| 摘要 |
PURPOSE:To enable accurate detection of the presence or absence of a flame with good accuracy even if the flame fluctuates by separating the signal emitted by the flame to plural frequency bands, detecting said bands, incorporating prescribed signals therein, comparing the signals with set threshold levels and detecting the flame. CONSTITUTION:The output signal of a pressure sensor 4 is amplified by an amplifier 5 and is separated by BPFs 9a, 9b, 9c to prescribed frequency bands, for example, 150-300Hz, 300-600Hz, 2-20kHz. The taken-out signals (AC signals) are converted to DC signals by detecting circuits 10a, 10b, 10c. The converted DC signals are converted by A/D converters 11a, 11b, 11c to digital signals. The converted digital signals (a), (b), (c) are inputted to an arithmetic processing unit 12. The input signals (a), (b), (c) inputted to the unit 12 are compared with threshold levels by a comparator in which said levels are set. The respectively correspondent high level signal and low level signal are obtd. from the comparator and are further passed through an OR circuit from which the signals indicating the presence and absence of the flame are outputted. |
