Ad. Gillespie et al., ALIGNMENT UNCERTAINTIES OF THE NIST WATT EXPERIMENT, IEEE transactions on instrumentation and measurement, 46(2), 1997, pp. 605-608
The effects of alignment uncertainties of the NIST watt balance with r
espect to local gravity and the magnetic flux density of the balance h
ave been analyzed. Techniques for measuring all quantities relevant to
misalignment have been developed. The components of the relative comb
ined standard uncertainty of the measured value of the watt due to ali
gnment uncertainties have been reduced to 20 nW/W, and potential impro
vements in the balance design have been identified which could ultimat
ely lead to a reduction of that uncertainty to below 10 nW/W.