US 4,455,487 AGranted

Fire detection system with IR and UV ratio detector

AssigneeArmtec Industries, Inc.

InventorRoger A. Wendt

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Abstract

An automatic fire detection system characterized by an extremely low incidence of false alarms utilizes two detection channels, one fed by an infrared (IR) detector and the other by an ultraviolet (UV) detector. Signal processing electronics in each channel produce a normalized output signal proportional to the power of incident IR and UV radiation within specific bandwidths. The system features a ratio detector that repeatedly forms a ratio of the normalized IR and UV inputs and compares the ratio to a known range of values for this ratio that are characteristic of a fire. A discriminator connected to the output of the ratio detector generates a fire alarm signal only if the majority of these ratio comparisons are fire-indicating. The system also includes a feedback loop in the IR processing channel that automatically adjusts the output of the channel to compensate for time-varying background IR radiation such as sunlight.

Claims12

Dependent claims

Means for automatically detecting flames in a preselected zone with an extremely low incidence of false alarms due to naturally occurring and man-made background radiation not generated by a flame comprising:

means for detecting ultraviolet (UV) radiation eminating from said preselected zone and generating a first signal corresponding to said UV radiation incident upon said UV detecting means;
means for detecting infrared (IR) radiation also eminating from said preselected zone and occurring in a narrow band, and generating a second signal corresponding to said IR radiation incident upon said IR detecting means;
electronic means for processing said first signal to produce a normalized UV signal;
electronic means for processing said second signal to produce a normalized IR signal;
and
electronic means for forming a ratio of said normalized UV signal to said normalized IR signal, comparing said ratio to a known range of values that is characteristic of the flames being detected, and generating a fire signal if said ratio falls within said range.

3 more elements

Dependencies are inferred from the claim text.