Improving char temperature measurement by pyrometry with digital camera

Paper in proceeding, 2015

Pyrometry with a digital camera offers considerable advantages over using optical probes for measurements of temperature in FBC. Two-colors are traditionally used (P2C) if the emissivity of the object is not known. In this paper we analyze the impact of the signal received from the sensor pixels on the accuracy of the calculated temperature using a digital camera in one or two spectral bands. It is concluded that the low limit of temperature that can be measured by P2C, which depends on the optical and electronic parameters, could be out of the range of interest in FBC applications. We propose an algorithm based on one-color pyrometry, using both the red and the green bands sequentially (P1C R-G). This method increases the accuracy and the range of the temperature to be measured compared to P2C. Although the emissivity has to be known for the application of P1C R-G, an average value (0.9 for char) provides a reasonable estimation, and thus, P1C R-G is a better choice than P2C for the measurement of temperature in FBC.