A novel surface calibrator using heat pipe for surface probe calibration Available to Purchase

In this paper, a unique surface calibrator using heat pipe technology was proposed to extend the calibration capability and enhance the accuracy of surface thermometer calibration in National Metrology Centre (NMC), A*STAR. A cesium (Cs) heat pipe, supplied by National Institute of Metrology of China (NIM, China), was applied for the first time in Singapore for surface thermometer calibration. A dedicated calibration system, including furnace design, heating and control system, was constructed by NMC to work together with the heat pipe as a complete surface calibrator, which could perform from 300 °C to 500 °C. This would extend NMC maximum surface calibration temperature from 300 ° to 500 °C with reduced measurement uncertainty. The surface calibrator system was characterized by evaluating the vertical inhomogeneity, surface temperature stability, surface uniformity, and loading effect. The measurement results showed that the surface temperature could be estimated using 3 PRTs placed beneath the heat pipe by using a linear extrapolation. The temperature stability was tested to be 0.02 °C within 10 minutes after the furnace was stabilized at 400 °C. Through the evaluation of surface uniformity, it was found that the maximum non-uniformity of the surface calibrator was 0.85 °C when surface temperature was at 300 °C, and that reduced to 0.39 °C and 0.47 °C when surface temperature was at 400 °C and 500 °C, respectively. Loading effect was checked based on the surface temperature difference by comparing the loading of one or two surface thermometers with no loading condition. These measurement results indicated that the loading effect could be as large as 1.52 °C, therefore, multi-surface thermometers calibration at one time was not recommended. With the analysis of the system measurement uncertainty at 400 °C, this novel surface calibrator system demonstrates better accuracy of 0.60 °C and can extend NMC higher temperature range from 300 °C to 500 °C. We will continue to collaborate with NIM, China to further reduce the dominant uncertainty component as the surface non-uniformity for this surface calibrator.