GB2065880A - Radiation Detector for a Fire Alarm - Google Patents
Radiation Detector for a Fire Alarm Download PDFInfo
- Publication number
- GB2065880A GB2065880A GB8103946A GB8103946A GB2065880A GB 2065880 A GB2065880 A GB 2065880A GB 8103946 A GB8103946 A GB 8103946A GB 8103946 A GB8103946 A GB 8103946A GB 2065880 A GB2065880 A GB 2065880A
- Authority
- GB
- United Kingdom
- Prior art keywords
- radiation
- filter
- radiation detector
- interference
- sensor
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
- 230000005855 radiation Effects 0.000 title claims abstract description 56
- 229910052732 germanium Inorganic materials 0.000 claims abstract description 7
- GNPVGFCGXDBREM-UHFFFAOYSA-N germanium atom Chemical compound [Ge] GNPVGFCGXDBREM-UHFFFAOYSA-N 0.000 claims abstract description 7
- 239000010453 quartz Substances 0.000 claims abstract description 7
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 7
- WSMQKESQZFQMFW-UHFFFAOYSA-N 5-methyl-pyrazole-3-carboxylic acid Chemical compound CC1=CC(C(O)=O)=NN1 WSMQKESQZFQMFW-UHFFFAOYSA-N 0.000 claims abstract description 3
- HFGPZNIAWCZYJU-UHFFFAOYSA-N lead zirconate titanate Chemical compound [O-2].[O-2].[O-2].[O-2].[O-2].[Ti+4].[Zr+4].[Pb+2] HFGPZNIAWCZYJU-UHFFFAOYSA-N 0.000 claims abstract description 3
- 229910052451 lead zirconate titanate Inorganic materials 0.000 claims abstract description 3
- 230000003595 spectral effect Effects 0.000 claims description 7
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 abstract description 20
- 229910002092 carbon dioxide Inorganic materials 0.000 abstract description 10
- 239000001569 carbon dioxide Substances 0.000 abstract description 10
- 230000005540 biological transmission Effects 0.000 abstract description 3
- 238000003466 welding Methods 0.000 abstract description 2
- 230000035945 sensitivity Effects 0.000 description 6
- 230000001788 irregular Effects 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 230000001629 suppression Effects 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 239000003989 dielectric material Substances 0.000 description 1
- 230000005669 field effect Effects 0.000 description 1
- 239000011368 organic material Substances 0.000 description 1
- GGYFMLJDMAMTAB-UHFFFAOYSA-N selanylidenelead Chemical compound [Pb]=[Se] GGYFMLJDMAMTAB-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
- G01J5/02—Constructional details
- G01J5/04—Casings
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
- G01J5/0014—Radiation pyrometry, e.g. infrared or optical thermometry for sensing the radiation from gases, flames
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
- G01J5/02—Constructional details
- G01J5/04—Casings
- G01J5/046—Materials; Selection of thermal materials
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
- G01J5/02—Constructional details
- G01J5/08—Optical arrangements
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
- G01J5/02—Constructional details
- G01J5/08—Optical arrangements
- G01J5/0801—Means for wavelength selection or discrimination
- G01J5/0802—Optical filters
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
- G01J5/02—Constructional details
- G01J5/08—Optical arrangements
- G01J5/0875—Windows; Arrangements for fastening thereof
-
- G—PHYSICS
- G08—SIGNALLING
- G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
- G08B17/00—Fire alarms; Alarms responsive to explosion
- G08B17/12—Actuation by presence of radiation or particles, e.g. of infrared radiation or of ions
Abstract
The radiation detector includes a radiation sensor which may be a pyroelectric element (4), e.g., lithium tantalate or lead zirconate titanate. In front of the sensor element (4) a filter combination is arranged, which consists of a quartz filter element (2) which may have a narrow-band filter layer (1) vapour-deposited onto it and which has a maximum transmission at about 4.3 mu m, as well as a germanium filter element (6). This filter combination shows a sharp maximum transmission at the resonance radiation from carbon dioxide at 4.3 mu m, whilst the whole of the other ranges of wave-lengths are damped by more than a factor 100, e.g., 1000. A fire alarm equipped with such a radiation detector responds extremely selectively to flame radiation but does not react to interference radiation such as sunlight or daylight, artificial sources of light and welding arcs, even when these exhibit an intensity of more than a thousandfold, so that flames of very low intensity may be detected surely, sensitively and without susceptibility to interference even in the presence of powerful interference radiation. <IMAGE>
Description
1
GB 2 065 880 A 1
SPECIFICATION
Radiation Detector for a Fire Alarm
This invention relates to a radiation detector for a fire alarm, said detector having a sensor 5 element and a filter arranged in front of said element.
Fire alarms are in practice exposed to different kinds of interference radiation, which may trigger a false alarm signal. From the Swiss Patents Nos. 10 509 633, 519 761, 537 066 or 558 577 fire alarms are known, for distinguishing a flame from interference radiation such as daylight, sunlight or artificial light source which bring into play characteristics different from flames; e.g., the 15 irregular flickering and the irregular fluctuations resulting therefrom in the intensity of the flame radiation, or the special colour temperature or spectral composition of the flame radiation. However, since certain interference radiations 20 may exhibit portions of radiation having characteristics similar to flames and such interference radiations in practice frequently are more intense by several orders of magnitude than a flame radiation, such known fire alarms are 25 therefore not totally proof against false alarms and cannot be set at the highest possible sensitivity.
From the French Patent No. 2 151 148 and K. Nakajima, Report of Fire Research Institute of 30 Japan, No. 30 (December 1969), pages 55—61 it is known that the radiation from a flame consists preponderantly of a narrow-band peak of intensity in the spectral range of the resonance radiation from carbon dioxide at about 4.3— 35 4.4(am, together with a considerably weaker broad-band spectral field in the range of visible radiation and the near infrared. The carbon dioxide resonance radiation occurs practically exclusively in the case of flames which arise upon 40 burning organic material but almost never, or at only negligible intensity, in the case of interference radiations. A fire alarm which besides other criteria detects essentially the resonance radiation from carbon dioxide is therefore - 45 considerably better proof against false alarms and less susceptible to interference than fire alarms which detect the ultraviolet radiation, visible light or near infrared.
Known fire alarms which detect the carbon 50 dioxide resonance radiation suffer from the disadvantages that the radiation detectors employed in them are too broad-band and let through other portions of radiation. Ordinary interference filters for 4.3jum have, for example, 55 sidebands which lie in the near infrared or in the visible range so that interference radiation in these spectral fields likewise is detected.
Nakajima therefore employs a special filter developed by the Optical Coating Laboratory, 60 which indeed spans the carbon dioxide resonance radiation but for practical use is still too broadband (3.9—5.2/um). In order to eliminate neighbouring interference radiation, a special lead selenide photoelectric cell available from the
Santa Barbara Research Center must therefore be employed, which cuts off radiation of longer wavelengths than 4.3/um. However, the disadvantage of this is that at normal temperatures the carbon dioxide resonance radiation is already lying at their cut-off point of sensitivity so that the flame radiation cannot be fully utilized and the sensitivity of the fire alarm does not reach the optimum value possible.
The object of the present invention is to avoid the aforesaid disadvantages and to provide a fire alarm having lower susceptibility to interference, lower susceptibility to false alarms and higher sensitivity.
According to the invention there is provided a radiation detector for a fire alarm having a sensor element and a filter arranged in front of said sensor element, characterized in that the filter comprises a quartz filter element and a germanium filter element. In addition a spectral band filter for wavelengths of 4.1 —4.8/um or a narrow-band filter for the carbon dioxide resonance radiation at 4.3—4.41am may be provided, which may be formed of interference filter layers. The sensor element may be a pyroelectric element, which guarantees an optimum sensitivity. Embodiments of the invention will now be described with reference to the accompanying drawing, the single Figure of which shows a part-sectional elevation of a radiation detector in accordance with the invention.
Referring to the drawing, the radiation detector comprises a combination filter generally referenced 8 consisting of a number of filter elements. These are a germanium layer or filter element 6, an optional narrow-band filter element 1, e.g., an interference filter for 4.3jum, and a quartz layer or filter element 2. These several elements lie in parallel planes, the thickness of the germanium layer 6 amounting to about 1 mm and that of the interference filter 1 to about 50,um, and the thickness of the quartz layer 2 to about 0.5mm. The diameter of these elements or respectively of the filter 8 amounts to about 8—-12mm. The interference filter element 1 may consist of a number of layers, each layer consisting of a dielectric material. The filter 8 is accommodated in a so called "TO—5" housing 7. Such a housing is obtainable on the market anywhere under this brand name. The housing is connected to the filter by an adhesive connection 3. In the housing a sensor element 4, possibly a field-effect transistor, is located for converting optical radiation entering the housing through filter 8 into electrical signals. These signals are fed, via leads 5, as input to an alarm circuit (not shown). The sensor element 4 may be a pyroelectric detector such as, e.g., lithium tantalate or lead zirconate titanate, or a NTC-thermistor or a photoconductor or a thermoelectric pile.
The advantage of this arrangement in a fire alarm is that the quartz filter element lets through practically no radiation above a wavelength of
65
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80
85
90
95
100
105
110
115
120
125
GB 2 065 880 A
4.5,um. The germanium filter element has a sharp cut-off at about 1 and to shorter wavelengths, in particular to visible light, is practically opaque. The interference filter element 5 1 preferably lets through only radiation in the spectral field of 4.3—4.4/zm. With this filter combination, the pass-range is restricted to the direct neighbourhood of the carbon dioxide resonance line at 4.3)«m. Radiation of longer 10 wavelength, above 4.5l«m, is practically completely eliminated by the quartz filter element 2, whilst radiation having a wavelength below 1 .5/^1 is practically completely blocked by the germanium filter element 6. In the range of 15 wavelength between 1.5«m and 4.2^tm the transmission is less than 1 % of the maximum value at 4.3ium to 4.4/um.
Thus the filter combination described exhibits in the near infrared a suppression of interference 20 by a factor of more than 100, in the range of visible light and in the far infrared above the resonance wavelength of carbon dioxide a suppression by more than a factor of 1000. Interference radiations such as sunlight and 25 daylight as well as artificial sources of light such as incandescent lamps, fluorescent lamps and other interference such as welding arcs, which exhibit no sharp maximum of intensity at the resonance wavelength of carbon dioxide, are 30 almost completely blocked from the sensor element even when their intensity is considerably higher, e.g., more than a thousand times higher, than the flame radiation. It is therefore possible to recognize the formation of flame in the initial 35 stage, even in the presence of light and other interference radiation, with extraordinary certainty and to distinguish it from other radiation. The filter combination described enables a specially sensitive sensor element, such as the pyroelectric
40 elements described, to be employed without any loss of sensitivity arising.
The radiation detector of this invention is suitable for use in the flame detector of our pending patent application No. 7914323, from
45 which the present application has been divided.
Claims (8)
1. A radiation detector for a fire alarm having a sensor element (4) and a filter (8) arranged in front of said sensor element, characterized in that
50 the filter comprises a quartz filter element (2) and a germanium filter element (6).
2. A radiation detector as claimed in claim 1, characterized in that said filter additionally includes a spectral band filter (1) for wavelengths
55 of 4.1 to 4.8/zm.
3. A radiation detector as claimed in claim 1, characterized in that said filter additionally includes a narrow-band filter element (1) for wavelengths of approximately
4.3 to 4.4/xm.
60 4. A radiation detector as claimed in claim 3, characterized in that the additional filter element (1) is constituted by interference filter layers.
5. A radiation detector as claimed in any of claims 1 to 4, characterized in that the sensor
65 element (4) is a pyroelectric sensor.
6. A radiation detector as claimed in claim 5, characterized in that the sensor element (4) comprises lithium tantalate.
7. A radiation detector as claimed in claim 5,
70 characterized in that the sensor element (4)
comprises lead zirconate titanate.
8. A radiation detector substantially as herein described with reference to the accompanying drawing.
Printed for Her Majesty's Stationery Office by the Courier Press, Leamington Spa, 1981. Published by the Patent Office, 25 Southampton Buildings, London, WC2A 1 AY, from which copies may be obtained.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CH446678A CH628171A5 (en) | 1978-04-25 | 1978-04-25 | FLAME DETECTOR. |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB2065880A true GB2065880A (en) | 1981-07-01 |
Family
ID=4276616
Family Applications (2)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB7914323A Expired GB2020417B (en) | 1978-04-25 | 1979-04-24 | Flame detector fire alarm |
| GB8103946A Withdrawn GB2065880A (en) | 1978-04-25 | 1979-04-24 | Radiation Detector for a Fire Alarm |
Family Applications Before (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB7914323A Expired GB2020417B (en) | 1978-04-25 | 1979-04-24 | Flame detector fire alarm |
Country Status (7)
| Country | Link |
|---|---|
| JP (1) | JPS54146596A (en) |
| AT (1) | AT381406B (en) |
| AU (1) | AU521239B2 (en) |
| CH (2) | CH628171A5 (en) |
| DE (2) | DE2857795C2 (en) |
| FR (2) | FR2424036A1 (en) |
| GB (2) | GB2020417B (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4742236A (en) * | 1985-04-27 | 1988-05-03 | Minolta Camera Kabushiki Kaisha | Flame detector for detecting phase difference in two different wavelengths of light |
| US8253106B2 (en) | 2009-05-13 | 2012-08-28 | Minimax Gmbh & Co. Kg | Device and method for detecting flames |
| US8400314B2 (en) | 2009-05-13 | 2013-03-19 | Minimax Gmbh & Co. Kg | Fire alarm |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CH648660A5 (en) * | 1980-12-03 | 1985-03-29 | Cerberus Ag | RADIATION DETECTOR FOR A FLAME DETECTOR. |
| DE3279061D1 (en) * | 1981-04-16 | 1988-10-27 | Emi Ltd | Flame detector |
| US4639598A (en) * | 1985-05-17 | 1987-01-27 | Santa Barbara Research Center | Fire sensor cross-correlator circuit and method |
| JP2622382B2 (en) * | 1987-07-30 | 1997-06-18 | バブコツク日立株式会社 | Flame detector |
| DE3924250A1 (en) * | 1989-07-21 | 1991-02-07 | Preussag Ag Feuerschutz | FIRE DETECTOR |
| US9587987B2 (en) * | 2012-03-12 | 2017-03-07 | Honeywell International Inc. | Method and device for detection of multiple flame types |
| DE102021004593A1 (en) | 2021-09-10 | 2023-03-16 | Promecon Process Measurement Control Gmbh | Metallurgical melting furnace and method for determining the amount of heteromolecular gas |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3665440A (en) * | 1969-08-19 | 1972-05-23 | Teeg Research Inc | Fire detector utilizing ultraviolet and infrared sensors |
| FR2151148A5 (en) * | 1971-08-20 | 1973-04-13 | Detection Electro Fse | |
| US3896311A (en) * | 1974-01-02 | 1975-07-22 | Minnesota Mining & Mfg | Pyroelectric motion and temperature sensitive infrared detector with conductive fingers |
| US3992110A (en) * | 1974-09-03 | 1976-11-16 | The United States Of America As Represented By The Secretary Of The Navy | Multi-spectral optical comparator |
-
1978
- 1978-04-25 CH CH446678A patent/CH628171A5/en not_active IP Right Cessation
- 1978-05-29 DE DE2857795A patent/DE2857795C2/en not_active Expired
- 1978-05-29 DE DE2823411A patent/DE2823411C2/en not_active Expired
-
1979
- 1979-04-05 AT AT0252479A patent/AT381406B/en not_active IP Right Cessation
- 1979-04-24 GB GB7914323A patent/GB2020417B/en not_active Expired
- 1979-04-24 FR FR7910356A patent/FR2424036A1/en active Granted
- 1979-04-24 JP JP4989979A patent/JPS54146596A/en active Granted
- 1979-04-24 GB GB8103946A patent/GB2065880A/en not_active Withdrawn
- 1979-04-26 AU AU46486/79A patent/AU521239B2/en not_active Ceased
-
1980
- 1980-11-19 CH CH854880A patent/CH640963A5/en not_active IP Right Cessation
- 1980-12-10 FR FR8026206A patent/FR2470418A1/en active Granted
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4742236A (en) * | 1985-04-27 | 1988-05-03 | Minolta Camera Kabushiki Kaisha | Flame detector for detecting phase difference in two different wavelengths of light |
| US8253106B2 (en) | 2009-05-13 | 2012-08-28 | Minimax Gmbh & Co. Kg | Device and method for detecting flames |
| US8400314B2 (en) | 2009-05-13 | 2013-03-19 | Minimax Gmbh & Co. Kg | Fire alarm |
Also Published As
| Publication number | Publication date |
|---|---|
| FR2470418B1 (en) | 1985-04-12 |
| DE2823411A1 (en) | 1979-11-08 |
| AU4648679A (en) | 1979-11-01 |
| AT381406B (en) | 1986-10-10 |
| DE2823411C2 (en) | 1982-06-03 |
| CH640963A5 (en) | 1984-01-31 |
| FR2424036B1 (en) | 1983-07-18 |
| FR2424036A1 (en) | 1979-11-23 |
| CH628171A5 (en) | 1982-02-15 |
| DE2857795C2 (en) | 1985-09-26 |
| AU521239B2 (en) | 1982-03-25 |
| GB2020417B (en) | 1982-11-24 |
| FR2470418A1 (en) | 1981-05-29 |
| JPS6239473B2 (en) | 1987-08-24 |
| GB2020417A (en) | 1979-11-14 |
| ATA252479A (en) | 1986-02-15 |
| JPS54146596A (en) | 1979-11-15 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |