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A report on the potential reduction in uncertainty from traceable comparisons of platinum-iridium and stainless steel kilogram mass standards in vacuum.

Davidson, S; Brown, S B; Berry, J (2004) A report on the potential reduction in uncertainty from traceable comparisons of platinum-iridium and stainless steel kilogram mass standards in vacuum. NPL Report. CMAM 88

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Abstract

Work has been undertaken to characterise the mass change of platinum-iridium and stainless steel weights on transfer between air and vacuum. Measurements were made on three 1- kilogram mass comparators; a Mettler HK1000MC in air and a similar instrument in vacuum (at 10 -6 mbar), and on the NPLone mass comparator at ambient pressure, at vacuum (10 -3 mbar) and at a partial pressure of 1 mbar. Specially designed sets of artefacts with different surface areas were used to calculate the mass change on exposure to vacuum and its repeatability. Results showed good repeatability and uncertainty evaluations indicate a potential reduction of the uncertainty for the calibration of stainless steel against platinum-iridium by comparison in vacuum, therefore eliminating the need for air buoyancy measurements. The work performed establishes traceability to mass in vacuum which will become increasingly important, not least because all the methods currently under investigation for the re-definition of the kilogram involve realising the unit of mass in vacuum.

Item Type: Report/Guide (NPL Report)
NPL Report No.: CMAM 88
Subjects: Engineering Measurements
Engineering Measurements > Mass, Force, Pressure
Last Modified: 02 Feb 2018 13:16
URI: http://eprintspublications.npl.co.uk/id/eprint/2898

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