The Design and Construction of the Joule Balance NIM-2

To make contribution for the redefinition of the kilogram with the Planck constant, the National Institute of Metrology (NIM, China), proposed a joule balance method. The first prototype NIM-1 has been built to check the feasibility of the principle and a relative uncertainty of $2.6\times 10^{-6}$ has been achieved in 2014. To get a better result, since 2013, the second generation joule balance NIM-2 has been designed with a series of new approaches to lower the main uncertainty contributions in the NIM-1. Since March 2015, the joule balance NIM-2 has been constructed and a series of preliminary measurements has been carried out in air to check if everything works well. At present, the fine adjustment and alignment are still in progress. The measurement in the vacuum will be started by the late of 2016.