CN116519596A - Gas concentration detection device - Google Patents
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Abstract
A gas concentration detection apparatus comprising: a photoacoustic mechanism comprising: the photoacoustic cell is internally filled with calibration gas; the laser emission module is suitable for emitting a calibration laser signal, wherein the calibration laser signal is a laser signal modulated by the first modulation signal; a microphone adapted to convert the first sound pressure signal into a first current signal; the photoelectric detector is suitable for detecting the calibrated laser signals transmitted through the photoacoustic cell to obtain photocurrent signals at different moments; the processing mechanism is suitable for obtaining a change curve of the photocurrent signal along with time according to the photocurrent signals at different moments, normalizing the change curve to obtain a normalized absorption peak curve, obtaining a cell constant of the photoacoustic cell according to the absorption peak curve and the first current signal, and calibrating the photoacoustic mechanism by the cell constant.
Description
Technical Field
The invention relates to the technical field of gas trace detection, in particular to a gas concentration detection device.
Background
The tunable semiconductor laser absorption spectroscopy (TDLAS) technology utilizes the absorption effect of gas on laser to detect the gas, and the concentration of the gas to be detected is usually calculated by analyzing the light intensity information of the laser before and after absorption, the TDLAS system has the capability of directly inverting the concentration, but the high sensitivity is usually realized by relying on the long-optical-path technology, and the long optical path usually means complex structure and volume, which is not beneficial to the application of a limited space.
The photoacoustic spectrum gas detection technology (PAS) is a novel technology for inverting the gas concentration by utilizing the photoacoustic effect of gas so as to detect the gas, has the advantages of no background absorption, electromagnetic interference resistance, high sensitivity, long-term online detection and the like, and is widely applied to industrial and agricultural production, atmospheric environment detection and medical treatment. The working principle is as follows: filling the gas to be measured into the photoacoustic cell to keep the gas in a static or uniform flow state; when the excitation wavelength corresponds to the absorption peak of the gas to be detected, the gas to be detected absorbs the modulated laser light to generate periodic heat fluctuation so as to cause pressure fluctuation; the pressure fluctuations are detected by a microphone within the photoacoustic cell; the gas concentration is identified from the measured sound signal.
The photoacoustic spectrum detection system mainly comprises a laser, an optical cavity and a microphone. Since the power of the laser and the parameters of the optical cavity are susceptible to ambient temperature and air pressure, the accuracy and sensitivity of the test system can be affected.
Disclosure of Invention
In view of the above, the present invention provides a gas concentration detection apparatus capable of achieving self-calibration of the apparatus.
To achieve the above object, a first aspect of the present invention discloses a gas concentration detection apparatus comprising:
a photoacoustic mechanism comprising:
the photoacoustic cell is internally filled with calibration gas;
the laser emission module is suitable for emitting a calibration laser signal, wherein the calibration laser signal is a laser signal modulated by a first modulation signal, the wavelength range of the calibration laser signal can scan the wavelength corresponding to the absorption peak position of the calibration gas, and the calibration laser signal irradiates the calibration gas, is absorbed by the calibration gas and generates a photoacoustic effect, so as to obtain a first sound pressure signal;
a microphone adapted to convert the first sound pressure signal into a first current signal;
the photoelectric detector is suitable for detecting the calibrated laser signals transmitted through the photoacoustic cell to obtain photocurrent signals at different moments;
the processing mechanism is suitable for obtaining a change curve of the photocurrent signal along with time according to the photocurrent signals at different moments, normalizing the change curve to obtain a normalized absorption peak curve, obtaining a cell constant of the photoacoustic cell according to the absorption peak curve and the first current signal, and calibrating the photoacoustic mechanism;
the calibrated photoacoustic mechanism is suitable for detecting the concentration of the gas to be detected.
According to an embodiment of the invention, the photo acoustic cell is a resonant photo acoustic cell, the frequency of the modulating signal being equal to the resonant frequency of the photo acoustic cell.
According to an embodiment of the present invention, a normalized absorption peak curve is obtained by normalizing a change curve, including:
obtaining a reference curve according to the change curve, wherein the reference curve represents the change of the power of the calibration laser signal along with time;
and obtaining a normalized absorption peak curve according to the change curve and the reference curve.
According to an embodiment of the present invention, obtaining cell constants of a photoacoustic cell from an absorption peak curve and a first current signal includes:
determining the value of a characteristic absorption peak of the calibration gas according to the normalized absorption peak curve;
the cell constant is determined from the value of the characteristic absorption peak of the calibration gas and the first current signal.
According to an embodiment of the invention, determining the value of the characteristic absorption peak of the calibration gas from the normalized absorption peak curve comprises:
and determining the value of the characteristic absorption peak of the calibration gas according to the normalized absorption peak curve based on a dynamic peak searching algorithm.
According to an embodiment of the invention, the pool constant is expressed as follows:
wherein C is cell Represent pool constant, S PA Representing a first current signal S mic Representing the sensitivity of the microphone, P light The optical power of the calibration laser at the characteristic absorption peak position is represented, α represents the absorption coefficient of the calibration gas, L represents the absorption path inside the photoacoustic cell, and absorption represents the value of the characteristic absorption peak of the calibration gas.
According to an embodiment of the present invention, the gas to be measured includes at least one component to be measured, and the calibrated photoacoustic mechanism is adapted to detect the concentration of the gas to be measured and includes: the calibrated photoacoustic mechanism is adapted for use in detecting at least one component to be measured,
the laser emission module includes:
a plurality of DFB lasers configured to emit an initial probing laser signal in a time division multiplexed manner;
the signal generator is suitable for sending out a first voltage signal and a second voltage signal;
the laser controller is suitable for converting the first voltage signal into a second modulation signal, converting the second voltage signal into a third modulation signal and sending out a temperature control signal, wherein under the action of the second modulation signal, the third modulation signal and the temperature control signal, the initial detection laser signal is converted into a specific detection laser signal, the wavelength range of the specific detection laser signal can scan the wavelength corresponding to the absorption peak position of the gas to be detected, the specific detection laser signal is suitable for being irradiated onto the gas to be detected of the photoacoustic cell, the absorption by the component to be detected and the photoacoustic effect occur, the second acoustic pressure signal is obtained, and the second acoustic pressure signal is suitable for determining the concentration of the component to be detected.
According to an embodiment of the present invention, the microphone is mounted at the maximum sound pressure of the photoacoustic cell.
According to an embodiment of the invention, the microphone is adapted to convert the second sound pressure signal into a second current signal when detecting the concentration of the gas to be detected;
the processing mechanism is also suitable for obtaining the concentration of the component to be detected according to the second current signal and the calibrated parameters of the photoacoustic mechanism.
According to the embodiment of the invention, the first modulation signal comprises a first sub-modulation signal and a second sub-modulation signal, the first sub-modulation signal is a sawtooth wave signal or a triangular wave signal, the second sub-modulation signal is a sine wave signal or a square wave signal, the center wavelength of the obtained calibration laser signal is the same as the wavelength corresponding to the absorption peak position of the calibration gas under the action of the first sub-modulation signal, and therefore the wavelength range of the calibration laser signal can sweep the wavelength corresponding to the absorption peak position of the calibration gas, and the second sub-modulation signal is applied at the wavelength position corresponding to the absorption peak position of the calibration gas so as to generate a photoacoustic effect.
According to the embodiment of the invention, the photoelectric detector is used for detecting the photoelectric current signals at different moments, the processing mechanism is used for processing the light to obtain the cell constant, the calibration of the photoacoustic mechanism is realized, and the gas concentration detection device is self-calibrated.
Drawings
FIG. 1 is a block diagram of a gas concentration detection apparatus provided by an embodiment of the present invention;
fig. 2 is a calibration step in gas concentration detection provided according to an embodiment of the present invention.
Reference numerals illustrate:
1: a photoacoustic mechanism;
11: a photoacoustic cell;
12: a laser emitting module;
121: a laser unit;
122: a signal generator;
123: a laser controller;
13: a microphone;
2: a photodetector;
3: a processing mechanism;
31: a data acquisition card;
32: and a data calculation module.
Detailed Description
In the process of realizing the invention, aiming at the photoacoustic spectrum detection system, the invention needs to provide a self-calibration algorithm for suppressing the interference of environmental factors and improving the stability of the photoacoustic spectrum system.
The present invention will be further described in detail below with reference to specific embodiments and with reference to the accompanying drawings, in order to make the objects, technical solutions and advantages of the present invention more apparent.
Fig. 1 is a block diagram of a gas concentration detection apparatus according to an embodiment of the present invention.
As shown in fig. 1, the gas concentration detection apparatus includes: a photoacoustic mechanism 1, a photodetector 2, and a processing mechanism 3.
A photoacoustic mechanism comprising: a photoacoustic cell 11, a laser emitting module 12 and a microphone 13. The photoacoustic cell 11 is filled with a calibration gas. The laser emitting module 12 is adapted to emit a calibration laser signal, where the calibration laser signal is a laser signal modulated by a first modulation signal, where a wavelength range of the calibration laser signal is capable of scanning a wavelength corresponding to an absorption peak position of the calibration gas, and the calibration laser signal irradiates the calibration gas, is absorbed by the calibration gas and generates a photoacoustic effect, so as to obtain a first sound pressure signal. The microphone 13 is adapted to convert the first sound pressure signal into a first current signal.
The photodetector 2 is adapted to detect the calibrated laser signal transmitted through the photoacoustic cell 11 to obtain photocurrent signals at different times. The processing mechanism 3 is adapted to obtain a change curve of the photocurrent signal along with time according to the photocurrent signals at different moments, to normalize the change curve to obtain a normalized absorption peak curve, and to obtain a cell constant of the photoacoustic cell 11 according to the absorption peak curve and the first current signal, the cell constant being adapted to achieve calibration of the photoacoustic mechanism 1. The calibrated photoacoustic mechanism 1 is suitable for detecting the concentration of the gas to be detected.
According to the embodiment of the invention, the photoelectric detector 2 is utilized to detect the photoelectric current signals at different moments by the processing mechanism 3, so that the cell constant is obtained, the calibration of the photoacoustic mechanism 1 is realized, and the gas concentration detection device is self-calibrated.
According to the gas concentration detection device provided by the embodiment of the invention, the device needs to be self-calibrated before the concentration of the gas to be detected is detected by using the device, so that the calibration gas used in the self-calibration stage can be water vapor in the gas exhaled by the human body.
According to the embodiment of the invention, the conventional photoacoustic spectroscopy gas detection device based on the photoacoustic spectroscopy gas detection technology (i.e., PAS technology) comprises the photoacoustic mechanism 1 in the embodiment of the invention, and the conventional gas detection device based on the tunable semiconductor laser absorption spectroscopy Technology (TDLAS) comprises the photoacoustic cell 11, the laser emitting module 12 and the photoelectric detector in the embodiment of the invention, so that the gas concentration detection device provided by the embodiment of the invention combines the PAS technology and the TDLAS technology, and realizes self calibration of the detection device, thereby solving the problem that parameters of the photoacoustic cell in the conventional photoacoustic spectroscopy technology are easily affected by environment.
According to the embodiment of the invention, the gas types of the calibration gas are known, but the concentration is unknown, and the calibration gas and the gas to be measured in the embodiment of the invention can be the same or different.
According to an embodiment of the invention, the processing means 3 comprise a data acquisition card 31 and a data calculation module 32. Wherein, in the self-calibration stage, the data acquisition card 31 is adapted to acquire the photocurrent signals and the first current signals at different moments, the calculation module 32 is adapted to obtain a time-dependent change curve of the photocurrent signals according to the photocurrent signals at different moments, to normalize the change curve to obtain a normalized absorption peak curve, and to obtain a cell constant of the photoacoustic cell 11 according to the absorption peak curve and the first current signals, and the cell constant is adapted to achieve calibration of the photoacoustic mechanism 1. The drift of the device can be compensated by comparing signals of the first input end and the second input end of the data acquisition card, and the self-calibration function is realized.
According to an embodiment of the present invention, the output end of the microphone 13 is connected to the first input end of the data acquisition card 31, and is used for extracting a signal generated by the photoacoustic effect as a basis for concentration detection. The output end of the photoelectric detector 2 is connected with the second input end of the data acquisition card 31, the output end of the data acquisition card 31 is connected with the input end of the data calculation module 32, and the data calculation module 32 can be a computer or a microprocessor.
According to an embodiment of the present invention, the photoacoustic cell 11 may be any one of an H-type, a T-type, a cylindrical type, or a combination thereof, and the photoacoustic cell 11 generally includes an air inlet, an air outlet, a gas chamber, and a microphone hole for collecting sound signals by the microphone 13, and the microphone 13 may be a piezoelectric microphone and a fiber microphone.
According to an embodiment of the present invention, the photoacoustic cell 11 is a resonant photoacoustic cell, and the frequency of the modulated signal is equal to the resonant frequency of the photoacoustic cell 11. Since the first sound pressure signal generated by the occurrence of the photoacoustic effect is weak, typically at the order of microppa, the frequency of the modulated signal needs to be set equal to the resonance frequency of the photoacoustic cell 11 to perform resonance amplification of the first sound pressure signal.
According to an embodiment of the present invention, a normalized absorption peak curve is obtained by normalizing a change curve, including: obtaining a reference curve according to the change curve, wherein the reference curve represents the change of the power of the calibration laser signal along with time; and obtaining a normalized absorption peak curve according to the change curve and the reference curve.
According to an embodiment of the present invention, obtaining the cell constant of the photoacoustic cell 11 from the absorption peak curve and the first current signal includes:
determining the value of a characteristic absorption peak of the calibration gas according to the normalized absorption peak curve; the cell constant is determined from the values of the characteristic absorption peaks of the calibration gas.
According to an embodiment of the invention, determining the value of the characteristic absorption peak of the calibration gas from the normalized absorption peak curve comprises: and determining the value of the characteristic absorption peak of the calibration gas according to the normalized absorption peak curve based on a dynamic peak searching algorithm.
According to an embodiment of the invention, the pool constant is expressed as follows:
wherein C is cell Represent pool constant, S PA Representing a first current signal S mic Representing the sensitivity of the microphone, P light The optical power of the calibration laser at the characteristic absorption peak position is represented, α represents the absorption coefficient of the calibration gas, L represents the absorption path inside the photoacoustic cell, and absorption represents the value of the characteristic absorption peak of the calibration gas.
According to an embodiment of the present invention, the gas to be measured includes at least one component to be measured, and the calibrated photoacoustic mechanism is adapted to detect the concentration of the gas to be measured and includes: the calibrated photoacoustic mechanism 1 is suitable for detecting at least one component to be measured, wherein the laser emitting module 12 comprises: a laser unit 121, a signal generator 122, a laser controller 123.
According to an embodiment of the present invention, the laser unit 121 includes a plurality of DFB lasers, which may be coupled through a fiber coupler or spatially coupled through a half mirror during a detection phase of a plurality of components to be detected of the gas to be detected, and are configured to emit an initial detection laser signal in a time division multiplexed manner. The wavelengths of the plurality of DFB lasers are different, and the wavelength emitted by each DFB laser can output a laser signal corresponding to a gas absorption peak. I.e., the wavelength of the laser signal emitted by one DFB laser is directed to at least one component to be measured in the gas to be measured. Therefore, the concentration measurement of various gas components in the confined space can be realized by adopting a plurality of DFB lasers in the embodiment of the invention.
According to an embodiment of the invention, the signal generator 122 is adapted to emit a first voltage signal and a second voltage signal.
According to an embodiment of the present invention, the laser controller 123 is adapted to convert the first voltage signal into the second modulation signal, convert the second voltage signal into the third modulation signal, and be adapted to send out the temperature control signal, wherein under the action of the second modulation signal, the third modulation signal, and the temperature control signal, the initial detection laser signal is converted into the specific detection laser signal, the wavelength range of the specific detection laser signal can scan the wavelength corresponding to the absorption peak position of the gas to be measured, and the specific detection laser signal is adapted to be irradiated onto the gas to be measured of the photoacoustic cell, and absorbed by the component to be measured and generate the photoacoustic effect, so as to obtain the second acoustic pressure signal, and the second acoustic pressure signal is adapted to determine the concentration of the component to be measured.
According to an embodiment of the present invention, the second modulation signal and the third modulation signal are both current signals, wherein the second modulation signal may also be called a scan bias current signal, and the second modulation signal is a sawtooth wave signal or a triangular wave signal. The second modulation signal and the temperature control signal are suitable for adjusting the wavelength of the initial detection laser signal, wherein the temperature control signal is suitable for realizing coarse adjustment of the wavelength of the initial detection laser signal by controlling the temperature of the DFB laser, and the second modulation signal is suitable for fine adjustment of the wavelength of the initial detection laser signal. Under the mediation of the second modulation signal and the temperature control signal, the wavelength range of the calibration laser signal can sweep the wavelength corresponding to the absorption peak position of the calibration gas.
According to the embodiment of the invention, the third modulation signal is also an electrical signal, and the third modulation signal is a sine wave signal or a square wave signal, and the third modulation signal is applied at a wavelength position corresponding to the absorption peak position of the component to be measured, so as to generate the photoacoustic effect.
According to an embodiment of the present invention, in the concentration detection stage of the plurality of components to be detected of the gas to be detected, the processing mechanism 3 is further adapted to implement concentration detection of the plurality of components to be detected according to the second acoustic pressure signal and the calibrated parameters of the photoacoustic mechanism 1.
According to an embodiment of the present invention, the output terminal of the signal generator 122 is connected to the input terminal of the laser controller 123 for generating a sine wave or square wave modulation signal, and the output terminal of the laser controller 123 is connected to the input terminal of the laser unit 121, thereby modulating the output wavelength of the DFB laser.
According to the embodiment of the present invention, the microphone 13 is installed at the maximum sound pressure of the photoacoustic cell 11, and the first sound pressure signal generated by the photoacoustic effect can be collected more efficiently.
According to an embodiment of the invention, the microphone is adapted to convert the second sound pressure signal into a second current signal when detecting the concentration of the gas to be detected; the processing means 13 are further adapted to obtain the concentration of the component to be measured from the second current signal and the calibrated parameters of the opto-acoustic means 1.
According to the embodiment of the invention, the first modulation signal comprises a first sub-modulation signal and a second sub-modulation signal, the first sub-modulation signal is a sawtooth wave signal or a triangular wave signal, the second sub-modulation signal is a positive-rotation sine wave signal or a square wave signal, the center wavelength of the obtained calibration laser signal is the same as the wavelength corresponding to the absorption peak position of the calibration gas under the action of the first sub-modulation signal, and therefore the wavelength range of the calibration laser signal can sweep the wavelength corresponding to the absorption peak position of the calibration gas, and the second sub-modulation signal is applied at the wavelength position corresponding to the absorption peak position of the calibration gas so as to generate a photoacoustic effect.
According to an embodiment of the invention, the second modulation signal also comprises two sub-signals, the first modulation signal and the second modulation signal being identical when the calibration gas and the gas to be measured are identical.
According to the embodiment of the invention, the signal generator 122, the laser controller 123, the photoelectric detector 2, the data acquisition card 31, the microphone 13 and the data acquisition card 31 are all connected through coaxial cables, so that noise interference in the signal transmission process can be reduced.
The following will describe how to detect the gas concentration by using the gas concentration detection apparatus according to the embodiment of the present invention.
Fig. 2 is a calibration step in gas concentration detection provided according to an embodiment of the present invention. As shown in connection with fig. 1-2, the calibration procedure is as follows:
step S1: the concentration of water vapor in the blown gas is detected by using a DFB laser having a wavelength of 1374nm as a light source, and the DFB laser is temperature-controlled by the signal generator 122, so that the wavelength of the DFB laser can be scanned by a wavelength corresponding to the absorption peak position of the water vapor.
Step S2: a sweep bias current signal from low to high is applied to the DFB laser with a signal generator 122 while a sine wave modulation signal of a particular frequency is applied such that the DFB laser produces a nominal laser signal sine wave frequency equal to the resonant frequency of photoacoustic cell 11.
Step S3: the calibration laser signal irradiates the calibration gas, is absorbed by the calibration gas and generates a photoacoustic effect to obtain a first sound pressure signal, records a photocurrent curve measured by the detector after absorption occurs, judges whether light absorption occurs in the photoacoustic cell 11 according to the photocurrent curve, if so, executes step S4, otherwise returns to step S2 to scan repeatedly, wherein the calibration gas is obtained by blowing air towards a cavity of a gas cavity of the photoacoustic cell through an air inlet of the photogenerated cell 11.
Step S4: fitting a reference curve through the absorption curve measured in the step S2, and taking the reference curve as an optical power signal of a calibration laser signal before absorption; and comparing the reference curve with the absorption curve to obtain a normalized absorption peak curve, wherein the maximum position of the normalized absorption peak curve corresponds to the position of the water vapor characteristic absorption peak, and simultaneously recording the first current signal acquired by the microphone 13.
Step S5: and (3) carrying out concentration inversion on the normalized absorption peak curve in the S4 according to the beer-lambert law.
The specific process of step S5 is as follows: according to the beer lambert law, the wavelength is lambda and the intensity is I 0 The (lambda) calibration laser signal passes through a certain gas with a certain concentration C in the photoacoustic cell 11 and enters the photoelectric detector 2 after passing through the absorption path of L, and the light intensity I of the calibration laser transmitted through the photoacoustic cell 11 is received by the photoelectric detector 2 t (lambda) and the nominal laser signal I emitted by the laser emitting module 12 0 The relationship of the light intensity of (λ) is:
I t (λ)＝I 0 (λ)exp(-αCL) (2)
where α is the absorption coefficient of the calibration gas for a calibrated laser signal having a wavelength λ. When alpha CL is more than 0.5, the ordinate corresponding to the maximum position of the normalized absorption peak curve is the value of the characteristic absorption peak of the calibration gas, namely absorption,
the concentration of the calibration gas can be deduced from equation (3). The concentration of calibration gas (i.e., water vapor) that can be derived from the geometric formulas (2) and (3).
C＝-ln(absorption)/αL (4)
Where α is the absorption coefficient of water vapor and L is the absorption path inside the photoacoustic cell.
Step S6: and calibrating the photoacoustic mechanism 1 according to the concentration obtained by S5 inversion and the first current signal acquired by S4, and calculating the correlation coefficient of the photoacoustic mechanism 1 according to the concentration.
Specifically, the microphone captures an acoustic signal S PA The microphone 13 sensitivity S can be used mic Calibrating the optical power P of the laser at the characteristic absorption peak position light Cell constant C cell The absorption coefficient α and the concentration C of water vapor satisfy the following relationship:
S PA ＝S mic ·P light ·C cell ·α·C (5)
the concentration of water vapor can also be expressed as follows according to formula (5):
C＝S PA /(S mic P light C cell α) (6)
from the formulas (4) and (6), the coefficient in the photoacoustic mechanism 1 can be obtained as
The formula (7) is transformed to obtain the formula (1).
The calibrated pool constant can be obtained through the steps, so that the photoacoustic mechanism 1 can be calibrated and calibrated, and the method can be used for online gas concentration detection.
The foregoing description of the embodiments has been provided for the purpose of illustrating the general principles of the invention, and is not meant to limit the invention thereto, but to limit the invention thereto, and any modifications, equivalents, improvements and equivalents thereof may be made without departing from the spirit and principles of the invention.
Claims (10)
1. A gas concentration detection apparatus comprising:
a photoacoustic mechanism comprising:
the photoacoustic cell is internally filled with calibration gas;
the laser emission module is suitable for emitting a calibration laser signal, wherein the calibration laser signal is a laser signal modulated by a first modulation signal, the wavelength range of the calibration laser signal can sweep the wavelength corresponding to the absorption peak position of the calibration gas, and the calibration laser signal irradiates the calibration gas, is absorbed by the calibration gas and generates a photoacoustic effect to obtain a first sound pressure signal;
a microphone adapted to convert the first sound pressure signal into a first current signal;
the photoelectric detector is suitable for detecting the calibrated laser signals transmitted through the photoacoustic cell to obtain photocurrent signals at different moments;
the processing mechanism is suitable for obtaining a change curve of the photocurrent signal along with time according to the photocurrent signals at different moments, normalizing the change curve to obtain a normalized absorption peak curve, and obtaining a cell constant of the photoacoustic cell according to the absorption peak curve and the first current signal, wherein the cell constant is suitable for realizing calibration of the photoacoustic mechanism;
the calibrated photoacoustic mechanism is suitable for detecting the concentration of the gas to be detected.
2. The gas concentration detection apparatus according to claim 1, wherein the photoacoustic cell is a resonant photoacoustic cell, and the frequency of the modulation signal is equal to the resonant frequency of the photoacoustic cell.
3. The gas concentration detection apparatus according to claim 2, wherein normalizing the change curve to obtain a normalized absorption peak curve comprises:
obtaining a reference curve according to the change curve, wherein the reference curve represents the change of the power of the calibration laser signal along with time;
and obtaining the normalized absorption peak curve according to the change curve and the reference curve.
4. The gas concentration detection apparatus according to claim 2, wherein deriving a cell constant of the photoacoustic cell from the absorption peak curve and the first current signal comprises:
determining the value of a characteristic absorption peak of the calibration gas according to the normalized absorption peak curve;
the cell constant is determined from the value of the characteristic absorption peak of the calibration gas and the first current signal.
5. The gas concentration detection apparatus of claim 4, wherein determining a value of a characteristic absorption peak of the calibration gas from the normalized absorption peak curve comprises:
and determining the value of the characteristic absorption peak of the calibration gas according to the normalized absorption peak curve based on a dynamic peak finding algorithm.
6. The gas concentration detection apparatus according to claim 4, wherein the cell constant is expressed as follows:
wherein C is cell Represent pool constant, S PA Representing the first current signal, S mic Representing the sensitivity of the microphoneDegree, P light Representing the optical power of the calibration laser at the characteristic absorption peak position, alpha represents the absorption coefficient of the calibration gas, L represents the absorption path inside the photoacoustic cell, and absorption represents the value of the characteristic absorption peak of the calibration gas.
7. The gas concentration detection apparatus according to claim 1, wherein the gas to be measured includes at least one component to be measured, and the calibrated photoacoustic mechanism is adapted to detect the concentration of the gas to be measured, comprising: the calibrated photoacoustic mechanism is adapted for detecting at least one component to be measured,
the laser emission module includes:
a laser unit including a plurality of DFB lasers configured to emit an initial detection laser signal in a time division multiplexed manner;
the signal generator is suitable for sending out a first voltage signal and a second voltage signal;
the laser controller is suitable for converting the first voltage signal into a second modulation signal, converting the second voltage signal into a third modulation signal and sending a temperature control signal, wherein under the action of the second modulation signal, the third modulation signal and the temperature control signal, the initial detection laser signal is converted into a specific detection laser signal, the wavelength range of the specific detection laser signal can scan the wavelength corresponding to the absorption peak position of the gas to be detected, and the specific detection laser signal is suitable for being irradiated onto the gas to be detected of the photoacoustic cell, is absorbed by the component to be detected and generates a photoacoustic effect, so as to obtain a second acoustic pressure signal, and the second acoustic pressure signal is suitable for determining the concentration of the component to be detected.
8. The gas concentration detection apparatus according to claim 1, wherein the microphone is mounted at a maximum sound pressure of the photoacoustic cell.
9. The gas concentration detection apparatus according to claim 7, wherein the microphone is adapted to convert the second sound pressure signal into a second current signal when detecting a concentration of a gas to be detected;
the processing mechanism is further adapted to obtain the concentration of the component to be measured according to the second current signal and the calibrated parameter of the photoacoustic mechanism.
10. The gas concentration detection apparatus according to claim 1, wherein the first modulation signal includes a first sub-modulation signal that is a sawtooth wave signal or a triangular wave signal, and a second sub-modulation signal that is a sine wave signal or a square wave signal, and the center wavelength of the calibration laser signal obtained is made the same as the wavelength corresponding to the absorption peak position of the calibration gas by the first sub-modulation signal, so that the wavelength range of the calibration laser signal can sweep the wavelength corresponding to the absorption peak position of the calibration gas, and the second sub-modulation signal is applied at the wavelength corresponding to the absorption peak position of the calibration gas to generate the photoacoustic effect.
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| CN117007531A (en) * | 2023-10-07 | 2023-11-07 | 之江实验室 | Gas concentration detection device and method based on Mie resonance transceiver pair |
| CN117007531B (en) * | 2023-10-07 | 2024-01-23 | 之江实验室 | Gas concentration detection device and method based on Mie resonance transceiver pair |
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