| 摘要 |
A flame sensing system according to the invention makes use of infra-red rays produced by resonant radiation of carbon dioxide in o flame and gives no wrong information duo to discharge of thunder or sunlight and has high sensitivity with good S/N ratio. The flame sensing system is characterized in that when a ratio of an output of intensity of a first radiation produced by resonant radiation of carbon dioxide to an output of intensity of a second radiation having a wavelength located in the vicinity of the wavelength of said first radiation in the region of wavelength in which there is little absorption by the carbon dioxide in the air exceeds a predetermined value, difference in intensity between said first radiation and said second radiation is detected either by increasing the output of said first radiation or by decreasing the output of said second radiation thereby to give a warning. |
