A gas monitoring self-calibration method and system

Abstract

The application provides a gas monitoring self-calibration method and system, comprising: a master terminal controlling a light source generation module to generate a modulated initial laser signal; the light source generation module inputs the initial laser signal to a full-fiber gas chamber group through a long optical cable; the full-fiber gas chamber group transmits a target laser signal after being absorbed by a to-be-detected gas to a data detection module through the long optical cable; the data detection module extracts demodulation signal data in the target laser signal and sends the demodulation signal data to the master terminal; the master terminal characterizes the demodulation signal data with a to-be-detected gas concentration and performs normalization processing to eliminate the light intensity of the to-be-detected gas at its absorption center, and determines the concentration of the to-be-detected gas by using a characterization formula of the normalized second harmonic signal. The application shields the light intensity of the to-be-detected gas at its absorption center from participating in concentration calculation by performing normalization processing on the collected data, thereby prolonging the service life of the laser or increasing the detection accuracy of the system.

Description

Technical Field

[0001] This application relates to the field of gas concentration measurement technology, and in particular to a gas monitoring self-calibration method and system. Background Technology

[0002] Tunable Diode Laser Absorption Spectroscopy (TDLAS) is a type of Laser Absorption Spectroscopy (LAS) technology. Depending on the laser's driving method, LAS technology can be divided into direct absorption and modulation absorption. Direct absorption requires locking the laser's drive current and does not require loading a 2f harmonic signal (second harmonic detection signal). It has a simple structure and low cost, but is susceptible to interference, especially low-frequency interference, resulting in relatively low sensitivity. Modulation absorption applies a sawtooth wave drive current signal to the laser while simultaneously loading a 2f harmonic signal onto the drive current, generating laser light that varies with the drive current. Its structure is relatively more complex and its cost is higher than direct absorption, but it has the advantages of high sensitivity and the ability to avoid low-frequency interference. Modulation absorption is further divided into wavelength modulation and frequency modulation types. Wavelength modulation requires a wider tuning range, while frequency modulation requires very high scanning and modulation frequencies, making the technology more complex and offering higher sensitivity.

[0003] TDLAS technology for the qualitative and quantitative analysis of gas molecules is based on the Lambert-Beer law (which describes the relationship between transmitted light intensity and molecular absorption coefficient, optical path length of light in the gas to be tested, incident light intensity, and concentration of the gas to be tested).

[0004] According to the Lambert-Beer model, when measuring gas concentration, the output power of the laser will fluctuate due to the influence of ambient air pressure, temperature, humidity, and the electrical parameters of the measurement system itself in different operating environments. This can lead to problems such as lower measurement sensitivity and inaccurate measurement results. Summary of the Invention

[0005] In view of this, the purpose of this application is to provide at least one gas monitoring self-calibration method and device, which, by normalizing the collected data, shields the light intensity of the gas to be measured at its absorption center from participating in the concentration calculation, thereby extending the lifespan of the laser or increasing the detection accuracy of the system.

[0006] This application mainly includes the following aspects: In a first aspect, embodiments of this application provide a gas monitoring self-calibration method applied to a gas monitoring self-calibration system. The gas monitoring self-calibration system includes a main control terminal, a light source generation module based on tunable diode laser absorption spectrum, an all-fiber gas chamber group, and a data detection module. The all-fiber gas chamber group is filled with a gas to be measured. The method includes: the main control terminal controlling the light source generation module to generate a modulated initial laser signal; the light source generation module inputting the initial laser signal into the all-fiber gas chamber group through a long optical cable; the all-fiber gas chamber group transmitting the target laser signal, after absorption by the gas to be measured, to the data detection module through the long optical cable; the data detection module extracting demodulated signal data from the target laser signal and sending it to the main control terminal; the main control terminal characterizing and normalizing the demodulated signal data using the concentration of the gas to be measured to eliminate the light intensity of the gas to be measured at its absorption center, and determining the concentration of the gas to be measured using the characterization formula of the normalized second harmonic signal.

[0007] In one possible implementation, the light source generation module includes a signal generator and a laser array, wherein the initial laser signal is generated by the following method: the main control terminal controls the signal generator to generate a modulation signal required by the gas monitoring self-calibration system; the signal generator inputs the modulation signal into the laser array; and the laser array responds to the modulation signal to generate the modulated initial laser signal.

[0008] In one possible implementation, the data detection module includes a photodetector, a preamplifier, a lock-in amplifier, and a data acquisition card. The method further includes: the photodetector receiving the target laser signal transmitted through the all-fiber gas chamber array, converting the target laser signal into a target electrical signal, and then transmitting it to the preamplifier for amplification; the preamplifier transmitting the amplified target electrical signal to the lock-in amplifier; and the lock-in amplifier demodulating the amplified target electrical signal to obtain demodulated signal data and sending it to the main control terminal.

[0009] In one possible implementation, the demodulated signal data includes the second harmonic signal, the fundamental signal, and the transmitted light intensity of the target laser signal after absorption by the gas to be measured.

[0010] In one possible implementation, the main control terminal determines the concentration of the gas to be measured by: analyzing the amplitude of the second harmonic signal corresponding to the second harmonic signal and the amplitude of the fundamental signal corresponding to the fundamental signal; calculating a first ratio between the amplitude of the second harmonic signal and the amplitude of the fundamental signal; and substituting the first ratio into the transmittance calibration formula to calculate the concentration of the gas to be measured, wherein the transmittance calibration formula describes the fitting relationship between the first ratio and the concentration of the gas to be measured.

[0011] In one possible implementation, the transmittance calibration formula is:

[0012] in, This represents the first ratio between the amplitude of the second harmonic signal and the amplitude of the fundamental signal. The conversion coefficient represents the light intensity corresponding to the high-frequency wavenumber change in the modulation of the scanning absorption spectral line. This represents the half-width at half-maximum (FWHM) of the absorption spectral line. , Represents the molecular number density. It is a temperature-dependent function. This indicates the optical path length of the laser in the gas being tested. , This indicates the DC component in the modulated output laser wavenumber. The laser wavenumber representing the gas absorption center, The coefficients represent the second-order Fourier coefficients after the Fourier expansion of the laser modulation broadening function. This represents the concentration of the gas to be measured, where, .

[0013] In one possible implementation, the main control terminal further determines the concentration of the gas to be measured by: analyzing the amplitude of the second harmonic signal corresponding to the second harmonic signal; calculating the second ratio between the amplitude of the second harmonic signal and the transmitted light intensity; and substituting the second ratio into a preset normalization formula to calculate the concentration of the gas to be measured, wherein the preset normalization formula describes the fitting relationship between the second ratio and the concentration of the gas to be measured.

[0014] In one possible implementation, the preset normalization formula is:

[0015] in, This represents the second ratio between the amplitude of the second harmonic signal and the intensity of the transmitted light. This represents the coefficient relating the transmitted light intensity to the incident light intensity. This represents the half-width at half-maximum (FWHM) of the absorption spectral line. , Represents the molecular number density. It is a temperature-dependent function. This indicates the optical path length of the laser in the gas being tested. , This indicates the DC component in the modulated output laser wavenumber. The laser wavenumber representing the gas absorption center, The coefficients represent the second-order Fourier coefficients after the Fourier expansion of the laser modulation broadening function. This represents the concentration of the gas to be measured, where, .

[0016] In one possible implementation, the main control terminal also performs the following: monitoring the operating status data of each device in the gas monitoring self-calibration system; and performing fault analysis on the devices based on the operating status data.

[0017] Secondly, embodiments of this application also provide a gas monitoring self-calibration system. The gas monitoring self-calibration system includes a main control terminal, a light source generation module based on tunable diode laser absorption spectrum, an all-fiber gas chamber assembly, and a data detection module. The all-fiber gas chamber assembly is filled with the gas to be measured. The main control terminal controls the light source generation module to generate a modulated initial laser signal. The light source generation module inputs the initial laser signal into the all-fiber gas chamber assembly via a long optical cable. The all-fiber gas chamber assembly transmits the target laser signal, after absorption by the gas to be measured, to the data detection module via the long optical cable. The data detection module extracts the demodulated signal data from the target laser signal and sends it to the main control terminal. The main control terminal characterizes and normalizes the demodulated signal data using the concentration of the gas to be measured to eliminate the light intensity at the absorption center of the gas to be measured. The concentration of the gas to be measured is determined using the characterization formula of the normalized second harmonic signal.

[0018] This application provides a gas monitoring self-calibration method and system, comprising: a main control terminal controlling a light source generation module to generate a modulated initial laser signal; the light source generation module inputting the initial laser signal into an all-fiber gas cell assembly via a long optical cable; the all-fiber gas cell assembly transmitting the target laser signal, after absorption by the gas to be measured, to a data detection module via the long optical cable; the data detection module extracting demodulated signal data from the target laser signal and sending it to the main control terminal; the main control terminal characterizing and normalizing the demodulated signal data using the concentration of the gas to be measured to eliminate the light intensity at the absorption center of the gas to be measured, and determining the concentration of the gas to be measured using the characterization formula of the normalized second harmonic signal. This application extends the lifespan of the laser or increases the detection accuracy of the system by normalizing the collected data to shield the light intensity at the absorption center of the gas to be measured from participating in the concentration calculation.

[0019] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1This illustration shows one of the structural schematic diagrams of a gas monitoring self-calibration system provided in an embodiment of this application; Figure 2 A flowchart of a gas monitoring self-calibration method provided in an embodiment of this application is shown; Figure 3 This is a second schematic diagram of the structure of a gas monitoring self-calibration system provided in an embodiment of this application. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. It should be understood that the drawings in this application are for illustrative and descriptive purposes only and are not intended to limit the scope of protection of this application. Furthermore, it should be understood that the schematic drawings are not drawn to scale. The flowcharts used in this application illustrate operations implemented according to some embodiments of this application. It should be understood that the operations in the flowcharts may not be implemented in sequence, and steps without logical contextual relationships may be reversed or implemented simultaneously. In addition, those skilled in the art, guided by the content of this application, may add one or more other operations to the flowcharts, or remove one or more operations from the flowcharts.

[0023] Furthermore, the described embodiments are merely some, not all, of the embodiments of this application. The components of the embodiments of this application described and illustrated herein can typically be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0024] TDLAS technology for the qualitative and quantitative analysis of gas molecules is based on the Lambert-Beer law (which describes the relationship between transmitted light intensity and molecular absorption coefficient, optical path length of light in the gas to be tested, incident light intensity, and concentration of the gas to be tested).

[0025] According to the Lambert-Beer model, when measuring gas concentration, the output power of the laser will fluctuate due to the influence of ambient air pressure, temperature, humidity, and the electrical parameters of the measurement system itself in different operating environments. This can lead to problems such as lower measurement sensitivity and inaccurate measurement results.

[0026] Based on this, embodiments of this application provide a gas monitoring self-calibration method and system. By normalizing the collected data, the light intensity at the absorption center of the gas to be measured is shielded from participating in the concentration calculation, thereby extending the lifespan of the laser or increasing the detection accuracy of the system, as detailed below: Please see Figure 1 , Figure 1 This diagram illustrates one of the structural schematics of a gas monitoring self-calibration system provided in an embodiment of this application. Please refer to [link / reference]. Figure 2 , Figure 2 A flowchart of a gas monitoring self-calibration method provided in an embodiment of this application is shown. Figure 1 As shown, the gas monitoring self-calibration system provided in this application includes a main control terminal 1, a light source generation module 2 based on tunable diode laser absorption spectroscopy (TDLAS), an all-fiber gas chamber group 3, and a data detection module 4.

[0027] like Figure 2 As shown, the gas monitoring self-calibration method provided in this application includes: S100, the main control terminal controls the light source generation module to generate the modulated initial laser signal.

[0028] S200, the light source generation module inputs the initial laser signal into the all-fiber gas chamber group through a long optical cable.

[0029] The S300, an all-fiber gas chamber assembly, transmits the target laser signal, after being absorbed by the gas to be tested, to the data detection module via a long optical cable.

[0030] The S400 data detection module extracts the demodulated signal data from the target laser signal and sends it to the main control terminal.

[0031] The S500 main control terminal uses the concentration of the gas to be measured to characterize and normalize the demodulated signal data to eliminate the light intensity of the gas to be measured at its absorption center. The concentration of the gas to be measured is determined using the characterization formula of the normalized second harmonic signal.

[0032] In a preferred embodiment, the main control terminal 1 is also used to: monitor the operating status data of each device in the gas monitoring self-calibration system, and display the operating status data and the concentration of the gas to be measured through a display device. At the same time, it can also perform operating condition evaluation, fault analysis and fault warning based on the operating status data of the monitoring device.

[0033] Specifically, the main control terminal 1 provides the following functions: Hardware control function: Controls the operation of all hardware devices in the gas monitoring self-calibration system and provides parameter modification function for different gases to be measured.

[0034] Data acquisition function: responsible for collecting operating parameter information that reflects all hardware devices in the gas monitoring self-calibration system, such as harmonic signals corresponding to transmitted light intensity. Concentration data processing function: For wavelength-modulated TDLAS schemes, there is often a lot of noise and redundant information. Before executing step S500, the received modulation signal is preprocessed, such as noise extraction, to improve the accuracy of subsequent calculation of the concentration of the gas to be measured.

[0035] Human-computer interaction function: Provides a human-computer interaction interface to enable users to select functions, set parameters, display concentration, query faults, etc.

[0036] Network communication extension function: A communication interface is reserved to facilitate communication between the gas monitoring self-calibration system and other monitoring systems.

[0037] Please see Figure 3 , Figure 3 This is a second schematic diagram of the structure of a gas monitoring self-calibration system provided in an embodiment of this application. (See attached diagram.) Figure 3 As shown, the light source generation module 2 provided in this application includes a signal generator 21 and a laser group 22, wherein the laser group 22 outputs a laser signal with a wavelength corresponding to the absorption spectrum line of the gas to be measured based on the modulation signal output by the signal generator 21.

[0038] In a preferred embodiment, the light source generation module 2 specifically performs the following: The main control terminal 1 controls the signal generator 21 to generate the modulation signal required by the gas monitoring self-calibration system. The signal generator 21 inputs the modulation signal into the laser group 22, and the laser group 22 responds to the modulation signal to generate the modulated initial laser signal.

[0039] In one specific embodiment, the laser group 22 provided in this application includes a laser and its corresponding laser driver. The laser can be a distributed feedback laser to provide the initial laser signal. Specifically, the signal generator 21 modulates the laser driver, and the laser driver responds to the modulation signal to drive the distributed feedback laser to generate the modulated initial laser signal.

[0040] In step S300 provided in this application, in one embodiment, the all-fiber gas chamber group 3 is installed in the mine and connected to the laser group 22 via a long optical cable. The all-fiber gas chamber group 3 is filled with the gas to be tested in the mine environment. The initial laser signal is input into the all-fiber gas chamber group 3 through the long optical cable. After the initial laser signal is absorbed by the gas in the all-fiber gas chamber group 3, the weakened target laser signal is transmitted to the data detection module 4 on the ground through the long optical cable.

[0041] In another preferred embodiment, such as Figure 3As shown, the data detection module 4 includes a photodetector 41, a preamplifier 42, a lock-in amplifier 43, and a data acquisition card 44. In S400, it further includes: The photodetector 41 receives the target laser signal transmitted through the all-fiber gas chamber group 3, converts the target laser signal into a target electrical signal, and then transmits it to the preamplifier 42 for amplification. The preamplifier 42 transmits the amplified target electrical signal to the lock-in amplifier 43. The lock-in amplifier 43 demodulates the amplified target electrical signal and sends the demodulated signal data to the main control terminal 1 through the data acquisition card 44.

[0042] In one specific embodiment, the demodulated signal data includes the second harmonic signal, the fundamental signal, and the transmitted light intensity of the target laser signal after absorption by the gas to be measured in the target laser signal.

[0043] In one specific embodiment, the main control terminal can determine the concentration of the gas to be measured in the following way: The amplitudes of the second harmonic signal and the fundamental signal are analyzed. The first ratio between the amplitudes of the second harmonic signal and the fundamental signal is calculated. The first ratio is then substituted into the transmittance calibration formula to calculate the concentration of the gas to be measured. The transmittance calibration formula describes the fitting relationship between the first ratio and the concentration of the gas to be measured.

[0044] Preferably, the transmittance calibration formula is:

[0045] in, This represents the first ratio between the amplitude of the second harmonic signal and the amplitude of the fundamental signal. The conversion coefficient represents the light intensity corresponding to the high-frequency wavenumber change in the modulation of the scanning absorption spectral line. This represents the half-width at half-maximum (FWHM) of the absorption spectral line. , Represents the molecular number density. It is a temperature-dependent function. This indicates the optical path length of the laser in the gas being tested. , This indicates the DC component in the modulated output laser wavenumber. The laser wavenumber representing the gas absorption center, The coefficients represent the second-order Fourier coefficients after the Fourier expansion of the laser modulation broadening function. This represents the concentration of the gas to be measured, where, .

[0046] In one specific embodiment, the process of determining the transmittance calibration formula described above in this application is as follows: By modulating the wavelength of a narrowband tunable laser (the laser provided in this application is a narrowband tunable laser), it is possible to modulate both the laser wavenumber and laser intensity, specifically as follows: (1) (2) in, The output laser wavenumber (in cm⁻¹) under the driving signal is used to describe the spectral characteristics. express The DC component, i.e. the wavenumber (rest wavelength) caused by the DC component in the driving signal corresponding to the narrowband tunable laser, is a constant quantity.

[0047] It is the output laser wavenumber The amplitude of the cosine signal, i.e., the modulation depth / modulation amplitude (the range of wavenumber changes caused by current modulation), is the wavenumber (dynamic wavelength) generated by the cosine signal in the driving current based on the stationary wavelength. The modulation angular frequency in a cosine signal represents the phase difference between the cosine signal and the driving signal. This indicates the phase shift, which is the phase difference between the driving signal and the wavenumber change.

[0048] (Unit: mW) represents the gas absorption center received by the modulated detector. The output light intensity, Indicates the gas absorption center without modulation The output light intensity, The half-width at half-maximum (HWHM) represents the half-maximum and half-maximum width (cm⁻¹) of the absorption spectral line of the gas to be measured. The conversion coefficient represents the light intensity corresponding to the low-frequency wavenumber change of the absorption spectrum of the gas being scanned. The conversion coefficient represents the light intensity corresponding to the high-frequency wavenumber change in the modulation of the scanning absorption spectral line.

[0049] Among them, the settings are: (3) (4) Lambert-Beer Law can be expressed by the following formula: (5) in, Indicates wave number The intensity of the transmitted light after the laser passes through the gas to be tested. Indicates the molecular absorption coefficient (unit: ). L represents the optical path length of the laser in the gas to be tested (in meters), and C represents the gas concentration of the gas to be tested (in ppm). Indicates wave number The incident light intensity corresponding to the laser.

[0050] Substituting formula (1) into formula (5), we get: (6) in, and Since they are consistent, we substitute formulas (2) to (4) into formula (6) for merging. Assuming the laboratory environment is stable and located in a room with normal temperature and pressure, we can obtain:

[0051] Gas molecule absorption coefficient Depends on temperature dependence function Molecular number density and laser modulation stretching function , Approximating it as a Lorentz line type, it can be represented as:

[0052] Performing a Fourier operation on the above expression and expanding it into a series n, we obtain:

[0053] Based on the relevant Fourier expansion formula, the relevant Fourier coefficients can be obtained as follows:

[0054]

[0055] Fourier coefficients calculated using Arndt R algorithm and It can be represented as follows:

[0056]

[0057] In the above formula , .

[0058] When the modulation coefficient When the value is 2.2, the Fourier coefficient at the gas absorption center The value of is the largest.

[0059] The modulated transmitted light is calculated as follows:

[0060] in, , .

[0061] After harmonic detection of the transmitted light, the formulas for the fundamental signal and the second harmonic signal are as follows:

[0062]

[0063] At the gas absorption center, or hour:

[0064] and and When the wavelength is very small, the fundamental signal of the transmitted light emitted from the region of the gas to be measured at the absorption center is... With second harmonic signal They are respectively:

[0065] From the above formula, we can obtain the peak value of the second harmonic signal and the gas concentration. There is a linear relationship between them.

[0066] Therefore, the absorbed laser signal can be fed into a lock-in amplifier for demodulation to obtain the second harmonic signal of the gas to be measured, which can then be substituted into the transmittance calibration formula to invert and obtain the concentration of the gas to be measured.

[0067]

[0068] Analyzing the fundamental and harmonic signals separately in the above equation reveals that both are related to the incident light intensity. They are directly proportional. If the two are compared, the light intensity can be eliminated. In other words, after obtaining the second harmonic signal, it can be normalized using data containing light intensity, thereby eliminating the light intensity at the absorption center. .

[0069] This theory enables the TDLAS system to perform self-calibration by eliminating light intensity at the absorption center. Calculating the concentration of the gas to be measured can shield against changes in light intensity caused by current fluctuations and environmental interference, extending the lifespan of the laser and increasing the detection accuracy of the system.

[0070] In another preferred embodiment, the main control terminal also determines the concentration of the gas to be measured in the following manner: The amplitude of the second harmonic signal corresponding to the second harmonic signal is analyzed, and the second ratio between the amplitude of the second harmonic signal and the transmitted light intensity is calculated. The second ratio is then substituted into a preset normalization formula to calculate the concentration of the gas to be measured. The preset normalization formula describes the fitting relationship between the second ratio and the concentration of the gas to be measured.

[0071] The default normalization formula is:

[0072] in, This represents the second ratio between the amplitude of the second harmonic signal and the intensity of the transmitted light. This represents the coefficient relating the transmitted light intensity to the incident light intensity. This represents the half-width at half-maximum (FWHM) of the absorption spectral line. , Represents the molecular number density. It is a temperature-dependent function. This indicates the optical path length of the laser in the gas being tested. , This indicates the DC component in the modulated output laser wavenumber. The laser wavenumber representing the gas absorption center, The coefficients represent the second-order Fourier coefficients after the Fourier expansion of the laser modulation broadening function. This represents the concentration of the gas to be measured, where, .

[0073] In another embodiment provided in this application, the elimination of second harmonics is related to light intensity. The parameters are normalized, and based on this, only a stable parameter needs to be selected to characterize the light intensity.

[0074] Therefore, this application proposes to acquire the transmitted light intensity while acquiring the second harmonic signal, and to use the transmitted light intensity to characterize the light intensity at the absorption center, while there is a certain proportional mapping relationship between the transmitted light intensity and the incident light intensity.

[0075] Specifically, set the transmitted light intensity With incident light intensity The relationship is as follows:

[0076] Among these, it can be obtained through fitting a large number of prior experiments. .

[0077] The data acquisition card is used to simultaneously acquire harmonic transmission signals and fundamental frequency transmission signals. The second harmonic transmission signal is normalized, and a preset normalization formula can be obtained similarly.

[0078] After the gas monitoring self-calibration system is set up and fixed, in addition to the concentration of the gas to be measured... Apart from that, other parameters in the formula remain relatively stable, and the concentration of the gas to be measured can be calculated using the second ratio. This method also normalizes the intensity of the incident light.

[0079] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems and devices described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here. In the several embodiments provided in this application, it should be understood that the disclosed systems, devices, and methods can be implemented in other ways. The device embodiments described above are merely illustrative. For example, the division of units is only a logical functional division; in actual implementation, there may be other division methods. Furthermore, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Another point is that the displayed or discussed mutual coupling or direct coupling or communication connection may be through some communication interfaces; the indirect coupling or communication connection of devices or units may be electrical, mechanical, or other forms.

[0080] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0081] In addition, the functional units in the various embodiments of this 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.

[0082] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a processor-executable, non-volatile, computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0083] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A gas monitoring self-calibration method, characterized in that, This technology is applied to a gas monitoring self-calibration system, which includes a main control terminal, a light source generation module based on tunable diode laser absorption spectroscopy, an all-fiber gas cell assembly, and a data detection module. The method includes: The main control terminal controls the light source generation module to generate a modulated initial laser signal; The light source generation module inputs the initial laser signal into the all-fiber gas chamber assembly through a long optical cable; The all-fiber gas chamber assembly transmits the target laser signal, after being absorbed by the gas to be tested, to the data detection module via a long optical cable. The data detection module extracts the demodulated signal data from the target laser signal and sends it to the main control terminal; The main control terminal uses the concentration of the gas to be measured to characterize and normalize the demodulated signal data to eliminate the light intensity of the gas to be measured at its absorption center. The concentration of the gas to be measured is determined using the characterization formula of the normalized second harmonic signal. The demodulated signal data includes the second harmonic signal, the fundamental signal, and the transmitted light intensity corresponding to the target laser signal in the target laser signal. The main control terminal determines the concentration of the gas to be measured in the following manner: Analyze the amplitude of the second harmonic signal corresponding to the second harmonic signal; Calculate the second ratio between the amplitude of the second harmonic signal and the intensity of the transmitted light; Substituting the second ratio into a preset normalization formula, the concentration of the gas to be measured is calculated. The preset normalization formula describes the fitting relationship between the second ratio and the concentration of the gas to be measured. The preset normalization formula is: in, This represents the second ratio between the amplitude of the second harmonic signal and the intensity of the transmitted light. This represents the coefficient relating the transmitted light intensity to the incident light intensity. This represents the half-width at half-maximum (FWHM) of the absorption spectral line. Represents the modulation coefficient. Represents the molecular number density. It is a temperature-dependent function. This indicates the optical path length of the laser in the gas being tested. , This indicates the DC component in the modulated output laser wavenumber. The laser wavenumber representing the gas absorption center, The coefficients represent the second-order Fourier coefficients after the Fourier expansion of the laser modulation broadening function. This represents the concentration of the gas to be measured, where, ; ， 。 2. The method according to claim 1, characterized in that, The light source generation module includes a signal generator and a laser array. The initial laser signal is generated in the following manner: The main control terminal controls the signal generator to generate the modulation signal required by the gas monitoring self-calibration system; The signal generator inputs the modulation signal into the laser array; The laser array responds to the modulation signal to generate the modulated initial laser signal.

3. The method according to claim 1, characterized in that, The data detection module includes a photodetector, a preamplifier, a lock-in amplifier, and a data acquisition card. The method further includes: The photodetector receives the target laser signal transmitted through the all-fiber gas chamber group, converts the target laser signal into a target electrical signal, and then transmits it to the preamplifier for amplification. The preamplifier transmits the amplified target electrical signal to the lock-in amplifier. The lock-in amplifier demodulates the amplified target electrical signal, and the resulting demodulated signal data is sent to the main control terminal via a data acquisition card.

4. The method according to claim 1, characterized in that, The main control terminal also performs: Monitor the operational status data of each device in the gas monitoring self-calibration system; Based on the aforementioned operational status data, fault analysis is performed on the equipment.

5. A gas monitoring self-calibration system, characterized in that, The gas monitoring self-calibration system, applicable to any one of claims 1-4, comprises a main control terminal, a light source generation module based on tunable diode laser absorption spectroscopy, an all-fiber gas chamber assembly, and a data detection module, wherein the all-fiber gas chamber assembly is filled with the gas to be measured. The main control terminal controls the light source generation module to generate a modulated initial laser signal; The light source generation module inputs the initial laser signal into the all-fiber gas chamber assembly through a long optical cable; The all-fiber gas chamber assembly transmits the target laser signal, after being absorbed by the gas to be tested, to the data detection module via a long optical cable. The data detection module extracts the demodulated signal data from the target laser signal and sends it to the main control terminal; The main control terminal uses the concentration of the gas to be measured to characterize and normalize the demodulated signal data to eliminate the light intensity of the gas to be measured at its absorption center. The concentration of the gas to be measured is determined using the characterization formula of the normalized second harmonic signal.

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