The problem of emissivity change on metal surface complicates the temperature measurement of molten pools in infrared (IR) radiation thermometry. Therefore, an emissivity correction is one of the most important subjects in IR radiation thermometry. The objective of the present investigation is to develop an ultraviolet (UV) radiation thermometry, which is an emissivity correction free method.
According to the Planck's law of radiation, it is evident that the effect of temperature on the spectral radiance is greater at the shorter wavelength, and radiation thermometry in UV range is expected to reduce the error caused by the emissivity change. Generally, the radiation energy in UV range is lower than that in IR range at the same temperature. A measurement system that is sensitive to the UV radiation has been developed in the present work. The system consists of an image intensifier, and multiple optical band-pass filters.
In the present paper, two-dimensional temperature distribution on TIG weld pool has been measured by using the developed UV radiation thermometer. It is made clear that the luminance temperature distributions measured by IR and UV range are quite different, and the surface temperature on molten pool is affected by sulfur concentration in the material.