– the intergovernmental organization through which Member States act together
     on matters related to measurement science and measurement standards.
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Calibration services

    The primary role of the BIPM's activity in Mass is to provide traceability to the kilogram.

    Calibrations of Pt-Ir prototypes and mass standards in stainless steel are carried out each year during the periods March to May and September to November.

    The BIPM is the pilot laboratory for the first key comparison of kg realizations, CCM.M-K8.2019. Therefore the mass calibration service will be temporarily suspended during the first half of 2020.


    1 kg prototypes in Pt-Ir

      The BIPM offers a calibration service for 1 kg national prototypes in Pt-Ir. This service is available free of charge to Member States. The Physical Metrology Department maintains a number of prototypes and other standards in Pt-Ir. A subset of these are used as working standards to calibrate national prototypes upon request. The remainder are used for quality control. Since 20 May 2019 the kilogram is defined with respect to the fixed numerical value of the Planck constant. Before the completion of the first key comparison of realization experiments, the traceability will be based on the known relationship between the mass of the International Prototype of the Kilogram (IPK) and the Planck constant. The combined standard uncertainty is about 0.012 mg. This uncertainty is dominated by the standard uncertainty of 0.010 mg of the mass of the IPK with respect to the Planck constant. The standard uncertainty of the prototype under calibration with respect to the IPK is about 0.005 mg.

      The BIPM also fabricates Pt-Ir prototypes for Member States upon request.

    • Request the calibration of a national prototype

    1 kg mass standards in stainless steel

      The BIPM offers a calibration service for 1 kg standards in stainless steel. This service is available free of charge to NMIs of Member States. The volume of the standard can be determined by hydrostatic weighing at the BIPM if this parameter is unknown (typical combined standard uncertainty obtained at the BIPM is 0.44 mm3 at the reference temperature of 20.0 °C). However, the volumetric thermal expansion near room temperature must be supplied by the NMI or the manufacturer of the standard. Since 20 May 2019 the kilogram is defined with respect to the fixed numerical value of the Planck constant. Before the completion of the first key comparison of realization experiments, the traceability will be based on the known relationship between the mass of the International Prototype of the Kilogram (IPK) and the Planck constant. The combined standard uncertainty is about 0.012 mg. This uncertainty is dominated by the standard uncertainty of 0.010 mg of the mass of the IPK with respect to the Planck constant. The standard uncertainty of the stainless steel standard under calibration with respect to the IPK is about 0.006 mg.

    • Request the calibration of a 1 kg standard in stainless steel