CN101718680B - Photoacoustic gas detecting method and photoacoustic gas detecting device capable of reducing environmental noise - Google Patents
Photoacoustic gas detecting method and photoacoustic gas detecting device capable of reducing environmental noise Download PDFInfo
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- CN101718680B CN101718680B CN 200910310515 CN200910310515A CN101718680B CN 101718680 B CN101718680 B CN 101718680B CN 200910310515 CN200910310515 CN 200910310515 CN 200910310515 A CN200910310515 A CN 200910310515A CN 101718680 B CN101718680 B CN 101718680B
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- photoacoustic cell
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Abstract
The invention discloses a photoacoustic gas detecting method and a photoacoustic gas detecting device capable of reducing the environmental noise. An external microphone is arranged outside a photoacoustic cell, and the signal detected by the external microphone is used for correcting the environmental noise in the signal detected by an internal microphone arranged inside the photoacoustic cell, thus the environment adapting ability of the photoacoustic gas detecting device can be strengthened, and the precision and the reliability the photoacoustic gas detecting device can be improved. The noise signal detected in the internal microphone is calibrated by the external microphone, thus the noise signal which has the same frequency and the same phase as the photoacoustic signal in the internal microphone can be eliminated, the influence of the outside noise to the precision of the photoacoustic gas detecting device can be effectively reduced, the environment adapting ability of the photoacoustic gas detecting device can be strengthened, and the photoacoustic gas detecting device can be miniaturized.
Description
Technical field
Invention relates to the optoacoustic gas detection range, particularly relates to a kind of optoacoustic gas pick-up unit and method that can reduce the neighbourhood noise influence in optoacoustic gas detects.
Background technology
It is a kind of method based on optoacoustic spectroscopy effect detection gas concentration that optoacoustic gas detects.Optoacoustic effect is the effect that produces acoustical signal behind the material absorbing modulation luminous energy, is a kind ofly to be transformed into the effect that heat energy, heat energy change into acoustical signal by luminous energy.The optoacoustic gas pick-up unit mainly is made of light source (as laser instrument), photoacoustic cell, sonic transducer (as microphone) and input processing module four parts.The light that light source emission intensity is modulated, inject photoacoustic cell, gas in the photoacoustic cell is because of intermittently absorbing luminous energy forms sound wave, sonic transducer detects acoustical signal and passes to the input processing module, according to the sound intensity of setting up in advance and the relation between the calibrating gas concentration, can detect the concentration of unknown gas.
Adopt microphone to measure voice signal during optoacoustic gas detects, this voice signal comprises photoacoustic signal and external world's (environment) noise signal, and noise signal will limit the accuracy of detection and the lowest detection level of gas concentration.For improving system's detection sensitivity, must manage to reduce the noise voltage level.Random signal in the external environment has bigger uncertainty, and will make the detected signal of microphone that bigger skew takes place when noise signal is big.Now generally adopt the noise in the lock-in amplifier elimination photoacoustic signal, but lock-in amplifier can not filtering and the same noise of homophase frequently of photoacoustic signal.With sustained sound signal and the impact noise signal of photoacoustic signal with frequency, can cause gas concentration deviation or the sudden change that continues to occur, bring adverse influence to gas detection.
Switzerland Siemens Company state's patent of invention 01803079.3 therein proposes " optoacoustic measuring arrangement and application thereof ", its method is applicable to the alarm threshold value judgement, requirement possesses reference cell, and is not suitable for the accurate measurement of wide dynamic range (from extremely low concentration, as ppt or ppm to 100%).
The Chinese invention patent 200580045418.3 of Holland electronics incorporated company of Philip imperial family application proposes " inhibition of background sound signal in the photo acoustic detector ", the transparent conducting coating and the second bundle light on the wall of chamber have mainly been used, make its phase place at the ground unrest of chamber wall and window, mutually opposite with the ground unrest position of the first bundle light, thus reach the purpose of eliminating the inner ground unrest in optoacoustic chamber; But it can not eliminate neighbourhood noise.
Summary of the invention
The present invention has overcome shortcoming of the prior art, a kind of optoacoustic gas pick-up unit that can effectively reduce ambient noise interference in optoacoustic gas detects is provided, and a kind of method that can in optoacoustic gas detects, effectively reduce ambient noise interference, strengthen the adaptive capacity to environment that optoacoustic gas detects, improve precision and reliability that optoacoustic gas detects, help the miniaturization of gas detecting instrument.
Technical scheme of the present invention is as follows: a kind of optoacoustic gas pick-up unit that can reduce neighbourhood noise, comprise photoacoustic cell, and microphone in installing in the resonance section of photoacoustic cell is installed light source outside the resonance section, make the light of light source can pass the resonance section; End at photoacoustic cell is provided with the air inlet port, the other end setting port of giving vent to anger, microphone outside outside described photoacoustic cell, being equipped with, interior microphone all is connected with the back end signal treatment circuit by signal transmission line with outer microphone, and the back end signal treatment circuit is connected with processor by signal transmission line.
The air inlet surge chamber is set and the surge chamber of giving vent to anger respectively at the two ends of described resonance section, the described air inlet port and the port of giving vent to anger are separately positioned on the air inlet surge chamber and the side of the surge chamber of giving vent to anger.
The described air inlet surge chamber and the surge chamber inside of giving vent to anger are square.
A kind ofly utilize the described optoacoustic gas pick-up unit that can reduce neighbourhood noise to detect the method for optoacoustic gas, comprise the steps:
The first step is provided with a noise source outside photoacoustic cell, produce the noise signal of a series of intensity, interior microphone and outer microphone acquired signal, and the signal that collects sent into the back end signal treatment circuit, draw noise signal amplitude with the frequency homophase; By measuring microphonic noise signal N in a group
1With outer microphonic noise signal N
2, obtain noise and outside photoacoustic cell, import inner attenuation coefficient f (N into
2);
Second step drove the light source luminescent in the photoacoustic cell, and light wavelength is that tested gas absorption wavelength and frequency are the resonant frequency of resonance section, interior microphone and outer microphone acquired signal;
The 3rd step, the signal of interior microphone and outer microphone collection is sent into the back end signal treatment circuit, the signal that the section of drawing and resonate resonant frequency is consistent, in processor according to formula N
1=N
2F (N
2) calculate useful photoacoustic signal.
Described noise source is arranged on the photoacoustic cell outside.
Compared with prior art, advantage of the present invention is: by microphone outside being provided with outside photoacoustic cell, with the detected signal of outer microphone, neighbourhood noise in proofreading and correct in the photoacoustic cell in the detected signal of microphone, strengthen the adaptive capacity to environment that optoacoustic gas detects, improve precision and reliability that optoacoustic gas detects; Use outer microphone to demarcate the noise signal that measures in the interior microphone, in eliminating in the microphone with photoacoustic signal with the noise signal of homophase frequently, can effectively reduce the influence of outside noise to optoacoustic gas detector precision, increase the adaptive capacity to environment of optoacoustic gas detector, help the miniaturization of gas detecting instrument again.
Description of drawings
The present invention will illustrate by example and with reference to the mode of accompanying drawing, wherein:
Fig. 1 is a synoptic diagram of the present invention.
Embodiment
Disclosed all features in this instructions, or the step in disclosed all methods or the process except mutually exclusive feature and/or step, all can make up by any way.
Disclosed arbitrary feature in this instructions (comprising any accessory claim, summary and accompanying drawing) is unless special narration all can be replaced by other equivalences or the alternative features with similar purpose.That is, unless special narration, each feature is an example in a series of equivalences or the similar characteristics.
As shown in Figure 1, a kind of optoacoustic gas pick-up unit that can reduce neighbourhood noise, comprise photoacoustic cell, microphone 3 in install at middle part in the resonance section 5 of photoacoustic cell, outer microphone 4 is installed in outside the photoacoustic cell, outside resonance section 5, light source 2 is installed, end in resonance section 5 is provided with air inlet port 8, at the other end setting of resonance section 5 port 9 of giving vent to anger, interior microphone 3 all is connected with back end signal treatment circuit 10 by signal transmission line with outer microphone 4, and back end signal treatment circuit 10 is connected with processor 11 by signal transmission line.
In order to reduce the neighbourhood noise that enters photoacoustic cell from the air inlet port 8 and the port 9 of giving vent to anger, also the air inlet surge chamber 6 and the surge chamber 7 of giving vent to anger can be set at the two ends of resonance section respectively, the air inlet surge chamber 6 and surge chamber 7 inside of giving vent to anger are cube, and the air inlet port 8 and the port 9 of giving vent to anger are separately positioned on the air inlet surge chamber 6 and the surge chamber 7 of giving vent to anger.
A kind of optoacoustic gas detection method that can reduce neighbourhood noise comprises the steps:
1) installs photoacoustic cell according to synoptic diagram shown in Figure 1, the stationkeeping of interior microphone 3 and outer microphone 4; Then tested gas is entered into air inlet surge chamber 6 from air inlet port 8, after the gas process resonance section 5, enter into the surge chamber 7 of giving vent to anger then, gas is discharged from the port 9 of giving vent to anger; From the neighbourhood noise that the air inlet port 8 and the port 9 of giving vent to anger enter photoacoustic cell, after through the air inlet surge chamber 6 and the surge chamber 7 of giving vent to anger, noise signal will be subdued greatly.
2) noise source is set artificially outside photoacoustic cell, produces the noise signal of a series of intensity.The signal that collects for microphone in making 3 and outer microphone 4 is not subjected to the influence of noise source position, noise source should be arranged on outside the photoacoustic cell than distant location, and this distance should be greater than the photoacoustic cell size.The signal that collects in interior microphone 3 and the outer microphone 4 is sent into back end signal treatment circuit 10, carry out phase-locked amplification and draw together the noise signal of homophase frequently, the noise signal N of microphone 3 in can drawing according to this signal intensity
1With the noise signal N in the outer microphone 4
2A corresponding relation, with formulae express be:
N
1＝N
2f(N
2)(1)
F (N in the formula
2) be noise signal N
2A function, be that noise imports inner attenuation coefficient into outside photoacoustic cell, relevant with the sealing property of photoacoustic cell; By people's neighbourhood noise for a change, reach and change N
2Purpose; By measuring one group of N
1And N
2Corresponding relation, obtain f (N
2).
3) light source 2 that drives in the photoacoustic cell is luminous, light wavelength is that tested gas absorption wavelength and frequency are the resonant frequency of resonance section 5, the light that light source 2 sends is injected in the resonance section along the center of resonance section 5, by gas absorption to be measured, gas generation thermal expansion then, the frequency of gas vibration and the intensity modulated frequency of light source are the resonant frequency of resonance section, producing photoacoustic signal this moment is gathered by interior microphone 3, the signal that collects in the microphone 3 in this moment comprises photoacoustic signal and noise signal two parts, the noise signal in outer microphone 4 testing environments.
4) signal of interior microphone 3 and outer microphone 4 is sent into back end signal treatment circuit 10, utilize the consistent signal of the phase-locked amplifying circuit section of detecting and resonate 5 resonant frequencies, the homogenous frequency signal that in processor 11 interior microphone 3 and outer microphone 4 is passed through after the phase-locked amplification calculates useful photoacoustic signal according to formula (1).
The present invention is not limited to aforesaid embodiment.The present invention expands to any new feature or any new combination that discloses in this manual, and the arbitrary new method that discloses or step or any new combination of process.
Claims (1)
1. method of utilizing the optoacoustic gas pick-up unit that to reduce neighbourhood noise to detect optoacoustic gas, described optoacoustic gas pick-up unit comprises photoacoustic cell, microphone in installing in the resonance section of photoacoustic cell is installed light source outside the resonance section, make the light of light source can pass the resonance section; End at photoacoustic cell is provided with the air inlet port, the other end setting port of giving vent to anger, microphone outside outside described photoacoustic cell, being equipped with, interior microphone all is connected with the back end signal treatment circuit by signal transmission line with outer microphone, and the back end signal treatment circuit is connected with processor by signal transmission line; It is characterized in that: comprise the steps:
The first step is provided with a noise source outside photoacoustic cell, produce the noise signal of a series of intensity, interior microphone and outer microphone acquired signal, and the signal that collects sent into the back end signal treatment circuit, draw noise signal amplitude with the frequency homophase; By measuring microphonic noise signal in a group
With outer microphonic noise signal
, obtain noise and outside photoacoustic cell, import inner attenuation coefficient into
Second step drove the light source luminescent in the photoacoustic cell, and light wavelength is that tested gas absorption wavelength and frequency are the resonant frequency of resonance section, interior microphone and outer microphone acquired signal;
The 3rd step, the signal of interior microphone and outer microphone collection is sent into the back end signal treatment circuit, the signal that the section of drawing and resonate resonant frequency is consistent, in processor according to formula
Calculate useful photoacoustic signal.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 200910310515 CN101718680B (en) | 2009-11-26 | 2009-11-26 | Photoacoustic gas detecting method and photoacoustic gas detecting device capable of reducing environmental noise |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 200910310515 CN101718680B (en) | 2009-11-26 | 2009-11-26 | Photoacoustic gas detecting method and photoacoustic gas detecting device capable of reducing environmental noise |
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| Publication Number | Publication Date |
|---|---|
| CN101718680A CN101718680A (en) | 2010-06-02 |
| CN101718680B true CN101718680B (en) | 2011-04-06 |
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Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP3441730B1 (en) * | 2017-08-10 | 2020-10-21 | Ricoh Company, Ltd. | Light measuring apparatus |
| CN110441241B (en) * | 2019-07-31 | 2023-01-06 | 中国电力科学研究院有限公司 | Performance evaluation device and method for photoacoustic spectroscopy multi-component gas analysis instrument |
| CN111323377B (en) * | 2020-04-16 | 2023-03-21 | 中国科学院电工研究所 | Photoacoustic spectroscopy device with active noise reduction function |
| CN112857571A (en) * | 2021-02-10 | 2021-05-28 | 王世有 | Photoacoustic spectrum detection system and calibration method for automatically calibrating working wavelength of laser |
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