National Physical Laboratory

Air-vacuum transfer; establishing traceability to the new kilogram.

Davison, S, Berry, J, Abbott, P*, Marti, K*, Green, R*, Malengo, A*, Nielsen, L*
Metrologia, 2016, 53, (5), A95-A113
NPL Doc. Ref:
PDB: 8189 | DDB: 7707
Document Type:
Periodical article

Note: An asterisk after an author's name indicates a non-NPL author.


The redefinition of the kilogram, along with another four of the base SI units, is scheduled for 2018. The current definition of the Si unit of mass is via the International Prototype Kilogram which is maintained and dissemination in air. The new definition, which will be from the Planck constant, involve the realisation of the mass unit in vacuum by the watt balance or Avogadro experiments. Thus, for the effective dissemination of the mass unit from the primary realisation experiments to end users, traceability of mass standards transferred between vacuum and air needs to be established and the associated uncertainties well understood. This paper describes means of achieving the link between a unit realised in vacuum and standards used in air and the ways in which their use can be optimised. It also investigates the likely uncertainty contribution introduced by the vacuum-air transfer process.

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