FIRE DETECTOR WITH RATIO DETECTOR FOR INFRARED RAY AND ULTRAVIOLET RAY

摘要

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.