Gas monitoring self-calibration method and system

Abstract

The invention provides a gas monitoring self-calibration method and system. The gas monitoring self-calibration method comprises the steps that a main control terminal controls a light source generation module to generate a modulated initial laser signal; the light source generation module inputs an initial laser signal into the all-fiber air chamber group through a long optical cable; the all-fiber gas chamber group transmits a target laser signal absorbed by the to-be-detected gas to the data detection module through a long optical cable; the data detection module extracts demodulation signal data in the target laser signal and sends the demodulation signal data to the main control terminal; and the main control terminal characterizes and normalizes the demodulation signal data by using the concentration of the to-be-detected gas so as to eliminate the light intensity of the to-be-detected gas at the absorption center of the to-be-detected gas, and determines the concentration of the to-be-detected gas by using the characterization formula of the normalized second harmonic signal. The collected data is normalized to shield the light intensity of the to-be-detected gas at the absorption center to participate in concentration calculation, so that the service life of the laser is prolonged or the detection accuracy of the system is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of gas concentration measurement, and in particular to a gas monitoring self-calibration method and system. BACKGROUND

[0002] TDLAS (Tunable Diode Laser Absorption Spectroscopy) technology is a kind of LAS (Laser Absorption Spectroscopy) technology, and according to different driving forms of the laser, the LAS technology can be divided into: direct absorption method and modulation absorption method. The direct absorption method needs to lock the driving current of the laser, does not need to load a 2f harmonic signal (second harmonic detection signal), has a simple structure and low cost, but is easily disturbed, especially low-frequency interference, so the sensitivity is relatively low. The modulation absorption method is to apply a sawtooth wave driving current signal to the laser, and load a 2f harmonic signal to the driving current, to generate laser varying with the driving current, which has a relatively complex structure and higher cost than the direct absorption method, but has the advantages of high sensitivity and avoidance of low-frequency interference. Among them, the modulation absorption method is further divided into wavelength modulation type and frequency modulation type, the wavelength modulation type needs a larger tuning range, and the frequency modulation type needs a very high scanning frequency and modulation frequency, which is complex in technology and has higher sensitivity.

[0003] The TDLAS technology for the quantification of gas molecules is based on the Lambert-Beer law (which describes the relationship between the transmitted light intensity, the molecular absorption coefficient, the light path in the measured gas, the incident light intensity and the concentration of the measured gas).

[0004] Based on the Lambert-Beer law, when measuring the concentration of gas, the output power of the laser will fluctuate due to the influence of environmental pressure, temperature, humidity and the drift of the electrical parameters of the measurement system itself in different use environments, thereby causing problems such as low measurement sensitivity and inaccurate measurement results. SUMMARY

[0005] Therefore, the purpose of the present application is to at least provide a gas monitoring self-calibration method and device, which shields the light intensity of the measured gas at its absorption center from participating in the concentration calculation by normalizing the collected data, thereby prolonging the service life of the laser or increasing the detection accuracy of the system.

[0006] The present application mainly includes the following aspects: In a first aspect, the embodiments of the present application provide a gas monitoring self-calibration method, which is applied to a gas monitoring self-calibration system. The gas monitoring self-calibration system comprises a master terminal, a light source generation module based on tunable diode laser absorption spectroscopy, a full-fiber gas chamber group, and a data detection module. The full-fiber gas chamber group is filled with a gas to be detected. The method comprises the following steps: the master terminal controls the light source generation module to generate an initial laser signal; the light source generation module inputs the initial laser signal into the full-fiber gas chamber group through a long optical cable; the full-fiber gas chamber group transmits a target laser signal after absorption by the gas to be detected to the 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 according to the concentration of the gas to be detected and performs normalization processing to eliminate the light intensity of the gas to be detected at its absorption center; and the concentration of the gas to be detected is determined by using a characterization formula of the normalized second harmonic signal.

[0007] In a possible implementation, the light source generation module comprises a signal generator and a laser group. The initial laser signal is generated in the following manner: the master 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 group; and the laser group generates the initial laser signal after modulation in response to the modulation signal.

[0008] In a possible implementation, the data detection module comprises a photodetector, a preamplifier, a lock-in amplifier, and a data acquisition card. The method further comprises the following steps: the photodetector receives the target laser signal transmitted by the full-fiber gas chamber group, converts the target laser signal into a target electrical signal, and then transmits the target electrical signal to the preamplifier for amplification processing; the preamplifier transmits the target electrical signal after amplification processing to the lock-in amplifier; and the lock-in amplifier demodulates the target electrical signal after amplification processing to obtain demodulation signal data and sends the demodulation signal data to the master terminal.

[0009] In a possible implementation, the demodulation signal data comprises a second harmonic signal in the target laser signal, a fundamental wave signal, and a transmission light intensity of the target laser signal after absorption by the gas to be detected.

[0010] In a possible implementation, the master terminal determines the concentration of the gas to be detected in the following manner: the second harmonic signal amplitude corresponding to the second harmonic signal and the fundamental wave signal amplitude corresponding to the fundamental wave signal are analyzed; a first ratio between the second harmonic signal amplitude and the fundamental wave signal amplitude is calculated; and the first ratio is brought into a transmittance calibration formula to calculate the concentration of the gas to be detected. The transmittance calibration formula describes a fitting relationship between the first ratio and the concentration of the gas to be detected.

[0011] In a possible implementation, the transmittance calibration formula is as follows: In a possible implementation, the transmittance calibration formula is as follows:

[0012] wherein, represents a first ratio between the amplitude of the second harmonic signal and the amplitude of the fundamental signal, represents a conversion coefficient of the high-frequency wave number variation of the modulation of the scanned absorption line to the light intensity, represents a full width at half maximum of the absorption line, , represents a molecular number density, is a temperature-dependent function, represents an optical path of the laser in the gas to be measured, , represents a direct current component in the modulated output laser wave number, represents a laser wave number of the gas absorption center, represents a second Fourier coefficient of the laser modulation broadening function after Fourier expansion, represents a concentration of the gas to be measured, wherein, .

[0013] In a possible implementation, the master 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 a second ratio between the amplitude of the second harmonic signal and the transmitted light intensity; and bringing the second ratio into a preset normalization formula to calculate the concentration of the gas to be measured, wherein the preset normalization formula describes a fitting relationship between the second ratio and the concentration of the gas to be measured.

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

[0015] wherein, represents a second ratio between the amplitude of the second harmonic signal and the transmitted light intensity, represents a relationship coefficient between the transmitted light intensity and the incident light intensity, represents a full width at half maximum of the absorption line, , represents a molecular number density, is a temperature-dependent function, represents an optical path of the laser in the gas to be measured, , represents a direct current component in the modulated output laser wave number, represents a laser wave number of the gas absorption center, represents a second Fourier coefficient of the laser modulation broadening function after Fourier expansion, represents a concentration of the gas to be measured, wherein, .

[0016] In a possible implementation, the master terminal further performs: monitoring operation state data of each device in the gas monitoring self-calibration system; and performing fault analysis on the device based on the operation state data.

[0017] In a second aspect, the embodiments of the present application further provide a gas monitoring self-calibration system, which comprises a master terminal, a light source generation module based on tunable diode laser absorption spectroscopy, a full-fiber gas chamber group, and a data detection module. The full-fiber gas chamber group is filled with a gas to be measured. The master terminal controls the light source generation module to generate an initial laser signal that is modulated. The light source generation module inputs the initial laser signal to the full-fiber gas chamber group through a long optical cable. The full-fiber gas chamber group transmits a target laser signal that has been absorbed by the gas to be measured to the 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 by using a concentration of the gas to be measured and performs normalization processing to eliminate light intensity at an absorption center of the gas to be measured. The master terminal determines the concentration of the gas to be measured by using a characterization formula of the normalized second harmonic signal.

[0018] The gas monitoring self-calibration method and system provided by the embodiments of the present application comprise: a master terminal controls a light source generation module to generate an initial laser signal that is modulated; 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 that has been absorbed by a gas to be measured 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; and the master terminal characterizes the demodulation signal data by using a concentration of the gas to be measured and performs normalization processing to eliminate light intensity at an absorption center of the gas to be measured. The master terminal determines the concentration of the gas to be measured by using a characterization formula of the normalized second harmonic signal. The present application shields the light intensity at the absorption center of the gas to be measured from participating in concentration calculation by performing normalization processing on collected data, thereby prolonging the service life of the laser or increasing the detection accuracy of the system.

[0019] In order to make the above objectives, characteristics and advantages of the present application more apparent and comprehensible, the following will specifically describe preferred embodiments in combination with the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some of the embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0021] Figure 1Fig. 1 shows a structural schematic diagram of a gas monitoring self-calibration system according to an embodiment of the present application; Figure 2 Fig. 2 shows a flowchart of a gas monitoring self-calibration method according to an embodiment of the present application; Figure 3 Fig. 3 shows another structural schematic diagram of a gas monitoring self-calibration system according to an embodiment of the present application. DETAILED DESCRIPTION

[0022] To make the objectives, technical solutions, and superiorities of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described below in connection with the drawings in the embodiments of the present application. It should be understood that the drawings in the present application merely serve the purpose of illustrating and describing and are not intended to limit the scope of protection of the present application. In addition, it should be understood that the schematic drawings are not drawn according to the actual proportions. The flowcharts in the present application show the operations implemented according to some embodiments of the present application. It should be understood that the operations in the flowcharts can not be implemented in sequence, and the steps without logical context relationship can be reversed in sequence or implemented simultaneously. In addition, one or more other operations can be added to the flowcharts or one or more operations can be removed from the flowcharts under the guidance of the content in the present application.

[0023] In addition, the described embodiments are merely some of the embodiments of the present application, but not all the embodiments. The components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but merely represents selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without making creative efforts fall within the scope of protection of the present application.

[0024] The quantification of gas molecules by TDLAS technology is based on the Lambert-Beer law (which describes the relationship between the transmitted light intensity, the molecular absorption coefficient, the optical path of light in the gas to be measured, the incident light intensity, and the concentration of the gas to be measured).

[0025] Based on the Lambert-Beer law, when measuring the gas concentration, in different use environments, the output power of the laser will fluctuate due to the influence of environmental pressure, temperature, humidity, and the drift of electrical parameters of the measurement system itself, thereby causing problems such as low measurement sensitivity and inaccurate measurement results.

[0026] Based on this, the embodiment of the application provides a gas monitoring self-calibration method and system, which shields the light intensity of the to-be-detected gas at the absorption center thereof from participating in concentration calculation through normalization processing on collected data, thereby prolonging the service life of the laser or increasing the detection accuracy of the system, and the specific implementation is as follows: Please refer to Figure 1 , Figure 1 The embodiment of the application shows a structural schematic diagram of a gas monitoring self-calibration system. Please refer to Figure 2 , Figure 2 The embodiment of the application shows a flowchart of a gas monitoring self-calibration method. As Figure 1 shown, the gas monitoring self-calibration system provided by the embodiment of the application comprises a master terminal 1, a light source generation module 2 based on tunable diode laser absorption spectroscopy (TDLAS), a full-fiber gas chamber group 3, and a data detection module 4.

[0027] As Figure 2 shown, the gas monitoring self-calibration method provided by the application comprises the following steps. S100, the master terminal controls the light source generation module to generate a modulated initial laser signal.

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

[0029] S300, the full-fiber gas chamber group transmits the target laser signal after being absorbed by the to-be-detected gas to the data detection module through the long optical cable.

[0030] S400, the data detection module extracts demodulation signal data in the target laser signal and sends the demodulation signal data to the master terminal.

[0031] S500, the master terminal characterizes the demodulation signal data by using the concentration of the to-be-detected gas and performs normalization processing to eliminate the light intensity of the to-be-detected gas at the absorption center thereof, and determines the concentration of the to-be-detected gas by using the characterization formula of the normalized second harmonic signal.

[0032] In a preferred embodiment, the master terminal 1 is further used for monitoring the running state data of each device in the gas monitoring self-calibration system, and displaying the running state data and the concentration of the to-be-detected gas through a display device, and can also perform working condition evaluation, fault analysis and fault early warning on the working condition of the monitoring device based on the running state data.

[0033] Specifically, the specific functions provided by the master terminal 1 are as follows: Hardware control function: control the operation of all hardware devices in the gas monitoring self-calibration system, and provide parameter modification functions for different to-be-detected gases.

[0034] Data acquisition function: responsible for collecting the operating parameter information of all hardware devices in the gas monitoring self-calibration system, for example, the harmonic signal corresponding to the transmitted light intensity. Concentration data processing function: for the wavelength modulation TDLAS scheme, there are often a large amount of noise and redundant information, before step S500 is executed, the received adjustment signal is preprocessed such as noise extraction, to improve the accuracy of subsequent calculation of the concentration of the measured gas.

[0035] Human-computer interaction function: provides a human-computer interaction function interface to enable the user to realize function selection, parameter setting, concentration display, fault query, etc.

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

[0037] Please refer to Figure 3 , Figure 3 Fig. 2 shows a structural schematic diagram of a gas monitoring self-calibration system provided by an embodiment of the present application. As shown in Figure 3 The light source generation module 2 provided by the present 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 measured gas 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 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 to the laser group 22, and the laser group 22 generates the initial laser signal after modulation in response to the modulation signal.

[0039] In a specific embodiment, the laser group 22 provided by the present application includes a laser and its corresponding laser driver, wherein the laser can use a distributed feedback laser to provide an initial laser signal, specifically, the signal generator 21 inputs the modulation signal to the laser driver, and the laser driver drives the distributed feedback laser to generate the initial laser signal after modulation in response to the modulation signal.

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

[0041] In another preferred embodiment, 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, and in S400 further includes: The photodetector 41 receives the target laser signal transmitted through the all-fiber gas cell set 3, converts the target laser signal into a target electric signal, and transmits the target electric signal to the preamplifier 42 for amplification processing. The preamplifier 42 transmits the amplified target electric signal to the lock-in amplifier 43. The lock-in amplifier 43 demodulates the amplified target electric signal to obtain demodulation signal data, which is sent to the host terminal 1 through the data acquisition card 44.

[0042] In a specific embodiment, the demodulation signal data includes a second harmonic signal in the target laser signal, a fundamental wave signal, and a transmitted light intensity after the target laser signal is absorbed by the gas to be measured.

[0043] In a specific embodiment, the host terminal can determine the concentration of the gas to be measured by the following method: The second harmonic signal amplitude corresponding to the second harmonic signal and the fundamental wave signal amplitude corresponding to the fundamental wave signal are analyzed, and a first ratio between the second harmonic signal amplitude and the fundamental wave signal amplitude is calculated. The first ratio is brought into a 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.

[0044] Preferably, the transmittance calibration formula is:

[0045] wherein, represents the first ratio between the second harmonic signal amplitude and the fundamental wave signal amplitude, represents the conversion coefficient of the high-frequency wave number change corresponding to the light intensity of the modulation of the scanned absorption spectrum line, represents the half-height half-width of the absorption spectrum line, , represents the molecular number density, is a temperature-dependent function, represents the optical path of the laser in the gas to be measured, , represents the direct current component in the modulated output laser wave number, represents the laser wave number of the gas absorption center, represents the second Fourier coefficient after Fourier expansion of the laser modulation broadening function, represents the concentration of the gas to be measured, wherein, .

[0046] In a specific embodiment, the determination process of the above transmittance calibration formula of the present application is as follows: The wavelength of the narrow-band tunable laser (the laser provided in the present application is a narrow-band tunable laser) is modulated by using current, which can realize the modulation of the laser wave number and the laser intensity, which is specifically expressed as: (1) (2) wherein, represents the output laser wave number (calculated in units of cm-1) under the driving signal, which is used to describe the spectral characteristics, represents the direct current component of , i.e. the wave number (static wavelength) caused by the direct current component in the driving signal of the narrow-band tunable laser, which is an invariable quantity.

[0047] is the cosine signal amplitude of the output laser wave number , i.e. the modulation depth / modulation amplitude (the range of wave number change caused by current modulation), i.e. the wave number (dynamic wavelength) produced by the cosine signal in the driving current on the basis of the static wavelength, represents the modulation angular frequency in the cosine signal, which is the phase difference between the cosine signal and the driving signal, represents the phase shift, i.e. the phase difference between the driving signal and the wave number change.

[0048] the output light intensity of the gas absorption center received by the detector after modulation (unit: mW), represents the output light intensity of the gas absorption center without modulation, represents the half-height half-width (HWHM, unit: cm-1) of the absorption spectrum line of the gas to be measured, represents the conversion coefficient of the low-frequency wave number change corresponding to the light intensity when scanning the absorption spectrum line of the gas to be measured, represents the conversion coefficient of the high-frequency wave number change corresponding to the light intensity when modulating the absorption spectrum line.

[0049] wherein, it is set that: (3) (4) The Lambert-Beer law is expressed by the formula as: (5) wherein, represents the transmitted light intensity of the laser with the wave number after passing through the gas to be measured, represents the molecular absorption coefficient (unit: ), L represents the optical path L (unit: m) of the laser in the gas to be measured, C represents the gas concentration (unit: ppm) of the gas to be measured, represents the incident light intensity corresponding to the laser with the wave number .

[0050] The above formula (1) is brought into formula (5), and the following formula (6) can be obtained: (6) wherein, and are consistent, so formula (2)~formula (4) are brought into formula (6) for merging, and it is assumed that the laboratory environment is stable, in a constant temperature and pressure space, the following formula (7) can be obtained:

[0051] The gas molecule absorption coefficient depends on the temperature dependent function , the molecular number density and the laser modulation broadening function , is approximately regarded as a Lorentz line type, and is expressed as:

[0052] The Fourier operation is performed on the above formula, and after the series n expansion, the following formula (8) is obtained:

[0053] According to the related Fourier expansion operation formula, the related Fourier coefficient can be obtained as follows:

[0054]

[0055] According to the Fourier coefficient calculated by the Arndt R algorithm and are expressed as follows:

[0056]

[0057] In the above formula, , .

[0058] When the modulation coefficient is 2.2, the Fourier coefficient at the gas absorption center has the maximum value.

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

[0060] wherein, , .

[0061] After harmonic detection of the transmitted light, the formulas of the fundamental wave signal and the second harmonic signal are respectively:

[0062]

[0063] And at the gas absorption center, or :

[0064] And and very small, the transmitted light emitted from the area to be measured gas at the absorption center The fundamental wave signal of the second harmonic signal of the second harmonic signal is respectively:

[0065] From the above formula, it can be seen that there is a linear relationship between the peak value of the second harmonic signal and the gas concentration .

[0066] Therefore, the laser signal after absorption can be input into a phase-locked amplifier for demodulation to obtain the second harmonic signal of the gas to be measured, so as to bring it into the transmittance calibration formula to obtain the concentration of the gas to be measured.

[0067]

[0068] Separate analysis of the fundamental wave signal and the frequency doubling signal of the above formula can find that both are proportional to the incident light intensity , and if they are compared, the light intensity can be eliminated, that is, after obtaining the second harmonic signal, the data with light intensity can be used to normalize it, thereby eliminating the light intensity at the absorption center.

[0069] Using this theory makes the TDLAS system self-calibrate, calculates the concentration of the gas to be measured by eliminating the light intensity at the absorption center, which can shield the light intensity changes caused by current fluctuations and environmental interference, prolong the service life of the laser, and increase the detection accuracy of the system.

[0070] In another preferred embodiment, the master terminal further determines the concentration of the gas to be measured by: ​​The second ratio between the second harmonic signal amplitude and the transmitted light intensity is calculated, the second ratio is brought into a preset normalization formula, and the concentration of the to-be-measured gas is calculated.

[0071] The preset normalization formula is:

[0072] wherein, the second ratio between the second harmonic signal amplitude and the transmitted light intensity, a relationship coefficient between the transmitted light intensity and the incident light intensity, a half-width of the absorption spectrum line, , a molecular number density, a temperature-dependent function, a light path of the laser in the to-be-measured gas, , a direct current component in the modulated output laser wave number, a laser wave number of a gas absorption center, a second Fourier coefficient after Fourier expansion of the laser modulation broadening function, a to-be-measured gas concentration, wherein, .

[0073] In another embodiment provided in the application, the second harmonic is used to eliminate the parameters related to the light intensity , to realize normalization, and based on this, only one stable parameter needs to be selected to represent the light intensity.

[0074] Therefore, the application proposes to collect the second harmonic signal and the transmitted light intensity at the same time, to use the transmitted light intensity to represent the light intensity at the absorption center, and there is a certain proportional mapping relationship between the transmitted light intensity and the incident light intensity.

[0075] Specifically, the relationship between the transmitted light intensity and the incident light intensity is:

[0076] wherein, the relationship coefficient can be obtained by a large number of prior experiments.

[0077] The data acquisition card is used to collect the harmonic transmitted signal and the fundamental frequency transmitted signal at the same time, the second harmonic transmitted signal is normalized, and the preset normalization formula can be obtained in the same way:

[0078] After the gas monitoring self-calibration system is built and fixed, except the concentration of the gas to be measured , other parameters in the formula remain relatively stable, and the concentration of the gas to be measured can be calculated through the second ratio. Meanwhile, the light intensity of the incident light is normalized through this method.

[0079] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working process of the system and device described above can refer to the corresponding process in the foregoing method embodiments, which will not be described here. In the several embodiments provided in the present application, it should be understood that the disclosed system, device and method can be implemented by other ways. The device embodiments described above are only schematic, for example, the division of the units is only a logical function division, and there can be another division manner in actual implementation, and for example, a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the coupling or direct coupling or communication connection between the units shown or discussed can be indirect coupling or communication connection through some communication interfaces, devices or units, and can be electrical, mechanical or other forms.

[0080] The units described as separate components can or can not be physically separate, and the components shown as units can or can not be physical units, that is, they can be located in one place, or can be distributed on a plurality of network units. Part or all of the units can be selected according to actual needs to achieve the purpose of the embodiment scheme.

[0081] In addition, the functional units in each embodiment of the present application can be integrated in one processing unit, or each unit can exist physically, or two or more units can be integrated in one unit.

[0082] If the functions are realized in the form of software function units and sold or used as independent products, they can be stored in a non-volatile computer readable storage medium executable by a processor. Based on this understanding, the technical solutions of the present application essentially or the parts of the prior art or the parts of the technical solutions can be embodied in the form of software products, and the computer software products are stored in a storage medium, including a plurality of instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present application. The foregoing storage medium includes: U disk, mobile hard disk, read-only memory (Read-Only Memory, ROM), random access memory (Random Access Memory, RAM), magnetic disk or optical disk, and various program code storage media.

[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.

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 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.

5. The method according to claim 4, characterized in that, The main control terminal determines the concentration of the gas to be measured in the following way: Analyze 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; Calculate the first ratio between the amplitude of the second harmonic signal and the amplitude of the fundamental signal; Substituting the first ratio into the transmittance calibration formula, the concentration of the gas to be measured is calculated. The transmittance calibration formula describes the fitting relationship between the first ratio and the concentration of the gas to be measured.

6. The method according to claim 5, characterized in that, The transmittance calibration formula is as follows: 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, .

7. The method according to claim 4, characterized in that, The main control terminal also determines the concentration of the gas to be measured in the following ways: 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.

8. The method according to claim 7, characterized in that, 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 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, .

9. The method according to claim 7, 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.

10. A gas monitoring self-calibration system, characterized in that, 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 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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