Patent ID: 6111511
Filing Date: 2000-08-29
Classification: G08B

Abstract:
A smoke and flame detector comprising:first and second photo-detectors operational within a near-infrared spectrum;first and second optical filter means coupled to said first and second photo-detectors respectively;an analog to digital (A/D) converter operatively coupled to said photo-detectors;a microprocessor operatively coupled to said A/D converter wherein said microprocessor further comprises light intensity value conversion and sampling means for converting light intensity input from said A/D converter to values in a near-infrared spectrum range and sampling said values for a predetermined period;memory means for storing information, said memory means coupled to said microprocessor and said A/D connector, wherein said memory means stores intensity values obtained from a predetermined sampling period and said detector utilizes said stored values to determine temperature PDF and noise normalized power special density;first and second photo-diodes;a digital to analog (D/A) converter operatively coupled to said photo-diodes;said microprocessor operatively coupled to said first and second photo-diodes and said D/A converter;a plurality of light sensing means for receiving light from at least one of said first and second diodes and passing the received light to said microprocessor;at least one of said light sensing means comprising a light absorption detection means for providing information to said microprocessor relating to the intensity of received light;at least another of said light sensing means comprising a scattered light detection means coupled to said microprocessor for receiving scattered light and passing the received scattered light to said microprocessor;wherein each said photo-detector, photo diode, light sensing means, and optical filter means comprises a calibration constant; andwherein a noise normalized ration E.sub.N (f) output is calculated using: ##EQU6## where E(f) is the power spectral density of voltage, intensity, or temperature, and S(f) is the power spectral density of random noise which is constant for a fixed sampling frequency.