The 2012 North American Watt Balance Absolute Gravity Comparison

We report on a 2012 absolute gravity comparison performed at the National Institute of Standards and Technology (NIST), Gaithersburg, MD. Unique to this work is the direct comparison of gravitational measurement systems used in the determination of the Planck constant by NIST and the National Research Council Canada (NRC) watt balances. The results will provide verification of the gravity values used in recently published Planck constant determinations that play a vital role in the redefinition effort of the International system of Units (SI).