Towards a final result from the NPL Mark II watt balance

The NPL Mk II watt balance made an initial series of measurements of Planck's constant in the period from October 2006 to March 2007. The results of these measurements differ significantly from those recently published by NIST. Watt balance research at NPL is continuing until March 2008 aiming to reduce the uncertainty associated with the NPL measurement and to further investigate possible sources of the difference.