Laser gas detection device and gas concentration detection method

Abstract

The application provides a laser gas detection device and a gas concentration detection method. The laser gas detection device comprises a laser, a to-be-detected gas chamber and a photoelectric detector. The to-be-detected gas chamber is an internal optical mechanical structure space of the laser gas detection device. The photoelectric detector comprises a detector main body and a reference gas chamber. The to-be-detected gas chamber is used for loading a to-be-detected gas. The laser is used for emitting laser and shooting the laser into the to-be-detected gas chamber. The reference gas chamber is used for transmitting the laser shot from the to-be-detected gas chamber. The detector main body is used for detecting the laser passing through the to-be-detected gas chamber and the reference gas chamber, so as to obtain an electric signal of the to-be-detected gas. The application can reduce the lower limit of gas concentration detection of the laser gas detection device and improve the performance of the laser gas detection device.

Description

Technical Field

[0001] This application relates to the field of laser gas sensor technology, specifically to a laser gas detection device and a gas concentration detection method. Background Technology

[0002] TDLAS (Tunable Diode Laser Absorption Spectroscopy) utilizes the tunable current characteristic of semiconductor lasers. A low-frequency periodic tuning current generated by a laser diode driver changes the narrow linewidth and wavelength of the laser output, allowing the laser wavelength to scan periodically within a fixed narrow linewidth range. The scanned wavelength range covers the specific absorption wavelength of the target gas, thereby obtaining the gas concentration and other properties by analyzing the characteristic spectrum of the gas absorbing the laser.

[0003] By utilizing the Lambert-Beer Law, which governs the relationship between light absorption intensity and gas concentration and length, precise detection of specific gas concentrations can be achieved by detecting changes in absorption intensity after the gas interacts with light of a specific wavelength. The lower limit of gas concentration detection is crucial for gas concentration monitoring. If low-concentration gases cannot be detected, it can lead to a series of hazards. For example, some harmful gases can threaten human health and production safety even at low concentrations. Failure to accurately detect these low-concentration harmful gases may result in undetected leaks, failing to effectively protect the occupational health and safety of on-site workers.

[0004] However, the inventors of this application discovered during the actual research and development process that when the laser gas detection device uses TDLAS technology to analyze gas concentration values, the lower limit of gas concentration detection of the laser gas detection device is relatively high, making it difficult to detect the concentration values ​​of low-concentration gases. Summary of the Invention

[0005] This application provides a laser gas detection device and a gas concentration detection method, which can reduce the lower limit of gas concentration detection of the laser gas detection device and improve the performance of the laser gas detection device.

[0006] In a first aspect, this application provides a laser gas detection device, which includes a laser, a gas chamber to be tested, and a photodetector. The gas chamber to be tested is the internal optomechanical structure space of the laser gas detection device, and the photodetector includes a detector body and a reference gas chamber.

[0007] The test chamber is used to load the gas to be tested.

[0008] A laser for emitting a laser beam and directing the laser beam into the gas chamber to be tested;

[0009] A reference chamber for transmitting laser light emitted from the test chamber;

[0010] The detector body is used to detect laser light passing through the gas chamber to be tested and the reference gas chamber, so as to obtain the electrical signal of the gas to be tested.

[0011] Secondly, this application provides a gas concentration detection method, the method comprising:

[0012] The laser gas detection device emits a laser and directs the laser beam into a test chamber containing the gas to be detected. The laser gas detection device includes a laser, a test chamber, and a photodetector. The test chamber is the internal optomechanical structure space of the laser gas detection device, and the photodetector includes a detector body and a reference chamber.

[0013] The detector body detects the laser light that passes through the gas chamber to be tested and the reference gas chamber to obtain the electrical signal of the gas to be tested.

[0014] Obtain the equivalent gas concentration value of the reference gas chamber;

[0015] The actual detection concentration of the gas to be detected is obtained by analyzing the equivalent gas concentration value and the electrical signal of the gas to be detected.

[0016] This application provides a laser gas detection device and a gas concentration detection method. The laser gas detection device includes a laser, a gas chamber to be tested, and a photodetector. The photodetector includes a detector body and a reference gas chamber. The gas chamber to be tested is used to load the gas to be tested. The laser is used to emit laser light and direct it into the gas chamber to be tested. The reference gas chamber is used to transmit the laser light emitted from the gas chamber to be tested. The detector body is used to detect the laser light passing through both the gas chamber to be tested and the reference gas chamber to obtain an electrical signal of the gas to be tested. Thus, by setting a reference gas chamber in the photodetector, the gas in the reference gas chamber absorbs the laser light passing through the gas chamber to be tested again. The equivalent gas concentration value of the reference gas chamber can be used for compensation, thereby enabling the photodetector to detect the absorption peak in the electrical signal. This allows the absorption peak to be detected even when the concentration of the gas to be tested in the gas chamber to be tested is low, solving the problem that the absorption peak could not be detected at low concentrations, and the gas concentration value could not be calculated. This allows the actual concentration value of the gas to be tested to be detected even when the concentration of the gas to be tested is low, reducing the lower limit of gas concentration detection of the laser gas detection device and improving the performance of the laser gas detection device. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the structure of the laser gas detection device provided in the embodiments of this application;

[0019] Figure 2 This is a schematic diagram of the structure of the photodetector 300 provided in the embodiments of this application;

[0020] Figure 3 This is another structural schematic diagram of the laser gas detection device provided in the embodiments of this application;

[0021] Figure 4 This is another structural schematic diagram of the laser gas detection device provided in the embodiments of this application;

[0022] Figure 5 This is another structural schematic diagram of the laser gas detection device provided in the embodiments of this application;

[0023] Figure 6 This is a schematic diagram of the principle structure of the laser gas detection device provided in the embodiments of this application;

[0024] Figure 7 This is a schematic flowchart of a gas concentration detection method provided in an embodiment of this application;

[0025] Figure 8 This is a schematic flowchart of a reference gas chamber 320 leak detection and equivalent gas concentration value calibration provided in the embodiments of this application;

[0026] Figure 9 This is a schematic diagram comparing the changes in gas electrical signals in the gas chamber 100 provided in this application embodiment when the gas to be detected is present and when the gas to be detected is absent. Detailed Implementation

[0027] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0028] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. The terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0029] The flowcharts shown in the accompanying drawings are merely illustrative and do not necessarily include all content and operations / steps, nor do they necessarily have to be performed in the described order. For example, some operations / steps may be broken down, combined, or partially merged, so the actual execution order may change depending on the actual situation. Any process or method description in the flowcharts or otherwise described herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing a specific logical function or process. Furthermore, the scope of the embodiments described in this application includes other implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order according to the functions involved, as should be understood by those skilled in the art to which the embodiments of this application pertain.

[0030] To enable any person skilled in the art to implement and use this application, the following description is provided. In this description, details are set forth for purposes of explanation. It should be understood that those skilled in the art will recognize that this application can be implemented without using these specific details. In other instances, well-known processes will not be described in detail to avoid obscuring the description of the embodiments of this application with unnecessary detail. Therefore, this application is not intended to be limited to the embodiments shown, but is consistent with the broadest scope of the principles and features disclosed in the embodiments of this application.

[0031] This application provides a laser gas detection device. Please refer to [link / reference]. Figure 1 and Figure 2 , Figure 1 This is a schematic diagram of a laser gas detection device provided in an embodiment of this application. Figure 2This is a schematic diagram of the structure of the photodetector 300 provided in the embodiment of this application. The laser gas detection device includes: a laser 100, a gas chamber to be tested 200 and a photodetector 300. The gas chamber to be tested 200 is the internal optomechanical structure space of the laser gas detection device. The photodetector 300 includes a detector body 310 and a reference gas chamber 320.

[0032] The test chamber 100 is used to load the gas to be tested.

[0033] Laser 200 is used to emit laser light and direct it into the gas chamber 100 to be tested.

[0034] Reference chamber 300 is used to transmit laser light emitted from test chamber 100.

[0035] The detector body 310 is used to detect the laser light passing through the gas chamber 100 and the reference gas chamber 320 to obtain the electrical signal of the gas to be detected.

[0036] For example, such as Figure 1 As shown, laser 200 emits laser I under the drive of laser driver. o And the laser I is injected into the test chamber 100. o After being absorbed and attenuated by the gas to be tested in the test chamber 100, the laser I is transmitted through the chamber. t The laser I is received by photodetector 300, which receives the absorbed and attenuated laser light. t The laser beam then passes through the reference gas chamber 320 and is detected by the detector body 310. The detector body 310 converts the detected laser light signal into an electrical signal, thereby detecting the electrical signal of the gas to be detected. Thus, by setting a reference gas chamber 320 in the photodetector 300, the gas in the reference gas chamber 320 absorbs the laser beam passing through the test gas chamber 100 again. The equivalent gas concentration value of the reference gas chamber 320 can be used for compensation, allowing the photodetector 300 to detect the absorption peak in the electrical signal. This solves the problem of not being able to detect the absorption peak and calculate the gas concentration value at low concentrations, even when the concentration of the gas to be detected in the test gas chamber 100 is low. This allows for the detection of the actual concentration value of the gas to be detected even at low concentrations, lowering the detection limit of the laser gas detection device and improving its performance.

[0037] In some embodiments, such as Figure 3 As shown, Figure 3This is another schematic diagram of the laser gas detection device provided in the embodiments of this application. The laser gas detection device also includes an analog-to-digital converter 400 and a digital processing module 500, which are connected. The analog-to-digital converter 400 is used to convert the electrical signal of the gas to be detected into a digital signal. The digital signal is transmitted to the digital processing module 500, which is used to collect the digital signal output by the analog-to-digital converter 400 and analyze the digital signal to obtain the actual detection concentration value of the gas to be detected. The digital processing module 500 can detect the target absorption peak and baseline voltage value of the gas to be detected based on the digital signal. By substituting the ratio of the target absorption peak and the baseline voltage value into the corresponding functional relationship, the preliminary detection concentration value of the gas chamber 100 can be calculated. The actual detection concentration value of the gas to be detected is obtained by subtracting the equivalent gas concentration value of the reference gas chamber from the preliminary detection concentration value of the gas chamber 100. Thus, by setting a reference gas chamber 320 on the photodetector 300, the laser can be attenuated more significantly by the gas absorption in the reference gas chamber 320, thereby increasing the peak value of the detected electrical signal absorption peak. This allows the absorption peak to still be detected even when the concentration of the gas to be detected is low, reducing the lower limit of gas concentration detection and avoiding the problem of gas concentration being difficult to detect due to the inability to detect the absorption peak when the gas concentration is low. The detailed implementation of the digital processing module 500 detecting the actual detection concentration value of the gas to be detected can be referred to the relevant description of the gas concentration detection method embodiment below. For the sake of simplicity, it will not be repeated here.

[0038] In some embodiments, such as Figure 4 As shown, the laser gas detection device also includes an electrical signal amplification component 600, which is connected to the photodetector 300. The electrical signal amplification component 600 receives the electrical signal output from the detector body 310 and amplifies the electrical signal of the gas to be detected. An analog-to-digital converter 400 converts the amplified electrical signal of the gas to be detected into a digital signal. Therefore, the digital processing module 500 can detect the actual concentration value of the gas to be detected based on the digital signal. Thus, the electrical signal amplification component 600, by receiving the electrical signal output from the detector body 310 and amplifying the electrical signal of the gas to be detected, can amplify weak electrical signals, facilitating subsequent analysis and improving gas detection accuracy.

[0039] In some embodiments, such as Figure 5As shown, the laser gas detection device may further include a low-pass filter 700, which is used to filter the electrical signal of the gas to be detected. In some embodiments, the laser gas detection device includes a low-pass filter 700 but does not include an electrical signal amplification component 600. The low-pass filter 700 can directly receive the electrical signal output by the detector body 310 and directly filter the electrical signal output by the detector body 310. In some embodiments, the laser gas detection device includes both a low-pass filter 700 and an electrical signal amplification component 600. The electrical signal amplification component 600 receives the electrical signal output by the detector body 310 and amplifies it. The low-pass filter 700 can then receive the amplified electrical signal from the electrical signal amplification component 600 and filter it. Thus, by using the low-pass filter 700 to filter the electrical signal of the gas to be detected, low-frequency signals can be allowed to pass, attenuated, or high-frequency signals can be blocked from passing, thereby effectively utilizing TDLAS technology to analyze gas concentration values ​​and ensuring the accuracy of gas concentration value analysis.

[0040] In some embodiments, such as Figure 6 As shown, the laser gas detection device also includes a digital-to-analog converter 800 and a laser driver 900. The digital processing module 500 generates digital signals through a signal generator. The digital-to-analog converter 800 converts the digital signals generated by the signal generator of the digital processing module 500 into analog signals. The laser driver 900 receives the analog signals from the digital-to-analog converter 800 and generates a low-frequency periodic tuning current under the action of the analog signals. The laser 200 emits laser light under the action of the current and directs the laser light into the gas chamber 100 to be tested. The laser driver 900 can be a laser diode driver, an adjustable power laser driver, a frequency-modulated laser driver, etc.

[0041] Please refer to Figure 6The working principle of this laser gas detection device is illustrated below with a specific example. First, the digital processing module 500 generates a digital signal through a signal generator. Then, the digital-to-analog converter 800 converts the digital signal generated by the signal generator of the digital processing module 500 into an analog signal. Next, the laser driver 900 receives the analog signal from the digital-to-analog converter 800 and generates a low-frequency periodic tuning current under the action of the analog signal. Then, the laser 200 emits a laser beam under the action of the low-frequency periodic tuning current and directs the laser beam into the gas chamber 100 to be tested. Afterward, the laser beam is absorbed and attenuated by the gas to be tested in the gas chamber 100 and then passes through. The absorbed and attenuated laser beam is received by the photodetector 300. The laser then passes through the reference gas chamber 320 and is detected by the detector body 310. The detector body 310 converts the detected laser light signal into an electrical signal, thereby detecting the electrical signal of the gas to be detected. Next, the electrical signal amplification component 600 receives the electrical signal output from the detector body 310 and amplifies it. The low-pass filter 700 receives the amplified electrical signal from the electrical signal amplification component 600 and filters it. Finally, the filtered electrical signal is converted into a digital signal by the analog-to-digital converter 400. The digital processing module 500 can detect the actual concentration value of the gas to be detected based on the digital signal obtained by the analog-to-digital converter 400.

[0042] Please see Figure 6 and Figure 7 , Figure 7 This is a schematic flowchart of a gas concentration detection method provided in an embodiment of this application. The gas concentration detection method includes steps 701 to 704, wherein:

[0043] 701. The laser 200 of the laser gas detection device emits a laser and directs the laser into the test chamber 100 containing the gas to be detected.

[0044] The laser gas detection device includes a laser 200, a gas chamber 100 to be tested, and a photodetector 300. The gas chamber 100 to be tested is the internal optomechanical structure space of the laser gas detection device. The photodetector 300 includes a detector body 310 and a reference gas chamber 320.

[0045] For example, such as Figure 6As shown, firstly, the digital processing module 500 generates a digital signal through a signal generator; then, the digital-to-analog converter 800 converts the digital signal generated by the signal generator of the digital processing module 500 into an analog signal; next, the laser driver 900 receives the analog signal from the digital-to-analog converter 800 and generates a low-frequency periodic tuning current under the action of the analog signal; then, the laser 200 emits a laser under the action of the low-frequency periodic tuning current and directs the laser into the gas chamber 100 under test.

[0046] To better understand this gas concentration detection method, the basic structure and principle of the laser gas detection device are introduced below. Please refer to [link / reference]. Figure 6 and Figure 9 , Figure 9 This is a schematic diagram comparing the changes in the gas electrical signal in the gas chamber 100 provided in this application embodiment when the gas to be detected is present and when the gas to be detected is absent. Figure 6 As shown, the laser gas detection device mainly consists of two parts: an optical path and a circuit. First, a digital signal is generated by the signal generator of the digital processing module 500. This signal is then converted into an analog signal by the digital-to-analog converter 800 (which converts the digital signal into an analog signal). This analog signal then drives the laser driver 900 (such as a laser diode driver) to generate a low-frequency periodic tuning current. The current passes through the laser 200 to emit a tuned laser. After collimation, the laser passes through the gas chamber 100 filled with the gas to be detected. The incident light is absorbed and attenuated by the gas and then received by the photoelectric sensor 300, which converts the detected optical signal into an electrical signal. This weak electrical signal is then amplified by the amplification component 600 (such as an amplification circuit), filtered by the low-pass filter 700, and finally processed and analyzed by the processor (which can be the digital processing module 500). The absorption peak of the gas is detected, and the concentration of the gas to be detected is calculated. The optical path is interconnected with the external environment. When there is no gas to be detected in the external environment, the filtered electrical signal is as follows: Figure 9 As shown in (a), it is a periodic wedge wave; when the gas to be detected is present in the external environment, the filtered electrical signal is as follows. Figure 9 As shown in (b), a downward absorption peak is generated at a specific wavelength.

[0047] 702. The detector body 310 detects the laser light passing through the gas chamber to be tested 100 and the reference gas chamber 320 to obtain the electrical signal of the gas to be tested.

[0048] For example, such as Figure 6As shown, firstly, the laser light passes through the gas chamber 100 and is absorbed and attenuated by the gas to be detected before being transmitted. The absorbed and attenuated laser light is then received by the photodetector 300. Next, after receiving the absorbed and attenuated laser light, the laser light passes through the reference gas chamber 320 and then through the detector body 310 to detect the laser light. The detector body 310 converts the optical signal of the detected laser light into an electrical signal, thereby detecting the electrical signal of the gas to be detected.

[0049] 703. Obtain the equivalent gas concentration value of the reference gas chamber 320.

[0050] There are several ways to implement step 703, including, for example:

[0051] (1) In some embodiments, the equivalent gas concentration value of the reference gas chamber 320 is calculated in real time. In this case, step 703 may specifically include: calculating the equivalent gas concentration value C of the reference gas chamber 320 based on the chamber length L1 of the reference gas chamber 320, the optical path length L2 of the laser gas detection device, the gas concentration value C1 in the reference gas chamber 320, and a preset equivalent concentration calculation formula. The preset equivalent concentration calculation formula is shown in Formula 1 below:

[0052]

[0053] For example, taking a point-type laser gas sensor as an example, assuming that the internal optical path length of the point-type laser gas sensor is 10cm (i.e., L2 = 10cm), the gas chamber length of the reference gas chamber 320 is 1cm (i.e., L1 = 1cm), and the gas concentration value encapsulated in the reference gas chamber 320 is set to 60% LEL (i.e., C1 = 60% LEL), then the equivalent gas concentration value C = 6% LEL of the reference gas chamber 320 can be calculated by referring to Formula 1.

[0054] Thus, when it is necessary to make the gas equivalent concentration of the reference gas chamber 320 6% LEL, the gas concentration value of the encapsulated gas in the reference gas chamber 320 can be set to 60% LEL. In this way, the gas concentration value of the encapsulated gas in the reference gas chamber 320 can be dynamically adjusted according to actual needs to adapt to the detection concentration lower limit requirements of different gases to be detected.

[0055] (2) In some embodiments, the equivalent gas concentration value of the reference gas chamber 320 can be pre-calculated and stored in the database with reference to Formula 1. In step 703, the equivalent gas concentration value of the reference gas chamber 320 can be directly read from the database.

[0056] 704. Based on the equivalent gas concentration value and the electrical signal of the gas to be detected, the actual detection concentration value of the gas to be detected is obtained.

[0057] For example, step 704 may specifically include the following steps A1 to A3:

[0058] A1. Based on the electrical signal of the gas to be detected, analyze and process it to obtain the target absorption peak and baseline voltage value of the gas to be detected.

[0059] There are multiple ways to implement step A1, including, for example, the following methods ①, ②, and ③:

[0060] Method ①: In some embodiments, the electrical signal of the gas to be detected detected by the detector body 310 is directly analyzed. For example... Figure 6 As shown, firstly, the laser light is absorbed and attenuated by the gas to be detected in the test chamber 100 before being transmitted. The attenuated laser light is then received by the photodetector 300. Next, after receiving the attenuated laser light, the photodetector 300 transmits it through the reference chamber 320 and then through the detector body 310. The detector body 310 converts the detected laser light signal into an electrical signal, thereby detecting the electrical signal of the gas to be detected. This electrical signal can be directly converted into a digital signal by the analog-to-digital converter 400, thus obtaining the digital signal of the gas to be detected. Next, the target absorption peak and baseline voltage value of the gas to be detected are obtained by analyzing the digital signal. Finally, utilizing the characteristic that the ratio of the target absorption peak to the baseline voltage value has a nonlinear functional relationship with the gas concentration (linear at low concentrations), the gas concentration value can be calculated by obtaining the ratio of the target absorption peak to the baseline voltage value and substituting it into the corresponding functional relationship.

[0061] The target absorption peak is the peak value of the absorption peak obtained by analyzing the electrical signal collected by the photodetector 300 after the laser is absorbed by the gas to be detected.

[0062] The baseline voltage value is the signal strength when the laser is not absorbed by the gas to be detected.

[0063] Method ②: In some embodiments, the electrical signal is amplified by the electrical signal amplification component 600 before analysis. For example... Figure 6As shown, firstly, the laser light is absorbed and attenuated by the gas to be detected in the test chamber 100 before being transmitted. The attenuated laser light is then received by the photodetector 300. Next, after receiving the attenuated laser light, the photodetector 300 transmits it through the reference chamber 320 and then through the detector body 310. The detector body 310 converts the detected laser light signal into an electrical signal, thereby detecting the electrical signal of the gas to be detected. Next, the electrical signal amplification component 600 receives the electrical signal output from the detector body 310 and amplifies it. The amplified electrical signal is then converted into a digital signal by the analog-to-digital converter 400, thus obtaining the digital signal of the gas to be detected. Next, the target absorption peak and baseline voltage value of the gas to be detected are obtained by analyzing the digital signal. Finally, utilizing the characteristic that the ratio of the target absorption peak to the baseline voltage value has a nonlinear functional relationship with the gas concentration (linear at low concentrations), the gas concentration value can be calculated by obtaining the ratio of the target absorption peak to the baseline voltage value and substituting it into the corresponding functional relationship.

[0064] Method ③: In some embodiments, the electrical signal is amplified by the electrical signal amplification component 600 and filtered by the low-pass filter 700 before analysis. For example... Figure 6 As shown, firstly, the laser light passes through the gas chamber 100 and is absorbed and attenuated by the gas to be detected before being transmitted. The absorbed and attenuated laser light is then received by the photodetector 300. Next, after receiving the absorbed and attenuated laser light, the laser light passes through the reference gas chamber 320 and then through the detector body 310 to detect the laser light. The detector body 310 converts the detected laser light signal into an electrical signal, thereby detecting the electrical signal of the gas to be detected. Next, the electrical signal amplification component 600 receives the electrical signal output from the detector body 310 and amplifies it. The low-pass filter 700 receives the amplified electrical signal from the electrical signal amplification component 600 and filters it. Finally, the filtered electrical signal is converted into a digital signal by the analog-to-digital converter 400. Next, the target absorption peak and baseline voltage value of the gas to be detected are obtained by analyzing the digital signal of the gas to be detected. Finally, taking advantage of the fact that the ratio of the target absorption peak and the baseline voltage value has a nonlinear functional relationship with the gas concentration (linear relationship at low concentrations), the gas concentration value can be calculated by obtaining the ratio of the target absorption peak and the baseline voltage value and substituting it into the corresponding functional relationship.

[0065] A2. Based on the target absorption peak and the baseline voltage value, obtain the preliminary detection concentration value of the gas chamber 100 to be tested.

[0066] Finally, taking advantage of the nonlinear functional relationship between the ratio of the target absorption peak to the baseline voltage value and the gas concentration, the gas concentration value is calculated as the preliminary detection concentration value of the gas chamber 100 to be tested by obtaining the ratio of the target absorption peak to the baseline voltage value and substituting it into the corresponding functional relationship.

[0067] A3. Based on the equivalent gas concentration value, the preliminary detection concentration value is compensated to obtain the compensated concentration value of the gas chamber 100 to be tested, which is used as the actual detection concentration value of the gas to be tested.

[0068] Specifically, the preliminary detection concentration value of the gas chamber 100 is subtracted from the equivalent gas concentration value of the reference gas chamber 320, and the result (i.e., the compensated concentration value of the gas chamber 100) is used as the actual detection concentration value of the gas to be detected. In this way, subtracting the equivalent gas concentration value of the reference gas chamber 320 from the preliminary detection concentration value of the gas chamber 100 compensates for the preliminary detection concentration value of the gas chamber 100, allowing the actual concentration value of the gas to be detected to still be detected even when the concentration of the gas to be detected is low. This lowers the detection limit of the laser gas detection device and improves its performance.

[0069] In some embodiments, steps A1 to A3 are implemented based on the digital processing module 500; in some embodiments, the digital signal of the gas to be detected obtained by the analog-to-digital converter 400 can also be sent to other processors, and the other processors can perform the concentration detection process of steps A1 to A3 based on the digital signal of the gas to be detected.

[0070] Further, please refer to Figure 8 , Figure 8 This is a schematic flowchart illustrating the leak detection and equivalent gas concentration value calibration of the reference gas chamber 320 provided in this application embodiment. The gas concentration detection method may further include the following steps B1 to B3:

[0071] B1. When the gas chamber 100 to be tested is not filled with the gas to be tested, obtain the current gas concentration value of the gas chamber 100 to be tested.

[0072] The current gas concentration value of the test chamber 100 is equal to the difference between the current preliminary detection concentration value and the equivalent gas concentration value. The method for determining the current preliminary detection concentration value of the test chamber 100 can be found in the relevant explanation of step A2, and will not be repeated here.

[0073] For example, such as Figure 6As shown, when the test chamber is not filled with the gas to be tested, firstly, the digital processing module 500 generates a digital signal through a signal generator; then, the digital-to-analog converter 800 converts the digital signal generated by the signal generator of the digital processing module 500 into an analog signal; next, the laser driver 900 receives the analog signal from the digital-to-analog converter 800 and generates a low-frequency periodic tuning current under the action of the analog signal; then, the laser 200 emits a laser under the action of the low-frequency periodic tuning current and directs the laser into the test chamber 100; after that, the laser passes through the test chamber 100 and is received by the photodetector 300, which then... After receiving the laser, the laser passes through the reference gas chamber 320 and then through the detector body 310 to detect the laser. The detector body 310 converts the detected laser light signal into an electrical signal, thereby detecting the electrical signal of the gas to be detected. Next, the electrical signal amplification component 600 receives the electrical signal output from the detector body 310 and amplifies it. The low-pass filter 700 receives the amplified electrical signal from the electrical signal amplification component 600 and filters it. Finally, the filtered electrical signal is converted into a digital signal by the analog-to-digital converter 400. Next, the digital signal obtained by the analog-to-digital converter 400 is analyzed to obtain the target absorption peak and baseline voltage value. Finally, taking advantage of the fact that the ratio of the target absorption peak and the baseline voltage value has a nonlinear functional relationship with the gas concentration (linear relationship at low concentrations), the gas concentration value is calculated as the preliminary detection concentration value by obtaining the ratio of the target absorption peak and the baseline voltage value and substituting it into the corresponding functional relationship. The equivalent gas concentration value of the reference gas chamber 320 is subtracted from the preliminary detection concentration value, and the result is taken as the current gas concentration value of the gas chamber to be tested 100.

[0074] B2. If the current gas concentration value of the gas chamber 100 to be tested is detected to be negative, then the duration for which the current gas concentration value of the gas chamber 100 to be tested is negative is detected.

[0075] B3. If the duration of the negative current gas concentration value of the test chamber 100 is greater than the preset duration, and the current gas concentration value is less than the preset concentration value within the preset duration, then a leak alarm is issued for the reference chamber.

[0076] B4. If the duration of the current gas concentration value of the gas chamber 100 being negative is greater than a preset duration, and the current gas concentration value is not less than a preset concentration value within the preset duration, then the equivalent gas concentration value is updated until the current gas concentration value obtained based on the updated equivalent gas concentration value is equal to zero.

[0077] Thus, by adding real-time judgment to determine whether the current gas concentration value is negative, and after detecting a negative value and stabilizing it for a period of time, the system can accurately screen out the case of slow leakage in the reference gas chamber 320 and perform real-time zeroing calibration by setting relevant parameter thresholds. This eliminates the influence of slow leakage in the reference gas chamber 320 and ensures the accuracy of gas concentration detection by the laser gas detection device.

[0078] For example, such as Figure 8 As shown, considering the possibility of slow leakage during long-term testing of the reference gas chamber 320, a real-time zeroing calibration method is proposed in steps B1-B4. Assuming the equivalent gas concentration of the reference gas chamber 320 is 6% LEL, firstly, it checks in real-time whether the current gas concentration value of the test gas chamber 100 is negative. If a negative value is detected, it checks whether the negative value has persisted for 300 seconds; otherwise, it outputs the current gas concentration value. If the negative value has persisted for 300 seconds, it checks whether all negative values ​​within 300 seconds are less than -6% LEL; otherwise... The system outputs the current concentration value. If all negative values ​​within 300 seconds are less than -6% LEL, a sensor fault is reported. Otherwise, it checks if the difference between the average of the previous 100 seconds and the average of the last 100 seconds is less than 1% LEL. If the difference is less than 1% LEL, a zeroing calibration of the current gas concentration value is performed (i.e., the equivalent gas concentration value is updated so that the current gas concentration value obtained based on the updated equivalent gas concentration value is equal to zero). Otherwise, a damage report is issued to the reference gas chamber 320. This real-time zeroing calibration process allows for real-time detection of slow leakage in the reference gas chamber 320 and eliminates its impact, ensuring the accuracy of gas concentration detection by the laser gas detection device.

[0079] For example, the specific operation of performing the zeroing calibration of the current gas concentration value (i.e., updating the equivalent gas concentration value so that the current gas concentration value obtained based on the updated equivalent gas concentration value is equal to zero) can be as follows: If the current gas concentration value is negative, the equivalent gas concentration value (e.g., 5%) of the reference gas chamber 320 after the leak can be deduced based on the current gas concentration value. The equivalent gas concentration value (e.g., 5%) of the reference gas chamber 320 after the leak = the preliminary detection concentration value (e.g., 5%) detected after the leak - the current actual gas concentration value of the gas chamber 100 under test (i.e., 0%, the gas chamber 100 under test is currently not loaded with gas).

[0080] As can be seen from the above, the laser 200 of the laser gas detection device emits a laser beam and directs it into the test chamber 100, which contains the gas to be detected. The detector body 310 detects the laser beam that passes through the test chamber 100 and the reference chamber 320 to obtain the electrical signal of the gas to be detected. The equivalent gas concentration value of the reference chamber 320 is obtained. Based on the equivalent gas concentration value and the electrical signal of the gas to be detected, the actual detection concentration value of the gas to be detected is obtained. Since the equivalent gas concentration value of the reference chamber 320 can be used for compensation, the absorption peak can still be detected even when the concentration of the gas to be detected is low. This solves the problem that the absorption peak could not be detected at low concentrations, and the gas concentration value could not be calculated. This allows the actual concentration value of the gas to be detected to be detected even when the concentration of the gas to be detected is low, reducing the lower limit of gas concentration detection of the laser gas detection device and improving the performance of the laser gas detection device.

[0081] The foregoing has provided a detailed description of a laser gas detection device and a gas concentration detection method according to embodiments of this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the embodiments above are merely for the purpose of helping to understand the method and its core ideas. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. For example, the various technical features in the above embodiments can be arbitrarily combined, as long as there is no conflict or contradiction between the combinations of features. Therefore, any combination of the various technical features in the above embodiments also falls within the scope of this specification. In conclusion, the content of this specification should not be construed as a limitation of this application.

Claims

1. A method for detecting gas concentration, characterized in that, The method includes: The laser gas detection device emits a laser and directs the laser beam into a test chamber containing the gas to be detected. The laser gas detection device includes a laser, a test chamber, and a photodetector. The test chamber is the internal optomechanical structure space of the laser gas detection device, and the photodetector includes a detector body and a reference chamber. The detector body detects the laser light that passes through the gas chamber to be tested and the reference gas chamber to obtain the electrical signal of the gas to be tested. Obtain the equivalent gas concentration value of the reference gas chamber; The actual detection concentration of the gas to be detected is obtained by analyzing the equivalent gas concentration value and the electrical signal of the gas to be detected. The actual detection concentration value of the gas to be tested is obtained by subtracting the equivalent gas concentration value of the reference gas chamber from the preliminary detection concentration value of the gas chamber to be tested. Obtaining the equivalent gas concentration value of the reference gas chamber includes: Based on the reference gas chamber length L1, the optical path length L2 of the laser gas detection device, the gas concentration value C1 within the reference gas chamber, and a preset equivalent concentration calculation formula, the equivalent gas concentration value C of the reference gas chamber is calculated. The preset equivalent concentration calculation formula is as follows: ; The method further includes: When the test chamber is not filled with the gas to be tested, the current gas concentration value of the test chamber is obtained. The current gas concentration value is equal to the difference between the current preliminary detection concentration value of the test chamber and the equivalent gas concentration value. If the current gas concentration value of the test chamber is detected to be negative, then the duration of the current gas concentration value of the test chamber being negative is detected. If the duration of the negative current gas concentration value in the test chamber is greater than a preset duration, and the current gas concentration value is less than a preset concentration value within the preset duration, then a leak alarm is issued for the reference chamber.

2. The gas concentration detection method according to claim 1, characterized in that, The step of analyzing the equivalent gas concentration value and the electrical signal of the gas to be detected to obtain the actual detection concentration value of the gas to be detected includes: The target absorption peak and baseline voltage value of the gas to be detected are obtained by analyzing and processing the electrical signal of the gas to be detected. Based on the target absorption peak and the baseline voltage value, the preliminary detection concentration value of the gas cell to be tested is obtained; The initial detection concentration value is compensated based on the equivalent gas concentration value to obtain the compensated concentration value of the gas chamber to be tested, which is then used as the actual detection concentration value of the gas to be tested.

3. The gas concentration detection method according to claim 1, characterized in that, The method further includes: If the duration of the current gas concentration value in the test chamber being negative is greater than a preset duration, and the current gas concentration value is not less than a preset concentration value within the preset duration, then the equivalent gas concentration value is updated until the current gas concentration value obtained based on the updated equivalent gas concentration value is equal to zero.

4. A laser gas detection device, characterized in that, The laser gas detection device includes a laser, a gas chamber to be tested, and a photodetector. The gas chamber to be tested is the internal optomechanical structure space of the laser gas detection device, and the photodetector includes a detector body and a reference gas chamber. The test chamber is used to load the gas to be tested. A laser for emitting a laser beam and directing the laser beam into the gas chamber to be tested; A reference chamber for transmitting laser light emitted from the test chamber; The detector body is used to detect laser light passing through the gas chamber to be tested and the reference gas chamber, so as to obtain the electrical signal of the gas to be tested; The actual detection concentration value of the gas to be detected is obtained by analyzing the equivalent gas concentration value of the reference gas chamber and the electrical signal of the gas to be detected. The laser gas detection device further includes an analog-to-digital converter and a digital processing module, which are connected together. The analog-to-digital converter is used to convert the electrical signal of the gas to be detected into a digital signal; The digital signal is transmitted to the digital processing module, which analyzes the digital signal to obtain the actual detection concentration value of the gas to be detected. The digital processing module calculates the equivalent gas concentration value C of the reference gas chamber based on the chamber length L1 of the reference gas chamber, the optical path length L2 of the laser gas detection device, the gas concentration value C1 in the reference gas chamber, and a preset equivalent concentration calculation formula. The preset equivalent concentration calculation formula is as follows: The actual detection concentration value of the gas to be tested is obtained by subtracting the equivalent gas concentration value of the reference gas chamber from the preliminary detection concentration value of the gas chamber to be tested. When the gas chamber to be tested is not filled with the gas to be tested, the digital processing module obtains the current gas concentration value of the gas chamber to be tested. The current gas concentration value is equal to the difference between the current preliminary detection concentration value of the gas chamber to be tested and the equivalent gas concentration value. If the current gas concentration value of the test chamber is detected to be negative, then the duration of the current gas concentration value of the test chamber being negative is detected. If the duration of the negative current gas concentration value in the test chamber is greater than a preset duration, and the current gas concentration value is less than a preset concentration value within the preset duration, then a leak alarm is issued for the reference chamber.

5. The laser gas detection device according to claim 4, characterized in that, The laser gas detection device further includes an electrical signal amplification component, which is connected to the photodetector. The electrical signal amplification component is used to receive the electrical signal output by the photodetector and amplify the electrical signal of the gas to be detected. The analog-to-digital converter converts the amplified electrical signal of the gas to be detected into a digital signal.

6. The laser gas detection device according to claim 4, characterized in that, The laser gas detection device also includes a low-pass filter, which is used to filter the electrical signal of the gas to be detected.

7. The laser gas detection device according to claim 4, characterized in that, The laser gas detection device further includes a laser driver, which generates a low-frequency periodic tuning current; the laser emits laser light under the action of the current and directs the laser light into the gas chamber to be tested.

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