High-sensitivity wide-range gas sensing system and related measurement method

Abstract

The embodiment of the invention discloses a high-sensitivity wide-range gas sensing system and a measuring method. The system comprises a light source module, a photoacoustic resonant cavity module and a data processing module. The light source module is used for generating incident light; the incident light is absorbed by the gas to be detected in the photoacoustic resonant cavity module to generate a photoacoustic signal; and the data processing module processes the photoacoustic signal and inverts the concentration of the gas to be detected. The detection sensitivity of the system is improved through an optical and acoustic dual-resonance method, high-concentration gas detection is realized by using a resonant frequency tracking technology, the problem of inaccurate detection of gas in a high-concentration range is solved, and ultra-wide-range measurement of gas is realized.

Description

Technical Field

[0001] The present application relates to the field of gas detection technology, and in particular to a high-sensitivity and wide-range gas sensing system and a related measurement method. Background Art

[0002] Gas concentration detection has a wide range of applications in the industrial field, such as the concentration detection of acetylene (C2H2) gas. C2H2 is a colorless and odorless gas that easily combines with air to form explosive mixtures within a wide concentration range. Low-concentration C2H2 detection provides an early warning for gas leaks, and high-concentration C2H2 detection can effectively prevent gas explosions. Therefore, the development of a highly sensitive, wide-range sensor is of great significance in the industrial field.

[0003] There are many methods for gas detection, such as gas chromatography, electrochemical method, catalytic combustion method, semiconductor method, etc. Compared with these traditional detection methods, spectroscopy has the advantages of good selectivity, high sensitivity, and fast measurement speed. Among them, photoacoustic spectroscopy is a gas detection method developed in recent years because it has almost no background absorption. Photoacoustic spectroscopy is a spectral detection technology based on the photoacoustic effect. It realizes detection by measuring the sound wave signal generated by the photoacoustic effect. It is an indirect measurement method without background signal interference.

[0004] However, the detection sensitivity of gas sensors based on photoacoustic spectroscopy is not high at present, and there is still a certain distance from practical application. In addition, as the gas concentration increases, the absorption capacity of gas molecules becomes nonlinear, the amplitude of the photoacoustic signal reaches saturation, and the acoustic resonance frequency will drift in the high concentration background, so it is difficult for a single sensor to accurately achieve ultra-wide range detection from ppb to % level. Summary of the invention

[0005] The embodiments of the present application provide a highly sensitive and wide-range gas sensing system and a related measurement method, which can improve the sensitivity of gas detection and realize gas concentration detection in an ultra-wide range.

[0006] In a first aspect, an embodiment of the present application provides a high-sensitivity wide-range gas sensing system, the high-sensitivity wide-range gas sensing system comprising a light source module, a photoacoustic resonant cavity module and a data processing module, wherein:

[0007] The light source module is used to generate incident light;

[0008] The photoacoustic resonant cavity module is connected to the light source module, and the incident light is absorbed by the gas to be measured in the photoacoustic resonant cavity module to generate a photoacoustic signal;

[0009] The data processing module is connected to the photoacoustic resonant cavity module and is used to process the photoacoustic signal and invert the concentration of the gas to be measured;

[0010] The light source module includes a laser, a current driver, a temperature controller and an optical fiber amplifier, wherein the laser outputs a laser beam according to a preset laser power, and the optical fiber amplifier amplifies the laser beam;

[0011] The photoacoustic resonant cavity module comprises a cavity-enhanced photoacoustic cell and a microphone, wherein the amplified laser beam is coupled into the cavity-enhanced photoacoustic cell at a preset angle, and the effective optical power of the laser beam is increased under the optical-acoustic dual resonance mode of the cavity-enhanced photoacoustic cell, so that the gas to be measured in the cavity-enhanced photoacoustic cell is fully excited to generate a photoacoustic signal;

[0012] The microphone is installed at the center of the cavity-enhanced photoacoustic cell to detect the photoacoustic signal;

[0013] The data processing module includes a phase-locked amplifier, a data acquisition card and a host computer, wherein the host computer controls the data acquisition card to generate a driving signal, controls the current driver according to the driving signal, and drives the laser through the current driver and the temperature controller;

[0014] The phase-locked amplifier extracts a photoacoustic signal related to the gas concentration from the cavity-enhanced photoacoustic cell, and transmits the photoacoustic signal to the host computer through the data acquisition card, so that the host computer performs high-sensitivity gas detection in a low concentration range based on the corresponding relationship between the amplitude of the preset photoacoustic signal and the gas concentration, and performs gas detection in a high concentration range for the gas to be tested using the resonance frequency tracking technology.

[0015] In a second aspect, an embodiment of the present application further provides a high-sensitivity wide-range gas concentration measurement method, which is applied to a data processing module in the high-sensitivity wide-range gas sensing system provided in the first aspect, and the method includes:

[0016] Acquire the photoacoustic signal corresponding to the gas to be tested transmitted by the data acquisition card;

[0017] Determining a target concentration range of the gas to be measured according to the photoacoustic signal;

[0018] If the target concentration range is a low concentration range, the target gas concentration of the gas to be measured is determined according to a preset corresponding relationship between the amplitude of the photoacoustic signal and the gas concentration and the amplitude of the target photoacoustic signal;

[0019] If the target concentration range is a high concentration range, determining the target resonant frequency corresponding to the gas to be measured according to a preset resonant frequency tracking technology;

[0020] The target gas concentration of the gas to be measured is determined according to the corresponding relationship between the preset resonant frequency and the gas concentration and the target resonant frequency.

[0021] In a third aspect, an embodiment of the present application further provides a high-sensitivity wide-range gas concentration measurement device, which is deployed in a data processing module and includes a transceiver unit and a processing unit, wherein:

[0022] The transceiver unit is used to obtain the photoacoustic signal corresponding to the gas to be measured transmitted by the data acquisition card;

[0023] The processing unit is used to determine the target concentration range of the gas to be measured according to the photoacoustic signal; if the target concentration range is a low concentration range, the target gas concentration of the gas to be measured is determined according to the corresponding relationship between the amplitude of the preset photoacoustic signal and the gas concentration and the amplitude of the target photoacoustic signal; if the target concentration range is a high concentration range, the target resonant frequency corresponding to the gas to be measured is determined according to the preset resonant frequency tracking technology; the target gas concentration of the gas to be measured is determined according to the corresponding relationship between the preset resonant frequency and the gas concentration and the target resonant frequency.

[0024] In a fourth aspect, an embodiment of the present application further provides a host computer, which includes a memory and a processor, wherein a computer program is stored in the memory, and when the processor executes the computer program, the method in the above-mentioned second aspect is implemented.

[0025] In a fifth aspect, an embodiment of the present application further provides a computer-readable storage medium, wherein the storage medium stores a computer program, wherein the computer program includes program instructions, and wherein the program instructions, when executed by a processor, can implement the method in the above-mentioned second aspect.

[0026] The embodiment of the present application provides a high-sensitivity and wide-range gas sensing system and related measurement methods. Among them, the high-sensitivity and wide-range gas sensing system includes a light source module, a photoacoustic resonant cavity module and a data processing module. On the one hand, the cavity-enhanced photoacoustic cell in the present application can increase the effective optical power of the laser beam, so that the gas to be measured in the cavity-enhanced photoacoustic cell is fully excited, thereby improving the sensitivity of gas detection; on the other hand, the upper computer is preset with the corresponding relationship between the amplitude of the photoacoustic signal and the gas concentration and the resonant frequency tracking technology. The corresponding relationship between the amplitude of the photoacoustic signal and the gas concentration can realize the gas concentration detection in the low concentration range, and the resonant frequency tracking technology can realize the gas concentration detection in the high concentration range. It can be seen that through the present application, a single sensor can be used to simultaneously realize high-sensitivity and ultra-wide range gas detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0028] Figure 1 A schematic diagram of the structure of a high-sensitivity and wide-range gas sensing system provided in an embodiment of the present application;

[0029] Figure 2 A detailed structural diagram of a high-sensitivity and wide-range gas sensing system provided in an embodiment of the present application;

[0030] Figure 3 A schematic diagram of the structure of a photoacoustic resonant cavity module provided in an embodiment of the present application;

[0031] Figure 4 A schematic diagram of a process for measuring gas concentration with high sensitivity and wide range provided in an embodiment of the present application;

[0032] Figure 5 A schematic diagram of a sub-process of a high-sensitivity and wide-range gas concentration measurement method provided in an embodiment of the present application;

[0033] Figure 6 A schematic block diagram of a highly sensitive and wide-range gas concentration measurement device provided in an embodiment of the present application;

[0034] Figure 7 A schematic block diagram of a host computer provided in an embodiment of the present application. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0036] It should be understood that when used in this specification and the appended claims, the terms "include" and "comprises" indicate the presence of described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof.

[0037] It should also be understood that the terms used in this application specification are only for the purpose of describing specific embodiments and are not intended to limit the application. As used in this application specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0038] It should be further understood that the term “and / or” used in the specification and appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0039] The embodiments of the present application provide a high-sensitivity and wide-range gas sensing system and a related measurement method.

[0040] The following is an explanation of some of the terms designed in this application:

[0041] Cavity-enhanced photoacoustic spectroscopy: a novel technique based on the coupling of photoacoustic spectroscopy and cavity-enhanced technology.

[0042] Photoacoustic spectroscopy: a new type of spectral analysis and detection technology based on the photoacoustic effect.

[0043] Photoacoustic signal: The acoustic signal generated when an object absorbs a pulsed laser.

[0044] Acoustic resonance frequency tracking technology: technology that automatically tracks the acoustic resonance frequency.

[0045] Detection limit: The lowest concentration or content of the substance being tested that can be accurately and quantitatively determined using a specific method, provided that the limited error meets the predetermined requirements.

[0046] Fineness: It is an important parameter of optical resonator, which is used to describe the performance of optical resonator. High fineness can be used to improve the sensitivity of sensor.

[0047] See also Figure 1 , Figure 1 This is a schematic diagram of the structure of a high-sensitivity wide-range gas sensing system provided in the present application. The high-sensitivity wide-range gas sensing system includes a light source module 10, a photoacoustic resonant cavity module 20 and a data processing module 30, wherein:

[0048] The light source module 10 is used to generate incident light;

[0049] The photoacoustic resonant cavity module 20 is used to connect to the light source module 10, and the incident light is absorbed by the gas to be measured in the photoacoustic resonant cavity module 20 to generate a photoacoustic signal;

[0050] The data processing module 30 is connected to the photoacoustic resonant cavity module 20 and is used to process the photoacoustic signal and invert the concentration of the gas to be measured.

[0051] See also Figure 2 , Figure 2 A specific structural schematic diagram of a high-sensitivity wide-range gas sensing system provided in this application, wherein:

[0052] The light source module 10 includes a laser 101, a current driver 102, a temperature controller 103 and a fiber amplifier 104, wherein the laser 101 outputs a laser beam according to a preset laser power, and the laser beam is amplified by the fiber amplifier 104;

[0053] The photoacoustic resonant cavity module 20 includes a cavity-enhanced photoacoustic cell 201 and a microphone 202, wherein the amplified laser beam is coupled into the cavity-enhanced photoacoustic cell 201 at a preset angle, and the effective optical power of the laser beam is increased in the optical-acoustic dual resonance mode of the cavity-enhanced photoacoustic cell 201, so that the gas to be measured in the cavity-enhanced photoacoustic cell 201 is fully excited to generate a photoacoustic signal;

[0054] A microphone 202 is installed at the center of the cavity-enhanced photoacoustic cell 201 to detect photoacoustic signals;

[0055] The data processing module 30 includes a phase-locked amplifier 301, a data acquisition card 302 and a host computer 303, wherein the host computer 303 controls the data acquisition card 302 to generate a driving signal, controls the current driver 102 according to the driving signal, and drives the laser 101 through the current driver 102 and the temperature controller 103;

[0056] The phase-locked amplifier 301 extracts the photoacoustic signal related to the gas concentration from the cavity-enhanced photoacoustic cell 201, and transmits the photoacoustic signal to the host computer 303 through the data acquisition card 302, so that the host computer 303 can perform high-sensitivity gas detection in a low concentration range based on the corresponding relationship between the amplitude of the preset photoacoustic signal and the gas concentration, and perform gas detection in a high concentration range for the gas to be tested using the resonant frequency tracking technology.

[0057] Specifically, the current driver 102 is responsible for controlling the output power and frequency of the laser 101 , while the temperature controller 103 is responsible for controlling the operating temperature of the laser 101 . Reasonable configuration and precise control of the two can not only improve the performance and working stability of the laser 101 , but also extend the service life of the laser 101 .

[0058] In some embodiments, the optical fiber amplifier 104 provided in the present application is an erbium-doped optical fiber amplifier, and the output power of the laser 101, that is, the preset laser power, is 10 mW-20 mW.

[0059] Furthermore, in some embodiments, the gas inlet of the cavity enhanced photoacoustic cell in the present application is connected to the gas mixing system, the gas outlet of the cavity enhanced photoacoustic cell 201 is connected to the vacuum pump, and the vacuum pump is connected to the exhaust gas tank.

[0060] The gas to be tested includes acetylene, ammonia or carbon dioxide gas.

[0061] When the gas to be tested is C2H2 gas, during the experiment, standard C2H2 gas and pure nitrogen (N2) can be used to prepare C2H2 gas of different concentrations through a gas mixing system to achieve dynamic measurement of the gas, wherein a vacuum pump is used to extract the gas in the cavity enhanced photoacoustic cell 201 and discharge the extracted gas into the exhaust gas pool to avoid polluting the environment.

[0062] See also Figure 3 , Figure 3 This is a structural schematic diagram of the photoacoustic resonant cavity module 20 provided in the present application. The cavity-enhanced photoacoustic cell 201 includes an acoustic resonator 2011, an optical resonator 2012 and two high-reflection mirrors 2013. The longitudinal mode of the optical resonator 2012 resonates with the frequency of the laser beam to form an optical standing wave between the two high-reflection mirrors 2013. The acoustic resonator 2011 uses a specially designed H-shaped structure to form an acoustic standing wave inside. The two high-reflection mirrors 2013 are respectively installed on both sides of the cavity-enhanced photoacoustic cell. In the present application, the reflectivity of the high-reflection mirror 2013 is 99%-99.999999%, and the microphone 202 is a micro-electromechanical system microphone.

[0063] Specifically, the present application places two high-reflectivity high-reflection mirrors 2013 on both sides of a specially designed H-type acoustic resonator to form a cavity-enhanced photoacoustic pool 201, realizes optical-acoustic double resonance, and can realize high-precision low-concentration gas detection, such as detecting C2H2 gas below 20%. When the frequency of the incident laser beam resonates with the longitudinal mode of the optical resonator 2012, a standing wave is formed between the two high-reflection mirrors 2013 of the optical resonator 2012. The high-fineness optical resonator 2012 in this embodiment significantly enhances the photoacoustic signal by increasing the effective laser power. In addition, the acoustic resonator 2011 in this embodiment can also amplify the photoacoustic signal by forming an acoustic standing wave inside it, and the microphone 202 is installed in the center of the resonant cavity, corresponding to the antinode of the acoustic standing wave. It can be seen that the cavity-enhanced photoacoustic pool 201 in this embodiment can greatly improve the sensitivity of photoacoustic spectroscopy detection through optical and acoustic double resonance.

[0064] Wherein, high reflective mirrors 2013 are arranged in the buffer cavities on both sides of the cavity enhanced photoacoustic cell 201. The fineness F of the high reflective mirrors 2013 is a key factor in determining the optical power accumulation. The fineness F can be expressed as:

[0065]

[0066] Where R is the reflectivity of the two high reflective mirrors 2013. When the laser frequency is locked with the fundamental mode of the optical resonant cavity, the power in the cavity will be significantly enhanced. The power enhancement factor G can be obtained by formula (2), that is:

[0067]

[0068] When R is 99.4%, the fineness F can be calculated from equations (1) and (2) to be 522, and the power enhancement factor G to be 166. It can be seen that the cavity-enhanced photoacoustic cell 201 provided in the present application has a strong optical power accumulation capability and a high gas concentration detection sensitivity.

[0069] When conducting experiments to verify the performance of the cavity-enhanced photoacoustic cell 201 provided in this application, a gas mixing system is used to prepare gas samples using a dynamic gas distribution method, and the prepared gas samples are introduced into the gas absorption cell in sequence, and each sample is measured continuously for 50 seconds. When the sensor system is configured as a single-pass photoacoustic cell, by observing the photoacoustic signal waveform of 2000ppm C2H2, the standard deviation noise is calculated to be 0.00185V, and the signal-to-noise ratio is calculated to be 962, and the corresponding detection limit is 2.08ppm. When the sensor system is configured as a cavity-enhanced photoacoustic cell 201, the standard deviation noise is 0.00173V, and the signal-to-noise ratio is calculated to be 569, and the corresponding detection limit is 35ppb. The gas concentration range that can be measured by this application is 35ppb to 100%.

[0070] It can be seen that compared with the single-pass photoacoustic cell, the photoacoustic signal enhancement factor of the cavity-enhanced photoacoustic cell 201 is 59. The laser output power after amplification by the fiber amplifier 104 is 29 mW, and the intracavity power is 1.7 W. Compared with the theoretical power enhancement factor of 166, the coupling efficiency of the high-fineness cavity is 36%. By optimizing the laser cavity mode matching, the cavity-enhanced photoacoustic cell 201 can obtain higher power enhancement and lower detection limit.

[0071] The embodiment of the present application also provides a high-sensitivity wide-range gas concentration measurement method. The execution subject of the high-sensitivity wide-range gas concentration measurement method can be the high-sensitivity wide-range gas concentration measurement device provided in the embodiment of the present application, or a host computer integrated with the high-sensitivity wide-range gas concentration measurement device. Specifically, the host computer is Figure 2 The host computer in the apparatus has a LabVIEW monitoring platform deployed therein, wherein the high-sensitivity and wide-range gas concentration measuring device can be implemented in hardware or software.

[0072] Figure 4 Schematic diagram of the process of the high-sensitivity and wide-range gas concentration measurement method provided in the embodiment of the present application. Figure 4 As shown, the method includes the following steps S110-S150.

[0073] S110, obtaining a photoacoustic signal corresponding to the gas to be measured.

[0074] In this embodiment, Figure 2 The cavity-enhanced photoacoustic cell shown is filled with a gas to be measured. The host computer in the present application obtains the photoacoustic signal corresponding to the gas to be measured transmitted by the data acquisition card, and specifically obtains the second harmonic signal (photoacoustic signal) of the gas to be measured in the cavity-enhanced photoacoustic cell to detect the concentration of the gas to be measured. In this embodiment, combined with Figure 2 In the high-sensitivity wide-range gas sensing system shown, the photoacoustic signal of the host computer is obtained by the following steps:

[0075] The host computer controls the data acquisition card to generate a driving signal, controls the current driver according to the driving signal, and drives the laser through the current driver and the temperature controller; the laser outputs a laser beam according to a preset laser power, and the laser beam is amplified by the optical fiber amplifier; the amplified laser beam is coupled into the cavity-enhanced photoacoustic cell at a preset angle, and the effective optical power of the laser beam is increased under the optical-acoustic dual resonance mode of the cavity-enhanced photoacoustic cell, so that the gas to be measured in the cavity-enhanced photoacoustic cell is fully excited to generate an acoustic pressure signal; the phase-locked amplifier extracts a photoacoustic signal related to the gas concentration from the acoustic pressure signal, and transmits the photoacoustic signal to the host computer through the data acquisition card.

[0076] S120. Determine the target concentration range of the gas to be measured according to the photoacoustic signal. If the target concentration range is a low concentration range, execute step S130. If the target concentration range is a high concentration range, execute steps S140-S150.

[0077] In this embodiment, the target concentration range of the current gas to be tested is first estimated by the photoacoustic signal. The host computer uses different concentration calculation methods for the low concentration range (such as 0-20% concentration range) and the high concentration range (such as 20%-100% concentration range).

[0078] Specifically, the host computer determines the target concentration range of the gas to be tested based on the signal amplitude of the photoacoustic signal. When the signal amplitude is less than a preset signal amplitude threshold (the signal amplitude threshold is different for the detection of different gases), it is determined that the gas to be tested is in a low concentration range; otherwise, it is determined that the gas to be tested is in a high concentration range.

[0079] The following explains why different concentration calculation methods are used for gases in different concentration ranges, taking C2H2 gas as an example:

[0080] High concentration of C2H2 gas will change the gas density in the absorption cell, thereby affecting the sound velocity and resonant frequency. When detecting high concentration of C2H2 gas, the C2H2 gas concentration will affect the change of sound velocity. When the detected gas changes within a lower concentration range, the sound velocity does not change much, then it can be considered that the resonant frequency is independent of the detected gas concentration. At this time, the modulation frequency of the light source can be fixed without tracking the acoustic resonant frequency. However, when some gas components change at higher concentrations, the sound velocity changes significantly, resulting in a resonant frequency shift, so the change in the photoacoustic signal intensity caused by the acoustic resonant frequency shift cannot be ignored at this time. Therefore, this application adopts different concentration calculation methods for gases in different concentration ranges.

[0081] S130: Determine the gas concentration of the gas to be measured based on the linear relationship.

[0082] Specifically, the target gas concentration of the gas to be measured is determined according to the corresponding relationship between the amplitude of the preset photoacoustic signal and the gas concentration and the amplitude of the target photoacoustic signal. In this embodiment, when the gas to be measured is in a low concentration range, the signal amplitude and the gas concentration show a linear relationship. At this time, the inversion measurement of the gas concentration can be achieved through the corresponding relationship between the amplitude of the preset photoacoustic signal and the gas concentration, and the amplitude of the photoacoustic signal corresponding to the current gas to be measured.

[0083] For example, when the C2H2 gas concentration is between 0% and 20%, since the signal amplitude is linearly related to the gas concentration, the gas concentration can be inverted through the corresponding relationship between the amplitude of the photoacoustic signal and the gas concentration, thereby successfully achieving measurement of the low-concentration range of gas.

[0084] S140. Determine the target resonant frequency of the gas to be measured based on the resonant frequency tracking technology.

[0085] Specifically, the target resonant frequency corresponding to the gas to be measured is determined according to a preset resonant frequency tracking technology. In this embodiment, since the signal amplitude and the gas concentration show a nonlinear relationship when the gas is in a high concentration range, the inventors found that when the gas is in a high concentration range, the gas concentration is proportional to the speed of sound, and the speed of sound is proportional to the resonant frequency. It can be seen that when the gas is in a high concentration range, the resonant frequency and the gas concentration are linearly related. At this time, the corresponding relationship between the resonant frequency and the gas concentration can be obtained in advance through experiments, and the gas concentration of the gas to be measured can be inverted through the corresponding relationship and the resonant frequency corresponding to the gas to be measured, thereby realizing high-concentration detection of the gas.

[0086] Specifically, this embodiment determines the target resonant frequency corresponding to the gas to be measured by the resonant frequency tracking technology. At this time, Figure 5 As shown, step S140 includes S1401-S1406:

[0087] S1401, determine the frequency search range [f min , f max ].

[0088] Specifically, the cavity-enhanced photoacoustic cell was modeled and simulated using COMSOL Multiphysics software to obtain the first-order resonance frequency, and a reasonable frequency search range [f min , f max ], where the minimum frequency is f min , the maximum frequency is f max .

[0089] S1402, control the modulation frequency of the laser according to the frequency search range, and obtain P(f max ) and P(f min ).

[0090] Among them, P(f min ) The first signal amplitude corresponding to the minimum frequency of the modulation frequency, P(f max ) is the second signal amplitude corresponding to the maximum frequency of the modulation frequency.

[0091] The minimum frequency is the minimum frequency in the frequency search range, and the maximum frequency is the maximum frequency in the frequency search range.

[0092] Specifically, the modulation frequency of the laser is adjusted within the above frequency search range, and the maximum frequency f is obtained by using wavelength modulation spectrum and second harmonic detection technology. max and minimum frequency f min The photoacoustic signal amplitude P(f max ) and P(f min ).

[0093] S1403, determine P(f max ) is greater than P(f min ) to get the judgment result.

[0094] S1404: Based on the binary search method, update the frequency search range according to the judgment result.

[0095] Specifically, if the judgment result is that the second signal amplitude is greater than the first signal amplitude, the minimum frequency and the average frequency of the maximum frequency are updated to the minimum frequency of the frequency search range, and the maximum frequency is kept unchanged; if the judgment result is that the second signal amplitude is less than or equal to the first signal amplitude, the average frequency is updated to the maximum frequency of the frequency search range, and the minimum frequency is kept unchanged.

[0096] For example, the average frequency of the minimum frequency and the maximum frequency is f i, that is, f i =(f max +f min ) / 2; when P(f max )>P(f min ), f min =f i , f max =f max Otherwise, f min =f min , f max =f i .

[0097] S1405. Determine whether the current number of iterations is less than the iteration number threshold. If so, return to execute step S1402; if not, execute step S1406.

[0098] In this embodiment, the initial number of iterations is set to 0, and each iteration increases the value of the current number of iterations by 1. The threshold of this iteration is obtained through previous experiments. The setting of the threshold of the number of iterations needs to take into account both the computational efficiency and the positioning accuracy of the frequency.

[0099] If the current number of iterations is less than the iteration number threshold, the next iteration is performed and the process returns to step S1402 ; otherwise, the iteration is stopped.

[0100] S1406: Determine a target resonant frequency according to the frequency search range.

[0101] Specifically, in this embodiment, if the current number of iterations is greater than or equal to the iteration number threshold, the average frequency of the minimum frequency and the maximum frequency in the frequency search range is determined as the target resonant frequency, that is, the current f i The output is the target resonant frequency.

[0102] S150 , determining the target gas concentration of the gas to be measured based on the corresponding relationship between the resonant frequency and the gas concentration.

[0103] In this example, after the target resonant frequency is obtained, the gas concentration corresponding to the target resonant frequency in the correspondence relationship between the preset resonant frequency and the gas concentration is determined as the target gas concentration.

[0104] To sum up, on the one hand, the cavity-enhanced photoacoustic cell in the present application can increase the effective optical power of the laser beam, so that the gas to be measured in the cavity-enhanced photoacoustic cell is fully excited, thereby improving the sensitivity of gas detection; on the second hand, the upper computer is preset with the correspondence between the amplitude of the photoacoustic signal and the gas concentration and the resonant frequency tracking technology. The correspondence between the amplitude of the photoacoustic signal and the gas concentration can be used to detect the gas concentration in a low concentration range, and the resonant frequency tracking technology can be used to detect the gas concentration in a high concentration range. It can be seen that through the present application, a single sensor can be used to simultaneously achieve high-sensitivity and ultra-wide range gas detection.

[0105] Figure 6 is a schematic block diagram of a highly sensitive and wide-range gas concentration measurement device 500 provided in an embodiment of the present application. Figure 6 As shown, corresponding to the above high-sensitivity wide-range gas concentration measurement method, the present application also provides a high-sensitivity wide-range gas concentration measurement device 500. The high-sensitivity wide-range gas concentration measurement device 500 includes a unit for executing the above high-sensitivity wide-range gas concentration measurement method. The high-sensitivity wide-range gas concentration measurement device 500 is deployed in Figure 2 In the host computer shown, please refer to Figure 6 The high-sensitivity and wide-range gas concentration measuring device 500 includes a transceiver unit 501 and a processing unit 502:

[0106] The transceiver unit 501 is used to obtain the photoacoustic signal corresponding to the gas to be measured transmitted by the data acquisition card;

[0107] The processing unit 502 is used to determine the target concentration range of the gas to be measured based on the photoacoustic signal; if the target concentration range is a low concentration range, the target gas concentration of the gas to be measured is determined based on the corresponding relationship between the amplitude of the preset photoacoustic signal and the gas concentration and the amplitude of the target photoacoustic signal; if the target concentration range is a high concentration range, the target resonant frequency corresponding to the gas to be measured is determined according to the preset resonant frequency tracking technology; the target gas concentration of the gas to be measured is determined based on the corresponding relationship between the preset resonant frequency and the gas concentration and the target resonant frequency.

[0108] In some embodiments, when the processing unit 502 executes the step of determining the target resonant frequency corresponding to the gas to be measured according to the preset resonant frequency tracking technology, it is specifically used to:

[0109] Determine a frequency search range; control the modulation frequency of the laser according to the frequency search range, and obtain a first signal amplitude corresponding to the minimum frequency when the modulation frequency is the minimum frequency, and obtain a second signal amplitude corresponding to the maximum frequency when the modulation frequency is the maximum frequency, wherein the minimum frequency is the minimum frequency in the frequency search range, and the maximum frequency is the maximum frequency in the frequency search range; determine whether the second signal amplitude is greater than the first signal amplitude, and obtain a determination result; based on a binary search method, update the frequency search range according to the determination result; determine whether the current number of iterations is less than a preset number of iterations threshold; if it is less than the number of iterations threshold, return to execute the steps of controlling the modulation frequency of the laser according to the frequency search range, and obtaining the first signal amplitude corresponding to the minimum frequency when the modulation frequency is the minimum frequency, and obtaining the second signal amplitude corresponding to the maximum frequency when the modulation frequency is the maximum frequency; if it is greater than or equal to the number of iterations threshold, determine the target resonant frequency according to the frequency search range.

[0110] In some embodiments, when the processing unit 502 executes the step of updating the frequency search range according to the judgment result based on the binary search method, it is specifically used to:

[0111] If the judgment result is that the second signal amplitude is greater than the first signal amplitude, the average frequency of the minimum frequency and the maximum frequency is updated to the minimum frequency of the frequency search range; if the judgment result is that the second signal amplitude is less than or equal to the first signal amplitude, the average frequency is updated to the maximum frequency of the frequency search range.

[0112] In some embodiments, when the processing unit 502 performs the step of determining the target resonant frequency according to the frequency search range, it is specifically configured to:

[0113] An average frequency of the minimum frequency and the maximum frequency of the frequency search range is determined as the target resonant frequency.

[0114] It should be noted that technicians in the relevant field can clearly understand that the specific implementation process of the above-mentioned high-sensitivity wide-range gas concentration measurement device and each unit can refer to the corresponding description in the aforementioned method embodiment, and for the convenience and brevity of description, it will not be repeated here.

[0115] The above-mentioned high-sensitivity wide-range gas concentration measuring device can be implemented in the form of a computer program. The computer program can be used in Figure 7 Run on the host computer shown.

[0116] See also Figure 7 , Figure 7 600 is a schematic block diagram of a host computer provided in an embodiment of the present application. Figure 2 The host computer in.

[0117] See also Figure 7 The host computer 600 includes a processor 602 , a memory and a network interface 605 connected via a system bus 601 , wherein the memory may include a non-volatile storage medium 603 and an internal memory 604 .

[0118] The non-volatile storage medium 603 can store an operating system 6031 and a computer program 6032. The computer program 6032 includes program instructions, and when the program instructions are executed, the processor 602 can execute a high-sensitivity and wide-range gas concentration measurement method.

[0119] The processor 602 is used to provide computing and control capabilities to support the operation of the entire host computer 600.

[0120] The internal memory 604 provides an environment for the operation of the computer program 6032 in the non-volatile storage medium 603. When the computer program 6032 is executed by the processor 602, the processor 602 can execute a high-sensitivity and wide-range gas concentration measurement method.

[0121] The network interface 605 is used to communicate with other devices over the network. Figure 7 The structure shown in the figure is merely a block diagram of a partial structure related to the scheme of the present application, and does not constitute a limitation on the host computer 600 to which the scheme of the present application is applied. The specific host computer 600 may include more or fewer components than those shown in the figure, or combine certain components, or have a different arrangement of components.

[0122] The processor 602 is used to run a computer program 6032 stored in the memory to implement the following steps:

[0123] Acquire the photoacoustic signal corresponding to the gas to be tested transmitted by the data acquisition card;

[0124] Determining a target concentration range of the gas to be measured according to the photoacoustic signal;

[0125] If the target concentration range is a low concentration range, the target gas concentration of the gas to be measured is determined according to a preset corresponding relationship between the amplitude of the photoacoustic signal and the gas concentration and the amplitude of the target photoacoustic signal;

[0126] If the target concentration range is a high concentration range, determining the target resonant frequency corresponding to the gas to be measured according to a preset resonant frequency tracking technology;

[0127] The target gas concentration of the gas to be measured is determined according to the corresponding relationship between the preset resonant frequency and the gas concentration and the target resonant frequency.

[0128] It should be understood that in the embodiment of the present application, the processor 602 may be a central processing unit (CPU), and the processor 602 may also be other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. Among them, the general-purpose processor may be a microprocessor or the processor may also be any conventional processor, etc.

[0129] It can be understood by those skilled in the art that all or part of the processes in the method for implementing the above embodiment can be completed by instructing the relevant hardware through a computer program. The computer program includes program instructions, and the computer program can be stored in a storage medium, which is a computer-readable storage medium. The program instructions are executed by at least one processor in the computer system to implement the process steps of the embodiment of the above method.

[0130] Therefore, the present application also provides a storage medium. The storage medium may be a computer-readable storage medium. The storage medium stores a computer program, wherein the computer program includes program instructions. When the program instructions are executed by a processor, the processor executes the following steps:

[0131] Acquire the photoacoustic signal corresponding to the gas to be tested transmitted by the data acquisition card;

[0132] Determining a target concentration range of the gas to be measured according to the photoacoustic signal;

[0133] If the target concentration range is a low concentration range, the target gas concentration of the gas to be measured is determined according to a preset corresponding relationship between the amplitude of the photoacoustic signal and the gas concentration and the amplitude of the target photoacoustic signal;

[0134] If the target concentration range is a high concentration range, determining the target resonant frequency corresponding to the gas to be measured according to a preset resonant frequency tracking technology;

[0135] The target gas concentration of the gas to be measured is determined according to the corresponding relationship between the preset resonant frequency and the gas concentration and the target resonant frequency.

[0136] The storage medium may be a USB flash drive, a mobile hard disk, a read-only memory (ROM), a magnetic disk, or an optical disk, etc., which are computer-readable storage media that can store program codes.

[0137] Those of ordinary skill in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in terms of function in the above description. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this application.

[0138] In the several embodiments provided in the present application, it should be understood that the devices and methods used can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of each unit is only a logical function division, and there may be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed.

[0139] The steps in the method of the embodiment of the present application can be adjusted in order, combined and deleted according to actual needs. The units in the device of the embodiment of the present application can be combined, divided and deleted according to actual needs. In addition, the functional units in the various embodiments of the present application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0140] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a storage medium. Based on this understanding, the technical solution of the present application is essentially or the part that contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including a number of instructions for a computer device (which can be a personal computer, terminal, or network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present application.

[0141] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed in the present application, and these modifications or replacements should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A high-sensitivity and wide-range gas sensing system, characterized in that: The high-sensitivity and wide-range gas sensing system comprises a light source module, a photoacoustic resonant cavity module and a data processing module, wherein: The light source module is used to generate incident light; The photoacoustic resonant cavity module is connected to the light source module, and the incident light is absorbed by the gas to be measured in the photoacoustic resonant cavity module to generate a photoacoustic signal; The data processing module is connected to the photoacoustic resonant cavity module, and is used to process the photoacoustic signal and invert the concentration of the gas to be measured, wherein the data processing module performs high-sensitivity gas detection in a low concentration range based on the corresponding relationship between the amplitude of the preset photoacoustic signal and the gas concentration, and performs gas detection in a high concentration range for the gas to be measured using the resonant frequency tracking technology.

2. A high-sensitivity wide-range gas sensing system according to claim 1, characterized in that: The light source module includes a laser, a current driver, a temperature controller and an optical fiber amplifier, wherein the laser outputs a laser beam according to a preset laser power, and the optical fiber amplifier amplifies the laser beam.

3. A high-sensitivity wide-range gas sensing system according to claim 2, characterized in that: The photoacoustic resonance cavity module includes a cavity-enhanced photoacoustic cell and a microphone, wherein the amplified laser beam is coupled into the cavity-enhanced photoacoustic cell at a preset angle, and the effective optical power of the laser beam is increased in the optical-acoustic dual resonance mode of the cavity-enhanced photoacoustic cell, so that the gas to be measured in the cavity-enhanced photoacoustic cell is fully excited to generate a photoacoustic signal.

4. A high-sensitivity wide-range gas sensing system according to claim 3, characterized in that: The microphone is installed at the center of the cavity enhanced photoacoustic cell for detecting photoacoustic signals.

5. A high-sensitivity wide-range gas sensing system according to claim 4, characterized in that: The data processing module includes a phase-locked amplifier, a data acquisition card and a host computer, wherein the host computer controls the data acquisition card to generate a driving signal, controls the current driver according to the driving signal, and drives the laser through the current driver and the temperature controller; The phase-locked amplifier extracts a photoacoustic signal related to the gas concentration from the cavity-enhanced photoacoustic cell, and transmits the photoacoustic signal to the host computer through the data acquisition card, so that the host computer performs high-sensitivity gas detection in a low concentration range based on the corresponding relationship between the amplitude of the preset photoacoustic signal and the gas concentration, and performs gas detection in a high concentration range for the gas to be tested using the resonance frequency tracking technology.

6. A high-sensitivity wide-range gas sensing system according to claim 3, characterized in that: The cavity-enhanced photoacoustic cell comprises an optical resonator, an acoustic resonator and two high-reflection mirrors. The longitudinal mode of the optical resonator resonates with the frequency of the laser beam to form an optical standing wave between the two high-reflection mirrors. The acoustic resonator forms an acoustic standing wave inside by using a specially designed H-shaped structure. The two high-reflection mirrors are respectively installed on both sides of the cavity-enhanced photoacoustic cell.

7. A high-sensitivity and wide-range gas concentration measurement method, characterized in that: The method is applied to a data processing module in a high-sensitivity and wide-range gas sensing system according to any one of claims 1 to 6, and the method comprises: Acquire the photoacoustic signal corresponding to the gas to be tested transmitted by the data acquisition card; Determining a target concentration range of the gas to be measured according to the photoacoustic signal; If the target concentration range is a low concentration range, the target gas concentration of the gas to be measured is determined according to a preset corresponding relationship between the amplitude of the photoacoustic signal and the gas concentration and the amplitude of the target photoacoustic signal; If the target concentration range is a high concentration range, determining the target resonant frequency corresponding to the gas to be measured according to a preset resonant frequency tracking technology; The target gas concentration of the gas to be measured is determined according to the corresponding relationship between the preset resonant frequency and the gas concentration and the target resonant frequency.

8. The method according to claim 7, characterized in that The step of determining the target resonant frequency corresponding to the gas to be measured according to a preset resonant frequency tracking technology includes: Determine the frequency search range; Controlling the modulation frequency of the laser according to the frequency search range, and obtaining a first signal amplitude corresponding to when the modulation frequency is a minimum frequency, and obtaining a second signal amplitude corresponding to when the modulation frequency is a maximum frequency, wherein the minimum frequency is the minimum frequency in the frequency search range, and the maximum frequency is the maximum frequency in the frequency search range; Determine whether the amplitude of the second signal is greater than the amplitude of the first signal, and obtain a determination result; Based on the dichotomy method, updating the frequency search range according to the judgment result; Determine whether the current number of iterations is less than a preset number of iterations threshold; If it is less than the iteration number threshold, return to the step of controlling the modulation frequency of the laser according to the frequency search range, and obtaining the first signal amplitude corresponding to the minimum frequency when the modulation frequency is the minimum frequency, and obtaining the second signal amplitude corresponding to the maximum frequency when the modulation frequency is the maximum frequency; If it is greater than or equal to the iteration number threshold, the target resonant frequency is determined according to the frequency search range.

9. The method according to claim 8, characterized in that The step of updating the frequency search range based on the dichotomy method according to the judgment result includes: If the determination result is that the second signal amplitude is greater than the first signal amplitude, updating the average frequency of the minimum frequency and the maximum frequency to the minimum frequency of the frequency search range; If the determination result is that the second signal amplitude is less than or equal to the first signal amplitude, the average frequency is updated to the maximum frequency of the frequency search range.

10. The method according to claim 8, characterized in that The determining the target resonant frequency according to the frequency search range includes: An average frequency of the minimum frequency and the maximum frequency of the frequency search range is determined as the target resonant frequency.

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