CN101153860A - Gas detection method and gas detection device - Google Patents
Gas detection method and gas detection device Download PDFInfo
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- CN101153860A CN101153860A CNA200710153107XA CN200710153107A CN101153860A CN 101153860 A CN101153860 A CN 101153860A CN A200710153107X A CNA200710153107X A CN A200710153107XA CN 200710153107 A CN200710153107 A CN 200710153107A CN 101153860 A CN101153860 A CN 101153860A
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- 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
- G01N21/1702—Systems in which incident light is modified in accordance with the properties of the material investigated with opto-acoustic detection, e.g. for gases or analysing solids
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Abstract
A gas detection method by using a photo acoustic near infrared gas sensor with a laser source and such a gas sensor comprising at least one amplitude modulated laser source, a gas chamber for receiving the gas to be detected, a microphone attached to the gas chamber, a photo detector for receiving the laser light after having passed through the gas filled gas chamber, processing means comprising a modulation frequency generator for providing a modulation signal for the at least one laser source and a control means for determining the gas concentration. The laser source changes it output wavelength across each cycle of the amplitude modulation between a minimum wavelength and a maximum wavelength. The result of this measurement scheme is that during each modulation cycle, the laser source scans its complete available wavelength range so that the absorption features of the target gas are levelled out to a mean value. This mean value is relatively insensitive to small variations of the laser's center wavelength; which are introduced by temperature variations.
Description
Technical field
The present invention relates to use the gas detection method of optoacoustic near infrared gas sensor with lasing light emitter, this gas sensor comprises at least one amplitude modulation lasing light emitter, receive the air chamber of the gas that will detect, be connected to air chamber microphone, be used to receive the laser of the air chamber by being filled with gas photodetector, be included as at least one lasing light emitter provide modulation signal frequency-modulated generator treating apparatus and be used for determining the control device of gas concentration.
Background technology
The principle that optoacoustic gas detects is known (Fig. 1): use is positioned at the preceding Infrared filter 2 of broadband emitter 1 ' (normally bulb) and selects the light of wavelength corresponding to the absorption line of object gas.Light with selected wavelength is propagated by gas zones 4 (usually in pipe 5), and gas zones 4 may contain object gas.If there is object gas, the light that it will absorption portion is the function of object gas concentration.
The temperature of the increase gas zones 4 that the light meeting that object gas absorbed is slight, if should almost seal in the zone, the increase of temperature can cause the increase of gaseous tension.If light source 1 ' is modulated, the absorption of object gas can be modulated the pressure in the absorption region 4, and this modulation meeting is picked up by microphone 3.The sound that microphone 3 picks up is directly proportional with the concentration of object gas.Light intensity is measured by photodiode 6.
So-called resonance optoacoustic is understood the susceptibility and the diffusivity of the gas in the strong raising absorption region.At this moment, select the length of modulating frequency and absorption region, make to absorb the acoustic resonance of the sound that produced corresponding to zone 4 by object gas.If selection sound eigenmode accurately, absorption region (promptly manage 5 end) can be open so.
The significant disadvantages of this measuring method is the limited modulating frequency of bulb, and it approximately is 100Hz.Under such frequency, device can pick up the noise of environment.Its performance of obstruction that this meeting is strong.Using chopper wheel to modulate can have higher frequency, but the vibration of dish can to produce just in time be the noise of modulating frequency.
Second shortcoming of low frequency is that for resonance absorption, the length of absorption region need be above 1 meter.
Use near infrared (NIR) acoustooptics (Fig. 2), thermolamp bubble and light filter are replaced by near infrared laser 1 (normally laser diode), and it can detect object gas at the harmonic wave place of basic absorption line.The advantage that the NIR laser diode is very big be can the frequency of utilization scope up to the switch modulation of MHz.
Opposite with above-described wherein light filter permission by the infrared light acoustics of the wavelength of about 100nm scope, use the laser diode of NIR acoustooptics to have the wavelength width of typical 0.1nm.This means the calibration that will keep gas sensor, the absorption spectrum that optical maser wavelength must lock onto exactly for object gas is known wavelength.
For the object gas of the narrow line with separation, and for the line that does not have to separate but as at the object gas for the spread spectrum in the higher hydrocarbon situation (extended spectrum), this locking is very important.
Summary of the invention
Therefore, an object of the present invention is to provide the method and the sensor of the object gas that can determine to have spread spectrum.
This purpose is realized by method in the claim and sensor.Further useful embodiment proposes protection in each dependent claims.According to the present invention, lasing light emitter is carried out amplitude modulation, make lasing light emitter circulate for each of the amplitude modulation between minimum wavelength and maximum wavelength, all can change its output wavelength.Optoacoustic near infrared gas sensor comprises frequency-modulated generator, and it provides modulation signal for lasing light emitter, and it all can change the output wavelength of lasing light emitter for each circulation of the amplitude modulation between minimum wavelength and maximum wavelength.This can realize by using several suitable modulation signals and corresponding device thereof.In a word, the fact of foundation of the present invention is that the wavelength of lasing light emitter is controlled by the temperature of lasing light emitter drive current and laser chip.
By the temperature of lasing light emitter lasing light emitter is adjusted to wavelength corresponding to interested absorption feature.According to an embodiment, the current-modulation of laser instrument is not to use switch modulation with dutycycle of 50% to carry out, but according to
Have preferred 50% dutycycle switch modulation and
The triangle sawtooth modulation of same frequency, these two switch modulation that multiplies each other is carried out.Therefore, during the cycle, drive current makes that lasing light emitter is oblique at the wavelength from threshold current to the maximum wavelength corresponding to maximum drive current " opening ".The present invention adopts the modulation of 4kHz, and this can be avoided picking up the noise on next door, and the length of absorption region can be reduced to 4cm.According to further embodiment, can use the Sine Modulated of lasing light emitter drive current.This scheme is compared the result with the foregoing description accurate a little, yet depend on the application of gas sensor, and the result is enough.Among another embodiment, what substitute is, with dutycycle the lasing light emitter drive current is modulated, and preferred 50% dutycycle, and, under the frequency identical, the temperature of lasing light emitter is modulated with the lasing light emitter drive current.This method requires temperature and each device to change fast.
The result of measurement scheme is that during each brew cycle, lasing light emitter scans available whole wavelength coverage, so the absorption feature of object gas can be evened up mean value.The little variation relative insensitivity of the laser center wavelength that this mean value causes temperature variation.
More feature and advantage of the present invention can be learnt from following description of preferred embodiments and in conjunction with claim and accompanying drawing.Single feature can be separately or is combined with embodiments of the invention and to understand.
Description of drawings
Fig. 1 is the schematic diagram of infrared gas sensor;
Fig. 2 is the schematic diagram of near infrared gas sensor;
Fig. 3 is the laser rays that scans during each brew cycle for the gas absorption feature;
Fig. 4 is the comparison of the absorption feature of optical maser wavelength width and gas;
Fig. 5 is the block diagram of the gas sensor of first embodiment;
Fig. 6 is the block diagram of the gas sensor of another embodiment;
Fig. 7 is the block diagram of the gas sensor of another embodiment.
Embodiment
Fig. 1 and Fig. 2 are the known principles of different photoacoustic sensors discussed above.
Fig. 3 and Fig. 4 are the graphs of a relation of gas absorption intensity GAS and laser intensity L1 and wavelength WL.These two figure have shown the variation of gas absorption.As shown in Figure 3, the laser intensity peak that locks onto definite wavelength only detects the gas absorption at this wavelength place that determines.Because the difference of the absorption intensity of broadband wave spectrum can make absorption intensity differ about 30-50% towards the mobile 0.1nm in one side of optical maser wavelength.Therefore, the result can change in very wide scope.By the length scanning laser peak that provides along Fig. 4, the absorption feature of object gas can be evened up mean value.
Although following the present invention describes as lasing light emitter with laser diode, the invention is not restricted to this device, other the suitable lasing light emitter with similar characteristics also can be used for obtaining similar result.And, as well known in the prior art, can use have suitable pick-up unit more than one lasing light emitter 1.
Fig. 5 has provided the principle of the gas sensor of the treating apparatus 15 with the processing signals of being used for.Lasing light emitter 1, diode laser preferably is connected with temperature unit 7 as well heater or refrigeratory, and the light that it sends is by chamber 5, and chamber 5 provides the absorption region 4 that is used for the object gas that will detect.Microphone 3 be arranged in absorption region 4 near.Photodiode 6 receives the light of self-excitation light source 1 as photodetector.By temperature unit 7, lasing light emitter 1 is adjusted to wavelength corresponding to interested absorption feature by the temperature of lasing light emitter.Frequency-modulated generator 9 comprises and is used to provide square modulation signal S
SM Square modulating device 10 and be used to provide sawtooth modulation signal S
STMSawtooth modulating device 11.Use signal S then
SMAnd S
STMThe modulation signal S that multiplies each other and obtain
MCome the drive current of modulated laser source 1.Square modulating device 10 provides the switch modulation with dutycycle of 50% for lasing light emitter 1, because sawtooth modulation 11, it is oblique to the maximum wavelength corresponding to maximum drive current that drive current makes its wavelength from threshold current.
Microphone 3 provides signal S
A, the absorption of the gas in it and the absorption region 4 is proportional, and photodiode 6 provides signal S
I, the light intensity of it and lasing light emitter 1 is proportional.The signal S that microphone 3 provides
ABe fed to lock-in amplifier 12, be used for this signal and the reference signal S that receives from frequency-modulated generator 9
RefMultiply each other, at last the signal that obtains is carried out integration.The signal that comes from photodiode 6 is fed to amplifier 13.Come from lock-in amplifier 12 and be fed to control module 14 with the signal that comes from amplifier 13.In control module 14, the absorption signal S that handles by lock-in amplifier 12
ABy with amplify from photodiode 6 and by amplifier 14 after strength signal S
IBe divided by, carry out standardization.The signal S that obtains
GCBe for the needed signal of gas concentration in the chamber 5.Control module 14 also provides corresponding signal S
TBe in temperature with the corresponding wavelength of interested absorption feature place to keep lasing light emitter 1 for temperature controller 8.
Fig. 6 is another embodiment, and wherein frequency-modulated generator 9 includes only sine wave modulation 16, and it provides lasing light emitter drive current modulation signal S
MSine wave modulation is the sine wave modulation of rectification.It by for example laser diode etc. by overturning sinusoidal wave negative part or remove negative part and obtain.
Fig. 7 has described another embodiment.Frequency-modulated generator 9 comprises square modulating device 10 and temperature control equipment 17.Square modulating device 10 is provided for the first modulation signal S of modulated laser source drive current
M1, temperature control equipment 17 is provided for coming by temperature unit 7 the second modulation signal S of the temperature of modulated laser source 1
M2
Claims (9)
1. gas detection method that uses optoacoustic near infrared gas sensor, this optoacoustic near infrared gas sensor uses near-infrared laser source (1), it is characterized in that: lasing light emitter (1) is carried out amplitude modulation, and lasing light emitter (1) all can change its output wavelength for each circulation of the amplitude modulation between minimum wavelength and maximum wavelength in the meantime.
2. gas detection method as claimed in claim 1 is characterized in that: the lasing light emitter drive current is modulated, and this comprises that the switch modulation of preferred 50% dutycycle and the sawtooth modulation of same frequency multiply each other.
3. gas detection method as claimed in claim 1 is characterized in that: the lasing light emitter drive current is carried out Sine Modulated.
4. gas detection method as claimed in claim 1, it is characterized in that: the lasing light emitter drive current is had dutycycle, the switch modulation of preferred 50% dutycycle and with lasing light emitter drive current modulation phase with frequency under the temperature of lasing light emitter is modulated.
5. the gas detection method in any one claim as described above is characterized in that: by the temperature of lasing light emitter lasing light emitter is adjusted to wavelength corresponding to interested absorption feature.
6. optoacoustic near infrared gas sensor, it has:
At least one amplitude modulation lasing light emitter (1);
Air chamber (5) is used to receive the gas that will detect;
Be connected to the microphone (3) of air chamber;
Photodetector (6) is used for the laser intensity of detection laser source (1);
Treating apparatus (15), it comprises and is used at least one lasing light emitter (1) that modulation signal (S is provided
M) frequency-modulated generator (9) and be used for determining the control device (8,12,13,14) of gas concentration;
It is characterized in that:
Described frequency-modulated generator (9) provides modulation signal (S for lasing light emitter (1)
M), it all can change the output wavelength of lasing light emitter (1) for each circulation of the amplitude modulation between minimum wavelength and maximum wavelength.
7. optoacoustic gas sensor as claimed in claim 6 is characterized in that:
Described frequency-modulated generator (9) comprises and is used to lasing light emitter that modulation signal (S is provided
M) square modulating device (10) and sawtooth modulating device (11), wherein modulation signal comprises the switch modulation signal (S of preferred 50% dutycycle
SM) with the sawtooth modulation signal (S of same frequency
STM) multiplied result.
8. optoacoustic gas sensor as claimed in claim 6 is characterized in that: described frequency-modulated generator (9) is included as lasing light emitter sinusoidal modulation signal (S is provided
M) device (16).
9. optoacoustic gas sensor as claimed in claim 6 is characterized in that: described frequency-modulated generator (9) is included as lasing light emitter and provides and have dutycycle, the switch modulation signal (S of preferred 50% dutycycle
M1) device (11), and with lasing light emitter modulation signal (S
M1) provide temperature modulation signal (S for the temperature of lasing light emitter (1) under the identical frequency
M2) device (17).
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| EP06020244.7 | 2006-09-27 | ||
| EP06020244 | 2006-09-27 | ||
| EP06021212.3 | 2006-10-10 |
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| CN101153860A true CN101153860A (en) | 2008-04-02 |
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| Application Number | Title | Priority Date | Filing Date |
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| CNA200710153107XA Pending CN101153860A (en) | 2006-09-27 | 2007-09-26 | Gas detection method and gas detection device |
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Cited By (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102169085A (en) * | 2010-12-10 | 2011-08-31 | 中国科学院安徽光学精密机械研究所 | Temperature-controlled photo-acoustic absorption spectrum measuring apparatus |
| CN102575981A (en) * | 2009-05-11 | 2012-07-11 | 加斯珀洛克斯公司 | Apparatus and method for non-intrusive assessment of gas in packages |
| CN103180698A (en) * | 2010-10-28 | 2013-06-26 | 英派尔科技开发有限公司 | Photoacoustic sensor |
| CN103592225A (en) * | 2013-10-31 | 2014-02-19 | 中国科学院南京土壤研究所 | Soil infrared photoacoustic spectrum rapid determinator and soil physical and chemical property determination method |
| CN104568790A (en) * | 2014-12-29 | 2015-04-29 | 南京大学 | Method for eliminating error caused by wavelength drift of laser during gas sensing |
| CN105466854A (en) * | 2015-12-30 | 2016-04-06 | 武汉精昱光传感系统研究院有限公司 | Active air-chamber structure and photoacoustic spectrometry gas sensing system |
| EP2918994A4 (en) * | 2012-11-09 | 2016-08-24 | Shandong Micro Photographic Electronic Co Ltd | Vcsel-based low-power-consumption gas detection method and device |
| CN109490210A (en) * | 2018-11-16 | 2019-03-19 | 安徽理工大学 | A kind of audio frequency adjustable acoustic pressure enhanced photo acoustic pond |
| CN110333190A (en) * | 2019-07-05 | 2019-10-15 | 大连理工大学 | A kind of diffusion type optoacoustic microcavity gas sensor |
| CN112098355A (en) * | 2020-09-07 | 2020-12-18 | 中国科学院合肥物质科学研究院 | Photoacoustic spectrum trace gas detection device suitable for wide-band divergent light beam |
| CN112969916A (en) * | 2018-08-03 | 2021-06-15 | 米尔森公司 | Photoacoustic gas sensor using modulated illumination wavelength method |
| CN117405627A (en) * | 2023-12-14 | 2024-01-16 | 北京中科智易科技股份有限公司 | Gas quality laser analysis system and analysis method |
-
2007
- 2007-09-26 CN CNA200710153107XA patent/CN101153860A/en active Pending
Cited By (18)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102575981A (en) * | 2009-05-11 | 2012-07-11 | 加斯珀洛克斯公司 | Apparatus and method for non-intrusive assessment of gas in packages |
| CN103180698B (en) * | 2010-10-28 | 2015-07-29 | 英派尔科技开发有限公司 | Photoacoustic sensors |
| CN103180698A (en) * | 2010-10-28 | 2013-06-26 | 英派尔科技开发有限公司 | Photoacoustic sensor |
| CN102169085B (en) * | 2010-12-10 | 2013-07-03 | 中国科学院安徽光学精密机械研究所 | Temperature-controlled photo-acoustic absorption spectrum measuring apparatus |
| CN102169085A (en) * | 2010-12-10 | 2011-08-31 | 中国科学院安徽光学精密机械研究所 | Temperature-controlled photo-acoustic absorption spectrum measuring apparatus |
| EP2918994A4 (en) * | 2012-11-09 | 2016-08-24 | Shandong Micro Photographic Electronic Co Ltd | Vcsel-based low-power-consumption gas detection method and device |
| CN103592225B (en) * | 2013-10-31 | 2016-08-17 | 中国科学院南京土壤研究所 | Soil infrared photoacoustic spectra Quick testing instrument and soil physico-chemical property assay method thereof |
| CN103592225A (en) * | 2013-10-31 | 2014-02-19 | 中国科学院南京土壤研究所 | Soil infrared photoacoustic spectrum rapid determinator and soil physical and chemical property determination method |
| CN104568790A (en) * | 2014-12-29 | 2015-04-29 | 南京大学 | Method for eliminating error caused by wavelength drift of laser during gas sensing |
| CN104568790B (en) * | 2014-12-29 | 2017-03-08 | 南京大学 | A kind of method that during elimination gas sensing, laser wavelength drift leads to error |
| CN105466854A (en) * | 2015-12-30 | 2016-04-06 | 武汉精昱光传感系统研究院有限公司 | Active air-chamber structure and photoacoustic spectrometry gas sensing system |
| CN112969916A (en) * | 2018-08-03 | 2021-06-15 | 米尔森公司 | Photoacoustic gas sensor using modulated illumination wavelength method |
| CN112969916B (en) * | 2018-08-03 | 2024-06-07 | 米尔森公司 | Photoacoustic gas sensor using method of modulating illumination wavelength |
| CN109490210A (en) * | 2018-11-16 | 2019-03-19 | 安徽理工大学 | A kind of audio frequency adjustable acoustic pressure enhanced photo acoustic pond |
| CN110333190A (en) * | 2019-07-05 | 2019-10-15 | 大连理工大学 | A kind of diffusion type optoacoustic microcavity gas sensor |
| CN112098355A (en) * | 2020-09-07 | 2020-12-18 | 中国科学院合肥物质科学研究院 | Photoacoustic spectrum trace gas detection device suitable for wide-band divergent light beam |
| CN117405627A (en) * | 2023-12-14 | 2024-01-16 | 北京中科智易科技股份有限公司 | Gas quality laser analysis system and analysis method |
| CN117405627B (en) * | 2023-12-14 | 2024-02-20 | 北京中科智易科技股份有限公司 | Gas quality laser analysis system and analysis method |
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