| 摘要 |
PURPOSE:To reduce influence caused by a radiation light of a furnace wall and improve reliability of the device by a method wherein only AC component made by a swinging of the flame is amplified and detected. CONSTITUTION:A lens 16 and an optical fiber 9 are arranged in such a way as a spot is focused on a radiation light radiated from a flame 2. The radiation light radiated from the flame 2 is guided to a safe circumstance through an optical fiber 9 together with the radiation light caused by the furnace wall 7, received by a photo-electrical conversion element 11 and converted into an electrical signal, DC component is shielded by AC amplifier 12 and only the AC component is amplified. This electrical signal is rectified by a detectoramplifier 12 and compared with a predetermined reference voltage by a comparator 14 and an electrical signal is fed. In the comparator 14, if an output signal from the detected rectifier 13 is lower than the predetermined reference voltage, it shows that the flame is not present and the AC component is generated by 'swinging' of the flame caused by the furnace wall 7. |
