GB2264170A - Infra-red absorption gas detector - Google Patents
Infra-red absorption gas detector Download PDFInfo
- Publication number
- GB2264170A GB2264170A GB9203013A GB9203013A GB2264170A GB 2264170 A GB2264170 A GB 2264170A GB 9203013 A GB9203013 A GB 9203013A GB 9203013 A GB9203013 A GB 9203013A GB 2264170 A GB2264170 A GB 2264170A
- Authority
- GB
- United Kingdom
- Prior art keywords
- detector
- gas
- emitters
- infra
- gas detector
- 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- Withdrawn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
- 238000010521 absorption reaction Methods 0.000 title abstract description 11
- 239000000835 fiber Substances 0.000 claims description 14
- 239000004065 semiconductor Substances 0.000 claims description 12
- 230000008878 coupling Effects 0.000 claims description 3
- 238000010168 coupling process Methods 0.000 claims description 3
- 238000005859 coupling reaction Methods 0.000 claims description 3
- 230000003213 activating effect Effects 0.000 claims description 2
- 239000004020 conductor Substances 0.000 claims description 2
- 238000005286 illumination Methods 0.000 claims description 2
- 230000031700 light absorption Effects 0.000 claims description 2
- 239000005383 fluoride glass Substances 0.000 claims 1
- 230000003287 optical effect Effects 0.000 abstract 2
- 239000007789 gas Substances 0.000 description 22
- 229910005542 GaSb Inorganic materials 0.000 description 4
- 229910000673 Indium arsenide Inorganic materials 0.000 description 4
- 238000001514 detection method Methods 0.000 description 4
- RPQDHPTXJYYUPQ-UHFFFAOYSA-N indium arsenide Chemical compound [In]#[As] RPQDHPTXJYYUPQ-UHFFFAOYSA-N 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 4
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 3
- MWUXSHHQAYIFBG-UHFFFAOYSA-N nitrogen oxide Inorganic materials O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 239000003344 environmental pollutant Substances 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 description 1
- 229910001245 Sb alloy Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 231100000719 pollutant Toxicity 0.000 description 1
- 239000010453 quartz Substances 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
- G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
- G01N21/3504—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light for analysing gases, e.g. multi-gas analysis
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/01—Arrangements or apparatus for facilitating the optical investigation
- G01N21/03—Cuvette constructions
- G01N21/031—Multipass arrangements
- G01N2021/0314—Double pass, autocollimated path
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2201/00—Features of devices classified in G01N21/00
- G01N2201/08—Optical fibres; light guides
Landscapes
- Physics & Mathematics (AREA)
- Spectroscopy & Molecular Physics (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Investigating Or Analysing Materials By Optical Means (AREA)
Abstract
An infra-red absorption gas detector has multiple infra-red light emitters 11-16 operating at different wavelengths and optically coupled to at least one light detector 17, via a cavity 4 containing a gas to be analysed, by way of optical fibres 7, 8 which may constitute optical filters. The emitters 11-16 operate sequentially to give a corresponding sequential detector output characteristic of the gas. <IMAGE>
Description
INFRA-RED ABSORPTION GAS DETECTOR
The invention relates to a gas detector which operates by detecting the absorption of infra-red light by gases.
Environmentally important gases, which are of particular interest, such as CO, CO2, H2 S, methane and nitrogen oxides have absorption bands in the wavelength range 1.5 to 10 microns. Single wavelength absorption detectors are available which operate with matched semiconductor light emitter/detector pairs at a few wavelengths. These can be used for the detection of water vapour, CO2 and methane. The two pairs may be incorporated in a single unit to give simultaneous detection for two gases. For accurate detection of other gases and mixtures of gases other more complicated and expensive types of analyser must be used. The present invention seeks to provide an improvement.
According to the invention there is provided a gas detector having a sensing head with a cavity for the admission of gas; a plurality of semiconductor infra-red light emitters operating at different wavelengths; at least one semiconductor infra-red light detector; an optic fibre light conductor arrangement coupling the emitters and the detector to the cavity; switching means for activating the emitters in turn to illuminate the gas with respective infra-red wavelengths in sequence; and output means connected to the detector, the arrangement being such that the detector responds to each wavelength illumination in accordance with the absorption of light by the gas and a sequential output signal is derived from the output means which, having regard to the switching sequences, is characteristic of the gas.
The optic fibre arrangement may comprise a single transmit fibre which transmits the emitter outputs, there being a collective emitter coupling to the fibre, and a single receive fibre which conveys the light from the cavity to the detector or detectors.
Preferably, however, each emitter and each detector has its own associated fibre in a fibre bundle.
The use of an optic fibre arrangement allows the remote positioning of the emitters and detectors so that the analyser may be used in hostile environments.
Furthermore, individual fibres may be matched optically to associated emitters and detectors to provide filtering whereby the wavelengths may be finely tuned. Conventional silica or quartz fibres would be used for short wavelengths and fluoride fibres for the longer wavelengths.
Wavelength tuning is facilitated by the choice of semiconductor compositions and manufacturing techniques. For example, emitter and detector diodes may include crossed band gap alignment semiconductors of an all n- or an all p-type. A suitable pair of semiconductors is InAs/GaSb and InAs/Ga1 xInxSb. With these materials and by arranging a suitable crossed band gap alignment it is possible to inject holes into a diode like structure fabricated entirely from n-type materials. This eliminates the need to produce abrupt doping profiles when fabricating the light emitter and detector structures. The use of GaSb and (Ga,In) Sb alloys and quantum wells as the active layers in the structure has potential in allowing emission and detection in the region 1.7 to 7 microns.
The use of specific wavelengths determined by the characteristics of the emitters, detectors and optic fibres means that a high degree of discrimination is possible by using the characteristics of more than one absorption band to obtain the absorption "fingerprint" of each gas. Further advantages may be obtained by the use of multiple detectors with optimised response at different wavelengths. Generally, however, there will be more emitters than detectors, at least some of the detectors being responsive to the outputs from different emitters. Sharp emission bands are not necessary and this is beneficial in allowing a spread of lines (typically + 0.1 microns) to be detected around the centre wavelength. Timing signals from the switching means allows the response to the different emitters to be differentiated. It is envisaged that there may be 3-15 emitters and 1-4 detectors.
The invention will further be described with reference to the accompanying drawings, of which:
Figure 1 is a diagram of a gas analyser according to the invention;
Figure 2 is a chart of absorption characteristics of potential pollutant gases, and
Figure 3 is a diagram illustrating the output "fingerprints" for CO2 and H2 S using the analyser of
Figure 1.
Referring to Figure 1 there is shown a gas analyser comprising a sensing head 1 which has a cylindrical wall 2 and an end cap 3 defining a cavity 4. The head is immersed in gas to be analysed and this enters the cavity by way of apertures 5.
At the end opposite the cap 3 the head fits the end of a bundle 6 of optic fibres. In this example there are six transmit fibres 7 which are disposed around a single receive fibre 8. The transmit fibres are optically coupled at their ends remote from the head to respective semiconductor infra-red light emitters 11 to 16. These are a variety of semiconductor diode emitters which typically include diodes based on the use of the materials system GaSb/In Ga XSb and may also include all n- or all p- type diodes formed with cross band gap alignment
InAs/GaSb and InAs/(Ga,In)Sb materials of such characteristics as to be tuned to respective infra-red wavelengths. The wavelengths of emitters 11 to 16 are respectively, in this example, 1.7; 2.1; 2.4; 2.7; 3.7 and 4.2 microns.
Coupled to the end of fibre 8 remote from the sensing head is a semiconductor detector diode 17 which responds to infra-red light over the band 1.7 to 4.7 microns. The diode 17 is connected to an output and display unit 18.
Emitters 11 to 16 are energised sequentially via a switching unit 19 so as to illuminate the gas in the cavity 4 cyclically in turn A mirror 20 is provided on the inside of cap 3 and this reflects light received from the transmit fibres 7 to the receive fibre 8. The amount of light received by the detector diode is a function of the absorption of the gas in the cavity 4. Thus a sequential output is obtained from the output and display unit 18 which represents respective responses to the sequentially transmitted wavelengths. The display output is a profile or "fingerprint" representative of the gas in the cavity.
Figure 2 shows a chart of gas absorption wavelengths for the principal environmental pollutant gases.
Figure 3 shows the form of the display output from the analyser of Figure 1 for (a) NO2, (b) CO2 and (c) H2S.
Claims (5)
1. A gas detector having a sensing head with a cavity for the admission of gas; a plurality of semiconductor infra-red light emitters operating at different wavelengths; at least one semiconductor infra-red light detector; an optic fibre light conductor arrangement coupling the emitters and the detector to the cavity; switching means for activating the emitters in turn to illuminate the gas with respective infra-red wavelengths in sequence; and output means connected to the detector, the arrangement being such that the detector responds to each wavelength illumination in accordance with the absorption of light by the gas and a sequential output signal is derived from the output means which, having regard to the switching sequences, is characteristic of the gas.
2. A gas detector as claimed in Claim 1 wherein the optic fibre arrangement comprises a bundle of fibres, there being a respective fibre for each emitter and the or each detector.
3. A gas detector as claimed in Claim 1 or Claim 2 wherein there are at least three emitters operating in the wavelength range 1.7 to 5 microns.
4. A gas detector as claimed in any of the preceding claims wherein at least some of the emitters are all n- or all p-type crossed band gap alignment semiconductor diodes.
5. A gas detector as claimed in any of the preceding claims when at least some of the fibres are of fluoride glass.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9203013A GB2264170A (en) | 1992-02-13 | 1992-02-13 | Infra-red absorption gas detector |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9203013A GB2264170A (en) | 1992-02-13 | 1992-02-13 | Infra-red absorption gas detector |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB9203013D0 GB9203013D0 (en) | 1992-03-25 |
| GB2264170A true GB2264170A (en) | 1993-08-18 |
Family
ID=10710298
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9203013A Withdrawn GB2264170A (en) | 1992-02-13 | 1992-02-13 | Infra-red absorption gas detector |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2264170A (en) |
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4438244C1 (en) * | 1994-10-26 | 1996-03-07 | Frobenius Wolf Dietrich Prof D | Gas component concn. in mixture measuring appts. for esp. carbon dioxide in atmos. |
| DE29504088U1 (en) * | 1995-03-10 | 1996-07-11 | Palocz-Andresen, Michael, Dr.-Ing.habil., 20459 Hamburg | On-board diagnostic / OBD / device on a micro scale for the continuous measurement of pollutant discharge from motor vehicles |
| FR2734906A1 (en) * | 1995-06-03 | 1996-12-06 | Draegerwerk Ag | INFRARED ABSORPTION MEASURING DEVICE |
| GB2303447A (en) * | 1995-07-07 | 1997-02-19 | Amg Systems Limited | Gas detection |
| DE19611290A1 (en) * | 1996-03-22 | 1997-09-25 | Draegerwerk Ag | Laser diode gas detector for spectroscopic measurement e.g. of chemical process or environment |
| DE19821136C2 (en) * | 1997-08-25 | 2000-06-08 | Wwu Wissenschaftliche Werkstat | Device for analyzing the exhaust gas from motor vehicles |
| DE19831457C2 (en) * | 1997-09-11 | 2000-08-31 | Wwu Wissenschaftliche Werkstat | Retrofit method for recording the exhaust gas composition in the motor vehicle for self-installation |
| WO2003046522A3 (en) * | 2001-11-30 | 2004-06-10 | Air Liquide | Apparatus and methods for launching and receiving a broad wavelength range source |
| CN113218906A (en) * | 2021-04-19 | 2021-08-06 | 国网江苏省电力有限公司检修分公司 | Sulfur hexafluoride decomposition component monitoring device and method based on laser transmission signals |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1402440A (en) * | 1972-12-13 | 1975-08-06 | British Leyland Motor Corp | Infra-red gas analyser |
| US3910701A (en) * | 1973-07-30 | 1975-10-07 | George R Henderson | Method and apparatus for measuring light reflectance absorption and or transmission |
| WO1982003688A1 (en) * | 1981-04-13 | 1982-10-28 | Ab Bonnierfoeretagen | Distinct wavelenght light reflectance measuring apparatus |
| US5066124A (en) * | 1989-07-21 | 1991-11-19 | Bodenseewerk Perkin Elmer Gmbh | Atomic absorption spectrophotometer for simultaneous multi-element analysis |
| US5070245A (en) * | 1988-11-04 | 1991-12-03 | Instrumentarium Corporation | Apparatus and method for the identification of gases |
-
1992
- 1992-02-13 GB GB9203013A patent/GB2264170A/en not_active Withdrawn
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1402440A (en) * | 1972-12-13 | 1975-08-06 | British Leyland Motor Corp | Infra-red gas analyser |
| US3910701A (en) * | 1973-07-30 | 1975-10-07 | George R Henderson | Method and apparatus for measuring light reflectance absorption and or transmission |
| WO1982003688A1 (en) * | 1981-04-13 | 1982-10-28 | Ab Bonnierfoeretagen | Distinct wavelenght light reflectance measuring apparatus |
| US5070245A (en) * | 1988-11-04 | 1991-12-03 | Instrumentarium Corporation | Apparatus and method for the identification of gases |
| US5066124A (en) * | 1989-07-21 | 1991-11-19 | Bodenseewerk Perkin Elmer Gmbh | Atomic absorption spectrophotometer for simultaneous multi-element analysis |
Cited By (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4438244C1 (en) * | 1994-10-26 | 1996-03-07 | Frobenius Wolf Dietrich Prof D | Gas component concn. in mixture measuring appts. for esp. carbon dioxide in atmos. |
| DE29504088U1 (en) * | 1995-03-10 | 1996-07-11 | Palocz-Andresen, Michael, Dr.-Ing.habil., 20459 Hamburg | On-board diagnostic / OBD / device on a micro scale for the continuous measurement of pollutant discharge from motor vehicles |
| FR2734906A1 (en) * | 1995-06-03 | 1996-12-06 | Draegerwerk Ag | INFRARED ABSORPTION MEASURING DEVICE |
| GB2301665A (en) * | 1995-06-03 | 1996-12-11 | Draegerwerk Ag | Measuring gas concentration using infrared absorbtion |
| GB2301665B (en) * | 1995-06-03 | 1997-04-23 | Draegerwerk Ag | Measuring device using infrared absorption |
| GB2303447A (en) * | 1995-07-07 | 1997-02-19 | Amg Systems Limited | Gas detection |
| DE19611290A1 (en) * | 1996-03-22 | 1997-09-25 | Draegerwerk Ag | Laser diode gas detector for spectroscopic measurement e.g. of chemical process or environment |
| DE19611290C2 (en) * | 1996-03-22 | 1998-04-16 | Draegerwerk Ag | Gas sensor |
| DE19821136C2 (en) * | 1997-08-25 | 2000-06-08 | Wwu Wissenschaftliche Werkstat | Device for analyzing the exhaust gas from motor vehicles |
| DE19831457C2 (en) * | 1997-09-11 | 2000-08-31 | Wwu Wissenschaftliche Werkstat | Retrofit method for recording the exhaust gas composition in the motor vehicle for self-installation |
| WO2003046522A3 (en) * | 2001-11-30 | 2004-06-10 | Air Liquide | Apparatus and methods for launching and receiving a broad wavelength range source |
| US7005645B2 (en) | 2001-11-30 | 2006-02-28 | Air Liquide America L.P. | Apparatus and methods for launching and receiving a broad wavelength range source |
| CN113218906A (en) * | 2021-04-19 | 2021-08-06 | 国网江苏省电力有限公司检修分公司 | Sulfur hexafluoride decomposition component monitoring device and method based on laser transmission signals |
Also Published As
| Publication number | Publication date |
|---|---|
| GB9203013D0 (en) | 1992-03-25 |
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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) |