Towards an electronic kilogram: an improved measurement of the Planck constant and electron mass

The electronic kilogram project of NIST has improved the watt balance method to obtain a new determination of the Planck constant h by measuring the ratio of the SI unit of power W to the electrical realization unit W90, based on the conventional values for the Josephson constant KJ-90 and von Klitz...

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Bibliographic Details
Published in:Metrologia 2005-10, Vol.42 (5), p.431-441
Main Authors: Steiner, Richard L, Williams, Edwin R, Newell, David B, Liu, Ruimin
Format: Article
Language:English
Subjects:
Metric system
Weights & measures
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Summary:The electronic kilogram project of NIST has improved the watt balance method to obtain a new determination of the Planck constant h by measuring the ratio of the SI unit of power W to the electrical realization unit W90, based on the conventional values for the Josephson constant KJ-90 and von Klitzing constant RK-90. The value h = 6.626 069 01(34) x 10-34 J s verifies the NIST result from 1998 with a lower combined relative standard uncertainty of 52 nW/W. A value for the electron mass me = 9.109 382 14(47) x 10-31 kg can also be obtained from this result. With uncertainties approaching the limit of those commercially applicable to mass calibrations at the level of 1 kg, an electronically-derived standard for the mass unit kilogram is closer to fruition.[PUBLICATION ABSTRACT]
ISSN:0026-1394
1681-7575
DOI:10.1088/0026-1394/42/5/014