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

D Haddad, F Seifert, L S Chao, A Possolo, D B Newell, J R Pratt, C J Williams, S Schlamminger
2017 Metrologia  
Researchers at the National Institute of Standards and Technology(NIST) have measured the value of the Planck constant to be $h =6.626\,069\,934(89)\times 10^{-34}\,$J$\,$s (relative standard uncertainty $13\times 10^{-9}$). The result is based on over 10$\,$000 weighings of masses with nominal values ranging from 0.5$\,$kg to 2$\,$kg with the Kibble balance NIST-4. The uncertainty has been reduced by more than twofold relative to a previous determination because of three factors: (1) a much
more » ... tors: (1) a much larger data set than previously available, allowing a more realistic, and smaller, Type A evaluation; (2) a more comprehensive measurement of the back action of the weighing current on the magnet by weighing masses up to 2$\,$kg, decreasing the uncertainty associated with magnet non-linearity; (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.
doi:10.1088/1681-7575/aa7bf2 fatcat:g23ia7npsrerfkb3rhpflztcoq