NEW DEVELOPMENTS IN STANDARD THERMOMETRY AT THE IMGC

Recent findings in precision platinum resistance and radiation thermom etry at the Istituto di Metrologia ''G. Colonnetti'' are described. Tw o issues concern high-temperature platinum resistance thermometers. Th e first is the use of gas-controlled heat pipes for comparing these th ermometers and the development of a novel approach to improve temperat ure stability and uniformity. The second deals with observations made at the freezing point of silver which suggest that humidity may lead t o electric leakage. In radiation thermometry the main recent achieveme nt has been the use of a photodiode-array thermometer to realize the I TS-90 above the silver point. Relative to single-detector thermometers , this new thermometer offers several advantages that are related to i ts spectral characteristics. Another issue of importance is the size-o f-source effect (SSE), Practical rules for minimizing SSE errors in in terlaboratory comparisons are given.