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Comparisons piloted by the BIPM

International comparisons take many forms. Some are carried out by the BIPM; others are organized by a Consultative Committee and may or may not include the BIPM; many more are organized and carried out, usually as part of the activities of a regional metrology organization, by the NMIs and other institutes participating in the CIPM MRA. Most BIPM comparisons are among the key comparisons chosen by the Consultative Committees to establish the degree of equivalence between national measurement standards.

For the comparisons carried out by the BIPM, the following procedures are used:

  • national standards are brought to the BIPM and compared with the BIPM standards, either individually or as a group, with similar standards from other national metrology institutes. The national standards may be either primary or secondary standards.

  • BIPM travelling primary standards are taken to a national metrology institute for comparison with those of that institute or, as increasingly happens, with standards from a group of national institutes from the same geographical region.

  • well-characterized BIPM travelling secondary standards are sent to a national metrology institute for comparison with the national standards of that institute.

This section lists the international comparisons piloted by the BIPM – mainly of the first type – many of which are ongoing BIPM key comparisons.

Mass Standards
  • CCM.M-K8.2019
  • Realization of the kilogram

    Resistance
  • BIPM.EM-K12
  • Quantum Hall resistance standards and their scaling to other resistance values (Resistance ratios: 100 ohms/RH(2), 10 kiloohms/100 ohms, and 100 ohms/1 ohm)
  • BIPM.EM-K13.a
  • Comparison of resistance standards (Resistance: 1 ohm)
  • BIPM.EM-K13.b
  • Comparison of resistance standards (Resistance: 10 kiloohms)

    DC Voltage and Current
  • BIPM.EM-K10.a
  • DC voltage, Josephson standards (DC voltage: 1.018 V)
  • BIPM.EM-K10.b
  • DC voltage, Josephson standards (DC voltage: 10 V)
  • BIPM.EM-K11.a
  • DC voltage, Zener diode (DC voltage: 1.018 V)
  • BIPM.EM-K11.b
  • DC voltage, Zener diode (DC voltage: 10 V)

    Capacitance
  • CCEM-K4.2017
  • Comparison of 10 pF capacitance standards – Optional: comparison of 100 pF capacitance standards (Capacitance at 10 pF (optional capacitance at 100 pF))
  • BIPM.EM-K14.a
  • Comparison of capacitors (Capacitance: 10 pF)
  • BIPM.EM-K14.b
  • Comparison of capacitors (Capacitance: 100 pF)

    Gases
  • BIPM.QM-K1
  • Ozone at ambient level (2007 -  )
  • CCQM-K68.2019
  • Nitrous oxide in air at ambient levels (2019 - 2020)
  • CCQM-K74
  • Nitrogen dioxide (NO2) in Nitrogen (N2) (2009 - 2010)
  • CCQM-K74.2017
  • Nitrogen dioxide (NO2) in Nitrogen (N2) (2017)
  • CCQM-K82
  • Methane in air : preparative comparison (2012)
  • CCQM-K90
  • Formaldehyde in Nitrogen (2015 - 2016)
  • CCQM-K120
  • Ambient CO2 (2017)
  • CCQM-K137
  • NO in Nitrogen (2017 - 2018)

    Organics
  • CCQM-K55.a
  • Purity assessment of high purity organic materials: 17beta-Estradiol (2008 - 2009)
  • CCQM-K55.b
  • Purity assessment of high purity organic materials: aldrin (2010 - 2011)
  • CCQM-K55.c
  • Purity assessment of high purity organic materials: L-(+)-Valine (2012)
  • CCQM-K55.d
  • Purity assessment of high purity organic materials: Folic acid (2015 - 2016)
  • CCQM-K78.a
  • Mass fraction assignment of organic analytes in a multi-component aqueous calibration solution (2016 - 2017)
  • CCQM-K148.a
  • Mass fraction assignment of Bisphenol-A high purity material (2018 - 2019)
  • CCQM-K154.a
  • Gravimetric preparation and value assignment of trans-zearalenone (ZEN) in acetonitrile (ACN) (2018)

    Protein Analysis
  • CCQM-K115
  • Peptide purity determination - synthetic human C peptide (HCP) (2014)
  • CCQM-K115.2018
  • Peptide purity determination - Hexapeptide of HbA0 (VHLTPE or VE) (2018 - 2020)
  • CCQM-K115.b
  • Peptide purity determination - synthetic oxytocin (OXT) (2018)
  • CCQM-K115.c
  • Peptide purity determination - Glycated hexapeptide of HbA1c (glcVHLTPE or GE) (2018 - 2020)

    Section I (x and gamma rays, electrons)
  • BIPM.RI(I)-K1
  • Measurement of air kerma for Cobalt 60
  • BIPM.RI(I)-K2
  • Measurement of air kerma for low energy X rays
  • BIPM.RI(I)-K3
  • Measurement of air kerma for medium energy X rays
  • BIPM.RI(I)-K4
  • Measurement of absorbed dose to water for Cobalt 60
  • BIPM.RI(I)-K5
  • Measurement of air kerma for Caesium 137
  • BIPM.RI(I)-K6
  • Measurement of absorbed dose to water for high-energy photon beams
  • BIPM.RI(I)-K7
  • Measurement of air kerma in mammography beams
  • BIPM.RI(I)-K8
  • Measurement of reference air kerma rate for HDR Ir-192 brachytherapy sources
  • CCRI(I)-K4
  • Measurement of absorbed dose to water for Cobalt 60
  • CCRI(I)-K6
  • Measurement of absorbed dose to water


    Section II (Measurement of Radionuclides)
  • BIPM.RI(II)-K1 series
  • Activity of radionuclide X
  • BIPM.RI(II)-K4 series
  • Activity of short-lived radionuclide X

    Time
  • CCTF-K001.UTC
  • Calculation of the reference time scale UTC (Coordinated Universal Time)

    Traceability to the SI through the BIPM
    Subject area:
    What is traceability?
    BIPM policy on stating uncertainties
    Summary charts: Technical services per Member State
    Chemistry
    Electricity
    Ionizing Radiation
    Mass
    Time
    Related articles:
    BIPM calibration and measurement services
    BIPM work programme
    Joint BIPM, OIML, ILAC and ISO declaration on metrological traceability