XIXth General Conference on Weights and Measures

XIXth General Conference on Weights and Measures
Name	XIXth General Conference on Weights and Measures
Date	2018-11
Location	Sèvres, Hauts-de-Seine
Venue	International Bureau of Weights and Measures
Participants	Member States of the International Bureau of Weights and Measures
Preceding	XVIIIth General Conference on Weights and Measures
Succeeding	XXth General Conference on Weights and Measures

XIXth General Conference on Weights and Measures.

The XIXth General Conference on Weights and Measures convened delegates from national metrology institutes, international organisations, and scientific bodies to ratify major revisions to measurement standards. The conference brought together representatives from the International Bureau of Weights and Measures, the International Committee for Weights and Measures, national laboratories such as National Institute of Standards and Technology, Physikalisch-Technische Bundesanstalt, and regional organisations including the European Association of National Metrology Institutes, Asia Pacific Metrology Programme, and Inter-American Metrology System.

Background and Purpose

The conference built on a lineage traced to the Metre Convention and successive general conferences that established the International System of Units and the role of the International Bureau of Weights and Measures. Its purpose was to review proposals from the International Committee for Weights and Measures and advisory bodies such as the Consultative Committee for Units, the Consultative Committee for Thermometry, and the Consultative Committee for Mass and Related Quantities regarding redefinitions of base units. Delegates included directors from institutions like National Physical Laboratory (United Kingdom), Laboratoire national de métrologie et d'essais, and representatives of treaty parties to the Metre Convention.

Preparations and Participants

Preparations involved technical committees, interlaboratory comparisons coordinated by organisations such as the International Organization for Standardization and the International Electrotechnical Commission, and input from research groups at universities and national labs like Massachusetts Institute of Technology, University of Cambridge, and École Normale Supérieure. Key participants included metrologists affiliated with Bureau International des Poids et Mesures projects, delegates from member states such as France, United States, Germany, China, Japan, United Kingdom, and representatives from regional bodies like the African Metrology Organisation. Observers included scientific unions such as the International Union of Pure and Applied Physics and the International Union of Pure and Applied Chemistry.

Decisions and Resolutions

Delegates considered resolutions drafted by the International Committee for Weights and Measures and endorsed changes backed by experimental results from institutions including National Research Council (Canada), NIST, and PTB. The conference reached consensus on amendments affecting definitions rooted in constants such as the Planck constant, the Boltzmann constant, and the Avogadro constant. Voting procedures referenced the statutes of the Metre Convention and precedent from earlier conferences such as the Eleventh General Conference on Weights and Measures. Resolutions formalised wording for the redefinition of base units and set timetables for legal and technical adoption by member states.

Impact on the International System of Units (SI)

The conference's resolutions effected a paradigm shift by tying SI base units to fundamental constants, impacting the kilogram, ampere, kelvin, and mole. Terminology and traceability chains used by laboratories such as VSL, METAS, and NPL required updates to align with new definitions, and national measurement infrastructures in countries including India and Brazil undertook legal changes referencing domestic acts and standards offices. The decision influenced metrology practices in high-precision fields associated with institutions like CERN, European Space Agency, and European Southern Observatory where measurements of mass, current, and temperature underpin experiments and engineering. Standardisation bodies such as ISO and IEC incorporated the revised SI wording into international standards and calibration procedures.

Scientific and Technical Discussions

Technical sessions reviewed experimental determinations of constants from experiments using the Kibble balance and the X-ray crystal density method conducted at laboratories including NIST, BNM-LNE, PTB, and KRISS. Presentations discussed advances in quantum electrical standards referencing the Josephson effect and the quantum Hall effect with contributions from researchers at University of Manchester and École Polytechnique Fédérale de Lausanne. Thermometry debates involved acoustic gas thermometry and dielectric constant gas thermometry results from teams at NPL and NMIJ. Measurement uncertainty evaluations cited the Guide to the Expression of Uncertainty in Measurement as practised by national metrology institutes. Liaison reports from the International Committee for Weights and Measures and consultative committees provided the scientific rationale underpinning the resolutions.

Implementation and Follow-up Measures

Following adoption, member states and laboratories initiated implementation plans coordinated by the International Bureau of Weights and Measures with timelines for legal metrology offices and calibration services in jurisdictions such as Sweden, South Africa, and Canada. Training and dissemination involved workshops led by the BIPM and collaborations with regional metrology organisations like COOMET and WELMEC. Technical follow-up included interlaboratory comparisons, new calibration certificates referencing fixed constants, and updates to reference materials hosted at facilities such as LNE and PTB. The conference mandated periodic reviews by the International Committee for Weights and Measures to monitor uptake and address practical issues, ensuring continuity with the historical framework established under the Metre Convention.

Category:Conferences