  The charge localization of single electrons on mesoscopic metallic islands
leads to a suppression of the electrical current, known as the Coulomb
blockade. When this correction is small, it enables primary electron
thermometry, as it was first demonstrated by Pekola et al. (Phys. Rev. Letters,
73, 2903 [1994]). However, in the low temperature limit, random charge offsets
influence the conductance and limit the universal behavior of a single metallic
island. In this work, we numerically investigate the conductance of a junction
array, and demonstrate the extension of the primary regime for large arrays,
even when the variations in the device parameters are taken into account. We
find that our simulations agree well with measured conductance traces in the
submillikelvin electron temperature regime.
