A determination of Planck's constant using the NRC watt balance

We have measured Planck's constant and have obtained a value of 6.626 070 34(12) 7 10-34 J s. To our knowledge this measurement of h has the lowest uncertainty reported to date. This result has been obtained from measurements of four masses of different material and nominal values varying from 1 kg to 250 g. The experimental procedures and the measurement uncertainties are described in detail.Peer reviewed: YesNRC publication: Ye

Gravimetry for watt balance measurements

In a watt balance (WB) the gravity on a known mass is used in the determination of the value of the Planck constant with a precision of <2 7 10-41 J s. To attain this precision the gravity value at the centre of a mass within the WB must be known with a relative uncertainty of <1 7 10-8. This necessitates laboratory gravity mapping in three dimensions, the establishment close to the WB of a gravity reference station, and modelling of the ties to the centre-of-mass location. The self-gravity of the WB must be accounted for, and since WB measurements run over several weeks, corrections for tidal, polar motion and atmospheric effects must be included. We describe the gravimetry carried out at the National Research Council of Canada WB laboratory, and include a discussion of past gravity variations in the vicinity of the WB, which suggest that seasonal variation may be of sufficient magnitude to affect results obtained with the balance.Peer reviewed: YesNRC publication: Ye

The Measurement of Gravitational Acceleration for the NRC Watt Balance

In 2009 NRC commenced construction of a new laboratory to house the NRC watt balance. We describe the procedures used and give results for the measurements of the acceleration due to gravity in the new laboratory. The data will be linked both to those laboratories participating in the Key Comparison CCM.G-K1 of 2009, and to the Canadian Gravity Standardization NetworkPeer reviewed: YesNRC publication: Ye

Corrigendum to the 2014 NRC determination of Planck\u2019s constant

Peer reviewed: YesNRC publication: Ye