The reliability of calibration for thermocouples in industry at around 1300 °C

Abstract

Recently, the eutectic points are being studied by many national institutes, and considered being useful for the calibration laboratories in industry to improve their uncertainty of thermocouple calibration at high temperature. To conduct a cooperative research for investigation on the reliability of thermocouple calibration in industry at high temperature, a working group has been established within the Japan Society for the Promotion of Science (JSPS). AIST and nine domestic laboratories participated to this working group. In this working group, thermocouple comparison measurements were performed at around 1300 °C in nine laboratories by using two Pt/Pd thermocouples and one type R thermocouple following calibration at Co-C eutectic point. It was found that the uncertainties of calibration at around 1300°C in industry would be improved by utilizing the calibration at Co-C eutectic point.

A comprehensive survey of thermoelectric homogeneity of commonly used thermocouple types

“…Type R Data in the literature for the unused inhomogeneity of Type R thermocouples is broad, with a range of measuring temperatures from 185 °C to 1324 °C. The plot in figure 1 was drawn using the results from the literature survey [11,[21][22][23][24][25][26][27][28]. Furthermore the comprehensive survey of Bentley [29] has also determined that the homogeneity of new Type R and S thermocouples exceeds 0.02% of the electromotive force (emf) in only 5% of cases; this result has been widely used in the provision of advice concerning homogeneity.…”

“…The literature on inhomogeneity of Pt/Pd thermocouples is the most extensive, and has a range of measuring temperatures from 140 °C to 1492 °C. The plot in figure 1 was drawn using the literature results [20,21,27,28,30,[34][35][36][37][38][39][40][41][42][43][44][45][46][47][48]. Only the NATA recommendations are shown [1] as the Euramet recommendations [2] are based on tolerance limits for letter-designated thermocouples, and there is not one for the Pt/Pd thermocouple.…”

Temperature Measurement Using Optical Fiber Methods: Overview and Evaluation

“…Their typical property is low levels of electrical current or voltage. When designing the measuring chain, account must be taken of the adverse effects of electrical and magnetic disturbances [9,10] on metallic conductors between the actual temperature sensor and the evaluation unit that converts the signal from the sensor to the amplifier or analogue digital converter [10].…”