Measurements of T-T90 in the range from 420 °C to 960 °C by primacy radiation thermometry at CEM

Abstract

In the frame of the EMPIR project 15SIB02 ¿Implementing the new kelvin 2¿ (InK2), measurements of t ¿ t90 from 420 °C (Zn fixed point) to 960 °C (Ag fixed point) have been performed. The t measurement is based on the absolute radiometric calibration of two commercial radiation thermometers: a KE LP4 (working at 650 nm and 900 nm wavelengths with a Si photodiode) and a KE LP5 (working at 1550 nm with an InGaAs photodiode). The absolute calibration has two steps [1]: firstly, two standards (a Si trap radiometer and an InGaAs single photodiode) have been calibrated against a cryogenic electrical substitution radiometer at IO-CSIC; secondly, a radiance comparison is made between the radiation thermometer and the standard detector. Two heat pipes of Cs and Na have been used to perform the t - t90 measurements in the range from 420 °C to 960 °C and two fixed points of Zn and Ag have been measured too. t90 measurements have been made with two standard platinum resistance thermometers (SPRTs) one of 25 for t < 600 °C and another of 0,25 for t > 600 °C, calibrated at fixed points. t measurements are made by absolute and relative primary thermometry using the two radiation thermometers. LP4 have been absolutely calibrated at 650 nm. LP4 at 900 nm and LP5 at 1550 nm are used to calculate t by extrapolation from the t Ag FP value. Preliminary results are shown in Figure 1 (mean values from different wavelengths and gain ratios calculated for both thermometers are shown). Differences obtained are below 80 mK in the whole range and the uncertainties range from 0.11 °C to 0.17 °C, from 420 °C to 960 °C. Uncertainty budget includes: absolute calibration of the radiation thermometers, calibration of the SPRTs at fixed points, emissivity of the blackbody (BB) cavities, conductivity between SPRT and BB, drifts, SPRTs thermal conduction, heat pipe stability and SPRTs self-heating. Figure 1. Preliminary results of t - t90 measurements. [1] M. J. Martin, J. M. Mantilla, D. del Campo, M. L. Herranz, A. Pons y J. Campos ¿Performance of different light sources for the absolute calibration of radiation thermometers¿ Int J Thermophys 38, 138, 2017 DOI 10.1007/s10765-017-2271-1