REALIZATION OF THE ITS-90 ABOVE 962-DEGREES-C WITH A PHOTODIODE-ARRAYRADIATION THERMOMETER

A precision monochromatic thermometer was constructed using a linear a rray of silicon photodiodes that in connection with a grating monochro mator acted as a wavelength-selective detector. The thermometer was us ed to realize the ITS-90 between 962 degrees C and 2100 degrees C acco rding to its formal definition. The estimated standard uncertainty (1 sigma level) in the scale realization ranged from 0,01 degrees C at 96 2 degrees C to 0,21 degrees C at 2100 degrees C. This scale was compar ed with the scale realized with the primary standard thermometer of th e Istituto di Metrologia ''G. Colonnetti'' using two pyrometric lamps as transfer sources. The average differences between the two scales ob tained from three measurement runs did not exceed 0,13 degrees C and w ere within the combined uncertainties in the realization of the scales over all the interval from 962 degrees C to 2100 degrees C.