Characterization of Yb2O3 based optical temperature sensor for high temperature applications

A rare earth oxide based high temperature sensor is presented in this work. The rare earth is used as a selective emitter, which emits narrow band radiation at a peak wavelength of 980 nm that falls within the band edge of the Si-photodetector. The radiation results from the transition of 4f electrons in the Yb3+ ions due to thermal excitation. The radiation from the emitter, and the output (short-circuit current) of the photocell, is a function of the temperature. By inversion of Planck's law, the short-circuit current can directly be used as a measurement of temperature. The rare earth shows better performance in the range >1500 °C. The sensor geometry has been tested under a variety of conditions such as varying distance (10–50 cm), area of photodetector (5 and 10 mm2) and materials such as pellets, coatings and powder. The temperature was calibrated by an optical pyrometer. It is found that the linearity of the sensor is within 5% over the temperature range 1200–1700 °C, accuracy is 2% and repeatability is 6% within the mentioned temperature range. The diverse material forms that the sensor lends itself to make it an ideal candidate for variety of applications.