Silicon carbide photodiode sensor for combustion control

A dual silicon carbide photodiode chip was developed to determine the temperature of a natural gas combustion flame. The concept uses the change in shape of the 260-350 nm OH band with temperature. One half of the chip was covered with a long-pass multiple layer dielectric filter with a short wavelength cutoff at about 315 nm. After amplification, the two signals produced by the filtered and unfiltered halves of the chip are divided to produce a ratio, which is very sensitive to changes in flame temperature. Sensitivity is about 0.35% per 20°F change in flame temperature for temperatures between 2700 and 3000°F. The temperature measured is the specific average temperature encompassed by the field of view of the sensor assembly.