Re-evaluation of uncertainty for calibration of $100$ M$\mathrm{\Omega }$ and $1$ G$\mathrm{\Omega }$ resistors at NPL

The uncertainty for calibrating $100$ M$\mathrm{\Omega }$ and $1$ G$\mathrm{\Omega }$ resistors using the NPL high-resistance CCC bridge has been re-evaluated, resulting in combined uncertainties of $\sim 0.1$ $\mu \mathrm{\Omega }\mathrm{/}\mathrm{\Omega }$, considerably smaller than the CMC entries of $0.4$ $\mu \mathrm{\Omega }\mathrm{/}\mathrm{\Omega }$ and $1.6$ $\mu \mathrm{\Omega }\mathrm{/}\mathrm{\Omega }$ respectively. This re-evaluation supports measurement of single electron pump currents with combined uncertainties of a few parts in ${10}^7$.