FLAME DETECTOR

摘要

: 17 : A flame detector arranged to detect flames includes a non-microphonic infra-red sensor having a broad band frequency response. To maximise the sensitivity to radiation from flames in the 4.3 ?m solar absorption band a narrow band optical interference filer, transmissive in the band 4.54 ?m to 4.38 ?m is chosen such that the integrated solar energy transmitted thereby is less than an alarm threshold. A further filter prevents re-radiated heat from the filter reaching the sensor. Another filter prevents radiation of wavelengths less than 4.38 ?m from reaching the other filters to reduce heating thereof and also to provide a series of filters to stop direct broad band transmission to the sensor through pin holes in the filters. A signal processor detects flames by virtue of the flame flicker frequencies and includes provision for compensating for the effects of low frequency components on the amplitude of radiation produced by flames.