Construction and performance of the NIST-4 magnet system

Seifert, F.; Panna, Alireza R.; Li, Shisong; Han, Bongtae; Chao, Leon; Cao, A.; Haddad, D.; Choi, Hyemi; Haley, Lori; Schlamminger, Stephan; Pratt, Jon R.

doi:10.1109/cpem.2014.6898413

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Dependence Of the Geometric Factor On The Weighing Current1

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2017

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“…Before the magnet was installed in NIST-4, the second derivative of the self inductance of a coil in the magnet with respect to its position was measured to be L = −346 H m −2 [28], which agrees with the measurement obtained here within one standard uncertainty. For the measurement in [28], the coil used was different, but had a similar number of turns.…”

Section: Dependence Of the Geometric Factor On The Weighing Currentsupporting

confidence: 85%

Measurement of the Planck constant at the National Institute of Standards and Technology from 2015 to 2017

et al. 2017

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Researchers at the National Institute of Standards and Technology(NIST) have measured the value of the Planck constant to be h = 6.626 069 934(89) × 10 −34 J s (relative standard uncertainty 13 × 10 −9 ). The result is based on over 10 000 weighings of masses with nominal values ranging from 0.5 kg to 2 kg with the Kibble balance NIST-4. The uncertainty has been reduced by more than twofold relative to a previous determination because of three factors: (1) a much larger data set than previously available, allowing a more realistic, and smaller, Type A evaluation; (2) a more comprehensive measurement of the back action of the weighing current on the magnet by weighing masses up to 2 kg, decreasing the uncertainty associated with magnet nonlinearity; (3) a rigorous investigation of the dependence of the geometric factor on the coil velocity reducing the uncertainty assigned to time-dependent leakage of current in the coil.

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Section: Dependence Of the Geometric Factor On The Weighing Currentsupporting

confidence: 85%