A correction method of thermal radiation errors for high-temperature measurement using thermographic phosphors

Abstract

In this study, a correction method based on background subtraction to remove thermal radiation from luminescent signal was proposed for intensity-based thermometry using thermographic phosphors. Mg4FGeO6:Mn was used as sensor material for a temperature range from 490 to 590 °C. A UV LED was used as excitation source and a spectrometer was used to collect the spectrum of both luminescence and thermal radiation for analysis. Then a CCD camera was used to conduct phosphor thermometry, including calibration and a jet impingement experiment. The calibration results showed that the measurement without correction would fail above 540 °C due to thermal radiation, whereas the correction method could effectively remove the effect of thermal radiation and extend the temperature range up to at least 590 °C. The use of band-pass filter around emission wavelength could reduce the effect of thermal radiation, but correction is still required for the case of higher temperature or lower excitation light. This correction method was then demonstrated in both steady and transient temperature measurements of a jet impingement experiment.