CN115096847A - Single-cavity type multi-component photoacoustic spectroscopy gas detection device and method - Google Patents
Single-cavity type multi-component photoacoustic spectroscopy gas detection device and method Download PDFInfo
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Abstract
The invention relates to a single-cavity multi-component photoacoustic spectrometry gas detection device and a method. The function signal generator outputs the superposition signal to the current driver and outputs the sine reference signal to the phase-locked amplifier. The optical switch controls the modulated laser in a time-sharing manner and outputs the modulated laser to the photoacoustic cell. Modulating laser to penetrate through the gas to be detected to generate a photoacoustic effect; the microphone detects the acoustic signal generated by the photoacoustic effect. The phase-locked amplifier extracts an amplitude signal of a specific wavelength frequency in the sound signal; and the calculation processing unit calculates the concentration information of the gas to be measured according to the amplitude signal. The invention utilizes the optical switch to control a plurality of near infrared lasers in a time-sharing manner, realizes that a single photoacoustic cell detects the concentration of multi-component gas, effectively reduces the cross interference among the multi-component gas and has high sensitivity; effectively reduce instrument cost and volume, anti external interference ability reinforce.
Description
Technical Field
The embodiment of the invention relates to the technical field of trace gas detection, in particular to a single-cavity type multi-component photoacoustic spectroscopy gas detection device and method.
Background
Multi-component trace gas detection has been widely used in the fields of environmental pollution monitoring, industrial production and emission measurement, medical diagnostics, agriculture and food safety. A better environment evaluation system can be formed by simultaneously monitoring various gases such as SO2, NO2, CO2 and the like in atmospheric pollution; when the transformer fails, gases such as CH4 (methane), C2H2 (acetylene), H2, CO2 and the like are generated, and the safety condition and the failure reason of the transformer can be judged according to the standard; in the medical field, various gases exhaled by human bodies can be used as biomarkers for medical diagnosis. Therefore, the simultaneous detection of multi-component gases has become a development trend of future gas detection.
Although conventional methods, such as electrochemical techniques, chemiluminescence and gas chromatography, have been used for gas detection, their sensitivity, selectivity, long-time measurement and off-line operation do not always meet the demanding requirements. The rapid development of the laser technology is benefited, and the photoacoustic spectroscopy technology which is high in speed, high in sensitivity, strong in selectivity and free of background has wide application prospect in the field of multi-component trace gas detection. The principle of the photoacoustic spectroscopy is based on the absorption of gas molecules to be detected on modulated light with a selected proper wavelength to complete the detection of sound waves generated in a gas chamber, and the amplitude of the sound waves is in direct proportion to the gas concentration.
The gas has strong absorption in the middle infrared band and certain coincidence in the near infrared band, so that the common multi-component photoacoustic spectrometry technology is concentrated in the middle infrared band, and the measurement of various gases can be realized by the scheme that a wide-spectrum infrared light source is matched with optical filters with different central wavelengths, so that the cost is low, but the measurement precision and sensitivity are not high, and the cross interference among various gas components is large. The mid-infrared laser is expensive and large in volume, the number of types of gas measured by using a mid-infrared tunable laser is limited, and the volume and cost of the instrument are greatly increased by adopting a plurality of mid-infrared lasers and a plurality of photoacoustic cells or multi-cavity photoacoustic cells. In addition, the middle infrared band optical fiber devices are not mature, and most of the devices adopt a reflector type optical path, so that the interference resistance is poor.
Disclosure of Invention
Aiming at the defects or improvement requirements of the prior art, the invention provides a single-cavity multi-component photoacoustic spectrometry gas detection device and method, which are used for solving the problems of large volume, high cost, poor external interference resistance and the like of the conventional mid-infrared band multi-component photoacoustic spectrometry technology and promoting the popularization and application of photoacoustic spectrometers.
In order to achieve the above object, in a first aspect, an embodiment of the present invention provides a single-cavity multi-component photoacoustic spectroscopy gas detection apparatus, including a function signal generator, a current driver, a laser module, an optical switch, a photoacoustic cell, a microphone, a lock-in amplifier, and a calculation processing unit;
the first output end of the function signal generator is connected with the input end of the current driver and is used for outputting a superposed signal of a sine wave and a sawtooth wave to the current driver; the second output end of the function signal generator is connected with the first input end of the phase-locked amplifier and used for outputting a sinusoidal reference signal to the phase-locked amplifier;
the output end of the current driver is connected with the input end of the laser module and is used for carrying out wavelength modulation on each near-infrared laser in the laser module according to the superposition signal;
the laser module comprises a plurality of near-infrared lasers, and the plurality of near-infrared lasers respectively output modulated lasers with different absorption wavelengths of the gas to be detected after the wavelengths of the plurality of near-infrared lasers are modulated by the current driver;
the input end of the optical switch is connected with the laser module, the output end of the optical switch is connected with the photoacoustic cell and used for time-sharing control over the multi-path modulated laser, and one path of modulated laser is output to the photoacoustic cell every time period;
the gas to be measured is put into the photoacoustic cell in advance, and modulated laser entering the photoacoustic cell penetrates through the gas to be measured to generate a photoacoustic effect;
the microphone is positioned on the photoacoustic cell and used for detecting a sound signal generated by a photoacoustic effect;
the second input end of the phase-locked amplifier is connected with the output end of the microphone and is used for extracting amplitude signals of specific wavelength frequencies in the sound signals according to the sinusoidal reference signals;
and the input end of the calculation processing unit is connected with the output end of the lock-in amplifier and is used for calculating the concentration information of the gas to be detected according to the extracted amplitude signal.
Preferably, the calculation processing unit is further configured to generate feedback control information according to the amplitude signal, and optimize parameters of the function signal generator and the lock-in amplifier through the feedback control information.
Preferably, the calculation processing unit generates feedback control information according to the amplitude signal, and optimizes parameters of the function signal generator and the lock-in amplifier through the feedback control information, which specifically includes:
the calculation processing unit controls the filtering order and the bandwidth of a low-pass filter in the phase-locked amplifier in a feedback mode according to the distortion condition of the amplitude signal waveform, and if the waveform has small peaks and distortion, the filtering order is increased and the filtering bandwidth is reduced; if the waveform is smooth but the signal peak is widened, the filtering order is reduced, and the filtering bandwidth is increased;
the calculation processing unit feeds back the amplitude of the sawtooth wave in the superposed signal output by the function signal generator according to whether the amplitude signal has interference of other gas absorption peaks; and the calculation processing unit feeds back and adjusts the bias current of the superposed signal output by the function signal generator according to the symmetry of the signal peak of the amplitude signal.
Preferably, the laser module is composed of a plurality of near-infrared lasers; the optical switch is provided with a plurality of input ports, and the output ports of the near-infrared lasers in the laser modules are respectively and correspondingly connected with the input ports of the optical switch; the output port of the optical switch is connected with an optical fiber collimator, and the optical fiber collimator is used for collimating laser output by the optical switch.
Preferably, the photoacoustic cell comprises a gas cavity, two buffer cavities, a gas inflow channel, a gas outflow channel and an adjusting frame; wherein, a microphone (8) is arranged at the opening of the upper end of the gas cavity, the two buffer cavities are arranged at the two sides of the gas cavity, and the gas inflow and outflow channels are positioned on the buffer cavities at the two ends; the adjusting frame is positioned at the input end of the photoacoustic cell and used for adjusting the optical fiber collimator to realize optical path calibration.
Preferably, the phase-locked amplifier is connected with the function signal generator through a band-pass filter, and the band-pass filter is used for filtering noise interference of the sinusoidal reference signal in a transmission process; the phase-locked amplifier comprises a low-pass filter, and the filtering order and the bandwidth of the low-pass filter are adjustable.
In a second aspect, an embodiment of the present invention provides a single-cavity multi-component photoacoustic spectroscopy gas detection method, including:
outputting a path of superposed signals of sine waves and sawtooth waves to a current driver through a function signal generator; the function signal generator outputs another path of sinusoidal reference signal to the phase-locked amplifier;
the current driver modulates the wavelength of each near-infrared laser in the laser module according to the superposition signal of the sine wave and the sawtooth wave, and respectively outputs modulated laser with different absorption wavelengths of the gas to be detected;
the multi-path modulated laser is controlled in a time-sharing mode through the optical switch, and one path of modulated laser is output to the photoacoustic cell at each time interval;
the modulated laser entering the photoacoustic cell passes through the gas to be measured which is put in the photoacoustic cell in advance to generate photoacoustic effect,
a microphone positioned above the photoacoustic cell detects a sound signal generated by a photoacoustic effect;
the phase-locked amplifier extracts an amplitude signal of a specific wavelength frequency in the sound signal according to the sinusoidal reference signal;
and the calculation processing unit calculates the concentration information of the gas to be measured according to the extracted amplitude signal.
Preferably, the method further comprises:
and the calculation processing unit generates feedback control information according to the amplitude signal, and optimizes the parameters of the function signal generator and the lock-in amplifier through the feedback control information.
In a third aspect, an embodiment of the present invention provides an electronic device, which includes a memory, a processor, and a computer program stored in the memory and executable on the processor, where the processor executes the computer program to implement the steps of the single-cavity multi-component photoacoustic spectroscopy gas detection method according to the embodiment of the second aspect of the present invention.
In a fourth aspect, embodiments of the present invention provide a non-transitory computer-readable storage medium, on which a computer program is stored, where the computer program, when executed by a processor, implements the steps of the single-cavity multi-component photoacoustic spectroscopy gas detection method according to embodiments of the second aspect of the present invention.
Compared with the prior art, the single-cavity multi-component photoacoustic spectroscopy gas detection device and method provided by the embodiment of the invention have the following beneficial effects:
1) the single-cavity type multi-component photoacoustic spectroscopy gas detection device and method provided by the invention can realize the rapid measurement of the concentration information of the multi-component gas in a single photoacoustic cell, and have high sensitivity.
2) According to the single-cavity multi-component photoacoustic spectroscopy gas detection device and method provided by the invention, the laser module, the optical switch and the photoacoustic cell are connected by adopting the optical fiber, and only one single-cavity photoacoustic cell is adopted.
3) The single-cavity type multi-component photoacoustic spectrometry gas detection device provided by the invention adopts the optical switch to control the output of each path of laser in a time-sharing manner, and each path of laser is separated, so that the cross interference among each component of gas can be effectively reduced.
4) According to the single-cavity type multi-component photoacoustic spectroscopy gas detection device and method, analysis is carried out according to the waveform of the amplitude signal, parameters of the function signal generator and the phase-locked amplifier are controlled in a feedback mode, laser modulation and phase-locked parameters are adjusted, signal quality is improved, and concentration measurement of multi-component gas is more accurate and stable.
Drawings
Fig. 1 is a schematic structural diagram of a single-cavity multi-component photoacoustic spectroscopy gas detection apparatus provided by an embodiment of the present invention;
FIG. 2 is a waveform diagram of an original amplitude signal provided by an embodiment of the present invention;
fig. 3 is a waveform diagram of an amplitude signal after feedback control optimizes system parameters according to an embodiment of the present invention;
FIG. 4 is a flow chart of a single-cavity multi-component photoacoustic spectroscopy gas detection method provided by an embodiment of the present invention;
FIG. 5 is another schematic flow chart of a single-cavity multi-component photoacoustic spectroscopy gas detection method provided by an embodiment of the present invention;
FIG. 6 is a schematic diagram of an electronic device according to an embodiment of the invention;
FIG. 7 is a schematic diagram of a computer-readable storage medium through which an embodiment of the invention is implemented.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The conventional methods, such as electrochemical technology, chemiluminescence method and gas chromatography, are already used for gas detection, but their sensitivity, selectivity, long-time measurement and off-line operation do not always meet the demanding requirements of applications. The rapid development of the laser technology is benefited, and the photoacoustic spectroscopy technology which is high in speed, high in sensitivity, strong in selectivity and free of background has wide application prospect in the field of multi-component trace gas detection.
The gas has strong absorption in the middle infrared band and certain coincidence in the near infrared band, so that the common multi-component photoacoustic spectrometry technology is concentrated in the middle infrared band, and the measurement of various gases can be realized by the scheme that a wide-spectrum infrared light source is matched with optical filters with different central wavelengths, so that the cost is low, but the measurement precision and sensitivity are not high, and the cross interference among various gas components is large. The mid-infrared laser is expensive and large in volume, the number of types of gas measured by using a mid-infrared tunable laser is limited, and the volume and cost of the instrument are greatly increased by adopting a plurality of mid-infrared lasers and a plurality of photoacoustic cells or multi-cavity photoacoustic cells. In addition, the middle infrared band optical fiber devices are not mature, and most of the devices adopt a reflector type optical path, so that the interference resistance is poor.
In view of the above problems in the prior art, the present invention considers that the near-infrared tunable fiber laser has the advantages of narrow line width, stable operation at room temperature, small size, low cost, etc., is easy for fiber coupling, is suitable for wavelength modulation, has no mode hopping within an adjustable range, and is more suitable for being used as a light source for developing an instrumented photoacoustic spectroscopy system. Therefore, the invention designs the near-infrared band multi-component photoacoustic spectroscopy gas detection device and method which have the advantages of compact structure, external interference resistance and high sensitivity and can effectively reduce the cross interference of multi-component gas. The following description and description will proceed with reference being made to several embodiments.
Fig. 1 provides a single-cavity multi-component photoacoustic spectroscopy gas detection apparatus according to an embodiment of the present invention, and referring to fig. 1, the apparatus includes a function signal generator 2, a current driver 1, a laser module 5, an optical switch 6, a photoacoustic cell 7, a microphone 8, a lock-in amplifier 3, and a calculation processing unit 4.
The first output end of the function signal generator 2 is connected with the input end of the current driver 1 and is used for outputting a superposed signal of a sine wave and a sawtooth wave to the current driver; a second output end of the function signal generator 2 is connected with a first input end of the phase-locked amplifier 3 and is used for outputting a sinusoidal reference signal to the phase-locked amplifier;
the output end of the current driver 1 is connected with the input end of the laser module 5, and is used for carrying out wavelength modulation on each near-infrared laser in the laser module 5 according to the superposition signal.
The laser module 5 comprises a plurality of near-infrared lasers, and the plurality of near-infrared lasers respectively output modulated lasers with different absorption wavelengths of the gas to be measured after being modulated by the wavelength of the current driver 1.
The input end of the optical switch 6 is connected with the laser module 5, the output end of the optical switch 6 is connected with the photoacoustic cell 7 and is used for time-sharing control of the multi-path modulated laser, and one path of modulated laser is output to the photoacoustic cell 7 every time period.
The gas to be measured is put into the photoacoustic cell 7 in advance, and the modulated laser entering the photoacoustic cell 7 penetrates through the gas to be measured to generate a photoacoustic effect.
The microphone 8 is located on the photoacoustic cell 7 and is used for detecting acoustic signals generated by the photoacoustic effect.
The second input end of the lock-in amplifier 3 is connected to the output end of the microphone 8, and is configured to extract an amplitude signal of a specific wavelength frequency in the sound signal according to the sinusoidal reference signal.
The input end of the calculation processing unit 4 is connected with the output end of the lock-in amplifier 3 and is used for calculating the concentration information of the gas to be measured according to the extracted amplitude signal.
Specifically, referring to fig. 1, the optical switch 6 has a plurality of input ports, and each input port of the optical switch 6 is connected to the output ports of the plurality of near-infrared lasers (51-56) of the laser module 5 through an optical fiber, so that compared with a scheme in which only a spatial light path can be adopted in a mid-infrared band, the structure is simple, and the interference immunity is strong. The optical switch 6 has an output port connected to an optical fiber collimator for collimating the laser light output from the optical switch 6. The laser of each modulation path of the laser module corresponds to the absorption wavelength of a gas to be measured, and therefore the measurement of the concentration information of the gas to be measured is achieved. The optical switch 6 outputs one path of modulated laser at a time in a time-sharing control mode, the switching speed is high, the cycle output of the modulated laser can be completed quickly, the measuring speed is greatly improved, the quick and high-sensitivity measurement of the multi-component gas is realized, and the detection of the multi-component gas is not interfered by the separation of the multi-path laser.
According to the single-cavity multi-component photoacoustic spectroscopy gas detection device provided by the invention, the laser module, the optical switch and the photoacoustic cell are connected by adopting the optical fiber, and only one single-cavity photoacoustic cell is adopted. The optical switch is adopted to control the output of each path of laser in a time-sharing way, and each path of laser is separated, so that the cross interference among each component gas can be effectively reduced.
On the basis of the above embodiment, the calculation processing unit 4 is further configured to generate feedback control information according to the amplitude signal, and optimize parameters of the function signal generator 2 and the lock-in amplifier 3 through the feedback control information.
Specifically, the calculation processing unit 4 feedback-controls the filtering order and bandwidth of the low-pass filter in the lock-in amplifier 3 according to the distortion condition of the amplitude signal waveform, and if the waveform has small peak and distortion, the filtering order is properly increased and the filtering bandwidth is reduced; if the waveform is smooth but the signal peak is widened, the filtering order is reduced, and the filtering bandwidth is increased; thereby extracting a more accurate amplitude signal.
The calculation processing unit 4 feeds back the amplitude of the sawtooth wave in the superimposed signal output by the adjustment function signal generator 2 according to whether the amplitude signal has interference of other gas absorption peaks, so as to adjust the wavelength scanning range of the laser and reduce the interference of other gases. The calculation processing unit 4 feeds back and adjusts the bias current of the superposition signal output by the function signal generator 2 according to the symmetry of the signal peak of the amplitude signal, so as to adjust the central wavelength in the wavelength scanning, so that the gas is fully absorbed, and the signal waveform is more accurate. As shown in fig. 2 and 3, the optimization effect is good when the amplitude signal waveforms before and after the feedback control of the calculation processing unit are calculated.
On the basis of the above embodiments, the laser module 5 is composed of a plurality of near-infrared lasers; the optical switch 6 has a plurality of input ports, and the output ports of the near-infrared lasers in the laser module 5 are respectively and correspondingly connected with the input ports of the optical switch 6; the output port of the optical switch 6 is connected with an optical fiber collimator, and the optical fiber collimator is used for collimating the laser output by the optical switch 6.
On the basis of the above embodiments, the photoacoustic cell 7 includes a gas cavity, two buffer cavities, a gas inflow channel, a gas outflow channel, and an adjustment frame; wherein, a microphone 8 is arranged at the opening of the upper end of the gas cavity, the two buffer cavities are arranged at the two sides of the gas cavity, and the gas inflow and outflow channels are positioned on the buffer cavities at the two ends; the adjusting frame is positioned at the input end of the photoacoustic cell and used for adjusting the optical fiber collimator to realize optical path calibration.
On the basis of the above embodiments, the lock-in amplifier 3 and the function signal generator 2 are connected through a band-pass filter, and the band-pass filter is used for filtering noise interference of the sinusoidal reference signal in the transmission process; the lock-in amplifier 3 comprises a low-pass filter, the filtering order and the bandwidth of which are adjustable.
Fig. 4 is a flowchart of a single-cavity multi-component photoacoustic spectroscopy gas detection method provided by an embodiment of the present invention, and referring to fig. 4, the method includes:
s1, outputting a path of superposed signal of sine wave and sawtooth wave to the current driver through the function signal generator; the function signal generator outputs another path of sinusoidal reference signal to the phase-locked amplifier;
s2, the current driver modulates the wavelength of each near-infrared laser in the laser module according to the superposition signal of the sine wave and the sawtooth wave, and respectively outputs modulated laser with different absorption wavelengths of the gas to be measured;
s3, time-sharing control is carried out on the multi-path modulated laser through the optical switch, and one path of modulated laser is output to the photoacoustic cell at each time interval;
s4, the modulated laser entering the photoacoustic cell passes through the gas to be measured which is put in the photoacoustic cell in advance to generate a photoacoustic effect, and a microphone positioned above the photoacoustic cell detects a sound signal generated by the photoacoustic effect;
s5, extracting amplitude signals of specific wavelength frequencies in the sound signals by the phase-locked amplifier according to the sinusoidal reference signals;
and S6, the calculation processing unit calculates the concentration information of the gas to be measured according to the extracted amplitude signal.
Furthermore, the calculation processing unit also generates feedback control information according to the amplitude signal, and optimizes the parameters of the function signal generator and the phase-locked amplifier through the feedback control information.
Specifically, the calculation processing unit 4 feedback-controls the filtering order and bandwidth of the low-pass filter in the lock-in amplifier 3 according to the distortion condition of the amplitude signal waveform, and if the waveform has small peak and distortion, the filtering order is properly increased and the filtering bandwidth is reduced; if the waveform is smooth but the signal peak is widened, the filtering order is reduced, and the filtering bandwidth is increased; thereby extracting a more accurate amplitude signal. The calculation processing unit 4 feeds back the amplitude of the sawtooth wave in the superimposed signal output by the adjustment function signal generator 2 according to whether the amplitude signal has interference of other gas absorption peaks, so as to adjust the wavelength scanning range of the laser and reduce the interference of other gases. The calculation processing unit 4 feeds back and adjusts the bias current of the superposed signal output by the function signal generator 2 according to the symmetry of the signal peak of the amplitude signal, so as to adjust the central wavelength in the wavelength scanning, so that the gas absorption is sufficient, and the signal waveform is more accurate. As shown in fig. 2 and 3, the optimization effect is good for the amplitude signal waveform before and after the feedback control of the calculation processing unit.
Fig. 5 is another schematic flow diagram of a single-cavity multi-component photoacoustic spectroscopy gas detection method provided in an embodiment of the present invention, and referring to fig. 5, in an embodiment, the single-cavity multi-component photoacoustic spectroscopy gas detection method includes the following steps 1 to 10:
And 2, the current driver modulates the wavelength of the near-infrared laser in the laser module according to the superposition signal of the sine wave and the sawtooth wave in the step 1, and outputs modulated laser corresponding to various gas absorption wavelengths.
And 3, carrying out time-sharing control on the multiple paths of laser in the step 2 by using an optical switch, outputting one path of laser every time, and collimating the laser at an output end by using an optical fiber collimator.
And 4, controlling the multi-component gas to be detected to enter the photoacoustic cell through the gas inflow and outflow channel of the photoacoustic cell, and enabling the collimated laser in the step 3 to penetrate through the gas to be detected to generate a photoacoustic effect.
And 5, detecting the sound signal generated by the photoacoustic effect in the step 4 by a microphone positioned above the photoacoustic cell.
And 6, extracting the amplitude of the specific frequency signal of the sound signal in the step 5 by using a phase-locked amplifier.
And 7, processing the amplitude signal in the step 6 by a calculation processing unit, analyzing the waveform of the amplitude signal, extracting the peak value of the waveform of the amplitude signal, and calculating the concentration information of the gas to be detected. And simultaneously analyzing the distortion condition of the amplitude signal waveform to generate a feedback control signal for optimization in the next round of cycle measurement.
And 8, completing the cyclic switching of each path of laser in a short time through the optical switch, and completing the rapid measurement of the concentration information of the multi-component gas.
The feedback control signals generated in step 9 and step 7 will optimize the parameters in the measurement system from the second round. According to the distortion condition of the amplitude signal waveform, the filtering order and the bandwidth of a low-pass filter in the phase-locked amplifier are controlled in a feedback mode, if the waveform has small peaks and distortion, the filtering order is properly increased, and the filtering bandwidth is reduced; if the waveform is smooth but the signal peak is widened, the filtering order is properly reduced, and the filtering bandwidth is increased; thereby extracting a more accurate amplitude signal; according to whether the amplitude signal has interference of other gas absorption peaks or not, the amplitude of a sawtooth wave in the current driving signal is adjusted in a feedback mode to adjust the wavelength scanning range of the laser and reduce interference of other gases; according to the symmetry of the signal peak, the bias current of the current driving signal is fed back and adjusted to adjust the central wavelength in wavelength scanning, so that gas absorption is sufficient, and the signal waveform is more accurate.
And step 10, circulating the steps 1 to 9 to obtain stable and accurate concentration information of the multi-component gas.
Fig. 6 is a schematic diagram of an embodiment of an electronic device according to an embodiment of the present invention. As shown in fig. 6, an embodiment of the present invention provides an electronic device 500, which includes a memory 510, a processor 520, and a computer program 511 stored in the memory 520 and executable on the processor 520, wherein the processor 520 executes the computer program 511 to implement the following steps:
outputting a path of superposed signals of sine waves and sawtooth waves to a current driver through a function signal generator; the function signal generator outputs another path of sinusoidal reference signal to the phase-locked amplifier;
the current driver modulates the wavelength of each near-infrared laser in the laser module according to the superposition signal of the sine wave and the sawtooth wave, and respectively outputs modulated laser with different absorption wavelengths of the gas to be detected;
the multi-path modulated laser is controlled in a time-sharing mode through the optical switch, and one path of modulated laser is output to the photoacoustic cell at each time interval;
the modulated laser entering the photoacoustic cell passes through the gas to be measured which is put into the photoacoustic cell in advance to generate a photoacoustic effect,
a microphone positioned above the photoacoustic cell detects a sound signal generated by a photoacoustic effect;
the phase-locked amplifier extracts an amplitude signal of a specific wavelength frequency in the sound signal according to the sinusoidal reference signal;
and the calculation processing unit calculates the concentration information of the gas to be measured according to the extracted amplitude signal.
Fig. 7 is a schematic diagram of an embodiment of a computer-readable storage medium according to an embodiment of the present invention. As shown in fig. 7, the present embodiment provides a computer-readable storage medium 600 having a computer program 611 stored thereon, the computer program 611, when executed by a processor, implementing the steps of:
outputting a path of superposed signals of sine waves and sawtooth waves to a current driver through a function signal generator; the function signal generator outputs the other path of sinusoidal reference signal to the phase-locked amplifier;
the current driver modulates the wavelength of each near-infrared laser in the laser module according to the superposition signal of the sine wave and the sawtooth wave, and respectively outputs modulated laser with different absorption wavelengths of the gas to be detected;
the multi-path modulated laser is controlled in a time-sharing mode through the optical switch, and one path of modulated laser is output to the photoacoustic cell at each time interval;
the modulated laser entering the photoacoustic cell passes through the gas to be measured which is put into the photoacoustic cell in advance to generate a photoacoustic effect,
a microphone positioned above the photoacoustic cell detects a sound signal generated by a photoacoustic effect;
the phase-locked amplifier extracts an amplitude signal of a specific wavelength frequency in the sound signal according to the sinusoidal reference signal;
and the calculation processing unit calculates the concentration information of the gas to be detected according to the extracted amplitude signal.
In summary, compared with the prior art, the single-cavity multi-component photoacoustic spectroscopy gas detection apparatus and method provided by the embodiment of the present invention have the following beneficial effects:
1) the single-cavity type multi-component photoacoustic spectroscopy gas detection device and method provided by the invention can realize the rapid measurement of the concentration information of the multi-component gas in a single photoacoustic cell, and have high sensitivity.
2) According to the single-cavity multi-component photoacoustic spectroscopy gas detection device and method provided by the invention, the laser module, the optical switch and the photoacoustic cell are connected by adopting the optical fiber, only one single-cavity photoacoustic cell is provided, compared with the scheme of a multi-photoacoustic cell or multi-cavity photoacoustic cell structure and a mid-infrared band space optical path in the prior art, the structure is simpler and more compact, the processing and assembly are simpler, the anti-interference capability is strong, and the laser adopts a near-infrared DFB laser, so that the cost can be effectively reduced.
3) The single-cavity type multi-component photoacoustic spectrometry gas detection device provided by the invention adopts the optical switch to control the output of each path of laser in a time-sharing manner, and each path of laser is separated, so that the cross interference among each component of gas can be effectively reduced.
4) According to the single-cavity type multi-component photoacoustic spectroscopy gas detection device and method, analysis is carried out according to the waveform of the amplitude signal, parameters of the function signal generator and the phase-locked amplifier are controlled in a feedback mode, laser modulation and phase-locked parameters are adjusted, signal quality is improved, and concentration measurement of multi-component gas is more accurate and stable.
It should be noted that, in the foregoing embodiments, the descriptions of the respective embodiments have respective emphasis, and reference may be made to relevant descriptions of other embodiments for parts that are not described in detail in a certain embodiment.
As will be appreciated by one skilled in the art, embodiments of the present invention may be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (10)
1. The single-cavity type multi-component photoacoustic spectroscopy gas detection device is characterized by comprising a function signal generator (2), a current driver (1), a laser module (5), an optical switch (6), a photoacoustic cell (7), a microphone (8), a phase-locked amplifier (3) and a calculation processing unit (4);
the first output end of the function signal generator (2) is connected with the input end of the current driver (1) and is used for outputting a superposed signal of a sine wave and a sawtooth wave to the current driver (1); the second output end of the function signal generator (2) is connected with the first input end of the phase-locked amplifier (3) and is used for outputting a sinusoidal reference signal to the phase-locked amplifier;
the output end of the current driver (1) is connected with the input end of the laser module (5) and is used for carrying out wavelength modulation on each near-infrared laser in the laser module (5) according to the superposition signal;
the laser module (5) comprises a plurality of near-infrared lasers, and the plurality of near-infrared lasers respectively output modulated lasers with different absorption wavelengths of the gas to be measured after the wavelengths of the plurality of near-infrared lasers are modulated by the current driver (1);
the input end of the optical switch (6) is connected with the laser module (5), the output end of the optical switch (6) is connected with the photoacoustic cell (7) and is used for time-sharing control over the multi-path modulated laser, and one path of modulated laser is output to the photoacoustic cell (7) at each time interval;
the gas to be detected is put into the photoacoustic cell (7) in advance, and the modulated laser entering the photoacoustic cell (7) penetrates through the gas to be detected to generate a photoacoustic effect;
the microphone (8) is positioned on the photoacoustic cell (7) and used for detecting a sound signal generated by a photoacoustic effect;
the second input end of the phase-locked amplifier (3) is connected with the output end of the microphone (8) and is used for extracting an amplitude signal of a specific wavelength frequency in the sound signal according to the sinusoidal reference signal;
the input end of the calculation processing unit (4) is connected with the output end of the phase-locked amplifier (3) and used for calculating the concentration information of the gas to be detected according to the extracted amplitude signal.
2. A single-chamber multi-component photoacoustic spectroscopy gas-detecting apparatus according to claim 1, characterized in that the calculation processing unit (4) is further configured to generate feedback control information from the amplitude signal, through which the parameters of the function-signal generator (2) and the lock-in amplifier (3) are optimized.
3. The gas detection apparatus according to claim 2, wherein the calculation processing unit (4) generates feedback control information according to the amplitude signal, and optimizes parameters of the function signal generator and the lock-in amplifier according to the feedback control information, and specifically comprises:
the calculation processing unit (4) controls the filtering order and the bandwidth of the low-pass filter in the phase-locked amplifier (3) in a feedback mode according to the distortion condition of the amplitude signal waveform, and if the waveform has small peaks and distortion, the filtering order is increased and the filtering bandwidth is reduced; if the waveform is smooth but the signal peak is widened, the filtering order is reduced, and the filtering bandwidth is increased;
the calculation processing unit (4) feeds back the amplitude of the sawtooth wave in the superposed signal output by the adjustment function signal generator (2) according to whether the amplitude signal has the interference of other gas absorption peaks; and the calculation processing unit (4) feeds back and adjusts the bias current of the superposed signal output by the function signal generator (2) according to the symmetry of the signal peak of the amplitude signal.
4. A single-cavity multicomponent photoacoustic spectrometry gas-detection apparatus according to claim 1, wherein said laser module (5) is composed of a plurality of near-infrared lasers; the optical switch (6) is provided with a plurality of input ports, and the output ports of the near-infrared lasers in the laser modules (5) are respectively and correspondingly connected with the input ports of the optical switch (6); the output port of the optical switch (6) is connected with an optical fiber collimator, and the optical fiber collimator is used for collimating the laser output by the optical switch (6).
5. A single-cavity multi-component photoacoustic spectroscopy gas-detecting device according to claim 1, characterized in that the photoacoustic cell (7) contains a gas cavity, two buffer cavities, a gas inflow channel, a gas outflow channel and a tuning frame; wherein, a microphone (8) is arranged at the opening of the upper end of the gas cavity, the two buffer cavities are arranged at the two sides of the gas cavity, and the gas inflow and outflow channels are positioned on the buffer cavities at the two ends; the adjusting frame is positioned at the input end of the photoacoustic cell and used for adjusting the optical fiber collimator to realize optical path calibration.
6. The gas detection apparatus according to claim 1, wherein the lock-in amplifier (3) and the functional signal generator (2) are connected via a band-pass filter, and the band-pass filter is used for filtering noise interference of the sinusoidal reference signal during transmission; the phase-locked amplifier (3) comprises a low-pass filter, and the filtering order and the bandwidth of the low-pass filter are adjustable.
7. A multi-component photoacoustic spectrometry gas detection method based on the single-cavity multi-component photoacoustic spectrometry gas detection apparatus according to any one of claims 1 to 6, comprising:
outputting a path of superposed signals of sine waves and sawtooth waves to a current driver through a function signal generator; the function signal generator outputs another path of sinusoidal reference signal to the phase-locked amplifier;
the current driver modulates the wavelength of each near-infrared laser in the laser module according to the superposition signal of the sine wave and the sawtooth wave, and respectively outputs modulated laser with different absorption wavelengths of the gas to be detected;
the multi-path modulated laser is controlled in a time-sharing mode through the optical switch, and one path of modulated laser is output to the photoacoustic cell at each time interval;
modulated laser entering the photoacoustic cell penetrates through gas to be detected which is put into the photoacoustic cell in advance to generate a photoacoustic effect, and a microphone positioned above the photoacoustic cell detects a sound signal generated by the photoacoustic effect;
the phase-locked amplifier extracts an amplitude signal of a specific wavelength frequency in the sound signal according to the sinusoidal reference signal;
and the calculation processing unit calculates the concentration information of the gas to be detected according to the extracted amplitude signal.
8. The multi-component photoacoustic spectroscopy gas-detection method of claim 7, further comprising:
and the calculation processing unit generates feedback control information according to the amplitude signal, and optimizes the parameters of the function signal generator and the phase-locked amplifier through the feedback control information.
9. An electronic device, comprising:
a memory for storing a computer software program;
a processor for reading and executing the computer software program to implement the single-cavity multi-component photoacoustic spectroscopy gas detection method of any one of claims 7 to 8.
10. A non-transitory computer readable storage medium, wherein the storage medium stores therein a computer software program for implementing the single-cavity multi-component photoacoustic spectroscopy gas detection method according to any one of claims 7 to 8.
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