How does a flame sensor work?
The pyroelectric detector of a flame sensor is detecting the typical spectral radiation of burning organic (hyrdocarbon) materials (wood, natural gas, petrol, plastics). Two criteria are used to distinguish a flame from the sun or any other light source. 1) A typical fire is “self-modulated” around 10Hz by flickering. 2) A hydrocarbon flame is producing the combustion gases of carbon CO and CO2. The emission bands of CO2 and CO in the infrared range are between 4.0 and 4.8m. A built-in IR bandpass is passing only the emission bands of both CO2 and CO to the pyroelectric element. Computing both flicker frequency and spectral information 4.0-4.8m will suppress false alarms effectively.
