CN111366535A - Enhanced photoacoustic spectroscopy gas detection device and method based on digital phase locking technology - Google Patents
Enhanced photoacoustic spectroscopy gas detection device and method based on digital phase locking technology Download PDFInfo
- Publication number
- CN111366535A CN111366535A CN202010196165.6A CN202010196165A CN111366535A CN 111366535 A CN111366535 A CN 111366535A CN 202010196165 A CN202010196165 A CN 202010196165A CN 111366535 A CN111366535 A CN 111366535A
- Authority
- CN
- China
- Prior art keywords
- gas
- digital phase
- dsp
- sampling
- reference signal
- 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.)
- Pending
Links
Images
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
- G01N21/1702—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
-
- 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
-
- 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
-
- 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
- G01N2021/1704—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 in gases
Abstract
The invention discloses an enhanced photoacoustic spectrometry gas detection device based on a digital phase locking technology, which comprises an excitation light source, a gas chamber, a pre-amplification circuit, a DSP and a function generator, wherein two miniature sound resonant cavities and quartz tuning forks are arranged in the gas chamber, the function generator realizes the wavelength modulation of laser by superposing sawtooth waves, the gas chamber is connected with an operational amplification circuit, and the operational amplification circuit is connected with the DSP. The invention adopts the technology of combining enhanced quartz tuning fork photoacoustic spectroscopy with digital phase locking for gas detection, realizes the generation of reference signals and the calculation of related detection by using the interior of a DSP, realizes the function of digital phase locking by the DSP, and effectively and quickly extracts second harmonic signals.
Description
Technical Field
The invention relates to the technical field of detection, in particular to an enhanced photoacoustic spectroscopy gas detection device and method based on a digital phase locking technology.
Background
The excess of certain trace gases in the atmosphere causes atmospheric pollution, sulfur oxides form acid rain, greenhouse gases such as CO2 and CH4 cause greenhouse effect, and nitrogen oxides, sulfur oxides and solid particles form haze. Therefore, it is necessary to detect these gases which seriously affect the living environment and health of human beings in time. At the present stage, researchers use the photoacoustic spectroscopy technology to monitor gases, and the photoacoustic spectroscopy technology is not only applied to monitoring atmospheric pollutants, but also widely applied in the fields of industry, power systems, medical departments and the like.
The quartz enhanced photoacoustic spectrometry is the optimization of the traditional microphone photoacoustic spectrometry, laser is focused to a slit between two arms of a quartz tuning fork, and when the laser modulation frequency reaches the resonance frequency of the quartz tuning fork, the acoustic frequency of the gas absorption light energy generating the photoacoustic effect is the same as the resonance frequency of the tuning fork, so that the quartz tuning fork resonates. According to the piezoelectric effect, the resonance generates piezoelectric current, the current signal is converted into a voltage signal through a pre-amplification circuit, and then the photoacoustic signal is obtained through demodulation of a phase-locked amplifier. Different gas molecules absorb different light wave wavelengths, and when the light source wavelength is coincident with the absorption wavelength of the gas molecules, the amplitude of the generated photoacoustic signal is maximum, so that the concentration of the gas can be calculated according to the positive correlation between the photoacoustic signal and the concentration of the gas.
The tunable laser spectrum absorption technology applied to gas detection is greatly influenced by factors such as a light source, environment and the like, so that the accuracy of an experimental result is influenced, and a part of circuits of a phase-locked amplifying device are all analog devices, so that the problem of aging exists, and the accuracy of a detection result is influenced.
Disclosure of Invention
In order to overcome the defects, the invention provides an enhanced photoacoustic spectroscopy gas detection device based on a digital phase locking technology.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
gaseous detection device of enhancement mode optoacoustic spectrum based on digital phase locking technique, its characterized in that: the laser excitation device comprises an excitation light source, an air chamber, a pre-amplification circuit, a DSP and a function generator, wherein two miniature sound resonant cavities and a quartz tuning fork are arranged in the air chamber, the function generator realizes wavelength modulation of laser emitted by the excitation light source through superposition of sawtooth waves, the air chamber is connected with an operational amplification circuit, and the operational amplification circuit is connected with the DSP.
As a limitation: the excitation light source is a tunable distributed feedback diode.
As a limitation: the gas chamber is a longitudinal resonance gas chamber, the sample detection gas chamber is provided with a gas inlet and a gas outlet, the gas inlet and the gas outlet are respectively provided with a gas inlet valve and a gas outlet valve, a laser incident window and an exit window are oppositely arranged in the gas chamber, and the laser incident window is correspondingly connected with the tunable laser diode.
As a limitation: and a serial communication interface module is arranged in the DSP and used for extracting harmonic signals and sending the harmonic signals to a computer.
A DSP digital phase-locked harmonic signal output method is characterized by comprising the following steps:
s01, generating reference signal by table look-up method, using MATLAB to generate trigonometric function value, converting it into hexadecimal system, sampling the trigonometric function value, storing the first quarter period sampling value in the table, the flow is: starting, calculating periodic sampling points, calculating sampling intervals, calculating the position of a sampling starting point in a table according to the phase, looking up the table to obtain the position of the sampling points, and ending;
s02: generating harmonic signals, using fs/4 sampling frequency, and when x (n) is input signals, the output and input relations are as follows:
the input signal and the orthogonal reference signal are respectively multiplied to obtain:
the sequence of the sine reference signal in one period contains 4 points, the sequence of the sine reference signal is {0, 1, 0, -1}, and the sequence of the cosine reference signal {1, 0, -1, 0} can be obtained as follows:
due to the adoption of the structure, compared with the prior art, the invention has the technical progress that:
the system adopts the enhanced quartz tuning fork type photoacoustic spectrometry technology to detect the atmospheric gas pollutants, avoids the influence caused by the light intensity change and reduces the influence of environmental noise, and realizes the detection with high sensitivity.
Aiming at the defects of large volume and high price of a digital phase-locked amplifier in the market, the system self-manufactures the digital phase-locked amplifier, uses a DSP as a core device, adopts a table look-up method to generate a reference signal, uses a quarter-period trigonometric function value and reduces the occupation of a DSP memory. The algorithm for realizing the related detection in the DSP adopts a method for reducing the sampling frequency to reduce the operation amount, thereby accelerating the system response.
The signal extraction in the whole system is realized by combining a wavelength modulation technology, a second harmonic signal extraction technology, an enhanced photoacoustic spectroscopy technology and a digital phase locking technology, so that the whole system has the advantages of quick response, small noise influence, high signal extraction precision and high sensitivity measurement.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention.
In the drawings:
fig. 1 is a schematic view of the overall structure of the present invention.
Fig. 2 is a circuit diagram of a pre-amplifier circuit.
Fig. 3 is a functional diagram of DSP implementation.
Fig. 4 is a schematic diagram of a flow chart for generating a reference signal.
In the figure: 1-excitation light source, 2-gas chamber, 3-preamplification circuit, 4-DSP, 5-function generator.
Detailed Description
Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for purposes of illustration and explanation only and are not intended to limit the present invention.
Referring to fig. 1 to 4, as shown in fig. 1, the optical fiber laser comprises an excitation light source 1, an air chamber 2, a pre-amplification circuit 3, a DSP4 and a function generator 5, wherein two micro resonant cavities and a quartz tuning fork are arranged in the air chamber 2, the function generator 5 modulates the wavelength of laser emitted by the excitation light source 1 by superimposing sawtooth waves, the air chamber 2 is connected with an operational amplification circuit, and the operational amplification circuit is connected with the DSP 4.
The invention aims to provide an enhanced photoacoustic spectrometry detection system device for detecting atmospheric gas pollutants, and designs a digital phase-locked amplifier, so as to provide a detection method with high accuracy and quick response for a gas detection process. The modulation of the light source is to modulate the wavelength of the laser by sending a sine signal which is half of the resonance frequency of the quartz tuning fork by a sawtooth wave superposition function generator 5 sent by a computer; the signal is generated by emitting laser to a slit between two arms of a quartz tuning fork in the photoacoustic cell, when gas between the two arms absorbs the light to generate sound waves, the frequency of the sound waves is the same as the resonance frequency of the quartz tuning fork, so that the quartz tuning fork generates resonance, a piezoelectric effect is generated, and a piezoelectric current signal is generated; the extraction of the signal mainly converts a current signal into a voltage signal through an operational amplifier circuit, the voltage signal is sent into the DSP4 to be used as an input signal, programming is carried out in the DSP4 to realize internal generation of a reference signal, relevant detection is realized on the reference signal, and a second harmonic signal is extracted.
The piezoelectric current signal is generated in the air chamber 2 and is composed of a pair of miniature sound resonant cavities, a quartz tuning fork, a window sheet and an air inlet and an air outlet.
The voltage signal obtained by the amplifying circuit is extracted into a second harmonic signal by a phase-locked amplifier, the phase-locked amplifier in the system uses a DSP4 as a core device to form a digital phase-locked amplifier, the related detection of a signal to be detected and a reference signal is realized in the DSP4, and the reference signal is realized by internal programming. The functions performed by the DSP4 are shown in fig. 3.
The DSP4 digital phase-locked harmonic signal output method comprises the following steps:
s01, generating a reference signal by using a table look-up method, generating a trigonometric function value by using MATLAB, converting the trigonometric function value into hexadecimal, sampling the trigonometric function value, and storing the sampling value of the first quarter period into a table, wherein the specific flow is shown in figure 4 and comprises the following steps: starting, calculating periodic sampling points, calculating sampling intervals, calculating the position of a sampling starting point in a table according to the phase, looking up the table to obtain the position of the sampling points, and ending;
s02: generating harmonic signals, using fs/4 sampling frequency, and when x (n) is input signals, the output and input relations are as follows:
the input signal and the orthogonal reference signal are respectively multiplied to obtain:
the sequence of the sine reference signal in one period contains 4 points, the sequence of the sine reference signal is {0, 1, 0, -1}, and the sequence of the cosine reference signal {1, 0, -1, 0} can be obtained as follows:
the function generator 5 of the invention emits sine waves with frequency f, realizes the wavelength modulation of laser by superposing sawtooth waves, realizes the focusing of the light beam by a lens before the light beam is emitted into the air chamber 2, because the light beam of DFB laser has the characteristic of divergence, two ends in the air chamber 2 are provided with window sheets, and the top end is provided with an air inlet and an air outlet which are controlled by an air valve. The main devices in the gas chamber 2 are a quartz tuning fork and two micro resonant cavities, so that light beams are focused and then enter the resonant cavities, and the gas absorbs light energy to form cylindrical waves, thereby realizing the signal amplification effect. When the laser modulation frequency is the same as the resonance frequency of the quartz tuning fork, the quartz tuning fork resonates, piezoelectric current is generated due to the piezoelectric effect, the current is converted into voltage through the operational amplification circuit, and weak signals are amplified. As shown in fig. 2, the operational amplifier circuit has a feedback resistance of 10M Ω, and amplifies and converts the piezoelectric current signal into a voltage signal. Before the signal to be measured is input into the DSP4, analog-to-digital conversion is carried out in the input DSP4, a sine function table of a quarter period is stored in the DSP4, an orthogonal reference signal is obtained through a table look-up method, related operation is realized in the DSP4 through programming, and the obtained amplitude and phase are sent to a computer.
Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the claims of the present invention.
Claims (5)
1. Gaseous detection device of enhancement mode optoacoustic spectrum based on digital phase locking technique, its characterized in that: the laser excitation device comprises an excitation light source, an air chamber, a pre-amplification circuit, a DSP and a function generator, wherein two micro resonant cavities and a quartz tuning fork are arranged in the air chamber, the function generator realizes wavelength modulation of laser emitted by the excitation light source through superposition of sawtooth waves, the air chamber is connected with an operational amplification circuit, and the operational amplification circuit is connected with the DSP.
2. The enhanced photoacoustic spectroscopy gas-detecting apparatus based on digital phase-locking technology of claim 1, wherein: the excitation light source is a tunable distributed feedback diode.
3. The enhanced photoacoustic spectroscopy gas-detecting apparatus based on digital phase-locking technology of claim 2, wherein: the gas chamber is a longitudinal resonance gas chamber, the sample detection gas chamber is provided with a gas inlet and a gas outlet, the gas inlet and the gas outlet are respectively provided with a gas inlet valve and a gas outlet valve, a laser incident window and an exit window are oppositely arranged in the gas chamber, and the laser incident window is correspondingly connected with the tunable laser diode.
4. The enhanced photoacoustic spectroscopy gas-detecting apparatus based on digital phase-locking technology of claim 1, wherein: and a serial communication interface module is arranged in the DSP and used for extracting harmonic signals and sending the harmonic signals to a computer.
5. A DSP digital phase-locked harmonic signal output method is characterized by comprising the following steps:
s01, generating reference signal by table look-up method, using MATLAB to generate trigonometric function value, converting it into hexadecimal system, sampling the trigonometric function value, storing the first quarter period sampling value in the table, the flow is: starting, calculating periodic sampling points, calculating sampling intervals, calculating the position of a sampling starting point in a table according to the phase, looking up the table to obtain the position of the sampling points, and ending;
s02: generating harmonic signals, using fs/4 sampling frequency, and when x (n) is input signals, the output and input relations are as follows:
the input signal and the orthogonal reference signal are respectively multiplied to obtain:
the sequence of the sine reference signal in one period contains 4 points, the sequence of the sine reference signal is {0, 1, 0, -1}, and the sequence of the cosine reference signal {1, 0, -1, 0} can be obtained as follows:
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010196165.6A CN111366535A (en) | 2020-03-19 | 2020-03-19 | Enhanced photoacoustic spectroscopy gas detection device and method based on digital phase locking technology |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010196165.6A CN111366535A (en) | 2020-03-19 | 2020-03-19 | Enhanced photoacoustic spectroscopy gas detection device and method based on digital phase locking technology |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN111366535A true CN111366535A (en) | 2020-07-03 |
Family
ID=71204524
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202010196165.6A Pending CN111366535A (en) | 2020-03-19 | 2020-03-19 | Enhanced photoacoustic spectroscopy gas detection device and method based on digital phase locking technology |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN111366535A (en) |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102884413A (en) * | 2010-03-02 | 2013-01-16 | 利康股份有限公司 | Method and apparatus for the photo-acoustic identification and quantification of analyte species in a gaseous or liquid medium |
| CN104237135A (en) * | 2014-10-22 | 2014-12-24 | 东北林业大学 | System and method for detecting CO gas based on quartz tuning fork enhanced photoacoustic spectrometry technology |
-
2020
- 2020-03-19 CN CN202010196165.6A patent/CN111366535A/en active Pending
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102884413A (en) * | 2010-03-02 | 2013-01-16 | 利康股份有限公司 | Method and apparatus for the photo-acoustic identification and quantification of analyte species in a gaseous or liquid medium |
| CN104237135A (en) * | 2014-10-22 | 2014-12-24 | 东北林业大学 | System and method for detecting CO gas based on quartz tuning fork enhanced photoacoustic spectrometry technology |
Non-Patent Citations (3)
| Title |
|---|
| 刘小利 等: "利用石英增强光声光谱技术在2.0μm处实现高灵敏CO2检测的实验研究", 《光谱学与光谱分学习》 * |
| 刘慧芳 等: "数字正交锁相放大器的验证及其在甲烷检测中的应用", 《光子学报》 * |
| 李凤鸣: "基于DSP的数字锁相放大器的设计", 《中国优秀硕士学位论文全文数据库 信息科技辑》 * |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN104237135B (en) | CO gas detecting systems and method based on quartz tuning fork strengthened optoacoustic spectroscopy | |
| CN108593763B (en) | Real-time detection device for multi-component gas based on quartz tuning fork frequency division demodulation | |
| CN108535184A (en) | A kind of optoacoustic spectroscopy multicomponent trace gas detection instrument and method | |
| CN112147076B (en) | Absorption optical path enhanced double-resonance photoacoustic spectrum trace gas detection system | |
| CN111157456B (en) | Gas detection system based on open type photoacoustic resonant cavity | |
| CN109490216B (en) | Calibration-free laser photoacoustic spectrum trace gas detection instrument and method | |
| CN104931427A (en) | Opto-acoustic gas detection device based on multiple reflections of optical path | |
| CN111707619A (en) | Photoacoustic cell based on MEMS microphone array and photoacoustic spectrum sensor | |
| CN105548023A (en) | Evanescent-wave type photoacoustic spectrum trace gas sensor based on optical fiber resonant cavity and measurement method | |
| CN112304872A (en) | Tuning fork acoustic-thermal integrated enhanced trace gas detection system and detection method thereof | |
| CN109507116B (en) | Photoacoustic spectroscopy gas sensing device and method based on polymer film microcavity | |
| CN111220513A (en) | Haze detection device and method based on digital phase locking and photoacoustic spectroscopy technology | |
| CN111366535A (en) | Enhanced photoacoustic spectroscopy gas detection device and method based on digital phase locking technology | |
| Tittel et al. | Sensitive detection of nitric oxide using a 5.26 μm external cavity quantum cascade laser based QEPAS sensor | |
| CN114002184B (en) | Multi-resonance enhanced photoacoustic spectrum multi-component gas simultaneous detection device and method | |
| Srivastava et al. | Design and Characterization of Macroscopic Indirect Photoacoustic Gas Sensor | |
| Spagnolo et al. | Part-per-trillion level detection of SF6 using a single-mode fiber-coupled quantum cascade laser and a quartz enhanced photoacoustic sensor | |
| CN116148187A (en) | Photoacoustic spectroscopy gas detection system based on open differential resonant cavity optical path enhancement | |
| Wang et al. | Three acoustic microresonator quartz-enhanced photoacoustic spectroscopy for trace gas sensing | |
| CN215574610U (en) | Single resonant cavity photoacoustic spectroscopy system for simultaneously detecting multiple gases | |
| CN218382393U (en) | Sensor circuit based on TDLAS | |
| CN111122444A (en) | Multiple resonant T-shaped enhanced multiple trace gas simultaneous detection device | |
| CN114235699A (en) | Trace gas concentration detection device | |
| CN114279996A (en) | Gas-phase hydrogen peroxide concentration detection system based on off-axis integration cavity | |
| Sari et al. | Acoustic energy harvesting from trace gas analyzing sensor |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| RJ01 | Rejection of invention patent application after publication | ||
| RJ01 | Rejection of invention patent application after publication |
Application publication date: 20200703 |