaling up collaboration and linking these high-precision measurements to wider networks, including satellite observations.”

The update is already being integrated into calibration services at NMIs, reflected in the BIPM.QM-K1 key comparison, and embedded in updated international standards, including ISO 13964 and ISO 10313.

Looking ahead

The adoption of the new ozone absorption cross-section is not an endpoint. In 2026 and beyond, international comparisons, training activities and continued cooperation through CCQM, GAWG, national institutes and atmospheric monitoring networks will further strengthen ozone measurement capability worldwide.

What this year has demonstrated most clearly is the value of sustained collaboration: when measurement scientists work together, the result is data that is more accurate, more comparable and more trusted — and ultimately more useful for protecting health, informing policy and safeguarding the air we breathe.

Delivering and sustaining this progress depends on collaboration well beyond any single institute or laboratory.

A pioneering radioactivity measurement method has been brought firmly into the 21st century through a joint project between the BIPM and the National Institute of Metrology (NIM), China.

Together, the institutes have modernized Selective Sampling—a technique first developed at the BIPM in the 1980s to improve the accuracy of activity measurements of beta-emitting radionuclides.

The BIPM’s 4πβ(LS)–γ detection system has been the central platform for applying this method. The upgrade replaces cumbersome analogue procedures with a streamlined digital system—using a high-speed CAEN digitizer and in-house software.

This improves how the instrument processes signals and will ensure more reliable results in applications for nuclear medicine, environmental monitoring, radiation safety and more.

By simplifying the architecture, improving background correction, and making the system easier to operate, the project opens the door for more National Metrology Institutes (NMIs) to benefit from a method that was once too complex to adopt.

The New System

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Image caption: Diagram and component overview of the 4πβ(LS)–γ digital selective sampling system.

Thank you

The BIPM warmly acknowledges the contribution of Dr Haoran Liu of the National Institute of Metrology (China), who spent 3 months on secondment at the BIPM to support this project. Bringing his expertise in radionuclide metrology and digital acquisition, Dr Liu worked side-by-side with colleagues to modernise the Selective Sampling system—helping to demonstrate how this technique can be given new life with today’s digital tools.

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Photo caption: Dr Haoran Liu (NIM) and Dr Romain Coulon (BIPM) working on Digital Selective Sampling at the BIPM headquarters in Sèvres.

As his secondment comes to an end, the BIPM extends its thanks for his dedication and technical insight, which have left a lasting impact on the project and the wider metrology community.

As the BIPM marks its 150th anniversary, ionizing radiation metrology also celebrated a set of major milestones in 2025: the 65th anniversary of the BIPM’s Ionizing Radiation Department and the 130th anniversary of Wilhelm Röntgen’s discovery of x-rays. To reflect on these achievements and look ahead to future priorities, experts from around the world gathered at the BIPM on 6 November for a dedicated Consultative Committee for Ionizing Radiation (CCRI) workshop.

More than 200 specialists joined the event — with 55 participants on-site and 152 attending online — underscoring global interest in the evolving roles of ionizing radiation metrology in medicine, environmental monitoring, public protection and emerging technologies.

Highlights from Past Achievements to Emerging Priorities

The morning sessions traced the development of ionizing radiation metrology from Marie Curie’s creation of the first international radium standard, which laid the foundations for today’s international standards. Speakers also outlined the growth of global structures that support consistent radiation measurements, including the ICRU (defining the ionizing radiation units), CCRI, the BIPM Ionizing Radiation Department, ICRM and the worldwide SSDL network, with tributes to pioneering figures who shaped the field.

Attention then turned to present and future demands in medical diagnostics, radiotherapy and environmental monitoring, including updated dosimetry protocols, new reference materials and improved testing capabilities. Fusion research also featured, particularly work on tritium and plasma diagnostics, alongside emerging approaches that combine advanced detection systems with AI-supported modelling to improve traceability in medicine, nuclear science and industry.

A Collaborative Vision for the Future

As the BIPM’s 150th anniversary draws to a close, the workshop served as a reminder of how far ionizing radiation metrology has come in the three areas that are dosimetry, radionuclides and neutrons— and how much more remains ahead for the new generation of metrologist as those that concluded the workshop. With coordinated research, robust standards and a growing international community, the BIPM and CCRI are helping ensure that ionizing radiation measurements remain reliable across borders and across disciplines, supporting better decisions in medicine, environmental monitoring and emerging technologies for years to come.

Photo caption: Participants at the CCRI Workshop on Ionizing Radiation Metrology, BIPM, November 2025.

A message of thanks and reflection

As I come to the end of my time at the BIPM, I do so with a deep sense of gratitude. Serving as Director over the past thirteen years has been both an honour and a privilege. I am sincerely thankful to the talented staff of the BIPM for their dedication and commitment to serving National Metrology Institutes (NMIs) around the world, as well as to the International Committee for Weights and Measures (CIPM) for its support throughout my tenure.

I have been particularly privileged to serve as Director this year, as we celebrated the 150th anniversary of the signing of the Metre Convention and the BIPM itself. This period has provided an opportunity to reflect on our history and be inspired by the technical and scientific achievements that established the metric system and the SI, while also recognising the significant progress made in recent years to incorporate the latest scientific advances into the SI. It has been an equally important moment to look ahead, towards a future in which all States around the world can be linked to the work of the BIPM.

One of the great pleasures of this role, for me, has been welcoming colleagues from across the international metrology community to meetings at the BIPM. It has been humbling to see the diversity of this community and the breadth of its achievements. We can all be proud that measurement science remains an area in which States choose to work together and that we have the international, regional and national structures in place to make this happen.

Looking ahead with confidence

As I prepare to leave my role as Director, I do so with confidence in the future of the organization and in the leadership that will guide it forward. Earlier this year, the CIPM appointed Dr Annette Koo of New Zealand as the next Director of the BIPM. I have valued the opportunity to work alongside Dr Koo in recent months and to hear some of her vision for the organization. I am confident that the BIPM, and the international metrology community it serves, are in very good hands.

I am also encouraged by the growing involvement of a new generation of metrologists, whose skills, perspectives and engagement with emerging technologies bring fresh opportunities for innovation, collaboration and impact across the international measurement system.

With sincere thanks

On a personal note, I have learned a great deal during my time as Director, and I hope I have been able to contribute just as much in return. My wife, Christine, and I have made many good friends during our years in France and have thoroughly enjoyed living in Sèvres. In recent weeks, it has been a pleasure to share memories with many of you and to say au revoir. We will now return to our home in England and look ahead to the next chapter with family and friends.

Finally, I would like to thank you all for your collaboration over the years. Working together, we have been able to meet the expectations placed on the BIPM and to support users around the world. I leave with pride in what has been achieved and with my warmest thanks to the entire BIPM community.

A newly signed Memorandum of Understanding (MoU) between the BIPM and the United Nations Educational, Scientific and Cultural Organization (UNESCO) aims to contribute to advancing the 2030 Agenda for Sustainable Development in the fields of education, science, and communication and information. The renewed partnership seeks to support shared strategic objectives, including strengthening metrology, supporting international scientific cooperation and promoting science-based decision-making.

The MoU was signed on 15 December 2025 at UNESCO Headquarters in Paris, France, by Martin Milton, Director of the BIPM, and Lidia Brito, Assistant Director-General of UNESCO for Natural Sciences. It updates and replaces the previous agreement signed in 1949 between UNESCO and the International Committee for Weights and Measures (CIPM), the BIPM’s non-plenary and executive body.

The BIPM and UNESCO, in line with their current strategic interests and shared priorities, will collaborate to promote and support mutually beneficial capacity-building activities, particularly in the areas of gender equality and youth engagement in basic sciences and engineering. The agreement reinforces a common commitment to inclusive scientific development and the global exchange of expertise.

Read the BIPM–UNESCO MoU

Background

In an era defined by rapid digital transformation, metrology—the science of measurement—is at a pivotal crossroads. As industries worldwide integrate artificial intelligence (AI), automation and digital infrastructures, the need for precise, interoperable and trustworthy measurement data has never been greater.

At the Bureau International des Poids et Mesures (BIPM’s) recent Forum on Metrology and Digitalization (FORUM-MD), global experts examined the impact of digital advances on measurement science.

The discussions underscored a fundamental truth: metrology is not just adapting to the digital age—it is shaping its very foundations. 

Building a Digital-Ready Metrology Framework

 At the core of digitalization lies data. But for measurement data to be useful in a connected world, it must adhere to FAIR principles—Findability, Accessibility, Interoperability and Reusability. Experts at the Forum emphasized that structured, machine-readable formats are essential to ensuring seamless integration into AI-driven systems, international regulatory frameworks and industrial processes.

 This shift requires globally recognized digital identifiers and standardized formats that enable cross-border comparability of measurement results. Without these safeguards, the digital ecosystem risks fragmentation—jeopardizing everything from precision manufacturing to medical technologies.

Automation and AI: Transforming Measurement Science  

One of the most significant developments is the transition from traditional paper-based calibration certificates to Digital Calibration Certificates (DCCs).

DCCs provide secure, tamper-proof and machine-readable records, ensuring that calibration data remains accurate and seamlessly integrated into digital infrastructures. By eliminating manual transcription errors and enhancing traceability, DCCs are paving the way for fully automated, real-time measurement systems.

Yet, as AI-driven tools become central to measurement science, experts in the Forum stressed the importance of robust data quality standards. AI models are only as reliable as the data they are trained on—meaning that any errors, biases or inconsistencies in measurement data could have far-reaching consequences.Metrology will be essential to underpin international protocols for AI and ensure trust and accuracy for AI applications.

Looking Ahead: The Global Challenge of Digital Metrology

As metrology enters the digital age, one thing is clear: collaboration is key. The shift to a fully digital measurement ecosystem requires cooperation between national metrology institutes, policymakers, industry leaders and AI experts.

The discussions at FORUM-MD 2025 highlighted the need for a unified approach to digital measurement standards—one that ensures interoperability across industries, enhances global trade and supports emerging technologies.

Photo depicts: Participants from Forum MD 2025.

As we close this milestone anniversary year, we were delighted to welcome colleagues, National Metrology Institutes (NMIs), and partners from around the world to our end-of-year webinar "Highlights from BIPM150". Thank you to everyone who joined us — and to those who contributed clips, photographs, and reflections from national celebrations throughout 2025.

This final gathering of the BIPM150 year offered a brief look back at the collaborations, scientific achievements, and community spirit that defined the 150th anniversary of the Metre Convention.

Watch the recording

The Programme

The programme began with opening reflections from BIPM Director, Dr Martin Milton OBE, who highlighted how international cooperation and shared scientific infrastructure remain central to the robustness of the SI and the success of the BIPM150 year. Looking ahead, he reflected on the contributions of a new generation of scientists whose passion for metrology and embrace of cutting-edge science offer strong momentum for the future.

Four NMIs then shared short highlights on some of the exhibitions, outreach campaigns and events that they organised in celebration of the 150th anniversary. These updates reflected the diversity of approaches taken to celebrate the Metre Convention, while reinforcing a common message: metrology remains essential to innovation and global trust in measurement.

The event concluded with closing remarks from Director Designate, Dr Annette Koo, who thanked colleagues and partners for their support throughout the years — and throughout this anniversary year in particular. Drawing on what she witnessed during the May celebrations and in her first weeks at the BIPM, she described an organisation that is "in very good heart": one that understands its origins, applies scientific metrology to real-world challenges, and moves forward with a shared sense of purpose. She closed with a message of confidence in the community’s ability to navigate what lies ahead: "I have every confidence, that as we navigate a future that only guarantees change, that we are going to continue to meet this change together."

As the webinar offered a snapshot of this milestone year, we invite you to explore the wider collection of BIPM150 resources — including videos, interviews, articles and posters — that capture the breadth of anniversary activities and contributions from around the world.

Although the BIPM150 campaign is coming to a close, the themes it highlighted continue to guide shared priorities across the metrology community — from the importance of accurate measurement in global trade and sustainable development, to emerging challenges such as digital transformation and the future of time.

Stay connected as we continue to share the final BIPM updates through the end of 2025.

• Subscribe to BIPM eNews for updates.
• Follow the BIPM on LinkedIn.

Don’t forget to register to attend — we would love to see you there!

As we approach the end of this milestone year, the BIPM is bringing the global metrology community together one last time to celebrate the conclusion of the 150th anniversary of the Metre Convention.

Our online event, “Highlights from BIPM150: A 30-minute special”, will offer a concise and engaging look back at the moments, collaborations and national celebrations that shaped 2025 — with contributions from across the world.

What to expect:

• opening reflections from BIPM Director, Dr Martin Milton OBE;
• a selection of national highlights presented by NMIs;
• video snapshots from the May anniversary events in Sèvres and at UNESCO;
• closing remarks from Director Designate, Dr Annette Koo, with a look ahead to 2026.

We hope you will join us for this final gathering of the BIPM150 year — open to all who wish to take part.

Date: 10 December 2025
Time: 11:00 UTC (12:00 CET)
Where: Online | Zoom

Register here: https://bipm-org.zoom.us/webinar/register/WN_pJo30S2XTSW6Banl5aq9QQ#/registration

The BIPM is proud to unveil the nine scientific posters selected for preview at the 150th Anniversary Scientific Conference, taking place at Palais des Congrès from 21–22 May 2025. 

Chosen from nearly 400 submissions received from around the world, these standout posters address some of the most pressing challenges in modern metrology—from quantum technologies and digital transformation to health, education and sustainability. 

Each winning poster was selected by the BIPM Poster Committee from one of nine key topic areas, reflecting the breadth and innovation driving the global metrology community. 

In addition, a special mention goes to Cristhian Alfredo Paredes Cardona, whose poster titled Perceptual Metrology: A Future Frontier in Human Well-Being was selected as part of our Young Metrologists feature for the 150th Anniversary. 

The lead authors of these nine selected posters will be invited to present their work during the live poster workshops on 21 May 2025 at the Palais des Congrès in Versailles, as part of the scientific programme marking the 150th anniversary. We warmly invite all attendees to join the session and hear directly from the researchers shaping the future of measurement. 

Additionally, all accepted posters are now available to explore as electronic posters on the BIPM150 website. We encourage you to browse the full collection and discover how measurement science is helping to address challenges across an extraordinary range of fields. 

We sincerely thank every contributor for their passion, creativity and insight — your work makes this 150th anniversary a truly global celebration of metrology in action. 

Against this backdrop, the 2025 Kibble Balance Technical Meeting (KBTM) was held at the BIPM from 18 to 20 November, bringing together experts to exchange updates, discuss new developments and—this year—share practical knowledge with the next generation of researchers.

Photo caption: Panellists during the KBTM Special Session – Knowledge Transfer on Kibble Balance Core Topics, and participants visiting the BIPM’s Kibble Balance lab. Copyright ©BIPM.

Over the first two days, the programme covered a wide range of technical topics central to current Kibble balance work, including:

• NMI-level Kibble balances for realizing the kilogram
• participation in the key comparison of realization experiments (CCM.M-K8)
• table-top balances for smaller mass ranges
• developments in mass, force and torque for industrial applications

These discussions brought together progress updates from institutes worldwide, providing valuable insight into the evolving capabilities of national Kibble balance programmes.

New in 2025: Special Session on Knowledge Transfer

For the first time, the meeting included a special Knowledge Transfer Session on Day 3. Six invited experts presented an overview of core topics in Kibble balance technology, offering structured guidance for NMIs and research groups entering or expanding this field.

The talks covered both foundational and specialised areas, including general considerations for building a Kibble balance, magnetic circuits, electrical measurements, mechanics and alignment, optical sensors and data synchronisation, and mass and gravity.

This session provided a unique opportunity for early-career metrologists, university researchers and new entrants to the field to engage directly with leading experts.

Key sessions:

• 0:00 – Introduction to the KBTM Special Session
• 0:02:40 – General considerations for building a Kibble balance – Ian Robinson (NPL)
• 0:26:38 – Optical sensors and data synchronization – Franck Bielsa (BIPM)
• 1:02:24 – Magnet/coil design and effects – Shisong Li (Tsinghua University)
• 1:44:46 – Mass and gravity – Richard Green (NRC)
• 2:17:35 – Mechanism and alignment – Darine Haddad (NIST)
• 2:41:38 – Electrical measurements – Ian Robinson (NPL)

A Strong Turnout and Growing Community

The 2025 KBTM attracted around 60 in-person participants, with more than 20 online attendees joining for the knowledge-transfer programme. Participants represented National Metrology Institutes (NMIs) and university research groups working on precision mass measurements and related technologies.

The high level of engagement reflects the continued importance of the Kibble balance to global metrology — both for maintaining the SI kilogram and for enabling new measurement capabilities across science and industry.

Photo caption: Group photo of participants at the 2025 Kibble Balance Technical Meeting (KBTM), held at the BIPM headquarters on 20 November 2025. ©BIPM.

As 2025 draws to a close, the BIPM invites the global metrology community to join a special online event marking the conclusion of the 150th anniversary of the Metre Convention.

“Highlights from BIPM150: A 30-minute special” will provide an opportunity to look back on a landmark year for international metrology and to acknowledge the contributions of our partners around the world.

The programme will include:

• a message from the BIPM Director, Dr Martin Milton OBE, reflecting on the impact of 2025;
• short contributions from National Metrology Institutes (NMIs) highlighting national BIPM150 activities;
• a selection of video highlights from the May celebrations;
• closing reflections from the Director Designate, Dr Annette Koo, including a look ahead to 2026.

This event is open to all.

Register here: https://bipm-org.zoom.us/webinar/register/WN_pJo30S2XTSW6Banl5aq9QQ#/registration

11 November 2025 | 15:00–16:30 (Room D, WTO Headquarters and online)

Metrology—the science of measurement—plays a fundamental role in ensuring trust in products, compliance with standards, and the smooth flow of goods across borders. To explore this essential link between measurement and global trade, the World Trade Organization (WTO) will hold a Thematic Session on the Role of Metrology in Facilitating Trade on 11 November 2025, with participation from representatives of the international metrology community, including the BIPM.

This session takes place in a milestone year, marking both the 150th anniversary of the Metre Convention and the 70th anniversary of the International Organization of Legal Metrology (OIML) Convention—two international agreements that continue to shape reliable and harmonized measurement worldwide.

Discussions will focus on how metrology supports the effective implementation of the WTO’s Technical Barriers to Trade (TBT) Agreement, reduces technical barriers, and enables developing and least-developed country Members to participate fully in the international measurement system.

Speakers will include representatives from National Metrology Institutes and international organizations from around the world, sharing perspectives on the role of metrology in areas such as new technologies, environmental protection, and health.

For more information and the full list of speakers, visit the official WTO event page.

Watch live here

The Consultative Committee for Time and Frequency (CCTF) met recently to review progress on key issues in time and frequency metrology. The meeting brought together experts from around the world to assess advances in optical frequency standards, the future of Coordinated Universal Time (UTC), and new timekeeping requirements for space exploration.

Watch the highlights, as seen by the CCTF President, Dr Noël Dimarcq, recorded following the meeting.

Highlights from the CCTF meeting at the BIPM

Further viewing: expert perspectives from BIPM150

Explore concise interviews and talks on optical clocks, redefining the second, and future challenges for global metrology.

Focus: harmonization of results in medical laboratories

The Joint Committee for Traceability in Laboratory Medicine (JCTLM) is pleased to announce that registration is now open for its Members’ and Stakeholders’ Meeting and Workshop, to be held on 1–2 December 2025 at the BIPM in Sèvres, France (hybrid format).

This year’s workshop, “Result harmonization in medical laboratories: accomplishments and challenges,” will explore the expectations and benefits of harmonized results, as well as the barriers to achieving them.

Who should attend: laboratory medicine specialists, EQA providers, IVD manufacturers, National Metrology Institutes (NMIs) and all those interested in traceability and method standardization.

For further information go to: Programme and registration details | or contact the JCTLM Secretariat at jctlm@bipm.org.

As microplastics degrade into ever-smaller particles, scientists are raising urgent concerns about the potential health impacts of nanoplastics — tiny fragments capable of crossing biological membranes and entering human tissues.

At the BIPM’s Scientific Symposium held during the 150th Anniversary of the Metre Convention, Dr Adrian Pegoraro from the National Research Council of Canada (NRC) presented a poster entitled “Transforming Food and Water Safety with Innovative Nanoscale Plastic Reference Materials.”

In his presentation, Dr Pegoraro highlighted a major challenge in addressing nanoplastic contamination: that there are currently no certified reference materials available that laboratories around the world can use to verify the accuracy of their measurements. This gap prevents reliable comparisons of data and hinders both environmental and health risk assessments.

“Without certified reference materials that everyone agrees on, it’s really difficult to assess exposure levels or compare findings across different labs and countries,” said Dr Pegoraro.

The team is working to create scalable and well-characterized plastic nanoparticles that can serve as a reliable reference for testing and calibration.

This work also supports the BIPM’s broader mission to facilitate comparability in global measurement systems and reflects the strategic vision outlined in the CIPM Strategy 2030+ — particularly in ensuring that measurements support health, environmental protection and food security.

The Poster

The poster was co-authored by Maohui Chen, Sadman Sakib, Zeina Maan, Zygmunt Jakubek and Shan Zou, all affiliated with the NRC’s Nanoscale Measurement Metrology Research Centre.

Listen to a 2-minute audio recording of Dr Pegoraro explaining their poster, here.

Watch Dr Pegoraro’s Presentation

In the lead-up to the International Day for Clean Air for Blue Skies on 7 September, the Bureau International des Poids et Mesures (BIPM) is highlighting how the science of measurement underpins efforts to monitor and improve air quality around the world. At the heart of this work is a global community committed to accurate, comparable ozone measurement — a cornerstone of clean air data and environmental monitoring.

The importance of accurate ozone measurement

Ozone is a key pollutant used to assess air quality, and measuring it accurately is vital for determining whether air is safe to breathe, identifying trends in pollution and ensuring public reporting is based on reliable science.

Recognising the need for stronger alignment and reduced uncertainty in ozone measurement, in recent years the international metrology community has taken significant steps to improve calibration practices and update reference values.

For example, between 2022 and early 2025, the CCQM-GAWG Task Group on Ozone Cross-Section Change — composed of national metrology institutes and international partners — coordinated a global update to the ultraviolet ozone absorption cross-section used in ozone calibration.

The updated value, CCQM.O3.2019, adopted in 2025, is approximately 1.2% lower and six times more precise than the previously used standard from the 1960s.

This value is now being implemented around the world, reinforced by the BIPM.QM-K1 key comparison programme — an ongoing, peer-reviewed comparison between national metrology institutes that underpins international equivalence in ozone photometry and supports the CIPM Mutual Recognition Arrangement (MRA).

This work ensures that ozone measurements around the world are not only accurate but comparable — enabling regulatory agencies, researchers and policymakers to base their decisions on consistent and scientifically validated data.

Visit and explore

To learn more about the BIPM’s role in supporting ozone measurement, visit our dedicated page: Better science for more accurate measurements of ground-level ozone — featuring technical guidance, metadata protocols and the latest results from international comparisons.

See our video testimonials from the 'Clean Air for Blue Skies' campaign here.

Photo credits for the images in this article go to air quality and atmospheric monitoring institutions around the world, including stations in Ushuaia, Cape Grim and Sydney, Sonnblick Observatory, the Cabo Verde Atmospheric Observatory, the National Physical Laboratory, Mount Waliguan, CVC and Cali’s Carrera 127 station, LNE, Izaña, Hohenpeissenberg, Bukit Kototabang, Mace Head, Anmyeondo and Baengnyeongdo, inNET Monitoring AG, and national institutions in Mexico and the Netherlands.

As quantum standards reshape the International System of Units (SI), researchers are seeking new ways to make these advances more accessible. Among the most challenging? Realizing the ohm — the unit of electrical resistance — under practical, scalable conditions.

At the BIPM’s Scientific Symposium held during the 150th Anniversary of the Metre Convention, Dr Martina Marzano of the Istituto Nazionale di Ricerca Metrologica (INRIM), Italy, presented a poster entitled “Towards an easier realisation of the ohm”.

The poster highlights the QuAHMET project, a major international effort to advance quantum resistance standards through a novel physical phenomenon: the Quantum Anomalous Hall Effect (QAHE).

Unlike the conventional Quantum Hall Effect (QHE) — which underpins the current definition of the ohm but requires high magnetic fields and ultra-low temperatures — this research explains how QAHE devices will be able to produce quantised resistance without an external magnetic field, once the devices have been magnetised.

By enabling a simpler, more robust realization of the ohm — without needing high magnetic fields — QAHE-based devices therefore hold real promise for expanding access to quantum resistance standards beyond specialized laboratories.

The Poster
 

The poster was co-authored by Luca Callegaro, Juan Medved, Charles Gould, Johannes Hoffmann, Nathaniel Huang, Nobu-Hisa Kaneko, Jan Kučera, Mehmet Cengiz Onbasli, Ayşe Gőkçe Őzbay, Hansjoerg Scherer and Susmit Kumar — with institutional affiliations spanning INRIM, PTB, METAS, AIST, CMI, NPL and universities across Europe and Asia.

Listen to a 2-minute audio recording of Dr Marzano explaining their poster, here.

Watch Dr Marzano’s Presentation

The BIPM is proud to announce that Dr Patrizia Tavella has been named the 2025 recipient of the I.I. Rabi Award, a prestigious international distinction in the field of time and frequency metrology.

Presented annually by the IEEE Ultrasonics, Ferroelectrics, and Frequency Control Society, the award honours individuals who have made outstanding technical contributions to atomic and molecular frequency standards, time transfer and timekeeping science.

Dr Tavella was recognised “for excellence in leadership in the coordination and realization of UTC, and advances in the statistics of precise timekeeping.”

Why this award matters

This honour highlights the strategic importance of metrology in today’s interconnected world. Through her leadership as the Director of the BIPM’s Time Department, Dr Tavella ensures that the realization of Coordinated Universal Time (UTC) remains robust, transparent and inclusive—reflecting the best scientific practices and enabling trust in timekeeping across all continents.

Furthermore, Dr Tavella’s contributions support the global comparability of time measurements and have helped strengthen international collaboration among national metrology institutes, and with other international organizations and stakeholders—in line with the objectives of the CIPM Strategy 2030+.

The BIPM congratulates Dr Tavella on this well-deserved recognition.

What does it take to keep the world in sync?

In the cool, high-altitude labs of CENAM in Querétaro, Mexico, timekeepers gathered not just to learn—but to connect, collaborate and reimagine their role in the global fabric of timekeeping.

The BIPM–SIM UTC Summer School, held in May and hosted by Mexico’s National Metrology Institute (CENAM), brought together participants from 18 countries for three days of expert-led training and technical exchange. The initiative is part of the BIPM’s ongoing efforts to build capacity and support global contributions to Coordinated Universal Time (UTC)—the time standard that underpins everything from energy grids to satellite navigation.

Caption: Participants in hands on tutorials and going on lab visits. Photo credits to Tara Fortier of the BIPM and Carlos Andres Ortiz Cardona of CENAM Mexico

Why It Matters

Across much of the SIM region, National Metrology Institutes (NMIs) have identified and expressed the need to address many of the same challenges: limited access to advanced infrastructure, constrained travel budgets, and a shortage of trained personnel to support ongoing UTC participation.

In response to these challenges, the BIPM–SIM UTC Summer School offered a blended programme of tutorials, lab demonstrations and peer learning. It gave career professionals the technical grounding, practical tools and community support to take on a greater role in UTC activities.

Participants trained in:

• GNSS time transfer and receiver calibration
• Timescale generation and analysis
• Time service distribution and national applications

This international effort was made possible thanks to the combined contributions of three key organizations—CENAM, the BIPM and the IEEE UFFC Society—each playing a vital role in delivering, hosting and expanding access to the programme:

• CENAM: CENAM’s laboratories provided a live, hands-on environment—introducing not only current best practices, but also emerging optical technologies that are key to the upcoming redefinition of the SI second.
• BIPM: The BIPM’s CBKT e-learning platform supports the learning journey beyond the event, offering online tools and education resources that participants can access for free from their home institutes.
• IEEE UFFC Society: Finally, the IEEE-UFFC-Society programme enabled broad participation, by providing travel support to NMIs where needed.
   

Caption: Group photo of participants and instructors at the BIPM–SIM UTC Summer School 2025, held at CENAM in Querétaro, Mexico.Photo credit to Tara Fortier of the BIPM

More Than a Course

While the technical content was robust, what participants valued most was the human connection.

“Participating in the SIM-BIPM Summer School was a great opportunity not only to stay up to date with the latest works in the Time and Frequency international community but also to share the knowledge and experiences each laboratory has on the road to developing their UTC(k). It was also a great opportunity for networking with colleagues and strengthening the ties within the SIM Time and Frequency community,” — Raul Solis, Metrologist at CENAMEP AIP

Structured networking sessions, shared meals, and cross-institute conversations all fostered a sense of purpose and collaboration—building a community of practice that extends well beyond the closing session.

As the BIPM celebrates its 150th anniversary, initiatives like the UTC Summer Schools underscore its enduring role: enabling all countries to contribute meaningfully to the world’s measurement systems and ensuring timekeeping remains a truly global endeavour.

On 2 July 2025, the BIPM hosted a live webinar to present and discuss a proposed new definition of one of the most fundamental concepts in metrology: measurement uncertainty.

Organized by the Joint Committee for Guides in Metrology (JCGM), the webinar attracted more than 2,000 participants across Zoom, YouTube and LinkedIn—demonstrating the global importance and wide-reaching interest in this foundational topic.

The proposed new definition has been developed by JCGM Working Groups 1 and 2, which are responsible for maintaining the Guide to the Expression of Uncertainty in Measurement (GUM) and the International Vocabulary of Metrology (VIM). This update will be featured in the next committee draft of the fourth edition of the VIM (VIM4).

The high level of engagement—reflected in the volume of questions and comments received during the webinar and via LinkedIn—confirms the relevance of this work to a broad range of stakeholders. These contributions are now being reviewed by the JCGM as part of the ongoing revision process.

Watch a recording of the webinar

Including presentations from members of the JCGM Working Groups and a live Q&A moderated by the BIPM

UPDATE: Quantum gravimetry at the BIPM

In March 2025, a new absolute gravity measurement was carried out using an AQG-B01 quantum gravimeter in the Kibble balance laboratory at the BIPM. The result confirms the gravity value currently used in kilogram realization work and strengthens the gravimetry link with the LNE gravity reference station in Trappes—reinforcing the BIPM’s site as a stable and reliable reference location.

This updated value will contribute to the laboratory’s result in the ongoing CCM.M-K8.2024 key comparison of kilogram realizations, coordinated by the BIPM.

The measurement was conducted in partnership with LNE-OP and PGravi in partnership with Action Spécifique Gravimétrie Epos-France, as part of a continuing effort to maintain a precisely characterized reference environment for high-accuracy mass metrology.

Image description: The absolute quantum gravimeter (AQG-B01) measuring gravitational acceleration in the Kibble balance laboratory at the BIPM.

Registrations are now open for two UTC summer schools in 2025 as part of the Consultative Committee for Time and Frequency (CCTF) programme of capacity building by resource sharing.

These workshops are designed to support institutes contributing to Coordinated Universal Time (UTC) through participation in BIPM Circular T and the Key Comparison CCTF-K001.UTC.

Both summer schools are generously sponsored by the IEEE UFFC Society, with the BIPM providing additional funding for participants attending the September course.

We invite institutes and professionals in metrology to join these workshops and help build a stronger, more connected global timekeeping community.

*Travel assistance may be available for students with demonstrated financial need relevant to their role in timekeeping.

Enhancing Consistency in Atmospheric Monitoring

Surface ozone monitoring networks worldwide are transitioning to a new ozone absorption cross-section value for ground-level ozone measurements, effective January 2025. This update marks a critical step forward in improving the accuracy and comparability of ozone data across the globe, and the Bureau International des Poids et Mesures (BIPM) is playing a key role in supporting this initiative.

What’s Changing?

Ground-level ozone is measured using ultraviolet (UV) photometry, which quantifies ozone concentration based on its absorption of UV light at a wavelength of 253.65 nm. The updated cross-section value— CCQM.O3.2019—has been validated through extensive international research and reflects the latest advances in metrology.

This change reduces uncertainties in ozone measurement, ensuring that data collected by environmental agencies, research institutions and policymakers is more accurate and comparable.

The new cross section has been adopted for the international comparison of primary ozone photometers (BIPM.QM-K1) and is being adopted in the calibration services offered by National Metrology Institutes for standard instruments operating in the range (0 to 1000) nmol/mol of ozone in air. The change has been coordinated with standardization organizations with implementation of the new cross section value in relevant normative standards including ISO 13964 and ISO 10313.

Why It Matters

Accurate ozone measurements are crucial for tracking air quality, assessing environmental health and informing policies aimed at mitigating pollution and protecting public health. The new methodology will reduce uncertainties in measurement methods and improve confidence in global ozone monitoring networks.

How Will This Be Implemented?

Guidance is being provided to ozone calibration laboratories, surface monitoring networks and instrument manufacturers, on how to implement the cross-section change, including the need for recalibration of instruments and meta-data provision.

• Guidance Document: How to Implement the New Absorption Cross-Section for Ozone Concentration Measurements
• Meta Data: Change in the Value of the UV Ozone Absorption Cross Section Recommendations for Metadata Provision

A Global Collaboration

This transition underscores the collective efforts of the global metrology and ozone monitoring communities, coordinated by the Consultative Committee for Amount of Substance: Metrology in Chemistry and Biology (CCQM), its Gas Analysis Working Group (GAWG) and its Task Group on Ozone Cross-Section Change Management. By adopting the refined cross-section value, an important step towards more reliable atmospheric monitoring has been taken, benefiting science, society and the environment.

For more details and access to technical resources, visit BIPM’s dedicated webpage on ozone measurement.

A New Era for Metrology and Science

The global metrology community stands on the brink of a transformative era with the launch of UNESCO’s International Year of Quantum Science and Technology. As quantum technologies begin to redefine the boundaries of science and industry, this year-long initiative highlights their growing importance across fields such as communication, computation and sensing. For metrology—the science of measurement—quantum advancements are not just an exciting frontier but an essential evolution, offering unprecedented levels of sensitivity and reliability.

Quantum’s Relevance to Metrology

Metrology has always been at the core of scientific progress, underpinning technological advancements and industrial growth. The integration of quantum principles into metrology is already reshaping how we define and measure fundamental quantities.

For example:

The 2019 revision of the SI provides a striking example of how quantum principles have reshaped metrology. Electrical units are now defined directly in relation to quantum phenomena, ensuring global uniformity. By anchoring the kilogram to the Planck constant, the new definition provides a stable and universally accessible standard for mass metrology. This shift replaces the dependence on a single, physical artifact—the International Prototype of the Kilogram—with a system that allows National Metrology Institutes worldwide to independently realize the kilogram with high levels of accuracy.

A key tool in this process is the Kibble balance (pictured below), which enables the practical realization of the kilogram by precisely measuring the relationship between mechanical power and electromagnetic power, the latter providing a direct link to the Planck constant.

Image Description: Depicted on the left, the International Prototype of the Kilogram, symbolizing the historical standard of mass. Depicted on the right, BIPM Principal Physicist Franck Biela is shown working on the Kibble balance, a modern instrument that realizes the kilogram based on the Planck constant.

Quantum technologies have also revolutionized timekeeping since 1967, when the second was redefined based on a hyperfine transition of the caesium-133 atom. This redefinition enabled the development of atomic clocks with extraordinary precision.

Today, a new generation of optical atomic clocks have achieved such precision that they can detect differences in gravitational potential at the centimetre scale. These advancements not only enhance the accuracy of Coordinated Universal Time (UTC) but also support critical applications such as global positioning systems, future space missions and fundamental physics experiments.

Image Description: On the left, a traditional analogue carriage clock, representing classic timekeeping. On the right, a scientist working on a Yb (ytterbium) optical lattice clock—an advanced timekeeping device known for its exceptional precision (image courtesy of and copyrighted to KRISS).

A Year of Celebration and Reflection

The International Year of Quantum Science and Technology underscores how far we have come as a global scientific community and how much further we can go.

From redefining the kilogram using Planck’s constant to advancing atomic clocks for hyper-accurate timekeeping, quantum metrology ensures that measurements remain at the forefront of innovation, supporting everything from global navigation systems to cutting-edge materials science.

"Advancements in quantum technologies open up new frontiers for precision measurement," said the Director of the Physical Metrology Department at the BIPM, Dr Michael Stock. "We remain committed to supporting the global metrology community in leveraging these innovations to achieve unprecedented levels of sensitivity and reliability across all scientific and industrial domains."

To delve deeper into these topics, we invite the scientific community to join us at two key events in 2025 that will delve deeper into quantum:

• The BIPM-UNESCO Symposium on May 20th: Held on World Metrology Day, this symposium will explore the broad impacts of metrology over the past 150 years and look ahead to its quantum-enabled future. As the primary event to mark the 150th Anniversary of the Metre Convention and the founding of the BIPM, this event offers a unique platform for interdisciplinary dialogue and opportunities to reflect on metrology’s role in driving innovation and societal progress.
• The Scientific Conference on May 21st-22nd: Taking place in Versailles, one of the key topics this conference will explore is that of cutting-edge quantum research and its applications in metrology. Beyond this, the conference explores topics such as the definition of the second, climate action and AI. It is an opportunity for the metrology community to exchange ideas and showcase groundbreaking work that pushes the boundaries of precision measurement.

Join the Conversation

The International Year of Quantum Science and Technology is a call to action for the global metrology community to embrace this quantum revolution. As we reflect on 150 years of metrological progress, let’s also envision a future shaped by quantum innovation.

World Food Safety Day – 7 June 2025

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When you sit down to eat, you rarely think about the precise science that ensures your food is safe. But for scientists working in national metrology institutes (NMIs) around the world, measurement is a frontline defence—particularly when it comes to invisible but dangerous threats like mycotoxins.

To mark World Food Safety Day, the Bureau International des Poids et Mesures (BIPM) is highlighting its Mycotoxin Metrology Capacity Building and Knowledge Transfer (MMCBKT) programme — an initiative that brings together dozens of countries to improve the reliability of food safety measurements.

A global health and trade issue

Mycotoxins—naturally occurring toxic compounds produced by certain moulds—can contaminate everyday foodstuffs such as cereals, nuts and fruits. Exposure can lead to serious health risks and disrupt international trade when different countries apply inconsistent testing standards.

Since 2016, the BIPM has worked with NMIs and Designated Institutes (DIs) to:

• Coordinate international comparisons of mycotoxin calibration standards.
• Develop and publish methods for reference material characterization.
• Build critical measurement capabilities through hands-on secondments and training.

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From lab bench to food chain

At the heart of this work is the BIPM’s qNMR facility, which (to-date) has hosted over a dozen visiting scientists from five continents. These experts receive intensive training in producing and validating reference materials—skills they return home with to strengthen national capabilities and local testing labs.

The programme has supported the development of calibration standards for several high-risk toxins: aflatoxin B1, zearalenone, deoxynivalenol, patulin, and ochratoxin A—each essential for reliable food safety monitoring.

The results of the programme—new Certified Reference Materials, published Purity Evaluation Guidelines and Calibrant Assessment Guidelines, and peer-reviewed technical papers—are already supporting food safety systems across Latin America, Africa, Asia and beyond.

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Photo: The purity of mycotoxin primary reference materials being measured with quantitative nuclear magnetic resonance (qNMR)

Celebrating 150 years of measurement science

As the BIPM marks its 150th anniversary, its role in helping countries meet the measurement challenges of food safety remains as vital as ever. From improving public health outcomes to ensuring fair market access, the science of measurement continues to deliver real-world impact.

#WorldFoodSafetyDay #BIPM150

From December 2025, the new CIPM MRA Comparison Reports (formerly categorized under the Technical Supplements in Metrologia) will be published and maintained directly by the BIPM on bipm.org.

This change marks the next step in improving access to formal reports that underpin international metrology.

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This change only applies to CIPM MRA Comparison Reports published from 1 December 2025, all previously published reports will remain in Metrologia’s Technical Supplement, as before, as well as being published in the BIPM’s Key Comparison Database (KCDB).

Hosting the new CIPM MRA Comparison Reports to bipm.org will:

• provide direct and central access through the BIPM’s own platform,
• ensure faster updates and publication workflows, and
• enhance discoverability and usability alongside other CIPM MRA resources.

While the move will involve migrating the submission process from a Word-based system to a more streamlined digital form, hosted by the BIPM, the key steps for submitting and publishing the reports (alongside their structure and content) will remain the same.

“Publishing the new CIPM MRA Comparison Reports on the BIPM website will make them easier to search and access, while more closely integrating them with the CIPM MRA framework,” says Dr Martin Milton, Director of the BIPM. “It also reflects our continuing efforts to further digitize and streamline how the CIPM MRA operates, and how the international metrology community engages with key comparison data.”

From every litre pumped and every parcel weighed, to every kilowatt billed, accurate and comparable measurements underpin public trust. But trust doesn't happen by accident. It is built through rigorous science, clear regulation and international cooperation.

On 12 October 2025, as the International Organization of Legal Metrology (OIML) marks its 70th anniversary, the global metrology community takes the opportunity to reflect on how legal metrology transforms scientific standards into frameworks that support consumer confidence, fair trade and regulatory integrity worldwide.

Legal metrology ensures that scientific measurement standards—maintained by the BIPM and national metrology institutes—are applied consistently and transparently in regulated areas of daily life. From fuel dispensers and electricity metres to weighing instruments and taximeters, it protects consumers, promotes fair trade and strengthens regulatory trust.

Shared Responsibilities, Complementary Roles

The BIPM and OIML operate as sister organizations within the large framework of the international metrology community. While the BIPM ensures the international coordination of the International System of Units (SI) and Coordinated Universal Time (UTC), the OIML works to ensure that these standards are legally recognized and implemented at the point of use.

This shared responsibility forms the backbone of a globally coherent measurement system—one that guarantees not only scientific rigour but legal certainty. It is this alignment that allows measurements to be compared across borders, trusted by regulators and relied on by citizens.

As the OIML enters its eighth decade, the BIPM congratulates our colleagues on 70 years of service to global society—and looks forward to continuing our collaboration in support of transparent, trusted measurement systems worldwide.

As science and technology evolve, the next generation of metrologists will be tasked with addressing new challenges—from digital transformation to emerging fields like quantum technologies. Preparing them with the skills, networks and international experience they need today is vital for the resilience of tomorrow’s global measurement system.

The BIPM–TÜBİTAK UME Project Placement Programme is one way the metrology community is rising to this challenge. Now in its eighth cycle, the initiative gives early-career metrologists the chance to deepen their technical expertise, gain international experience, and strengthen their understanding of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Starting from 1 September 2025, the latest cycle brings together 10 young metrologists from Albania, Azerbaijan, Bosnia and Herzegovina, Colombia, Egypt, Malaysia, Norway, Ukraine, Uzbekistan and Vietnam. Each participant is carrying out a dedicated project in TÜBİTAK UME’s laboratories, while also taking part in e-learning and seminars led by experts from the BIPM and TÜBİTAK UME.

Group photo of some of the participants from the BIPM–TÜBİTAK UME Project Placement Programme- with BIPM and TÜBİTAK UME colleagues - at the CIPM MRA Seminar (1-2 October)

A forum for learning and exchange

The programme provides much more than laboratory training. It also gives participants the chance to explore the mechanisms of the CIPM MRA, exchange ideas with peers, and build professional networks that will support their future work. As part of this programme, participants attended a CIPM MRA Seminar 1-2 October.

“What made this a truly special event for me was the chance to exchange ideas with these talented young metrologists, who will be running measurement science in the future. Their ambitions, questions and reflections on achieving international acceptance of measurements were inspiring.” — Chingis Kuanbayev, CBKT Programme Manager, BIPM 

By equipping young metrologists with hands-on skills and knowledge of international best practices, the programme helps National Metrology Institutes (NMIs) to strengthen their own capabilities. In turn, this supports the global system by ensuring more NMIs can contribute actively to comparisons, calibration services and the recognition of measurements worldwide.

Caption: Participants engaged in the October 2025 CIPM MRA Seminar, led by experts from BIPM and TÜBİTAK UME.

From classrooms to laboratories, the global push for better education on the International System of Units (SI) is vital for building the next generation of metrologists — and improving scientific literacy for all.

At the BIPM’s Scientific Symposium, held during the 150th Anniversary of the Metre Convention, Ms Elizabeth Benham of the United States’ National Institute of Standards and Technology (NIST) presented a poster entitled “Building the Next Generation of Metrologists: Opportunities to Improve SI Education and Scientific Literacy at 150 Years and Beyond.”

Her presentation explored systemic challenges in SI teaching across age groups and made the case for a globally coordinated effort to improve learning outcomes, beginning with clear, consistent messaging.

Two examples of hands-on resources highlighted in the poster include the SI Units Card Deck and DIY Kibble Balance. Ms Benham explained that through resources like these we can make abstract concepts more accessible and fun — and therefore make measurement science engaging and intuitive for everyone from early learners to seasoned professionals.

The Poster

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Listen to a 2-minute audio recording of Ms Benham explaining the poster, here.

The poster was co-authored with Katrice Lippa, Chief of the NIST Office of Weights and Measures, and drew from their collective experience leading the NIST Metric Program.

Watch Elizabeth Benham’s Presentation

Watch all 9 poster presentations at the BIPM 150th Anniversary Scientific Conference on the BIPM YouTube channel.

As countries across the Asia-Pacific region advance their energy transitions, coordinated measurement efforts are proving vital to ensure progress is consistent, traceable and equitable.

At the BIPM’s Scientific Symposium held during the 150th Anniversary of the Metre Convention, Dr Oijai Ongrai from National Institute of Metrology (Thailand) presented a poster on behalf of the Asia Pacific Metrology Programme (APMP) Energy Efficiency Focus Group (EEFG).

Her poster entitled, “Collaborative metrology efforts for sustainable energy solutions in the Asia-Pacific,” explores how joint technical activities are helping to strengthen regional energy measurement capabilities.

The research underscores the need for collective efforts to close energy measurement, reporting and verification (MRV) capability gaps and support countries at different stages of economic development and energy system maturity.

Priority areas addressed include hydrogen energy, electric vehicles, smart electricity grids and metrology for energy efficiency.

The Poster

Listen to a 2-minute audio recording of Dr Ongrai explaining her poster, here.

This project reflects the CIPM Strategy 2030+ goal of enabling impactful science for global benefit, and the BIPM’s mission to support internationally harmonized measurements.

Watch the Presentation

Artificial intelligence is revolutionizing healthcare — from diagnostics to personalized treatment — but concerns remain about the safety and fairness of AI systems trained on complex and often opaque datasets.

At the BIPM’s Scientific Symposium held during the 150th Anniversary of the Metre Convention, Dr Daniel Schwabe of the Physikalisch-Technische Bundesanstalt (PTB), presented a poster entitled “On the path to quality assurance of trustworthy AI in medicine: the METRIC-framework for systematically assessing medical training and test data.”

His poster explores how metrology can help assess the quality of data used in machine learning for medical applications — a critical concern as Europe moves towards regulating high-risk AI under the EU AI Act.

“One of the biggest levers we have to assess and improve AI performance lies in the data — especially training and test data.” – Dr Schwabe explained.

Machine learning models are only as good as the information they learn from, and how datasets are collected is equally important from a traceability, transparency and standardization standpoint.

Dr Schwabe’s poster outlines how the METRIC-framework can support conformity assessment procedures and provides a pathway toward regulatory readiness. It also highlights future directions, including the development of automated tools to assess dataset quality and to quantify how shortcomings in data may affect the behaviour of AI systems — such as their predictive accuracy or fairness across patient populations.

Poster

The METRIC-framework was co-authored by Katinka Becker, Martin Seyferth, Andreas Klaß and Tobias Schäffter, in collaboration with partners from PTB, the Technical University of Berlin, and the Einstein Centre for Digital Future.

Listen to a 3 minute audio recording of Dr Schwabe explaining their poster, here.

Watch Dr Schwabe’s Presentation

Watch all 9 poster presentations at the BIPM 150th Anniversary Scientific Conference on the BIPM YouTube channel.

As society becomes increasingly digitized and sensor-driven, the ways we perceive and quantify experiences like comfort, sound, or flavour are gaining scientific importance.

At the BIPM’s Scientific Symposium held during the 150th Anniversary of the Metre Convention, Mr Cristhian Paredes from Colombia’s Instituto Nacional de Metrología (INM) presented his poster, “Perceptual Metrology: A Future Frontier in Human Well-Being.”

His poster explores how metrology could evolve to include the quantification of sensory and perceptual experiences, alongside traditional physical measurements.

Mr Paredes Cardona explained that perceptual metrics — such as how sound is heard, how light is experienced, or how food tastes — are becoming increasingly relevant in high-tech industries, quality-of-life assessments and digital technologies.

“Metrology today is not only for the technical aspects. It is also for society and well-being,” — Mr Paredes emphasised.

While still in the early stages of development, perceptual metrology could pave the way for more inclusive and responsive systems in healthcare, workplace safety, consumer products and digital interaction. Mr Paredes’s poster explores potential pathways to building consensus on what it means to measure perception and how such measurements could be standardized.

The Poster

Listen to a 2-minute audio recording of Mr Paredes explaining his poster, here.

Watch the Presentation

A newly signed Memorandum of Understanding (MoU) between the BIPM and the International Commission on Illumination (CIE) reinforces their joint commitment to advancing global comparability in optical measurements, including photometry, radiometry and digital metrology.

The agreement was signed on 15 July 2025 in Varenna, Italy, by Martin Milton, Director of the BIPM and Diana Wernisch, Secretary General of the CIE. The MoU updates and replaces the previous agreement signed in 2007.

It formalizes collaboration in several key areas:

• ensuring data related to measurements of light, optical radiation, colour, optical properties of materials, photobiological and photochemical quantities are properly based on units traceable to the International System of Units (SI) and internationally recognized through the CIPM MRA,
• ensuring the definition of photometric units based on the constant for the luminous efficacy of defined visible radiation, K_cd, remains fit for purpose,
• collaborating on the development, implementation and promotion of the SI Digital Framework.

This renewed partnership reflects the BIPM’s broader mission to strengthen international measurement systems and support scientific and technological progress across sectors.

Read the BIPM–CIE MoU

Le Bureau international des poids et mesures (BIPM) exprime sa profonde tristesse à l’annonce du décès de M. Barry Inglis, ancien président du CIPM, le 4 juillet 2025.

M. Barry Inglis a été le PDG fondateur du National Measurement Institute, Australia (NMIA) dont il a été le premier directeur général en 2004, responsable de la métrologie de l’Australie. Membre du Comité international des poids et mesures (CIPM) de 2000 à 2019, il en a été vice-président de 2002 à 2011.

En 2011, il a été élu président du CIPM, devenant ainsi le premier Australien et seulement le deuxième non-Européen à occuper ce poste. Il a exercé cette fonction pendant huit ans, jusqu’en 2019. En tant que président du CIPM, il a dirigé l'organisation lors de deux réunions de la General Conférence générale des poids et mesures (CGPM). Il a initié une importante réforme de la gouvernance du CIPM et de ses processus internes. Il a notamment contribué de manière déterminante à l’adoption, en 2018, de la révision historique du Système international d’unités (SI).

En octobre 2019, le CIPM lui a décerné le titre de membre honoraire en reconnaissance de son engagement exceptionnel et de ses réalisations remarquables en tant que président.

Tous les membres du BIPM se souviendront de M. Inglis pour ses qualités humaines et son profond engagement envers le personnel.

Nous adressons nos plus sincères condoléances à son épouse Kay, à ses enfants et à ses petits-enfants.

From 20 to 22 May 2025, the global metrology community came together in Paris and Versailles to mark 150 years since the signing of the Metre Convention—a milestone that celebrates both the legacy and future of international scientific cooperation.

The #BIPM150 programme was more than a commemoration, it served as a platform for scientific exchange, policy dialogue and strategic reflection.

Over three days of keynote addresses, panel discussions and thematic sessions, speakers explored how metrology supports progress across trade, technology, sustainability and space science.

This summary highlights the key messages and calls to action that emerged—centred on global collaboration, scientific innovation and sustainable development.

• Full programme and speaker details
• Watch sessions on the BIPM YouTube Channel

Key messages from the BIPM 150th anniversary events

Celebrating 150 years of the Metre Convention and its impact on science and innovation.

The discussions throughout the week stressed that the ongoing work of the BIPM in metrology gives hope for a better world and shows what can be achieved when people work together to advance science and society.

The celebrations included two keynote addresses:

Prof. William D. Phillips, Nobel Prize laureate 1997, National Institute of Standards and Technology (NIST), USA, on “The SI - a tool for all mankind”.

Prof. Ken Alder, Professor of History and author of “The Measure of All Things” Northwestern University, USA, on “From the Metric System to the Metre Convention”.

Highlighting the importance of accurate measurement for global trade, sustainable development and scientific collaboration

Many of the speakers mentioned the need to reinforce the message to policy makers and governments about the vital role of metrology to society, industry and innovation. This included detailed explanations of the economic impact of metrology.

• Precision in measurement is the cornerstone of global progress and innovation. (Ms Amal Kasry, Chief of Section for Basic Science, research, Innovation and Engineering, UNESCO - Closing session)
• Quality infrastructure (QI) is a driver of innovation in emerging economies and metrology is at its heart. [...] Metrology is (also) critical in adding value to raw materials and manufactured goods produced within Africa, particularly in the context of the African Continental Free Trade Area (AfCFTA). (Dr Henry Rotich, Director General, Kenya Bureau of Standards (KEBS) – Session 4).

Exploring emerging challenges and future directions in metrology and its role in addressing the United Nations Sustainable Development Goals (SDGs)

There was a common call during the events that global cooperation, equitable access and inclusive innovation must shape the next era of measurement. This aligns powerfully with the frameworks that guide the collective vision for metrology, particularly the International Decade of Sciences for Sustainable Development and the International Year of Quantum Science and Technology (IYQ).

• Meeting future challenges will require resilience, the ability to embrace complexity, to view challenges as opportunities and to learn from mistakes. (Dr Nathalie von Siemens, Advisory Board Member, Physikalisch-Technische Bundesanstalt (PTB), Germany – Session 4)
• The motivation and benefits must be explained for countries to participate in “big-science” projects such as CERN and the Square Kilometre Array (SKA). (Prof. Alessandro de Angelis, Scientific Attaché at the Permanent Delegation of Italy to the International Organisations in Paris – Session 2)
• The international time and frequency community needs to continue to build on the success of the reference time scale Universal Coordinated Time (UTC) [...] A new definition of the second is needed to account for data from new frequency standards [...] and a reference time scale is required for the Moon. (Dr Pascale Defraigne, Time and Frequency Service, Royal Observatory of Belgium – Session 4)
• The BIPM’s 150-year legacy reflects its strength in adapting to change, embracing digitalization and supporting open science. (Prof. Alessandro de Angelis – Session 2).

Fostering multilateral dialogue on capacity building and innovation in metrology

Cooperation has been a guiding principle of the BIPM over the last 150 years. To meet future challenges for global metrology it is essential to continue with this principle and to engage actively with young metrologists. The importance of education and understanding the needs of stakeholders are vital to meet future challenges in metrology.

• The importance of scientific diplomacy, local engagement and cross-sector collaboration must be reinforced. (Mr Shaofeng Hu, Director, Division of Science Policy and Basic Sciences, Natural Sciences Sector, UNESCO – Session 2)
• The value of regional metrology cooperation in building quality infrastructure that benefits individual nations. (Dr Sharonmae Smith-Walker, CEO, CARICOM Regional Organisation for Standards and Quality (CROSQ), Jamaica – Session 2)
• The value of 'open science' and the need to communicate the long-term societal value of international scientific cooperation. (Prof. Alessandro de Angelis – Session 2)
• Capacity building and knowledge transfer must be prioritized. (Prof. Mustafa Çetintaş, Director, TÜBITAK Ulusal Metroloji Enstitüsü (TÜBİTAK UME), Türkiye – Session 2)
• STEM education is vital to improve public understanding of metrology. (Dr Nathalie von Siemens – Session 4)
• “Observership” in the CIPM could bring significant benefits to emerging economies. (Dr Victoria Coleman, CIPM member and National Measurement Institute, Australia (NMIA) – Session 2; Dr Henry Rotich – Session 4).

Watch the sessions

All sessions from the BIPM150 celebrations are available to watch on-demand via the BIPM YouTube Channel.

Keynote Addresses

“The SI - a tool for all mankind”

“From the Metric System to the Metre Convention”

BIPM-UNESCO World Metrology Day Symposium

Opening session | Panel Discussion Navigating the Future of Metrology: Addressing the challenges of Scientific and Technical Multilateralism | Session 3: 150 years of international use of the Metric System | Panel Discussion Future challenges for global metrology |

150^th Anniversary Scientific Conference

Session 1: Metrology in the quantum era | Session 2: Metrology for climate science | Session 3: The FAIR digital revolution | Session 4: Poster preview session

The BIPM is delighted to announce that its Director, Dr Martin Milton, has been appointed an Officer of the Order of the British Empire (OBE) in the 2025 King’s Birthday Honours.

The award, granted by His Majesty King Charles III, highlights Dr Milton’s global impact on scientific measurement and international cooperation.

Since assuming leadership in 2013, Dr Milton has guided the BIPM through critical scientific and institutional milestones:

• He played a central role in the redefinition of the International System of Units (SI), marking a new era in which units are defined by unchanging constants of nature.
• He strengthened partnerships with national and regional metrology institutes, promoting measurement standards that support international trade, innovation and research.
• He spearheaded capacity-building initiatives to extend metrological expertise and infrastructure to less-resourced nations.

Why this award matters

Recognition from His Majesty King Charles III, granted on the occasion of the King’s Official Birthday, underscores the global importance of measurement science.

Dr Milton’s work helps ensure global traceability in science, trade, health and climate measurement—vital in an era of digital transformation and evolving global challenges.

The BIPM’s 150th anniversary this year highlights the enduring legacy and international collaboration rooted in the 1875 Metre Convention.

This honour reflects not only his personal leadership but also the collective efforts of the BIPM and its global partners.

As the global measurement system adapts to a fast-changing scientific and policy landscape, the CIPM Strategy 2030+ sets out a clear vision for how metrology can continue to support innovation, resilience and inclusive development.

Launched just in time for the 150th Anniversary of the Metre Convention, on the BIPM website, the strategy outlines the priorities of the International Committee for Weights and Measures (CIPM). It serves as a guiding framework for the work of the BIPM, the Consultative Committees of the CIPM and supports alignment across national and regional metrology systems.

Five Strategic Priorities

The strategy is built around five key priorities (indicated on page 4) to strengthen and modernize the international metrology system:

1. Responding to evolving needs for metrology
2. Addressing key scientific challenges to advance the global measurement system
3. Deepening engagement with other international organizations on measurement
4. Universal adherence to the Metre Convention
5. Modernizing the operations of the Organization

Click here to download the full CIPM Strategy 2030+

What does the science of measurement look like through the lens of a camera?

From a kilogram prototype to satellite-synchronized quantum clocks—and the people behind them—the newly published book The International Bureau of Weights and Measures, 150 Years of Measures for the World is a richly illustrated history that brings the evolution of international metrology to life through photographs, stories and archival insight.

Launched at the Palais des Congrès in Versailles during the BIPM’s 150th Anniversary Scientific Symposium on 21 May 2025, this commemorative publication celebrates the long, complex and profoundly human story of building a global measurement system.

Written by Céline Fellag Ariouet, Head of the Executive and Meetings Office at the BIPM, who is completing her PhD on the history of the BIPM, the book blends institutional access with personal perspective—capturing both the scale and soul of the international metrology community retracing 150 years of BIPM history.

A Story in Images

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Far more than an illustrated history, this is a narrative told through archive documents, photographs and historical reflection—charting 150 years of scientific diplomacy and cooperation. Inside, readers will find:

• Rare archival material from the BIPM’s own collections
• Behind-the-scenes glimpses of the BIPM laboratories
• Historical and modern portraits of the metrology community and famous scientists like Pierre and Marie Curie, Albert Einstein, Gustave Eiffel who have been involved in the work of the BIPM
• Accompanying stories that give voice to the people, instruments and events that shaped the global measurement system

The book also includes a series of unique and historic images of the BIPM taken by the world-famous French photographer Robert Doisneau in 1942. These photographs had been stored in the BIPM archives until they were recently re-discovered by Céline Fellag Ariouet, the book’s author. Doisneau is probably best known for his 1950 image Le baiser de l'hôtel de ville (The Kiss by the City Hall), which was taken for the magazine Life.

The BIPM also commissioned contemporary photographer Raphaël Dallaporta to take a series of modern images at the BIPM to echo the work of Doisneau.

​

Notes from the Community

Measurement may be one of the most invisible forces in our lives—but it is also one of the most essential. What this book reveals is not only the technical progress of metrology, but the human endeavour behind it: the collective commitment to build something enduring, together, at a global scale.

Among those who have spoken most eloquently about the BIPM’s broader significance is palaeontologist and member of the Académie des sciences, Philippe Taquet, who in 2014 described it as:

“The BIPM is an organization that is a perfect and magnificent example of a work of peace. It symbolizes in a unique manner what people are able to achieve when they pool their wills, their knowledge, their talents and their abilities.”

From a historian’s vantage point, the challenge of establishing such global uniformity is not to be underestimated. In his foreword to the book, internationally renowned scholar and Professor of History at Northwestern University, Ken Alder, writes:

“Extracting uniformity from nature… is no simple task. And enlisting nations to join a common endeavour is more difficult still.”

This commemorative volume brings that very struggle into focus—tracing the path from the fragmented chaos of Old Regime France, where more than 800 units of measurement once coexisted, to the creation of a unified system that now connects economies across the globe through shared standards.

As Dr Martin Milton, Director of the BIPM, reflects, the book is:

“a narrative told through the achievements” of the institution—and a reminder of what can be accomplished not through competition, but through cooperation. Its legacy is all around us: in the time we keep, the medicine we take, and the trust we place in the world working as one.

150 Years of Measures for the World is available now in French bookshops and on the internet.

From UNESCO to Versailles—and far beyond—social media comes alive with moments of science, celebration and global connection.

As the Bureau International des Poids et Mesures (BIPM) marks 150 years since the signing of the Metre Convention, the global metrology community has turned to social media to share its enthusiasm, pride and participation in this historic moment.

LinkedIn, in particular, has seen an outpouring of activity as scientists, delegates, technical experts and communicators from across the world reflect on their role in the anniversary celebrations—both in person and from afar.

Photos from the Field

From formal group portraits at UNESCO headquarters in Paris to snapshots from the Scientific Conference at the Palais des Congrès in Versailles, attendees have posted a rich visual tapestry of the events held from 20–22 May 2025.

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See the full posts: Georgette Macdonald | Callie McAulay | Tara Cubel Liebisch | CFM Collège Français de Métrologie | Kangyoung Sung | Rahima Guliyeva

One post from Chemical Metrologist Hwee Tong Tan captured the spirit of the BIPM–UNESCO Symposium, calling it “an opportunity to celebrate with old friends and make new ones, united by a shared commitment to science, accuracy, and progress.”

Another from Metrologist Dorothy Mringie highlighted her contribution to the Versailles Scientific Conference, noting that she “was honored to present at Bureau International des Poids et Mesures (BIPM), alongside those who define the SI units and are shaping the future of time itself.”

Georja Calvin-Smith (Broadcast Journalist and Master of Ceremonies for the BIPM–UNESCO Symposium on 20 May) added to the outpouring of messages, posting an enthusiastic overview of her experience of the event and introduction to the world of metrology.

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And Edgar Flores Jardines, of the BIPM Chemistry Department, shared photos of the Poster Portion of the BIPM’s celebrations, noting that “when people from around the world come together to share ideas, we all move forward.”

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Celebrations Beyond France

Beyond Paris, institutions from every continent marked the Anniversary in their own way—posting photos of in-house exhibitions, scientific poster displays and technical presentations, all echoing this year’s shared theme:

“Measurements for all times, for all people.”

One of the most notable posts came from INRiM - Istituto Nazionale di Ricerca Metrologica, who posted photos of the Mole Antonelliana Torino lit up with the BIPM’s 150th Anniversary logo.

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See their full post here

Adding to the moment, the UK National Measurement Laboratory (NML) at LGC shared a photo of their mouthwatering 150th Anniversary cupcakes, handed out during their own celebrations. The sweet treats were part of a larger event that included a poster exhibition highlighting “how our science is helping to address some of the challenges facing the world today.”

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See their full post here

Taking a slightly more “thrill-seeking” approach to their celebrations, VSL National Metrology Institute in the Netherlands posted moments from a metrology-inspired Escape Room! We are told that the winning team managed to crack all the puzzles and escape in an impressive 5.47 minutes!

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See their full post here

And finally (for this round of outstanding LinkedIn posts at least) the National Metrology Institute of Malaysia, SIRIM (NMIM-SIRIM)’s account posted a series of lively video interviews. The clips captured participants’ key takeaways, lessons learned and personal impressions of World Metrology Day.

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See their account for all their videos here

Nous aurons le plaisir d’accueillir des participants du monde entier à l’occasion des 150 ans de la Convention du Mètre qui seront célébrer du 20 au 22 mai, à Paris et à Versailles.

Que vous participiez au Symposium de la Journée mondiale de la métrologie à l’UNESCO ou à la conférence scientifique à Versailles, assurez-vous d’avoir tout ce dont vous avez besoin !

INFORMATIONS ESSENTIELLES

CONSEILS PRATIQUES

1. Prévoyez suffisamment de temps pour passer les contrôles de sécurité et obtenir votre badge

Nous vous recommandons d’arriver sur chaque site au moins 30 minutes à l’avance afin de passer les contrôles de sécurité, procéder aux formalités d’accueil et rencontrer les autres participants.

2. Vérifiez où se trouve chaque site et planifiez votre itinéraire

L'UNESCO se trouve dans Paris et est accessible en métro. Le Palais des Congrès de Versailles est en dehors de Paris — planifiez votre itinéraire et prévoyez assez de temps pour vos déplacements.

3. Consultez le programme et la liste des conférenciers

Découvrez le programme exceptionnel de ces célébrations où vous aurez l’occasion d’écouter des personnalités de premier plan dans les domaines de la science, de l’industrie et de la coopération internationale. Voir le programme

4. Parlez du 150^e anniversaire avant et pendant les célébrations

Faites savoir à vos collègues et à vos réseaux que vous serez présent et partagez vos réflexions et les points forts de l'événement en utilisant #BIPM150 et @BIPM.Vous pouvez utiliser les graphiques et messages ‘prêts à l’emploi’ de notre Boîte à outils pour réseaux sociaux. Nous prévoyons de relayer vos publications et de mettre en avant vos contributions tout au long de la semaine.

Nous avons hâte de vous retrouver dans UNE SEMAINE pour célébrer de manière inspirante et avec un regard tourné vers l’avenir la métrologie mondiale.

Écrivons ensemble l’histoire — et le futur ! #BIPM150

Ces trois journées ont été synonymes de partage scientifique, de célébrations et de rencontres et ce 150^e anniversaire de la Convention du Mètre sera réellement inoubliable.

Que vous ayez assisté aux passionnantes sessions, à l’UNESCO, ou aux conférences mettant en lumière la collaboration scientifique, à Versailles, ou que vous ayez suivi l’anniversaire en ligne — nous vous remercions d’avoir pris part à cet événement historique !

Regardez notre vidéo récapitulative

Revivez l’énergie et l’enthousiasme de cette semaine d’anniversaire avec cette vidéo qui a été magnifiquement réalisée par notre talentueuse stagiaire Zhili Xu et présentée en avant première lors de la session finale de la conférence scientifique.

Feuilletez l’album photo

Des discours d’ouverture aux nombreux sourires ayant conclu les célébrations, découvrez l’album de l’anniversaire ici.

Regardez les moments marquants

Ne manquez pas notre playlist de l’anniversaire qui comprend, entre autres :

• la vidéo d’ouverture de la Journée mondiale de la métrologie à l’UNESCO,
• le message du directeur du BIPM à l’occasion des 150 ans de la Convention du Mètre,
• des messages de notre communauté mondiale de la métrologie.

Regardez la playlist de l’anniversaire ici : Playlist

Partagez et publiez !

Nous serions heureux de découvrir vos moments marquants !

Taggez @BureauInternationaldesPoidsetMesures (BIPM) et utilisez #BIPM150 | #WorldMetrologyDay | #MetrologyMatters

Nous mesurons combien cet anniversaire a été exceptionnel — et nous vous remercions !

Aux 150 prochaines années de métrologie !

Cette année 2025 marque le 150^e anniversaire de la signature de la Convention du Mètre.

Rejoignez le Bureau international des poids et mesures (BIPM) ainsi que des acteurs clés de la métrologiepour célébrer cet événement historique !

Dates : 20-22 mai 2025

Lieux : Paris | Versailles

Programme : Consultez le programme des trois jours !

Ces journées spéciales permettront de revenir sur les accomplissements de la métrologie lors de ces 150 années depuis la création du BIPM et de reconnaître l'importance fondamentale de la science des mesures dans tous les aspects de notre vie.

Cet anniversaire sera l'occasion d'honorer le passé mais aussi de présenter notre vision du futur, en explorant les innovations qui contribueront à définir le paysage de la métrologie lors des 50 prochaines années et au-delà.

Nous espérons vous compter parmi nous !

*Si vous ne pouvez pas venir en personne, suivez la retransmission en direct de la journée du 20 mai et partagez vos impressions sur LinkedIn - #BIPM150.

The BIPM has appointed Dr Kazuaki Yamazawa from the Asia Pacific Metrology Programme (APMP) as the new Executive Secretary of the Joint Committee of the Regional Metrology Organizations and the BIPM (JCRB), bringing over 25 years of experience in measurement science, quality systems and international cooperation.

Dr Yamazawa began his career at the National Metrology Institute of Japan (NMIJ, AIST) in 1999—the same year the CIPM MRA was signed. With a background in electrical engineering and thermometry, he has since held key positions in metrology and accreditation, including as Quality Manager at NMIJ and Chair of the APMP Technical Committee for Quality Systems. He has also contributed to international frameworks such as OIML-CS and ILAC AIC.

“It is a coincidence that I entered metrology the same year the CIPM MRA was signed,” Dr Yamazawa said. “Having worked in both technical and quality-focused roles, I hope to support the continued global trust in the CIPM MRA and strengthen engagement across our regions.”

As Executive Secretary, Dr Yamazawa will help coordinate with the six Regional Metrology Organizations, ensuring continued alignment and development of the CIPM MRA.

Mr Ibrahim Ahmed (left) welcomes Dr Kazuaki Yamazawa (right) as the new Executive Secretary of the JCRB at the BIPM.

Dr Yamazawa succeeds Mr Ibrahim Ahmed (Kenya), who will return to KEBS in June 2025 after two years in the post. During his time at the BIPM, Mr Ahmed has played a vital role in strengthening coordination among Regional Metrology Organizations (RMOs), advancing the objectives of the CIPM MRA, and supporting the global metrology community with professionalism and insight.

Reflecting on his secondment, Mr Ahmed shared:

“My experience at the BIPM was truly enriching—professionally and personally. I will carry forward the global networks, knowledge and coordination skills I gained to support improvements at KEBS and in the AFRIMETS community,” Mr Ahmed said.

The BIPM extends its sincere thanks to Mr Ahmed for his dedication and valuable contributions over the past two years. His commitment to international collaboration and capacity-building has left a lasting impact, and we wish him continued success.

The BIPM also warmly welcomes Dr Yamazawa to the role and looks forward to the perspectives and expertise he will bring to the continued development of the JCRB and the CIPM MRA.

We’re just one month away from celebrating 150 years of the Metre Convention—a landmark in the history of international scientific cooperation.

To mark this moment, BIPM Director Dr Martin Milton shares a personal message reflecting on the origins of the Convention, its global impact today and what lies ahead for international metrology.

This video follows the joint written statement from the Directors of the BIPM and the OIML, published last month, which launched the official anniversary campaign:

We are excited to announce that over 80% of the scientific posters submitted for the 150th Anniversary of the Metre Convention and the Bureau International des Poids et Mesures (BIPM) are now available online!

• ➤ Browse the Posters

These posters, contributed by metrologists from around the world, showcase research that reflects the global impact of measurement science. From fundamental metrology and quantum technologies to digital transformation and advancements in health, industry, and energy, this collection highlights how metrology is driving innovation across multiple disciplines.

Key Topics Include:

• SI Units and Fundamental Metrology
• Health and Life Sciences
• Safe Food and Water
• Energy
• Industry and Advanced Manufacturing
• Digital Transformation, AI, and Systems Metrology
• Metrology for Quantum Technologies
• New Opportunities for Metrology

2025, A Historic Milestone

As we begin 2025, a year of great significance for the global metrology community, the Directors of the BIPM and the BIML have issued a joint statement to mark the 150th Anniversary of the Metre Convention. This foundational agreement established the BIPM and laid the groundwork for international collaboration in measurement science.

In their message, the Directors reflect on the transformative impact of metrology over the past 150 years and emphasize its vital role in addressing global challenges. The statement sets the tone for the celebrations leading up to World Metrology Day on May 20th, when the world will come together to honour this historic milestone.

Read the full statement here and join us in celebrating the enduring legacy and bright future of metrology.

Focus areas: climate science, quantum technologies and the digital transformation

We are pleased to announce that applications are now open for the 2025 Varenna Summer School on Metrology, organised by the Italian Physical Society (SIF), with support from the BIPM. The course will take place from 9 to 18 July 2025 at the historic Villa Monastero in Varenna, Italy, as part of the renowned Enrico Fermi International School of Physics series.

This year’s theme, “Future needs for metrology: Climate science, quantum technologies and the digital transformation,” brings together leading experts to explore how metrology is evolving to meet global challenges across science and society.

Participants may choose to attend the full 10-day programme or opt for a focused 7-day track by selecting one optional module 

Application deadline: 24 April 2025 

More information and programme details

Opportunities for sponsorship

In laboratories around the world, women are shaping the future of measurement science. Their expertise underpins everything from medical breakthroughs to environmental sustainability, space exploration and global trade.

Yet, despite the fundamental role metrology plays in our daily lives, the voices of women in this field are not always equally heard.

On this International Day for Women and Girls in Science 2025, six leading female metrologists are sharing their advice to young women aspiring to careers in their field. We hope that their voices will contribute global conversation on this important day and beyond.

On Navigating Perceptions

Curiosity is the key to thriving in any scientific field, no matter the gender balance in the room. The science is what should captivate you and that passion is what will carry you through.

"Don't ask yourself whether this field is “women-friendly” says Dr Hao Fang, Principal Physicist – Mass, Kibble Balance, the Bureau International des Poids et Mesures (BIPM)  “Simply approach it with enthusiasm and curiosity.”

“It makes me laugh when people call me 'Mr Fang' in emails. The first time I became acutely aware of the gender imbalance in metrology was during one of the very first technical meetings of the Kibble Balance, when the director of the hosting institute remarked in surprise, ‘Oh, there’s a woman sitting in the meeting room.’

But the truth is, after 20 years working on in this field, I no longer think about the fact that I am the only woman in a room. I think about how to get more time in the lab, diving deeper into this fascinating and complex experiment.”

On Career Paths in Metrology

For women in science, metrology offers a uniquely rewarding career path, where real-world impact meets intellectual challenge. Metrology bridges the gap between theory and application, providing measurable solutions to global challenges.

“Unlike research or publication alone, this profession has tangible real-world impacts [that extend to and instil confidence in] testing laboratories, patients, consumers, regulators, policymakers, standards and conformance bodies,” says Dr Tang Lin Teo, Division Director, Chemical Metrology Division, Health Sciences Authority (HSA).

My team and I tackle emerging measurement challenges daily, applying metrological expertise to public health issues and engaging with diverse stakeholders.

It is a career that marries scientific rigor with societal relevance, where every advancement contributes to building trust and safeguarding well-being.

So, for young women who desire to make a difference through science like me, you can be sure that a career in chemical metrology is fulfilling, dynamic and impactful.

Beyond technical expertise, women in metrology bring new perspectives, collaborative leadership and innovative thinking to the field.

“Women bring invaluable contributions to the field of metrology," asserts Shamsa Saleh Al Kayyoomi, Senior Electricity, Time and Frequency Metrologist at the Emirates Metrology Institute.

From “enhancing accuracy and research” to “the application of measurement technologies,” women’s contributions are essential for “ever more innovative and impactful results."

And, in fields like medical physics, where precision can mean the difference between life and death, Dr Zakithi Msimang, Medical Radiation Physicist - SSDL Officer, Division of Human Health, Department of Nuclear Sciences and Applications, the International Atomic Energy Agency (IAEA), reminds us that collaboration and confidence in your abilities are essential.

Her advice to women pursuing a career in metrology is to:

“Be passionate about your work, build upon your strengths and embrace opportunities to learn from your team members. Your greatest competition is yourself.”

In summary, if you trust your skills and stay open to learning from others, the rewards will be immeasurable—not just for your own career but for the people whose lives your work impacts.

On Expanding Your Horizons

Finally, a career in metrology is not confined to a single laboratory or country—it is a truly global science.

For young women entering the field, metrology can offer opportunities to work alongside scientists from diverse backgrounds, contribute to groundbreaking research and see first-hand how measurement science shapes policies, industries and lives on a global scale.

“The future is interdisciplinary” says Dr Victoria Coleman, Section Manager, Nanometrology, National Measurement Institute, Australia (NMIA) ; International Committee for Weights and Measures (CIPM) Member; and Consultative Committee for Length (CCL) President.

“There are so many opportunities to bring different experiences and technical backgrounds together to solve complex problems. Know that in this field, your voice and your experience will make a difference!”

Continuing this theme, Dr Anna Cypionka, Director of the International Liaison and Communication Department at the Bureau International des Poids et Mesures (BIPM) reminds young scientists that “Embracing mobility and cross-border cooperation can open unexpected doors”

"I couldn't have imagined, when I started my career as a biochemist in Germany, that it would take me across continents (from Latin America and South East Asia to France), connecting with experts to solve challenges that impact trade, healthcare and environmental monitoring.

My advice to young women considering a career in metrology is to stay curious and open to opportunities beyond national borders—your contributions could be invaluable on the world stage."

A Call to the Next Generation

From laboratories in national institutes to global collaborations, the future of metrology depends on attracting young minds from all walks of life who will drive the next wave of scientific advancement.

On this International Day for Women and Girls in Science and during this, our 150th Anniversary year, the BIPM would like to reaffirm its commitment to fostering a global metrology community that is forward thinking and represents the needs and voices of people everywhere. 

Celebrating “Measurements for all times, for all people”

The BIPM and OIML are proud to unveil the official World Metrology Day 2025 poster, marking the 150th anniversary of the Metre Convention. This year’s theme, “Measurements for all times, for all people,” highlights the enduring and universal importance of accurate measurements in science, industry and daily life.

A Resource to Promote Metrology

We encourage National Metrology Institutes, academic institutions, industry partners and policymakers to download and use the poster in their World Metrology Day activities. The poster can be displayed at events, shared on social media and incorporated into educational materials to:

• Highlight the critical role of measurement science in addressing global challenges.
• Raise awareness of the Metre Convention’s historical and ongoing impact.
• Inspire discussions on metrology’s role in achieving sustainability and innovation.

The poster is available in multiple formats, including Adobe® PhotoShop® and PDF, and can be customized with your organization’s logo and translated to suit local audiences.

Download and Translate the Poster

Visit our Media and Resources page to download the official poster and access guidelines for its use. Share your translated versions and details of your activities to help amplify the global celebration of metrology on our World Metrology Day website.

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Join Us in Celebrating 150 Years of Metrology

World Metrology Day 2025 is a unique opportunity to honour metrology’s vital role in society and its future potential. By using and promoting this poster, you contribute to a global effort to highlight the importance of measurements for all people, everywhere.

For further information, visit the official website.

How can governments design regulatory frameworks that are trusted, effective and fit for future challenges?

On 22 January 2026, the Organisation for Economic Co-operation and Development (OECD), in partnership with the Bureau International des Poids et Mesures (BIPM), Physikalisch-Technische Bundesanstalt (PTB) and the British Standards Institution (BSI), will host a joint public webinar titled:

“Building Trust in Regulation: The Role of Standards, Measurement, and Assurance.”

The webinar will take place online from 11:00 to 12:30 CET (10:00–11:30 UTC) and is open to all members of the international quality infrastructure, regulatory and policy communities.

Register for the webinar

Why this webinar matters

Trust in regulation underpins economic growth, market access, innovation and public confidence — particularly at a time when governments are navigating complex global challenges, from climate transition to digital transformation.

The webinar builds on the recently published joint report, Reinforcing Regulatory Frameworks through Standards, Measurements and Assurance: Making Better Use of Quality Infrastructure in Policymaking, which examines how quality infrastructure (QI) systems can better support regulatory objectives and policy outcomes.

Speakers will present key findings from the report and share perspectives from across the QI ecosystem, highlighting how coordinated use of standards, measurement and conformity assessment can strengthen regulatory frameworks and support future-ready policymaking.

Programme highlights

The 90-minute webinar will include:

• Opening remarks from the OECD
• Presentation of the joint QI report, outlining opportunities and gaps in current regulatory–QI linkages
• Thematic contributions covering:
  • QI for competitiveness, trade and market access
  • Governance and capacity building for effective national QI systems
  • Modernizing the QI system to support innovation and tackle global challenges
• Q&A with speakers

The session will conclude with a short wrap-up highlighting key takeaways for policymakers and the international metrology and standards community.

A major milestone has been reached in electrical metrology with the successful completion of the first key comparison of Josephson voltage standards for AC voltage, carried out between the Bureau International des Poids et Mesures (BIPM) and the Physikalisch-Technische Bundesanstalt (PTB).

The comparison, completed in 2025, covered AC voltage amplitudes of 0.75 V and 7 V across a frequency range from 62.5 Hz to 1.25 kHz, demonstrating agreement between the two systems at the level of a few tens of nanovolts per volt.

This comparison represents an important step in extending the international measurement infrastructure for electrical quantities, supporting traceability and equivalence for AC voltage at the highest level. It strengthens confidence that AC voltage measurements realized in different countries are consistent, comparable and anchored to the same quantum-defined reference.

Photo caption: Stéphane Solve and Régis Chayramy (BIPM) preparing and operating the measurement setup used for the key comparison of Josephson standards for AC voltage.

 

How the comparison was carried out

The comparison was carried out using a stable AC voltage source as a transfer standard, which was alternatively measured by the PTB and BIPM AC quantum voltage standards. The AC quantum voltage standards generated a stepwise-approximated sinewave of the same frequency and the same nominal root-mean-square value as the transfer standard. The small voltage differences between the transfer standard and the AC quantum voltmeters were measured with a synchronized sampler. The measured voltage differences together with the predictable quantized voltages allowed us to determine the root-mean-square value of the signal from the transfer standard.

The results: Across both voltage amplitudes and nearly all frequencies, the two systems showed excellent agreement, with relative differences at the level of a few tens of nanovolts per volt, confirming the robustness and maturity of quantum-based AC voltage measurements.

This confirms that Josephson-based techniques can deliver highly reliable and reproducible AC voltage measurements, suitable for key comparison purposes.

The full comparison results have been published in Metrologia and can be accessed here.

Background

Since the early 1990s, the BIPM has coordinated an on-site, on-going key comparisons programme of Josephson voltage standards for DC voltage, supporting global equivalence in electrical measurements through comparisons such as BIPM.EM-K10. As the international use of quantum measurement technology has expanded into AC applications, the need for equivalent comparison capabilities has grown.

In response, the Consultative Committee for Electricity and Magnetism (CCEM) tasked the BIPM with extending the key comparison BIPM.EM-K10 to AC voltage. Over the past seven years, the BIPM — with significant technical collaboration from PTB, NIST and KRISS — has carried out pilot studies to develop suitable measurement methods, assessed AC signal generators, and established a robust comparison protocol. This protocol was formally approved by the CCEM in 2023.

Photo caption: From left to right: Luis Palafox (PTB), Stéphane Solve and Régis Chayramy (BIPM) and Ralf Behr (PTB) in the voltage laboratory at the PTB (Braunschweig) during the bilateral AC Josephson voltage key comparison.

Published 21 January 2026

Le BIPM compte 64 États Parties à la Convention du Mètre ("États Membres") et 37 États et entités économiques associés.

États Membres Associés

L'Arrangement de reconnaissance mutuelle du CIPM (CIPM MRA) est la structure permettant aux laboratoires nationaux de métrologie de démontrer l'équivalence internationale de leurs étalons de mesure et des certificats d'étalonnage et de mesurage qu’ils émettent.

Le CIPM MRA assure ainsi la reconnaissance internationale des aptitudes en matière de mesures et d'étalonnages (CMCs) (examinées et approuvées par les pairs) des laboratoires participants. Les CMCs, une fois approuvées, sont publiées dans la base de données du CIPM MRA (KCDB), qui contient également d'autres informations techniques sur les comparaisons effectuées.

Au sujet de la KCDB

Bureau du directeur

Département des relations internationales et de la communication

Département de la chimie Département des rayonnements ionisants

Département de la métrologie en physique Département du temps

Services généraux Services informatiques

Le SI est le système pratique d'unités de mesure recommandées.

Depuis l'adoption historique de la Résolution 1 par la CGPM en 2018, toutes les unités du SI sont définies à partir de constantes de la nature, ce qui permet d'assurer la stabilité du SI dans le futur et ouvre la voie à l'utilisation de nouvelles technologies, y compris celles quantiques, pour mettre en pratique les définitions.

Définitions des unités

Le Programme du BIPM de renforcement des capacités et de transfert des connaissances (CBKT) a pour objectif d’accroître l’efficacité de la participation des États Membres et Associés au système métrologique mondial coordonné.

En 2020, le programme CBKT du BIPM a été enrichi avec le lancement d'une plateforme d'apprentissage en ligne destinée au personnel des laboratoires nationaux et désignés des États Membres et Associés. Cette plateforme propose des cours spécifiques sur les activités de la métrologie scientifique, notamment sur les mécanismes du CIPM MRA. Le développement de la plateforme se poursuit afin d'offrir la possibilité d'héberger du contenu pour les organisations régionales de métrologie.

Programme CBKT du BIPM e-learning.bipm.org

As we begin 2026, the Bureau International des Poids et Mesures (BIPM) extends its warmest wishes to the international metrology community for the year ahead.

The coming months will be an important period for our community. In 2026, preparations will advance toward the 28th meeting of the General Conference on Weights and Measures (CGPM), which will discuss and make decisions on scientific, institutional and financial matters related to the BIPM and its work. At the same time, the BIPM enters a new chapter with Dr Annette Koo taking up her role as Director.

Throughout the year, the BIPM will continue to support coordination across the metrology system, deliver technical work, capacity-building activities, and provide a forum for conversation and collaboration.

To stay connected in 2026, we invite our community to subscribe to BIPM eNews and to follow and engage with us on LinkedIn and YouTube, where we will share our latest updates, resources and insights from across the world of metrology.

We look forward to working together in the year ahead.

Le SI est le système pratique d'unités de mesure recommandées.

Depuis l'adoption historique de la Résolution 1 par la CGPM en 2018, toutes les unités du SI sont définies à partir de constantes de la nature, ce qui permet d'assurer la stabilité du SI dans le futur et ouvre la voie à l'utilisation de nouvelles technologies, y compris celles quantiques, pour mettre en pratique les définitions.

Définitions des unités

Depuis le 8 février 2022, le BIPM compte 63 États Parties à la Convention du Mètre ("États Membres") et 40 États et entités économiques associés.

États Membres Associés

Le SI est le système pratique d'unités de mesure recommandées.

Depuis l'adoption historique de la Résolution 1 par la CGPM en 2018, toutes les unités du SI sont définies à partir de constantes de la nature, ce qui permet d'assurer la stabilité du SI dans le futur et ouvre la voie à l'utilisation de nouvelles technologies, y compris celles quantiques, pour mettre en pratique les définitions.

Définitions des unités

Le BIPM est l'organisation intergouvernementale créée par la Convention du Mètre ; ses États Membres agissent en commun en ce qui concerne les sujets liés à la science des mesures et aux étalons de mesure.

Vision

Notre vision est d'être universellement reconnu comme l'organisation de référence internationale concernant le système mondial de mesure.

Mission

Notre mission est de travailler au niveau international avec les laboratoires nationaux de métrologie de ses États Membres, les organisations régionales de métrologie, ainsi que ses partenaires stratégiques, et de tirer parti de son statut d'organisation internationale et impartiale pour promouvoir et faire avancer la comparabilité mondiale des mesures pour :

• la découverte et l'innovation scientifique,
• la production industrielle et le commerce international,
• l'amélioration de la qualité de vie et la préservation de l'environnement.

Objectifs

• Représenter la communauté métrologique internationale afin d'en maximiser la reconnaissance et l'impact.
  • Nous coopérons avec les organisations intergouvernementales pertinentes ainsi qu'avec d'autres organismes internationaux afin de développer les possibilités de tirer parti de la métrologie pour relever les défis mondiaux.


• Être un centre de collaboration scientifique et technique entre les États Membres, leur permettant de développer des aptitudes pour les comparaisons internationales de mesure, sur le principe des frais partagés.
  • Nous coordonnons des comparaisons internationales des étalons de mesure nationaux considérées comme de la plus haute priorité.
  • Nous établissons et maintenons des étalons de référence appropriés utilisés pour conduire, au plus haut niveau métrologique, des comparaisons clés internationales et assurons des étalonnages dans le cadre de ces comparaisons.


• Coordonner le système mondial de mesure, en garantissant la comparabilité et la reconnaissance au niveau international des résultats de mesures obtenus.
  • Nous coordonnons des activités entre les laboratoires nationaux de métrologie des États Membres et les organisations régionales de métrologie, notamment en proposant des services techniques en soutien au CIPM MRA et en fournissant l'infrastructure nécessaire au développement et à la promotion du SI.

Notre mission et nos objectifs du BIPM sont étayés par notre travail dans les domaines suivants :

• le renforcement des capacités, avec pour objectif de parvenir à un équilibre global des aptitudes métrologiques des États Membres ;


• le transfert de connaissances, qui permet de garantir que le travail du BIPM a le plus grand impact possible.

Le Programme du BIPM de renforcement des capacités et de transfert des connaissances (CBKT) a pour objectif d’accroître l’efficacité de la participation des États Membres et Associés au système métrologique mondial coordonné.

En 2020, le programme CBKT du BIPM a été enrichi avec le lancement d'une plateforme d'apprentissage en ligne destinée au personnel des laboratoires nationaux et désignés des États Membres et Associés. Cette plateforme propose des cours spécifiques sur les activités de la métrologie scientifique, notamment sur les mécanismes du CIPM MRA. Le développement de la plateforme se poursuit afin d'offrir la possibilité d'héberger du contenu pour les organisations régionales de métrologie.

Programme CBKT du BIPM e-learning.bipm.org

L'Arrangement de reconnaissance mutuelle du CIPM (CIPM MRA) est la structure permettant aux laboratoires nationaux de métrologie de démontrer l'équivalence internationale de leurs étalons de mesure et des certificats d'étalonnage et de mesurage qu’ils émettent.

Le CIPM MRA assure ainsi la reconnaissance internationale des aptitudes en matière de mesures et d'étalonnages (CMCs) (examinées et approuvées par les pairs) des laboratoires participants. Les CMCs, une fois approuvées, sont publiées dans la base de données du CIPM MRA (KCDB), qui contient également d'autres informations techniques sur les comparaisons effectuées.

Au sujet de la KCDB

Bureau du directeur

Département des relations internationales et de la communication

Département de la chimie Département des rayonnements ionisants

Département de la métrologie en physique Département du temps

Services généraux Services informatiques

In response to overwhelming interest, the BIPM is pleased to announce that the deadline for poster abstract submissions for the 150th anniversary of the Metre Convention has been extended to 15 February 2025.

This extension ensures that researchers, scientists and innovators from around the globe have ample time to participate in this historic celebration of measurement science.

Why Participate?

As part of this special anniversary, selected posters will spotlight groundbreaking advancements and solutions in metrology. Lead authors will also have the opportunity to present their work during a high-profile event in Versailles on 21 May 2025.

Key Themes for Posters:

The Bureau International des Poids et Mesures (BIPM) invites abstracts that explore metrology challenges and innovations across nine key topics:

• SI Units and Fundamental Metrology
• Environment and Climate Change
• Health and Life Sciences
• Safe Food and Water
• Energy
• Industry and Advanced Manufacturing
• Digital Transformation, AI and Systems Metrology
• Metrology for Quantum Technologies
• New Opportunities for Metrology

How to Submit:

Abstract submissions (up to 500 words) must be in English and describe a metrology challenge, its significance and progress or future needs in the field.

Abstract Deadline: 15 February 2025

Accepted abstracts will require an electronic poster (PDF) and a 3-minute audio presentation (MP3) by 15 March 2025.

What’s in it for You?

By submitting a poster, you’ll gain the opportunity to:

• Showcase your research to a global audience of metrology experts.
• Contribute to the 150th anniversary celebration of the Metre Convention.
• Have your work featured on our 150th Anniversary Event website.

International Atomic Time (TAI) achieves its stability from more than 450 atomic clocks world-wide and its accuracy from a small number of primary and secondary frequency standards which aim at realizing the SI second with the smallest uncertainty. Each month the BIPM publishes, in section 3 of Circular T [1], an estimation of the TAI frequency accuracy as measured by those individual frequency standards, as well as an ensemble average computed by the BIPM. In November 2021, sixteen different frequency standards operated in eleven laboratories contributed to this estimation, including ten Cs fountains, one Rb fountain, one Sr optical lattice and two Yb optical lattice clocks, in addition to the two legacy Cs beams operated by the PTB. This constitutes a record level of participation, both in terms of the number of different standards and the number of different laboratories.

Optical clocks have reached a proven accuracy of order 10⁻¹⁸ in relative frequency, surpassing the present Cs fountains by two orders of magnitude and driving the Consultative Committee for Time and Frequency (CCTF) to initiate work towards a redefinition of the second [2]. The CCTF has set-up a wide-ranging task force of experts, which worked to define a number of mandatory criteria to be achieved before changing the definition. One of the mandatory criteria states that optical standards should regularly contribute to TAI, with a goal of at least three contributions per month, with a total uncertainty not larger than 2 × 10⁻¹⁶. This criterion is intended to ensure that the accuracy of TAI is at least maintained and hopefully improved when the redefinition takes place and that it will be based on a robust set of optical frequency standards. Indeed after redefinition Cs fountains will become secondary standards with enlarged uncertainty while the uncertainty of optical standards will be reduced and it is important to ensure that the overall effect of the change is beneficial to TAI.

In 2021, 13 evaluations of optical frequency standards could be used to calibrate TAI, this is more than twice as many as the total number in the preceding three years (PSFS chart). Furthermore, two of them had a total uncertainty around 2.5 × 10⁻¹⁶, which is close to the requirement set in the criterion for redefinition. While this is only a first step towards achieving one of the mandatory criteria, this shows the strong impetus from NMIs and DIs to operate optical frequency standards and move towards the redefinition. The results show significant progress in the operational capabilities, with optical clock uptime exceeding 90 % in some cases. This allows longer operating period and reduced frequency transfer uncertainty, key factors to achieve contributions of optical standards to TAI with a total uncertainty not larger than 2 × 10⁻¹⁶ as required. Looking at the past history of Cs fountain development (PSFS chart) we expect that a similar trend will occur for optical standards, so that the redefinition of the second could take place in 2030 as in the current CCTF plans.

Contact Gérard Petit for more information.

1. https://webtai.bipm.org/ftp/pub/tai/Circular-T/cirthtm/cirt.407.html
2. https://www.bipm.org/en/committees/cc/cctf/22-_1-2020