CN101949838B - Dispersive infrared absorption gas detection device and method - Google Patents
Dispersive infrared absorption gas detection device and method Download PDFInfo
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- CN101949838B CN101949838B CN 201010270268 CN201010270268A CN101949838B CN 101949838 B CN101949838 B CN 101949838B CN 201010270268 CN201010270268 CN 201010270268 CN 201010270268 A CN201010270268 A CN 201010270268A CN 101949838 B CN101949838 B CN 101949838B
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Abstract
The invention discloses a dispersive infrared absorption gas detection device and a method. In the device and the method, based on infrared spectrum adoption theory, methane and carbon monoxide with the wavelengths of 3.433mu m and 4.65mu m are adopted; infrared light emitted by adopting an MEMS infrared light source is projected to a blazed grating through a collimated light component, and is split to acquire infrared lines with the wavelengths of 3.433mu m and 4.65mu m; and concentration detection on methane and carbon oxide in sample gas can be realized through an open air chamber. The device can detect the gas selectively, quickly and stably by combining the method, improves the corresponding accuracy, can realize simultaneous detection on the methane and the carbon oxide, and reduces cost.
Description
Technical field
The present invention relates to the mine gas detection range, particularly a kind of beam split type infrared absorption type gas detecting device and method.
Background technology
Gas accident is one of main threat of Safety of Coal Mine Production, is the great difficult problem of puzzlement mining industry always, and brings very big loss for country and enterprise.The principal ingredient of coal-mine gas is methane and carbon monoxide, and the two is flammable explosive gas, is reached at 5.3%～15% o'clock like methane concentration in atmosphere, has explosivity.Therefore, need carry out early stage detection, detect gas density in time, mine safety production and personal safety are all had crucial effect Minepit environment gas.
At present, the detection method of two kinds of hazardous gas methane and carbon monoxide has electrochemical method, optical means, semiconductor process, vapor-phase chromatography and infrared absorption method etc. multiple in the coal mine.The methane that generally uses both at home and abroad and the infrared absorption sensor of CO gas all are on-dispersive infrared absorption type gas sensors.This sensor is to utilize light emitting diode or incandescent lamp as light source; Utilize its light that sends after the over-sampling air chamber is absorbed; Utilize filter plate to leach the intrinsic absorbing wavelength of methane or carbon monoxide; Utilize photodetector to carry out photoelectricity again and transform, and carry out the detection of gas concentration through signal processing circuit; Or utilize semiconductor laser directly to send the intrinsic absorbing wavelength infrared light of methane or carbon monoxide, obtain gas concentration through being handled by photodetector and signal processing circuit behind the sampling air chamber, detecting.
But; Mainly there is following problem in the NDIR absorption type gas sensor: (1) adopts light emitting diode or incandescent lamp as light source; Though cheap, the filtered IR wave band of the filter plate in its system broad influences accuracy of detection; And the narrow bandwidth filter plate is made difficulty, costs an arm and a leg.(2) adopt semiconductor laser, though accuracy of detection is higher, the laser instrument cost is expensive, and it is higher to detect cost.Therefore, develop a kind of highly sensitive, cheap, reliable and secure gas detection system and have very important social meaning and economic outlook.
Summary of the invention
The objective of the invention is to overcome the shortcoming of above-mentioned prior art; A kind of beam split type infrared absorption type gas detecting device and method are provided; This device combine this method not only can high selectivity, fast, stably methane gas is detected; Improve corresponding precision, and can also realize that methane and carbon monoxide detect simultaneously, and reduce cost.
The objective of the invention is to solve through following technical scheme:
This beam split type infrared absorption type gas detecting device; Comprise air chamber and quasi-parallel optical assembly; Be provided with two plane reflection blazed gratings in the said air chamber, the upper end of air chamber is provided with two pyroelectric detectors, and the light exit side of said quasi-parallel optical assembly stretches in the said air chamber; The light incident side of quasi-parallel optical assembly is provided with the MEMS infrared light supply, and said two pyroelectric detectors are connected with signal processing circuit respectively; Said air chamber is fed gas to be detected, is given vent to anger by the lower end by the upper end; The emission light of said MEMS infrared light supply is handled in the laggard air inlet chamber through the quasi-parallel optical assembly; Reflex to respectively on said two pyroelectric detectors by two plane reflection blazed gratings that are set to different angles; Said two pyroelectric detectors transform test signal photoelectricity; Transfer to signal processing circuit at last, judge whether overrun of methane and carbonomonoxide concentration by signal processing circuit, and make warning; Said quasi-parallel optical assembly (2) length is 6cm, and the outgoing hole diameter is 5mm.
The inside of above-mentioned quasi-parallel optical assembly is circular hole; And carried out anodic metal oxide; Prevent parasitic light at intracavity reflecting, the incident end of this quasi-parallel optical assembly is connected with the exit end of MEMS infrared light supply, and the exit end of quasi-parallel optical assembly exceeds and makes the tiny circular hole of shooting angle.
The surface of above-mentioned two plane reflection blazed gratings is zigzag fashion.
Based on above device, the present invention also proposes a kind of gas measuring method, may further comprise the steps:
1) at first, make gas to be detected constantly feed in the air chamber by the upper end;
2) the infrared light process quasi-parallel optical assembly that the MEMS infrared light supply is sent; The quasi-parallel light of said quasi-parallel optical assembly outgoing is incident to two plane reflection blazed gratings; Making two plane reflection blazed gratings split with methane and carbon monoxide intrinsic absorbing wavelength respectively is the narrow bandwidth infrared light at center; This infrared light through with the air chamber that is full of gas to be detected after, utilize two pyroelectric detectors to survey two bundle narrow bandwidth infrared lights respectively again
3) make two pyroelectric detectors that test signal is carried out respectively transferring to signal processing circuit after photoelectricity transforms, utilize infrared absorption principle to realize the detection of gas concentration to be detected by signal processing circuit.
Further, above-mentioned MEMS infrared light supply adopts centre wavelength at 4 μ m, and satisfy 3.433 μ m, there is higher radiant quantity at 4.65 μ m places.
The present invention has following beneficial effect:
(1) ultimate principle of detection method of the present invention adopts blazed grating beam split acquisition methane and carbon monoxide intrinsic absorbing wavelength 3.433 μ m, 4.65 μ m arrowband infrared lights to test; Thereby have more high sensitivity, and reduced of the interference of other gas measurement result;
(2) the required blazed grating of device of the present invention, the cost of single-piece blazed grating can be very low under the MEMS batch machining, detects and the early warning system cost thereby reduce;
(3) the present invention adopts quasi-parallel optical assembly outgoing quasi-parallel light incident grating, guarantees also to have reduced the difficulty of system optics component placement under the situation of spectrophotometric result.
(4) device of the present invention utilizes the corresponding different centre wavelength of the different blazing angles of blazed grating, thereby can be applicable to the detection of other gas, is methane gas not only, uses more extensive.
Description of drawings
Fig. 1 is a synoptic diagram of the present invention;
Wherein, 1 is the MEMS infrared light supply, the 2 directional light assemblies that are as the criterion, and 3 and 4 is the plane reflection blazed grating, and 5 and 6 is pyroelectric detector, and 7 is signal processing circuit, and 8 is air chamber;
Fig. 2 is plane reflection blazed grating light-dividing principle figure;
Fig. 3 obtains the position view of intrinsic wavelength and pyroelectric detector for the blazed grating beam split.
Embodiment
This beam split type infrared absorption type gas detecting device and method that the present invention provides, its innovative design thought are mainly reflected in utilizes quasi-parallel optical assembly and blazed grating to carry out beam split, and design concept is the blazed grating light-dividing principle.
Referring to Fig. 1, pick-up unit structure of the present invention is: this device comprises air chamber 8 and quasi-parallel optical assembly 2, and the surface that in air chamber 8, is provided with 3,4, two plane reflection blazed gratings 3,4 of two plane reflection blazed gratings is zigzag fashion.The upper end of air chamber 8 is provided with two pyroelectric detectors 5,6.The inside of quasi-parallel optical assembly 2 is circular hole; And carried out anodic metal oxide; Prevent that parasitic light is at intracavity reflecting; The incident end of this quasi-parallel optical assembly 2 is connected with the exit end of MEMS (MEMS) infrared light supply 1, and the exit end of quasi-parallel optical assembly 2 exceeds and makes the tiny circular hole of shooting angle.The light exit side of quasi-parallel optical assembly 2 stretches in the air chamber 8, and the light incident side of quasi-parallel optical assembly 2 is provided with 1, two pyroelectric detector of MEMS infrared light supply 5,6 and is connected with signal processing circuit 7 respectively; The upper end of air chamber 8 is provided with gas feed, the lower end is provided with gas vent, and therefore, air chamber 8 is to be fed gas to be detected, given vent to anger by the lower end by the upper end; The emission light of said MEMS infrared light supply 1 gets in the air chamber 8 through the quasi-parallel light of the certain dispersion angle of quasi-parallel optical assembly 2 outgoing; 2 outgoing of quasi-parallel optical assembly have certain areal extent; Two plane reflection blazed gratings 3,4 place quasi-parallel optical assembly 2 outgoing zone; And calculate according to the blazed grating formula and to settle fixing (introducing in detail) after the angle below in conjunction with Fig. 2; Be set to two plane reflection blazed gratings 3,4 of different angles, the emergent light with quasi-parallel optical assembly 2 is incident on two plane reflection blazed gratings 3,4 respectively, and it is the narrow bandwidth infrared light at center that two plane reflection blazed gratings 3,4 split with methane and carbon monoxide intrinsic absorbing wavelength respectively; This infrared light through the open air chamber 8 that is full of gas to be measured after, utilize pyroelectric detector 5,6 to survey two bundle narrow bandwidth infrared lights respectively again.Two pyroelectric detectors 5,6 are surveyed methane and the carbon monoxide intrinsic absorbing wavelength light that two plane reflection blazed gratings 3,4 split respectively; And test signal photoelectricity transformed; Transfer to signal processing circuit 7 at last; Judge whether overrun of methane and carbonomonoxide concentration by signal processing circuit 7, and make warning.Wherein, in order to detect methane and carbon monoxide, require MEMS infrared light supply 1 to adopt centre wavelength at 4 μ m, there is higher radiant quantity at satisfied 3.433 μ m, 4.65 μ m places.
Above quasi-parallel optical assembly 2 adopts circular hole inner chamber and aperture outgoing, the row metal anodic oxidation of going forward side by side; Blazed grating adopts the plane blazed grating, shows indentation; Air chamber has adopted and has openly linked to each other with environmental gas.
Referring to Fig. 2, this figure is the synoptic diagram of grating beam splitting principle.Wherein, N is the normal direction of bottom surface, i.e. the grating normal; N is the normal direction on sawtooth inclined-plane; D is a grating constant;
is incident angle, i.e. the angle of incident direction and grating normal; θ is an angle of diffraction, i.e. the angle of diffraction direction and grating normal.Blazed grating can focus on most of light intensity in certain certain wavelengths spectrum, and can not have the zero utmost point principal maximum of chromatic dispersion to occupy most of light intensity as transmission grating.
According to the blazed grating light-dividing principle:
In the formula:
θ---angle of diffraction (angle of diffraction direction and grating normal)/°;
D---blazed grating constant/μ m;
M---the order of diffraction is inferior;
θ
Kb---blazing angle/°;
After confirming grating constant; Incidence angles can produce different blaze wavelengths; And identical incident angle can be at different diffraction angle diffraction different wavelengths of light; So design the wavelength coverage of narrow bandwidth infrared light according to the width of the intrinsic absorption peak of methane and carbon monoxide, design the angle of the quasi-parallel light of quasi-parallel optical assembly 2 outgoing through this wavelength coverage.Thereby aspect the space, confirm the arrangement angle of two pyroelectric detectors 5,6.
Referring to Fig. 3,3 (4) beam split obtain gas absorption intrinsic wavelength through the plane reflection blazed grating, utilize pyroelectric detector 5 (6) to carry out surveying and opto-electronic conversion in intrinsic wavelength angle again.
For example, in the present invention, adopting quasi-parallel optical assembly length is 6cm, and the outgoing hole diameter is 5mm, and then utilizing trigonometric function to calculate can get, and the angle of divergence is 4.7 °, less than 5 °.Selecting 31.7 ° of grating constants of blazing angle respectively is that 3.33 μ m and blazing angle are that 30 ° of grating constants are that the plane blazed grating 3 and 4 of 5 μ m is as spectrum groupware; Utilize formula (2) then can calculate two blocks of gratings incident angle and emergence angle under 3.433 μ m, 4.65 μ m diffraction wavelengths respectively; Be respectively: grating 3 corresponding φ=43.19 °, θ=20.21 °; Grating 4 corresponding φ=51.57 °, θ=8.43 °.And when ranges of incidence angles below 5 ° the time; Be φ=43.19 ° ± 2.5 ° or φ=51.57 ° ± 2.5 °; Utilize its diffraction wavelength scope of formula (2) within 3.433 μ m ± 50nm and 4.65 μ m ± 50nm; And this bandwidth range belongs in the infrared absorption spectrum of methane and carbon monoxide, is fit to measure.The angle of arranging pyroelectric detector 5 and 6 simultaneously is respectively 20.21 ° and 8.43 ° and can accomplishes detection.Above-mentioned angle is a benchmark with the blazed grating normal all.
And according to infrared absorption principle formula Lambert-beer law, the absorption law of light just:
I＝I
0?exp(-αLc) (4)
c＝ln(I
0/I)/αL (5)
In the formula:
Transmitted light intensity/cd after I---light absorbs through medium;
I
0Light intensity/the cd of-incident medium;
α---be the absorption coefficient of medium;
C---concentration of medium/%;
L---be the length/m of light through medium.
Visible by above-mentioned formula, as the absorption coefficient of medium, light length L, transmitted light intensity I, incident intensity I through medium
0In the time of certain, can obtain the concentration of purpose gas.
Based on above pick-up unit of the present invention, the concrete steps of gas measuring method of the present invention are following:
1) at first, gas to be detected is constantly fed in the air chamber 8 by the upper end, gas is fed by the upper end, is full of air chamber 8 backs and is discharged by the lower end;
2) make the MEMS infrared light supply adopt centre wavelength at 4 μ m; And satisfy 3.433 μ m, there is higher radiant quantity at 4.65 μ m places; The infrared light process quasi-parallel optical assembly 2 that MEMS infrared light supply 1 is sent; The quasi-parallel light of these quasi-parallel optical assembly 2 outgoing is incident to two plane reflection blazed gratings 3,4, and making two plane reflection blazed gratings 3,4 split with methane and carbon monoxide intrinsic absorbing wavelength respectively is the narrow bandwidth infrared light at center, this infrared light through with the air chamber that is full of gas to be detected 8 after; Utilize two pyroelectric detectors 5,6 to survey two bundle narrow bandwidth infrared lights respectively again
3) make two pyroelectric detectors 5,6 that test signal is carried out respectively transferring to signal processing circuit 7 after photoelectricity transforms, utilize above-mentioned infrared absorption principle to realize the detection of gas concentration to be detected by signal processing circuit 7.
In sum; The present invention utilizes quasi-parallel light and blazed grating to obtain the intrinsic wavelength of methane and carbon monoxide infrared absorption; Realize methane and carbon monoxide detectable concentration simultaneously, both improved the precision that system gas detects, simplified assembling and processing again; And reduce cost, solved the problem that traditional NDIR Absorbing Sensor price is high, improve the precision difficulty.In addition, the present invention can also realize the detection of other gas through change regulating the plane reflection blazed grating, also can be used for vehicle exhaust detection etc., can be continuously to the gas such as the CO of routine
2, CO, CH
4, NO, SO
2Measure Deng gas, it possibly progressively replace gas detecting device in the past.
Claims (5)
1. beam split type infrared absorption type gas detecting device; It is characterized in that: comprise air chamber (8) and quasi-parallel optical assembly (2); Be provided with two plane reflection blazed gratings (3,4) in the said air chamber (8); The upper end of air chamber (8) is provided with two pyroelectric detectors (5,6); The light exit side of said quasi-parallel optical assembly (2) stretches in the said air chamber (8), and the light incident side of quasi-parallel optical assembly (2) is provided with MEMS infrared light supply (1), and said two pyroelectric detectors (5,6) are connected with signal processing circuit (7) respectively; Said air chamber (8) is fed gas to be detected, is given vent to anger by the lower end by the upper end; The emission light of said MEMS infrared light supply (1) is handled in the laggard air inlet chamber (8) through quasi-parallel optical assembly (2); Reflex to respectively on said two pyroelectric detectors (5,6) by the two plane reflection blazed gratings (3,4) that are set to different angles; Said two pyroelectric detectors (5,6) transform test signal photoelectricity; Transfer to signal processing circuit (7) at last, judge whether overrun of methane and carbonomonoxide concentration by signal processing circuit (7), and make warning; Said quasi-parallel optical assembly (2) length is 6cm, and the outgoing hole diameter is 5mm.
2. beam split type infrared absorption type gas detecting device according to claim 1; It is characterized in that: the inside of said quasi-parallel assembly (2) is circular hole; And carried out anodic metal oxide; Prevent parasitic light at intracavity reflecting, the incident end of this quasi-parallel optical assembly (2) is connected with the exit end of MEMS infrared light supply (1), and the exit end of quasi-parallel assembly (2) exceeds and makes the tiny circular hole of shooting angle.
3. beam split type infrared absorption type gas detecting device according to claim 1 is characterized in that the surface of said two plane reflection blazed gratings (3,4) is zigzag fashion.
4. the gas measuring method based on the said device of claim 1 is characterized in that, may further comprise the steps:
1) at first, gas to be detected is constantly fed in the air chamber (8) by the upper end;
2) the infrared light process quasi-parallel optical assembly (2) that MEMS infrared light supply (1) is sent; The quasi-parallel light of said quasi-parallel optical assembly (2) outgoing is incident to two plane reflection blazed gratings (3,4); Making two plane reflection blazed gratings (3,4) split with methane and carbon monoxide intrinsic absorbing wavelength respectively is the narrow bandwidth infrared light at center; This infrared light through with the air chamber that is full of gas to be detected (8) after, utilize two pyroelectric detectors (5,6) to survey two bundle narrow bandwidth infrared lights respectively again
3) make two pyroelectric detectors (5,6) that test signal is carried out respectively transferring to signal processing circuit (7) after photoelectricity transforms, utilize infrared absorption principle to realize the detection of gas concentration to be detected by signal processing circuit (7).
5. gas measuring method according to claim 4 is characterized in that: said MEMS infrared light supply adopts centre wavelength at 4 μ m, and satisfy 3.433 μ m, there is higher radiant quantity at 4.65 μ m places.
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| JP5973969B2 (en) * | 2013-07-31 | 2016-08-23 | 国立大学法人徳島大学 | Inline densitometer and concentration detection method |
| CN103926209B (en) * | 2013-12-26 | 2017-01-18 | 安徽理工大学 | DOAS double sampling technology based coal seam gas combined measurement system |
| CN105445216A (en) * | 2015-11-13 | 2016-03-30 | 华中科技大学 | Super-surface-based infrared absorption type multi-gas-concentration measurement sensor |
| CN111123422A (en) * | 2020-01-07 | 2020-05-08 | 南京大学 | Novel terahertz dynamic adjustable grating and preparation method thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| US4060327A (en) * | 1976-09-13 | 1977-11-29 | International Business Machines Corporation | Wide band grating spectrometer |
| US5757483A (en) * | 1997-08-06 | 1998-05-26 | Stellarnet, Inc. | Dual beam optical spectrograph |
| CN100468049C (en) * | 2007-04-30 | 2009-03-11 | 西安交通大学 | Detection method for Optical-fiber transmitting infrared absorption type methane gas |
| CN101504367B (en) * | 2009-03-10 | 2011-07-20 | 哈尔滨工业大学 | Apparatus for simultaneously monitoring concentration of carbon monoxide and carbon dioxide |
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