| 摘要 |
PROBLEM TO BE SOLVED: To provide a flame sensor at a low cost and with high certainty by preparing two filters which transmit a wide band of line spectra of carbon dioxide resonance radiation and transmit only the line spectra respectively and a photodetector which transducers the transmitted light into the electric signals. SOLUTION: A filter 1 transmits the spectra of 3.4 to 5.4μ, for example, around 4.4μof the wavelength of carbon dioxide resonance radiation in a wider range than a line spectrum. The transmission band width of the filter 1 is set at w1. A filter 2 transmits only a band of flame resonance radiation of 4.4μ, e.g. the spectra of 4.3 to 4.5μ. The transmission band width of the filter 2 is set at w2. Then, the value of w1/w2 is selected at 1.5 or more (about 5 to 10). The infrared rays that passed through both filters 1 and 2 are converted into the electric signals by a photodetector 3. These two electric signals are sent to a calculation circuit 6 through the amplifier circuits 4 and 5 respectively.
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