Ruimin Liu

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 Klitzing constant RK−90. The value h = 6.626 069 01(34) × 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) × 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.

Determination of the Planck constant using a watt balance with a superconducting magnet system at the National Institute of Standards and Technology

For the past two years, measurements have been performed with a watt balance at the National Institute of Standards and Technology (NIST) to determine the Planck constant. A detailed analysis of these measurements and their uncertainties has led to the value h = 6.626 069 79(30) × 10−34 J s. The relative standard uncertainty is 45 × 10−9. This result is 141 × 10−9 fractionally higher than h90. Here h90 is the conventional value of the Planck constant given by , where KJ-90 and RK-90 denote the conventional values of the Josephson and von Klitzing constants, respectively.

Linking air and vacuum mass measurement by magnetic levitation

This paper describes a new approach to link air and vacuum mass measurements using magnetic levitation techniques. This procedure provides direct traceability to national standards, presently defined in ambient air. We describe the basic principles, challenges, initial modelling calculations and performance expectations.

A summary of the Planck constant measurements using a watt balance with a superconducting solenoid at NIST

Researchers at the National Institute of Standards and Technology have been using a watt balance, NIST-3, to measure the Planck constant

Hysteresis and Related Error Mechanisms in the NIST Watt Balance Experiment.

h

The NIST project for the electronic realization of the kilogram

for over ten years. Two recently published values disagree by more than one standard uncertainty. The motivation for the present manuscript is twofold. First, we correct the latest published number to take into account a recently discovered systematic error in mass dissemination at the Bureau International des Poids et Mesures (BIPM). Second, we provide guidance on how to combine the two numbers into one final result. In order to adequately reflect the discrepancy, we added an additional systematic uncertainty to the published uncertainty budgets. The final value of

Balance Pan Damping Using Rings of Tuned Sloshing Liquids

h

Status of the NIST "electronic kilogram" experiment

measured with NIST-3 is

In situ correction of abbe offset error in the watt balance experiment

h = 6.626\,069\,36(37)\times 10^{-34}\,\mbox{J\,s}

Estimating uncertainty limits in the NIST-2008 electronic kilogram

. This result is