https://www.nist.gov/publications/construction-watt-balance-aim-realize-kilogram-national-institute-standards-and
A redefinition of the International System of Units, the SI, is impending and could occur as early as 2017.
watt balancewith theconstructionaimrealize
https://www.nist.gov/publications/towards-fixed-value-planck-constant-reproducibility-and-updated-nist-3-watt-balance
The scientific community is presently engaged in a historic attempt to fix the value of the Planck constant h so that it might ultimately serve as a base consta
planck constanttowardsfixedvaluereproducibility
https://www.nist.gov/publications/design-table-top-watt-balance
Measurements of the Planck constant with watt balances using 1 kg masses have achieved relative standard uncertainties below 2 x 10-8.
table topwatt balancedesignnist