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| Research on the calibration method of non-standard short uncompensated wire iridium-rhodium thermocouple |
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Abstract Non - standardized short thermocouples (with a length of 80 - 150 mm) without compensating wires usually have significant deviations in measurement or calibration because of their short length and the incapability of extending the cold junction. In this research, a short iridium-rhodium thermocouple is used as an example. The calibration was carried out by using a dry - block furnace and a thermal equalization block device. Three different cold - junction treatments methods were adopted: air cooling, using a circulating water - cooled plate, and immersion water cooling. All of these were corrected with K - type thermocouples. The thermoelectric potential-temperature relationship of a long iridium - rhodium thermocouple from the same source was taken as a reference for the short thermocouple. It was found that the deviation of the reference values from the national standard was over 1%, and the differences in the calibration results at the In, Sn, and Zn fixed points were 0.23°C, 0.32°C, and 0.48°C, respectively. The experimental results indicate that within the temperature range of 0 - 500°C, by using the circulating water - cooled plate to control the cold junction and applying temperature correction during calibration, the error of the short iridium - rhodium thermocouple was less than 1%, with uncertainties ranging from 0.9°C to 3.2 °C.
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Received: 01 November 2024
Published: 19 March 2025
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ZHOU Ning, FENG Jianmin, SONG Hao, YAO Jianping, ZHAO Qidi, ZHANG Huijun, HUANG Xiaolong, YIN Wei, GAO Zhanpeng, WU Jun, YU Chong. Research on Metrology Calibration Technology for the Multi-points Pasted Strain-gauges System On-line[J]. Acta Metrologica Sinica, 2025, 46(2): 204-212. |
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2025, Vol. 46 
