https://ris.utwente.nl/ws/files/93794425/how_hot.pdf

How hot is the wire: Optical, electrical, and combined methods to determine filament temperature

Calibration of a W/Re thermocouple using Pd-C, Pt-C and Ru-C eutectic cells at NIM

There are presented results of experimental research on calibration of tungsten–rhenium thermocouples at the temperatures exceeding the upper limit of measurements (1700 °C) of standard type B thermocouple. The research was carried out using the high-temperature installation UKT-2500 designed for practical use in production of temperature sensors based on refractory thermocouples. Available types of insulating ceramics for thermocouples have been tested in the temperature range of (1500–2500) °C. The effects of signal shunting and thermocouples stability in inert atmosphere have been investigated at upper limit of the operating temperature range. There was proved practical feasibility of the method for calibration of several contact temperature sensors (up to 10) in one run relative to radiation pyrometer readings. Its suitability for thermocouple calibration and certifying of thermocouple wires in the temperature range (1200–2200) °C was shown. Installation enables to use reference fixed-points of Me-C type to get the highest accuracy calibration of a single tungsten–rhenium thermocouple. Type A bare-wire thermocouple was calibrated in the whole measuring range from 1200 °C to 2500 °C against an accurate radiation pyrometer. 

/pdf/tungsten-rhenium-thermocouples-calibration-in-ultra-high-lo61u11g.pdf

Tungsten–Rhenium Thermocouples Calibration in Ultra-High Temperature Range

Miniature fixed-point cells for self-calibration of type C high-temperature thermocouples

Abstract There are presented results of experimental research on calibration of tungsten-rhenium thermocouples at the temperatures exceeding the upper limit of measurements (1700 ℃) of standard type B thermocouple. The research was carried out using the high-temperature installation UKT-2500, designed for practical use in production of temperature sensors based on refractory thermocouples. The available electrical insulating materials for thermoelements have been tested in the temperature range of (1500–2500) ℃. The effects of signal shunting and thermocouples stability in an inert atmosphere have been investigated at upper limit of the operating temperature range. There was proved practical feasibility of the method for calibration of several contact temperature sensors (up to 10) in one run relative to radiation pyrometer readings. Its suitability for thermocouple calibration and certifying of thermoelement wires in the temperature range (1200–2200) ℃ was shown. Calibration of a single tungsten-rhenium thermocouple made at the reference fixed point Ru-C demonstrated the highest accuracy. Using bare wire thermoelements W-Re5% and W-Re20%, type A thermocouple was calibrated in the whole measuring range from 1200 ℃ to 2500 ℃ against an accurate radiation pyrometer. 

Tungsten-Rhenium Thermocouples Calibration in Ultra-High Temperature Range

Tungsten–rhenium thermocouples (type C thermocouples) are used to measure temperatures higher than 1500 
 $${^{\circ }}$$
 C under protective, inert, or vacuum conditions in a wide range of industries, such as metallurgy, power generation, and aerospace. Generally, the measurement uncertainty of a new tungsten–rhenium thermocouple is about 1 % (20 
 $${^{\circ }}$$
 C at 2000 
 $${^{\circ }}$$
 C), and a significant drift is always observed above 1200 
 $${^{\circ }}$$
 C. Recently, the National Institute of Metrology, China, has spent great efforts to calibrate tungsten–rhenium thermocouples with high-temperature fixed points of up to 2000 
 $${^{\circ }}$$
 C. In the present work, three tungsten–rhenium thermocouples made by two manufacturers were calibrated at the Pt–C eutectic fixed point (1738 
 $${^{\circ }}$$
 C) and their stability was investigated. A linear fitting and extrapolation method was developed to determine the melting and freezing temperatures of the Pt–C eutectic fixed point for avoiding the effect of thermal resistance caused by the sheath and protection tube. The results show that the repeatability of the calibration is better than 0.9 
 $${^{\circ }}$$
 C from the melting curve of the Pt–C fixed point and better than 1.2 
 $${^{\circ }}$$
 C from the freezing curve of the Pt–C fixed point, and a good agreement was obtained for the calibration with the melting and freezing temperature plateau through the linear fitting and extrapolation method. The calibration uncertainty of the thermocouples at the Pt–C eutectic fixed point was 3.1 
 $${^{\circ }}$$
 C (k $$=$$
 2).

Stability Evaluation and Calibration of Type C Thermocouples at the Pt–C Eutectic Fixed Point

Supercontinuum laser-based absorptance measurement for materials in the solar spectral band

Accurate measurement of the true surface temperature of high-temperature materials is very important in many fields, such as modern industrial systems, solar heat utilization and metrology. At present, passive radiation thermometry is mainly used to measure the real surface temperature of high-temperature materials. This technology cannot get rid of the influence of emissivity on temperature measurement accuracy. The active laser infrared radiation thermometry is a new emissive-free temperature measurement technology. Based on the active thermometry of dual-wavelength infrared laser, with the condition of environmental reflection interference and unknown emissivity, the true surface temperature of high-temperature material is precisely measured and studied. Based on the theoretical model of active dual-wavelength infrared laser thermometry, an active laser thermometry system was built and upgraded in this study. The active temperature measurement experiments of changing laser power were carried out to analyze the influence of laser power on the accuracy of active temperature measurement. Then the active temperature measurement experiments were carried out by changing the laser modulation frequency to analyze the influence of the laser modulation frequency on the active temperature measurement accuracy. The results show that the reasonable selection of laser parameters(laser power and laser modulation frequency) is the key to carrying out precision temperature measurement based on active laser infrared radiation thermometry.

Experimental study of the effect of laser parameters on active laser infrared radiation thermometry

With the efficient use of energy, the study of emissivity is considered to be of great importance. In industrial production, temperature measurement technology, and many other fields, emissivity research is performed an important role. The emissivity is considered to be an important quantitative parameter for the infrared radiation characteristics of high-temperature coatings. Although the experimental measurement technique for high-temperature infrared spectral emissivity by the integrated blackbody method has been studied, little research has been reported on the integrated blackbody temperature field measurement and the simulation study of the emissivity of the integrated blackbody cavity. Therefore, in this paper, the temperature distribution of integrated blackbody cavity with the graphite cavity bottom is measured at 800°C, 1000°C. Besides, the above results are adopted, and the effective emissivity of the integrated blackbody is numerically simulated, based on the measurement results and the Monte-Carlo ray-tracing method. Thus, the feasibility of integrating the blackbody is demonstrated, the infrared radiation properties of integrated blackbodies are also studied as influenced by the temperature of the blackbody cavity.

Research of temperature distribution and radiation characteristics of integrated blackbody on high-temperature

The radiometry hybrid method, by introducing a lens to the irradiance method with a 900 nm filter radiometer, was adopted to measure the thermodynamic temperature of the aluminum-copper (Al–Cu) eutectic point, aluminum (Al) freezing point, silver (Ag) freezing point, copper (Cu) freezing point and cobalt carbon (Co–C) eutectic point at the National Institute of Metrology, China. By scanning the uniformity of fixed-point blackbodies, the effective diameters were accurately estimated according to the size of the source effect (SSE). The lens transmittance measurement with the closest diameter aperture was adjusted to reduce the uncertainty of SSE. The discrepancy between the thermodynamic temperature and ITS-90 values (T-T 90) of Al–Cu, Al, Ag, Cu and Co–C fixed point blackbodies were concluded as 0.022 °C, 0.014 °C, 0.097 °C, 0.137 °C and 0.317 °C, respectively. The standard uncertainty of the fixed point thermodynamic temperature was estimated to be (0.1 to 0.3) °C (k = 2).

Thermodynamic temperature measurements of Al–Cu, Al, Ag, Cu and Co–C fixed points by radiometry hybrid method

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