Improvements on INRIM Coaxial Microcalorimeter and Outcome of a Model Comparison

This paper describes hardware and software improvements of the Istituto Nazionale di Ricerca Metrologica (INRIM) coaxial microcalorimeter together with their outcome on the primary power standard realization in the frequency band 0.05-40 GHz. A better temperature and power stabilization turned out to provide an improved signal/noise ratio and a drift reduction in every working condition of the microcalorimeter. The INRIM correction model is also compared with a traditional, but faster, one in terms of measurement uncertainty. The outcomes are presented in form of a 2.92-mm thermoelectric power sensor calibration together with the results that show an improved stability and repeatability of the measurement system.