Dual wavelength fire detection method and apparatus
First Claim
1. A method for detecting a fire in the presence of a false fire source, comprising the steps of:
- (a) receiving a total radiant energy from both fire and non-fire sources at a first wavelength during a measurement time interval, and converting the total radiant energy at the first wavelength to a first electrical signal,(b) receiving a total radiant energy the both fire and non-fire sources at a second wavelength during the measurement time interval, and converting the total radiant energy at the second wavelength to a second electrical signal,(c) extracting a magnitude of a flicker frequency signal in the first electrical signal at a plurality of flicker frequencies to produce a first magnitude at each flicker frequency,(d) extracting a magnitude of a flicker frequency signal in the second electrical signal at the same plurality of flicker frequencies to produce a second magnitude at each flicker frequency,(e) calculating a ratio of the first magnitude to the second magnitude for each flicker frequency,(f) comparing the ratio at each flicker frequency to a first threshold and generating a ratio indicator if the ratio exceeds the first threshold,(g) correlating the flicker frequency signal at the first wavelength with the flicker frequency signal at the second wavelength at each flicker frequency and generating a correlation indicator if the correlation is positive, and(h) generating a positive indicator at each flicker frequency if the ratio indicator and the correlation indicator are both present.
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Accused Products
Abstract
A method for extracting a number of temporal frequencies occurring in a fire and false fire condition concurrently from two or more radiation detectors for receiving signals, a correlation detector for each frequency and sensor, and a storage buffer for the temporal frequencies extracted and sensors employed, so as to distinguish a small fire signal in the presence of a much larger false fire signal whether random in nature or not. The ratio of each extracted frequency following proper qualification is compared to the ratio band for fire and an output signal is generated when the ratio at one or more temporal frequencies indicates a fire.
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Citations
28 Claims
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1. A method for detecting a fire in the presence of a false fire source, comprising the steps of:
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(a) receiving a total radiant energy from both fire and non-fire sources at a first wavelength during a measurement time interval, and converting the total radiant energy at the first wavelength to a first electrical signal, (b) receiving a total radiant energy the both fire and non-fire sources at a second wavelength during the measurement time interval, and converting the total radiant energy at the second wavelength to a second electrical signal, (c) extracting a magnitude of a flicker frequency signal in the first electrical signal at a plurality of flicker frequencies to produce a first magnitude at each flicker frequency, (d) extracting a magnitude of a flicker frequency signal in the second electrical signal at the same plurality of flicker frequencies to produce a second magnitude at each flicker frequency, (e) calculating a ratio of the first magnitude to the second magnitude for each flicker frequency, (f) comparing the ratio at each flicker frequency to a first threshold and generating a ratio indicator if the ratio exceeds the first threshold, (g) correlating the flicker frequency signal at the first wavelength with the flicker frequency signal at the second wavelength at each flicker frequency and generating a correlation indicator if the correlation is positive, and (h) generating a positive indicator at each flicker frequency if the ratio indicator and the correlation indicator are both present. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. Apparatus for detecting a fire in the presence of a false fire source, comprising:
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first and second detectors to detect total radiant energy of both fire and non-fire sources at first and second wavelengths respectively and to produce respective first and second electrical signals in response thereto; first and second flicker filters coupled respectively to the first and second detectors to filter the respective first and second electrical signals at a selected flicker frequency to produce first and second filtered signals; a flicker frequency generator coupled to the first and second flicker frequency filters to select the flicker frequency from a plurality of flicker frequencies; a ratio circuit to produce a ratio signal from the first and second filtered signals; and a comparator coupled to the ratio circuit to receive the ratio signal and produce a ratio indicator if the ratio signal exceeds a first threshold. - View Dependent Claims (17, 18, 19, 20, 21)
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22. Apparatus for detecting a fire in the presence of a plurality of false fire sources, comprising:
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first and second detectors to detect total radiant energy of both fire and non-fire sources at first and second wavelengths respectively and to produce respective first and second electrical signals in response thereto; a sinusoidal generator to generate sine and cosine signals at a selected flicker frequency, and adapted to multiply the first and second electrical signals by the sine and cosine signals separately to produce a first sine signal, a first cosine signal, a second sine signal and a second cosine signal; integrators coupled to integrate each of the first sine and cosine signals and the second sine and cosine signals individually; a first magnitude circuit coupled to the first sine and cosine signals to produce a first magnitude signal, the first magnitude signal indicating a magnitude of the total radiant energy at the first wavelength at the selected flicker frequency; a second magnitude circuit coupled to the second sine and cosine signals to produce a second magnitude signal, the second magnitude signal indicating a magnitude of the total radiant energy at the second wavelength at the selected flicker frequency; a comparator coupled to the first and second magnitude circuits to generate a ratio in response to the first and second magnitude signals and to compare the ratio with a first fire threshold level to produce a first comparison signal; and an indicator to indicate the presence of a fire in response to the first comparison signal. - View Dependent Claims (23, 24, 25, 26, 27, 28)
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Specification