Towards the next generation NPL watt balance

To gain the maximum benefit from the forthcoming redefinition of the SI unit of mass, the kilogram, there is a need for an accurate but relatively simple-to-operate method of realising mass from the new definition. Recent advances in the theory and methods of operation of watt balances have made it possible to consider building a next generation of watt balances to fulfill this need. The paper summarises the recent advances and describes the path NPL intends to take to produce a new design of watt balance which is aimed at the routine realisation of SI mass.