Improving the performance of the force comparator in a watt balance based on pressure balances

A watt balance based on pressure balances has been proposed for a measurement of the Planck constant and for a non-artefact realisation of the kilogram. This watt balance uses twin gas-operated pressure balances as the force comparator to compare the gravitational force on a test mass with the electromagnetic force on a current-carrying coil in a magnetic field. In this paper the results of initial trials with a twin pressure balance as a mass/force comparator are presented and ways of improving this performance are investigated. The focus is on reducing the damping in the force comparator.