Digital multi-frequency infrared flame detector

• US 6,150,659 A
• Filed: 04/10/1998
• Issued: 11/21/2000
• Est. Priority Date: 04/10/1998
• Status: Expired due to Term

• Current Assignee: General Monitors, Inc. (MSA Safety, Inc.)
• Original Assignee: General Monitors, Inc. (MSA Safety, Inc.)
• Inventors: Baliga, Shankar, Bleacher, Brett, Rabe, Herbert H.
• Primary Examiner(s): Ham, Seungsook
• Assistant Examiner(s): PATTI, JOHN J
• Application Number:
  US09/058,662
• Time in Patent Office: 956 Days
• Field of Search: 250/339.15, 250/339.14, 250/342, 356/346, 356/213, 356/226, 356/904, 136/213, 340/584, 340/500, 340/501
• US Class Current: 250/339.15
• CPC Class Codes: G01J 1/1626 Arrangements with two photodetectors, the signals of which are compared
• CPC Class Codes: G01J 5/0014 for sensing the radiation from gases, flames
• CPC Class Codes: G01J 5/02 Constructional details
• CPC Class Codes: G01J 5/025 Interfacing a pyrometer to an external device or network; User interface
• CPC Class Codes: G01J 5/026 Control of working procedures of a pyrometer, other than calibration; Bandwidth calculation; Gain control
• CPC Class Codes: G01J 5/08 Optical arrangements
• CPC Class Codes: G01J 5/0846 having multiple detectors for performing different types of detection, e.g. using radiometry and reflectometry channels

Abstract

A flame detector consisting of a first infrared radiation detector for detecting radiation from combustion of hydrocarbon and other carbon containing compounds in conjunction with a second infrared radiation detector for distinguishing radiation from other sources such as modulated sunlight, reflections, artificial as well as natural hot objects, illuminating light sources, and arc welders. The flame detector uses two electronic circuits following the first infrared detector such that a fire is sensed by either of the two circuits depending on its size, one circuit being optimized for flicker frequencies present in a large fire while the second circuit simultaneously checks for optical signals at flicker frequencies dominant in a smaller fire. The two electronic outputs along with the output of the second infrared detector are digitally processed and analyzed for spectral and temporal characteristics to distinguish the presence of a real fire from that of various false alarm sources. The flame detector is provided with digital serial communications so as to output its status, permit changes in the programming of operating parameters and modes and permit troubleshooting via remote control.

Claims

1. A flame detection apparatus for detecting fires, comprising:

first and second infrared detectors, said first detector sensitive to a wavelength emitted by combustion of hydrocarbons and other carbon containing materials, said second detector sensitive to infrared wavelengths present in sunlight and emitted by artificial radiation sources;

a data acquisition system coupled to outputs of said first and second infrared detectors, said system adapted to analyze and interpret the signals generated by the two infrared detectors to detect radiation from a fire while distinguishing sunlight and artificial radiation sources, said system including a first channel coupled to a first detector output of said first detector for analyzing the flicker rate of low frequency components of said first detector output to detect amplitude fluctuations characteristic of small fires, and a second channel coupled to said first detector output for analyzing the flicker rate of high frequency components of said first detector output to detect amplitude fluctuations characteristic of large fires.

2. The apparatus of claim 1 wherein said data acquisition system includes a third channel responsive to an output of said second infrared detector to determine an amplitude of a signal produced by said second infrared detector, and apparatus for rejecting, as a false alarm, signals in which the ratio of amplitudes of signals produced by said second and first infrared detectors exceeds a threshold.

3. The apparatus of claim 1 wherein said first channel rejects, as a false alarm, small amplitude output signals from said first infrared detector and signal of time duration below a threshold time duration.

4. The flame detection apparatus of claim 1, wherein the first and second infrared detectors are photoconductive lead selenide infrared detectors.

5. The flame detection apparatus of claim 1, wherein the first infrared detector is responsive in the 4.2 to 4.8 micron wavelength region.

6. The flame detection apparatus of claim 1, wherein the second infrared detector is responsive to the 2.0 to 2.4 micron wavelength region.

7. The flame detection apparatus of claim 1, wherein the said data acquisition system comprises a microprocessor adapted to execute an algorithm to indicate the occurrence of a hydrocarbon fire or a carbon containing fire.

8. An optical flame detection apparatus with ability to detect fires, comprising:

first and second infrared detectors, said first detector sensitive to a wavelength emitted by combustion of hydrocarbons and other carbon containing materials, said second detector sensitive to infrared wavelengths present in sunlight and emitted by artificial radiation sources, said second detector insensitive to said wavelength emitted by combustion of hydrocarbons and other carbon containing materials;

a first low frequency bandpass filter coupled to an output of said first infrared detector;

a second low frequency bandpass filter coupled to an output of said second infrared detector;

a high frequency bandpass filter coupled to said output of said first infrared detector;

a data acquisition system coupled to outputs of said first and second low frequency bandpass filter and said high frequency bandpass filter, said system adapted to analyze and interpret the signals generated by the two infrared detectors to detect radiation from a fire while distinguishing sunlight and artificial radiation sources.

9. The flame detection apparatus of claim 8, further comprising a digital communication link connecting said data acquisition system to an external central processor.

10. The flame detection apparatus of claim 8, wherein the first and second infrared detectors are photoconductive lead selenide infrared detectors.

11. The flame detection apparatus of claim 8, wherein the first infrared detector is responsive in the 4.2 to 4.8 micron wavelength region.

12. The flame detection apparatus of claim 8, wherein the second infrared detector is responsive to the 2.0 to 2.4 micron wavelength region.

13. The flame detection apparatus of claim 8, wherein the said data acquisition system comprises a microprocessor adapted to execute an algorithm to indicate the occurrence of a hydrocarbon fire or a carbon containing fire, by analyzing the outputs of the low and high frequency amplifiers.

14. The flame detection apparatus of claim 8, wherein the data acquisition system comprises a microprocessor adapted to execute an algorithm to distinguish the infrared radiation emitted by a fire from that emitted by false alarm sources, including modulated or reflected sunlight, arc welders, hot objects or artificial lights.

15. The flame detection apparatus of claim 14, wherein said microprocessor comprises an algorithm to detect and respond to radiation from a fire in the presence of radiation from said false alarm sources.

16. The flame detection apparatus of claim 8, wherein the said data acquisition system comprises a microprocessor adapted to execute an algorithm to distinguish the infrared radiation emitted by a fire from that emitted by steady or D.C. false alarm radiation sources including hot objects and artificial lights, wherein said flame detection apparatus is immune to presence of said steady or D.C. false alarm radiation sources.

17. The flame detection apparatus of claim 8, wherein said first low frequency filter has a nominal bandpass of between 2 Hz and 12 Hz to analyze flame flicker characteristic of small fires produced by the combustion of hydrocarbons and carbon containing compounds.

18. The flame detection apparatus of claim 8, wherein said high frequency filter has a nominal bandpass of between 40 Hz and 100 Hz to analyze flame flicker characteristic of large or steady fires produced by the combustion of hydrocarbons and carbon containing compounds.

19. A flame detection system, comprising:

a central controller;

a plurality of remotely located programmable optical flame detection apparatus;

a digital data bus connecting said central controller and said plurality of flame detection apparatus to exchange data including programming data instructions between said central controller and said plurality of flame detection apparatus;

wherein each of said optical flame detection apparatus includes;

first and second infrared detectors, said first detector sensitive to a wavelength emitted by combustion of hydrocarbons and other carbon containing materials, said second detector sensitive to infrared wavelengths present in sunlight and emitted by artificial radiation sources;

a data acquisition system coupled to outputs of said first and second infrared detectors, said system adapted to analyze and interpret the signals generated by the two infrared detectors to detect radiation from a fire while distinguishing sunlight and artificial radiation sources, said system including a first channel coupled to a first detector output of said first detector for analyzing the flicker rate of low frequency components of said first detector output to detect amplitude fluctuations characteristic of small fires, and a second channel coupled to said first detector output for analyzing the flicker rate of high frequency components of said first detector output to detect amplitude fluctuations characteristic of large fires.

20. The system of claim 19 wherein said plurality of flame detector apparatus are each responsive to said programming data instructions to adjust detector sensitivity.

21. The system of claim 19 wherein each of said optical flame detection apparatus is assigned a unique address and is individually programmable in response to programming data commands addressed to said unique address.

22. An optical flame detection apparatus with ability to detect fires, comprising:

first and second infrared detectors, said first detector sensitive to a wavelength emitted by combustion of hydrocarbons and other carbon containing materials, said second detector sensitive to infrared wavelengths present in sunlight and emitted by artificial radiation sources, said second detector insensitive to said wavelength emitted by combustion of hydrocarbons and other carbon containing materials;

a first low frequency amplifier and a high frequency amplifier for amplifying respective low and high components of the signals generated by the second detector;

a second low frequency amplifier for amplifying low frequency components of the signals generated by the first detector;

a microprocessor based data acquisition system, said system to analyze and interpret the amplified signals generated by the two infrared detectors;

a digital communication link to an external central processor.

23. The flame detection apparatus of claim 22, wherein the first and second infrared detectors are photoconductive lead selenide infrared detectors.

24. The flame detection apparatus of claim 22, wherein the first and second infrared detectors are responsive in the 4.2 to 4.8 micron and 2.0 to 2.4 micron wavelength region respectively.

25. The flame detection apparatus of claim 22, further including analog-to-digital apparatus for digitizing outputs of said first low and high frequency amplifiers, wherein the said data acquisition system microprocessor is adapted to execute an algorithm to indicate the occurrence of a hydrocarbon fire or a carbon containing fire, by analyzing digitized outputs of the low and high frequency amplifiers.