Dual spectrum frequency responding fire sensor
First Claim
1. A dual channel fire sensor circuit comprising:
- a first detector adapted to generate an electrical signal in response to long wavelength radiation;
a second detector adapted to generate an electrical signal in response to short wavelength radiation;
first and second signal channels coupled respectively to the first and second detectors, each of said channels having a bandpass filter and a threshold circuit in series with the output of the corresponding detector; and
means for providing a signal indicative of the detection of radiation in response to corresponding electrical signals at the output of the threshold circuits of both channels;
wherein the passband of the bandpass filter in said first signal channel is approximately 2-5 Hz and the passband of the bandpass filter in said second signal channel is approximately 6-12 Hz.
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Accused Products
Abstract
Apparatus for sensing the existence of a fire and providing a warning, if desired, with improved discrimination against the possibility of false alarms. Dual channel detectors are used, one detector being set to respond to incident radiation having a wavelength in the range of 0.8 to 1.1 microns while the other wavelength range is significantly displaced therefrom, being selected for wavelengths in the range from 14 to 25 microns. Reliability of true signal detection is further improved by the provision of separate flame flicker bandpass filters in the respective channels, these bandpass filters being set for different passbands. Circuits providing ratio discrimination, threshold detectors and delay circuitry are combined with the dual spectrum detectors and disparate flicker frequency filters to achieve improved performance. In addition, the dynamic range of instrument sensitivity is substantially increased by utilizing preamplifiers with wide gain variability controlled by automatic gain control circuits in the dual channel circuitry.
49 Citations
23 Claims
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1. A dual channel fire sensor circuit comprising:
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a first detector adapted to generate an electrical signal in response to long wavelength radiation; a second detector adapted to generate an electrical signal in response to short wavelength radiation; first and second signal channels coupled respectively to the first and second detectors, each of said channels having a bandpass filter and a threshold circuit in series with the output of the corresponding detector; and means for providing a signal indicative of the detection of radiation in response to corresponding electrical signals at the output of the threshold circuits of both channels; wherein the passband of the bandpass filter in said first signal channel is approximately 2-5 Hz and the passband of the bandpass filter in said second signal channel is approximately 6-12 Hz. - View Dependent Claims (2, 3)
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4. A dual channel fire sensor circuit comprising:
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a first detector adapted to generate an electrical signal in response to long wavelength radiation; a second detector adapted to generate an electrical signal in response to short wavelength radiation; a plurality of dual narrowband channels connected in parallel to said first and second detectors for processing said electrical signals, each of said plurality of dual narrowband channels comprising first and second signal processing paths including a narrowband filter at each of the inputs thereof of like passband characteristics, a threshold circuit coupled in series with the output of said narrowband filter and logic means for providing an output signal in response to corresponding electrical signals at the outputs of the threshold circuits of both of said first and second signal processing paths;
the narrowband filters in any one of said plurality of dual narrowband channels being different and non-overlapping in passband characteristics from the narrowband filters in the other of said dual narrowband channels;a pair of pre-amplifiers coupled to the outputs of the corresponding radiation detectors, each pre-amplifier having a large gain variability, and automatic gain control circuitry coupled to said amplifiers for controlling the gain thereof in response to the level of signals developed in the signal paths of one of said channels; and output gating means responsive to said output signals for providing a signal indicative of the detection of radiation.
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5. A dual channel fire sensor circuit comprising:
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a first detector adapted to generate an electrical signal in response to long wavelength radiation; a second detector adapted to generate an electrical signal in response to short wavelength radiation; a plurality of dual narrowband channels connected in parallel to said first and second detectors for processing said electrical signals, each of said plurality of dual narrowband channels comprising first and second signal processing paths including a narrowband filter at each of the inputs thereof of like passband characteristics, a threshold circuit coupled in series with the output of said narrowband filter and logic means for providing an output signal in response to corresponding electrical signals at the outputs of the threshold circuits of both of said first and second signal processing paths;
the narrowband filters in any one of said plurality of dual narrowband channels being different and non-overlapping in passband characteristics from the narrowband filters in the other of said dual narrowband channels;
each of said plurality of dual narrowband channels including a pair of ratio comparators respectively connected in series with the signal paths of said channel and interconnected to provide a ratio window above and below which the short-to-long wavelength signal amplitude ratio does not develop a fire detection signal; andoutput gating means responsive to said output signals for providing a signal indicative of the detection of radiation. - View Dependent Claims (6, 7, 8)
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9. A dual channel fire sensor circuit comprising:
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a first detector adapted to generate an electrical signal in response to long wavelength radiation; a second detector adapted to generate an electrical signal in response to short wavelength radiation; a plurality of dual narrowband channels connected in parallel to said first and second detectors for processing said electrical signals, each of said plurality of dual narrowband channels comprising first and second signal processing paths including a narrowband filter at each of the inputs thereof of like passband characteristics, a threshold circuit coupled in series with the output of said narrowband filter and logic means for providing an output signal in response to corresponding electrical signals at the outputs of the threshold circuits of both of said first and second signal processing paths;
the narrowband filters in any one of said plurality of dual narrowband channels being different and non-overlapping in passband characteristics from the narrowband filters in the other of said dual narrowband channels;output gating means responsive to said output signals for providing a signal indicative of the detection of radiation; and a pair of periodic signal detectors connected to said first and second detectors in respective parallel circuit paths with a pair of dual narrowband channel stages and coupled to inhibit said output gating means in the event of the detection of periodic signals by either of said periodic signal detectors. - View Dependent Claims (10, 11, 12, 13)
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14. A fire sensor circuit comprising:
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first and second detectors responsive to radiation from a fire source, each detector being responsive to radiation in a different spectral range and effective to generate electrical signals corresponding thereto; a plurality of electrical signal channels coupled to said detectors, each channel including signal paths equal in number to the number of detectors, each path being coupled to a corresponding one of said detectors and including a bandpass filter and threshold circuit in series, the bandpass filters in signal paths within a given channel being selected to have like passband characteristics but different from and non-overlapping with respect to the passband characteristics of the bandpass filters in other channels, a ratio comparator cross-coupled between the signal paths and in parallel with the threshold circuits, said ratio comparator comprising a pair of amplifiers having dual inputs, one input of each amplifier being connected directly to an associated signal path and the other input being connected through a voltage divider to the other signal path in order to combine signals from the two signal paths in a selected signal ratio in each amplifier; and means for providing a signal indicative of the detection of radiation from a fire source in response to corresponding electrical signals at the outputs of the respective threshold circuits. - View Dependent Claims (15, 16, 17, 18)
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19. A fire sensor circuit comprising:
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first and second detectors responsive to radiation from a fire source, each detector being responsive to radiation in a different spectral range and effective to generate electrical signals corresponding thereto; first and second spectrum analyzing means connected respectively to said first and second detectors for receiving the electrical signals therefrom, said first and second spectrum analyzing means each having a plurality of like frequency output ports corresponding to different preselected frequencies and being adapted to produce output signals at one or more of said frequency output ports in accordance with the frequency content of said electrical signal from said respective detector; and a corresponding plurality of ratio comparators for receiving the output signals from corresponding frequency output ports from said first and second spectrum analyzing means for generating an output fire warning signal upon the detection of incident radiation of like flicker frequency by said first and second detectors. - View Dependent Claims (20, 21, 22, 23)
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Specification