  This work reports on the upgrades made to the direct emissivity measurement
facility of the UPV/EHU. The instrumental improvements consist of, among
others, a high-vacuum system and a wider temperature range (300-1273 K).
Methodological developments include a refined measurement equation with updated
parameters and a reworked ISO-compliant uncertainty budget, and a Monte Carlo
procedure for accurate calculations of total emissivities from spectral data.
These upgrades have been demonstrated and validated in measurements of both
metallic and ceramic materials. The results obtained in this work are
applicable to similar experimental devices for emissivity measurements in order
to report reliable emissivity data.
