Long Term Drift Characterisation of Noble Metal Thermocouples Using High Temperature Fized Points
In a previous paperi1 we described the implementation of a Co-C high temperature fixed point (HTFP),melting temperature 1324℃, at thermocouple manufacturers CCPI Europe Ltd., for the assessment of the calibration of noble metal thermocouples. In that project, a set of alumina-sheathed bare-wire Type S thermocouples were constructed by CCPI and calibrated in their ISO17025 accredited laboratory by comparison with a working standard thermocouple. The working standard thermocouple calibration uncertainty was ±2℃, and consequently the Type S thermocouple uncertainty was ±3℃ (k=2) in line with their accreditation. The same thermocouples were also calibrated using, in addition to the Au and Pd-wire points, the Co-C eutectic fixed point. The estimated uncertainty of the working standard calibration in this case was ±0.9℃ (k=2). Here we report on the drift performance of the thermoeouples after use in a heat treatment furnace at Bodycote Heat Treatments Ltd. over a period of 6 months. The results showed that the indicated temperature difference for these thermocouples between the newly constructed state and the extensively used state was considerably less than 1 ℃ at and below the Co-C temperature. This is a remarkable result given how extensively these thermoeouples had been used. Given that the current accredited calibration uncertainty of CCPI is ±3℃(k=2), the use of the Co-C point was critical in confirming, with low uncertainties, the excellent performance of these thermocouples.
Metrology Thermoeouples High temperature fized points Eutectic Contact thermometry
Jonathan V.Pearce Graham Machin Trevor Ford Steve Wardle
National Physical Laboratory,Teddington, United Kingdom National Physical Laboratory, Teddington, United Kingdom CCPI Europe Ltd., Killamarsh, United Kingdom Bodycote Heat Treatments Ltd., Derby, United Kingdom
国际会议
2008年国际温度与热物性测量会议(TEMP BEIJING 2008)
北京
英文
86-89
2008-10-20（万方平台首次上网日期，不代表论文的发表时间）