Comparison between multiwavelength infrared and visible pyrometry: Application to metals

Analogous of Wien's law for the optimal wavelengths selection in bi-spectral method used for temperature measurement of surfaces exhibiting non-uniform emissivity, and general methodology for the multi-spectral method

“…The inscription "FT25" is indistinguishable at 2μm but appears more and more clearly up to 4μm. The result of the temperature estimation by inversion of Planck's law (assuming unit emissivity) is given in Figure 12 for the wavelength at 4μm, corresponding to the experimental wavelength closest to the theoretical optimal wavelength defined by (4). As expected, we note that this simple estimation assuming a uniform emissivity does not correct the emissivity field because the pattern "FT25" is still visible on the calculated temperature field.…”

“…The measurement difficulties are numerous, such as taking into account the reflection on the sample, or spatial and temporal variations of the emissivity of the material, making it non-uniform over the sample surface, especially at high temperature where significant oxidation phenomena can occur. One solution is to make a measurement by the multi-spectral method [2][3][4][5][6][7][8][9], of which a state-of-theart has been made by [4,8]. Even if the idea is interesting, its implementation is tricky because of the difficulty to choose the adapted wavelengths λi.…”

Application of multispectral radiation thermometry in temperature measurement of thermal barrier coated surfaces

“…In order to use this technique to determine surface temperature of a target, emissivity model, appropriate for the target surface has to be identified. Several mathematical models of spectral emissivity which can be employed in this technique have been proposed [10,[19][20][21][22][23][24]29] and mainly tested for use in metallic surfaces with minimal consideration of the influence of ambient radiation. In this work, 10 emissivity models listed below were tested for possible application in ceramic thermal barrier coatings of different thickness.…”

“…This dynamic behavior of spectral emissivity poses a great challenge in the use of radiation thermometers. Multispectral radiation thermometry (MRT) can be used to address the above challenges and has widely been used in many applications [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] to measure temperature, mainly targeting metallic surfaces. Effectiveness of this technique is greatly dependent on emissivity model used.…”

Optimisation of wavelengths selection used for the multi-spectral temperature measurement by ordinary least squares method of surfaces exhibiting non-uniform emissivity

“…The difficulty with this type of measurement is the spatial and temporal variation of the emissivity of the material making it non-uniform over the sample surface, especially at high temperatures where significant oxidation phenomena can occur. One solution is to make a measurement by the multi-spectral method [2][3][4][5][6][7], a state of the art of which has been made in [7]. Even if the idea is interesting, its implementation is tricky because of the difficulty to choose the adapted wavelengths λ i .…”