CN203745372U - Intermediate infrared tunable semiconductor light source spectrum absorption technology-based methane concentration detection device - Google Patents
Intermediate infrared tunable semiconductor light source spectrum absorption technology-based methane concentration detection device Download PDFInfo
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- CN203745372U CN203745372U CN201420128012.8U CN201420128012U CN203745372U CN 203745372 U CN203745372 U CN 203745372U CN 201420128012 U CN201420128012 U CN 201420128012U CN 203745372 U CN203745372 U CN 203745372U
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Abstract
The utility model discloses an intermediate infrared tunable semiconductor light source spectrum absorption technology-based methane concentration detection device, and belongs to the field of spectrum absorption. The device comprises a signal generator, an LED (light-emitting diode) driving circuit, an LED, a gas chamber, a photoelectric detector, a digital phase-locked amplifier, a computer with a data acquisition card and a self-focusing lens. According to the device, the electrically modulated intermediate infrared LED is used as a light source, and a wavelength modulation technology and a harmonic detection technology are combined to detect the concentration of methane; the signal generator is used for generating a low-frequency serrated driving signal and a high-frequency sinusoidal modulation signal to modulate the frequency and intensity of light emitted by the LED light source to stabilize the central wavelength of the light emitted by the LED to be 3.43 microns, the light emitted by the LED is absorbed by the methane when passing through the gas chamber, and the phase-locked amplifier is used for extracting a secondary harmonic signal to calculate the concentration of the methane to be detected; the device is free of refrigeration, low in cost and high in measurement sensitivity, a measurement result is accurate, and the application range of a tunable semiconductor light source spectrum absorption technology is widened.
Description
Technical field
The present invention relates to the methane concentration pick-up unit of spectral absorption technology, be specifically related to a kind of methane concentration pick-up unit based on middle tunable IR semiconductor light sources absorption spectroscopy techniques.
Background technology
Methane is common flammable explosive gas.Gas is the important root of colliery disaster, and the principal ingredient of gas is methane, accounts for 83～89%.Methane is also considered to one of topmost gas of greenhouse effect, it is reported that methane adsorption infrared capable is 15～30 times of carbon dioxide, occupies 15% of whole greenhouse contribution amount.The generation source, source of leaks and the concentration that detect in time, exactly methane gas, have important effect for industrial and mineral safe operation, personal safety and environmental protection.
Spectral absorption method is the method that the variation by detecting gas transmitted light intensity or reflective light intensity detects gas concentration.Every kind of gas molecule has the absorption spectra feature of oneself, and the overlapping part of the emission spectrum of light source and gas absorption spectrum is just received, and the light intensity after absorption will change.In the time that the emission wavelength of light source and the absorbing wavelength of gas match, will there is resonance absorption, its absorption intensity is relevant with the concentration of this gas, absorbs by measurement the concentration that light intensity just can measurement gas.Wavelength-modulation technique is modulated laser by low-frequency current, make it with low frequency serrated signal scanning absorption line, and the high frequency sinusoidal signal of reinjecting is modulated laser frequency and intensity.Wavelength-modulation technique and spectral absorption technology are combined to improve measuring accuracy and sensitivity.Methane molecule has 4 proper vibration, corresponding wavelength is respectively: 3.43 μ m, 6.53 μ m, 3.31 μ m, 7.66 μ m, are all positioned at middle-infrared band, and the light absorption methane gas of this wave band detects 3.31 μ m place absorbing wavelength for multiselect at present, but because the LASER Light Source of this wave band needs cryogenic refrigeration, and the expensive popularization that has limited it.At present both at home and abroad, large more options methane gas is absorption line in general frequency and the combination of near-infrared band frequently, and wavelength is respectively 1.65 μ m and 1.33 μ m, utilizes TDLAS commercial measurement methane concentration.But methane is in absorption absorption in middle-infrared band much smaller than it of near-infrared band.
Summary of the invention
The object of the present invention is to provide a kind of based on middle tunable IR semiconductor light sources absorption spectroscopy techniques methane concentration pick-up unit, be on middle tunable IR Diode Laser Absorption Spectroscopy basis, in using, infrared LED replaces middle infrared laser to detect the pick-up unit of methane concentration.
The technical scheme that technical solution problem of the present invention adopts is:
The present invention includes signal generator, LED drive circuit, LED, air chamber, photodetector, digital lock-in amplifier, computer and GRIN Lens with data collecting card; The light that LED sends enters air chamber by tail optical fiber, reenters and is mapped to photodetector, and the signal wire of photodetector is connected with digital lock-in amplifier, and the signal wire of digital lock-in amplifier is connected with the computer that data collecting card is housed; The signal wire of signal generator is connected with digital lock-in amplifier with LED drive circuit respectively; The GRIN Lens of air chamber one end is connected with LED tail optical fiber, and other end GRIN Lens connects optical fiber and is connected with photodetector.
Described air chamber is the cylinder airtight cavity that length is 9mm for 82cm diameter, air chamber both sides have the small sircle hole of same size, air chamber inside is that 2mm place is covered with 80cm guide rail apart from its base height, the GRIN Lens can move freely is equipped with at guide rail two ends, and the 3cm place, both sides that finds range on air chamber has diameter and is 8mm air intake opening and gas outlet.
Described semiconductor light sources LED is mid-infrared light source, and its spectral energy is concentrated, and good stability is cheap, is convenient to electrical modulation.
The invention has the beneficial effects as follows:
Tunable semiconductor light source light spectrum absorption techniques and harmonic detecting technique are combined and improved measuring accuracy and sensitivity.Utilization can electrical modulation middle infrared LED make light source and replace middle infrared laser, without refrigeration, and low price, be easy to promote.
Brief description of the drawings
Fig. 1 is structured flowchart of the present invention.
Fig. 2 is the structural representation of air chamber.
In figure: 1, signal generator, 2, LED drive circuit, 3, LED, 4, air chamber, 5, photodetector, 6, lock-in amplifier, 7, computer, 8, GRIN Lens, 9, GRIN Lens, 10, guide rail, 11, air intake opening, 12, gas outlet, 13, small sircle hole, 14, small sircle hole.
Embodiment
Below in conjunction with the drawings and specific embodiments, the present invention will be further described.
When a branch of light intensity is I
0input directional light when being mixed with the air chamber of methane and air, if light source blanketing gas Absorption Line, light is decayed during by gas.According to lambert's one Beer law, output intensity I
twith input light intensity I
0with pass between gas concentration is:
In formula, P is gas total pressure, and L is beam absorption light path, and X is concentration of methane gas to be measured, the line strength that S (T) is spectral line,
for the linear function of molecule absorption, α (υ) is spectral absorption.When light source Injection Current is carried out to high frequency Sine Modulated that angular frequency is, the instantaneous frequency of light beam is
a is modulation amplitude, definition m=a/ Δ γ, and 1/2nd half-breadths that Δ γ is absorption line are high.Lambert's one Beer law is carried out to Taylor series approximation, and can to obtain each harmonic amplitude expression formula as follows:
Each harmonic amplitude is all directly proportional with gas concentration, because second harmonic peak signal amplitude is large, signal to noise ratio (S/N ratio) is high, therefore be often used, just can obtain the concentration of gas to be measured by detecting second harmonic peak signal.
As shown in Figure 1, the present invention includes signal generator (1), LED drive circuit (2), LED (3), air chamber (4), photodetector (5), digital lock-in amplifier (6), computer (7) and GRIN Lens (8) with data collecting card.The light that LED (3) sends enters air chamber (4) by tail optical fiber, reenter and be mapped to photodetector (5), the signal wire of photodetector (5) is connected with digital lock-in amplifier (6), and the signal wire of digital lock-in amplifier (6) is connected with the computer (7) that data collecting card is housed; The signal wire of signal generator (1) is connected with digital lock-in amplifier (6) with LED drive circuit (2) respectively.The GRIN Lens (8) of air chamber (4) one end is connected with LED tail optical fiber, and other end GRIN Lens (9) connects optical fiber and is connected with photodetector (5).
This device signal generator model is AFG3252, and LED model is LMS34LED, and photodetector is selected InGaAs photodiode, and lock-in amplifier model is SR830, and data collecting card is America NI PCI-6034E.
Air chamber is as shown in Figure 2 the cylinder airtight cavity that length is 9mm for 82cm diameter, air chamber both sides have the small sircle hole of same size, air chamber inside is that 2mm place is covered with 80cm guide rail apart from its base height, the GRIN Lens can move freely is equipped with at guide rail two ends, and the 3cm place, both sides that finds range on air chamber has diameter and is 8mm air intake opening and gas outlet.
Detecting step of the present invention is:
1) taking middle infrared LED 3 that can electrical modulation as light source, LED drive circuit for adjusting 2 makes the light beam stable output wavelength of LED3 at 3.43 μ m places;
2) one of them passage of signal generator 1 produces the superposed signal of the high frequency sine of 50Hz low frequency sawtooth and 5KHz, be input to LED drive circuit 2, with infrared LED 3 output frequencies in modulation, by regulating sinusoidal signal amplitude, make the index of modulation be stabilized in 2.1-2.3; Another passage produces high frequency sinusoidal signal input lock-in amplifier 6 conducts of 10KHz with reference to signal;
3) air chamber is evacuated and again methane gas to be measured is poured to air chamber, pressure is controlled at 0.1atm, and temperature is 296K, and light path L is 76cm, extracts the second harmonic signal of lock-in amplifier by data collecting card and labview software
4) extract the strong S of corresponding line (T) from HITRAN database, use Fu Yite linear function
obtain methane concentration to be measured according to formula (3).
The present invention is the methane concentration pick-up unit of building on middle tunable IR semiconductor light sources absorption spectroscopy techniques.Make light source with middle infrared LED that can electrical modulation, adopt wavelength-modulation technique and the harmonic detecting technique detection methane concentration that combines.The present invention is without refrigeration, low price, and measurement result is accurate, measures highly sensitively, has widened the range of application of tunable semiconductor light source absorption spectroscopy techniques.
Claims (3)
1. the methane concentration pick-up unit based on middle tunable IR semiconductor light sources absorption spectroscopy techniques, is characterized in that: comprise signal generator (1), LED drive circuit (2), LED (3), air chamber (4), photodetector (5), digital lock-in amplifier (6), computer (7) and GRIN Lens (8) with data collecting card; The light that LED (3) sends enters air chamber (4) by tail optical fiber, reenter and be mapped to photodetector (5), the signal wire of photodetector (5) is connected with digital lock-in amplifier (6), and the signal wire of digital lock-in amplifier (6) is connected with the computer (7) that data collecting card is housed; The signal wire of signal generator (1) is connected with digital lock-in amplifier (6) with LED drive circuit (2) respectively; The GRIN Lens (8) of air chamber (4) one end is connected with LED tail optical fiber, and other end GRIN Lens (9) connects optical fiber and is connected with photodetector (5).
2. a kind of methane concentration pick-up unit based on middle tunable IR semiconductor light sources absorption spectroscopy techniques according to claim 1, it is characterized in that: the cylinder airtight cavity that described air chamber (4) is 9mm for length for 82cm diameter, air chamber both sides have the small sircle hole (13 of same size, 14), air chamber inside is that 2mm place is covered with 80cm guide rail (10) apart from its base height, the GRIN Lens (8 can move freely is equipped with at guide rail (10) two ends, 9), the 3cm place, both sides that finds range on air chamber has diameter and is 8mm air intake opening (11) and gas outlet (12).
3. a kind of methane concentration pick-up unit based on middle tunable IR semiconductor light sources absorption spectroscopy techniques according to claim 1, it is characterized in that: described semiconductor light sources LED is mid-infrared light source, its spectral energy is concentrated, good stability, cheap, be convenient to electrical modulation.
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| CN201420128012.8U CN203745372U (en) | 2014-03-19 | 2014-03-19 | Intermediate infrared tunable semiconductor light source spectrum absorption technology-based methane concentration detection device |
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Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105388113A (en) * | 2015-11-20 | 2016-03-09 | 上海斐讯数据通信技术有限公司 | Gas detection equipment |
| CN107941737A (en) * | 2017-11-21 | 2018-04-20 | 北京东宇宏达科技有限公司 | Methane gas quality inspection device and its detection method |
| CN108507966A (en) * | 2018-07-02 | 2018-09-07 | 青岛海纳光电环保有限公司 | A kind of infrared spectrum gas sensor and data processing method |
| CN109490249A (en) * | 2018-10-22 | 2019-03-19 | 安徽辰控智能科技有限公司 | Combustible gas monitoring equipment, method and system |
| CN110006835A (en) * | 2018-01-05 | 2019-07-12 | 英飞凌科技股份有限公司 | System and method for estimating gas concentration |
| CN111398203A (en) * | 2020-03-24 | 2020-07-10 | 中煤科工集团重庆研究院有限公司 | Low-power consumption methane detection device and method |
| CN111521581A (en) * | 2020-04-24 | 2020-08-11 | 北京航天控制仪器研究所 | Method and device for judging components of carbon monoxide and methane and detecting concentration of components of carbon monoxide and methane and application of method and device |
| CN112304900A (en) * | 2020-10-23 | 2021-02-02 | 西安智光物联科技有限公司 | Shoulder-back type absorption spectrum methane detector |
| CN114324209A (en) * | 2021-12-29 | 2022-04-12 | 杭州谱育科技发展有限公司 | Fluid detection device and method based on absorption spectrum technology |
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2014
- 2014-03-19 CN CN201420128012.8U patent/CN203745372U/en not_active Expired - Fee Related
Cited By (12)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN105388113A (en) * | 2015-11-20 | 2016-03-09 | 上海斐讯数据通信技术有限公司 | Gas detection equipment |
| CN105388113B (en) * | 2015-11-20 | 2019-05-31 | 上海斐讯数据通信技术有限公司 | Gas detection equipment |
| CN107941737A (en) * | 2017-11-21 | 2018-04-20 | 北京东宇宏达科技有限公司 | Methane gas quality inspection device and its detection method |
| CN110006835A (en) * | 2018-01-05 | 2019-07-12 | 英飞凌科技股份有限公司 | System and method for estimating gas concentration |
| CN110006835B (en) * | 2018-01-05 | 2023-10-20 | 英飞凌科技股份有限公司 | System and method for estimating gas concentration |
| CN108507966A (en) * | 2018-07-02 | 2018-09-07 | 青岛海纳光电环保有限公司 | A kind of infrared spectrum gas sensor and data processing method |
| CN109490249A (en) * | 2018-10-22 | 2019-03-19 | 安徽辰控智能科技有限公司 | Combustible gas monitoring equipment, method and system |
| CN111398203A (en) * | 2020-03-24 | 2020-07-10 | 中煤科工集团重庆研究院有限公司 | Low-power consumption methane detection device and method |
| CN111521581A (en) * | 2020-04-24 | 2020-08-11 | 北京航天控制仪器研究所 | Method and device for judging components of carbon monoxide and methane and detecting concentration of components of carbon monoxide and methane and application of method and device |
| CN111521581B (en) * | 2020-04-24 | 2023-02-03 | 北京航天控制仪器研究所 | Method and device for judging components of carbon monoxide and methane and detecting concentration of components of carbon monoxide and methane and application of method and device |
| CN112304900A (en) * | 2020-10-23 | 2021-02-02 | 西安智光物联科技有限公司 | Shoulder-back type absorption spectrum methane detector |
| CN114324209A (en) * | 2021-12-29 | 2022-04-12 | 杭州谱育科技发展有限公司 | Fluid detection device and method based on absorption spectrum technology |
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