TDLAS (Tunable Diode Laser Absorption Spectroscopy) gas detection device with built-in standard gas chamber and self-detection method

Abstract

The invention discloses a TDLAS (Tunable Diode Laser Absorption Spectroscopy) gas detection device with a built-in standard gas chamber and a self-detection method, the device comprises a laser, a to-be-detected gas channel, a laser receiver, a signal processing unit and a fault detection and self-calibration module, the standard gas chamber is arranged in the laser, and standard gas with the fixed concentration of X standard is sealed in the standard gas chamber. During detection, laser sequentially penetrates through the standard gas chamber and the to-be-detected gas channel, the laser receiver converts an optical signal into an electric signal, the signal processing unit calculates the total gas concentration X total based on the TDLAS principle, and detection, fault recognition and self-calibration are achieved by comparing the theoretical relation between X total and X standard and the theoretical relation between X to-be-detected gas concentration X to-be-detected. The device solves the problems that an existing TDLAS device is sensitive in environmental interference and cannot detect sensor failure in real time, has the advantages of being high in measurement precision, low in maintenance cost and high in safety, is widely applied to industrial production, environmental protection monitoring and other scenes, and effectively guarantees the reliability of a detection result and the use safety.

Description

A TDLAS gas detection device with a built-in standard gas chamber and its self-testing method Technical Field

[0001] This invention belongs to the field of gas detection technology, and particularly relates to a gas detection device and self-detection method based on the principle of tunable semiconductor laser absorption spectroscopy (TDLAS) and having a self-detection function. Background Technology

[0002] With the increasing demands for accuracy and reliability in gas concentration detection from industrial production and environmental protection sectors, traditional gas detection methods are no longer sufficient. TDLAS technology, due to its advantages such as high sensitivity, rapid response, and non-contact measurement, has been widely applied in the field of gas detection.

[0003] Existing TDLAS gas detection devices typically rely on external calibration equipment or periodic manual calibration. They primarily utilize lasers to detect the standard gas in a standard gas storage unit. The gas concentration in the storage unit is calculated based on calibration coefficients stored at the processor's factory settings and compared to a preset known standard gas concentration. If they differ, it indicates a potential malfunction in the detection unit or a need to adjust the calibration coefficients. During detection, a laser drive unit generates a laser drive signal to modulate the temperature and current of a tuned semiconductor laser. The detection signal is then processed by a multi-channel filtering and amplification unit. The processor performs time-division or simultaneous filtering, phase-locked amplification, and derives the first and second harmonics. The concentration of the gas to be detected is then calculated based on the factory-stored calibration coefficients. When the calculated gas concentration in the standard gas storage unit differs from the preset known standard gas concentration, the gas concentration to be detected is multiplied by a compensation coefficient to obtain the accurate concentration, and the result is output.

[0004] However, existing TDLAS gas detection devices have many drawbacks: they rely excessively on external standard gas calibration, and traditional devices require periodic calibration with standard gas, which is complex and costly; they are sensitive to environmental interference, and laser wavelength drift or gas chamber contamination can lead to detection errors, requiring frequent maintenance; they have complex structures, and multi-component detection requires multiple lasers or adjustable optical paths, increasing costs; and during long-term use, factors such as laser aging, optical component contamination, or environmental changes may cause a decrease in measurement accuracy, making it difficult to detect and calibrate these problems in a timely manner, affecting the reliability of the detection results, and there is also the problem of laser sensor failure that cannot be detected. Summary of the Invention

[0005] The purpose of this invention is to address the problem that existing TDLAS gas detection devices cannot detect laser sensor failures in a timely manner, and to provide a TDLAS gas detection device with a built-in standard gas chamber and a self-testing method. This device has self-testing and self-calibration functions, which can improve detection accuracy, reduce usage costs and enhance usage safety.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A TDLAS gas detection device with a built-in standard gas chamber includes:

[0008] A laser, used to emit laser light of a specific wavelength, has a sealed standard gas chamber inside, which contains a standard gas of a fixed concentration.

[0009] The gas channel to be tested is connected to the laser output end of the laser, and it is provided with a gas inlet for introducing the gas to be tested or the calibration gas.

[0010] A laser receiver is positioned opposite the laser output end of the gas channel under test to receive laser signals and convert them into electrical signals.

[0011] Used for signal processing, concentration calculation, and accuracy determination;

[0012] The fault detection and self-calibration module is electrically connected to the signal processing unit and the laser, respectively. It is used to receive the detection data transmitted by the signal processing unit in real time, determine whether there is a standard gas absorption signal, and trigger a fault prompt when there is no standard gas absorption signal. At the same time, it sends a control signal to the laser to adjust the laser's emission parameters to achieve the self-calibration function.

[0013] As a further description of the above technical solution: the standard gas is methane.

[0014] As a further description of the above technical solution: the transmission parameters include the transmission wavelength and the transmission power.

[0015] This invention also provides a self-testing method for the above-mentioned TDLAS gas detection device with a built-in standard gas chamber, comprising the following steps:

[0016] S1. Introduce the gas to be tested into the gas channel through the gas inlet;

[0017] S2. Start the device; the laser emits a specific wavelength of laser light, which passes sequentially through a concentration of X. 标准 The standard gas and the gas to be tested both exhibit two characteristic absorptions.

[0018] S3. The laser receiver receives the laser signal after two characteristic absorptions, converts it into an electrical signal, and transmits it to the signal processing unit.

[0019] S4. The signal processing unit calculates the total gas concentration X based on the TDLAS principle. 总 Calculate and output the concentration of the gas to be measured after the device's detection accuracy has been corrected;

[0020] S5, the fault detection and self-calibration module receives the detection data transmitted by the signal processing unit in real time, and calculates the total gas concentration X. 总 Compared with standard gas concentration X 标准 The system determines whether a standard gas absorption signal is present. If no standard gas absorption signal is present, a fault prompt is triggered and the self-calibration function is activated. The device is then restored to normal measurement status by adjusting the laser's emission parameters.

[0021] As a further description of the above technical solution: Step S5, determining whether a standard gas absorption signal exists, specifically involves: if X 总 ≥X 标准 If X 总 <X 标准 If the standard gas signal is missing (e.g., gas leakage in the standard gas chamber leads to a decrease in standard gas concentration X), it is determined that the standard gas signal is absent. 标准 =0 or failure of the laser sensor, resulting in the inability to detect the standard gas concentration.

[0022] As a further description of the above technical solution: the transmission parameters include the transmission wavelength and the transmission power.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. Improve measurement accuracy: With a built-in standard gas chamber and self-calibration function, the detection results can be calibrated and compensated in real time, eliminating measurement errors caused by environmental changes, equipment aging and other factors, and improving the accuracy and precision of gas concentration detection.

[0025] 2. Enhance market competitiveness: TDLAS gas detection devices with self-testing functions can provide more reliable and accurate detection results, meeting users' needs for high performance and high stability in gas detection devices. This helps companies establish a good brand image in the market, improve the market competitiveness of their products, and promote the economic development of enterprises.

[0026] 3. Enhanced Safety: The self-diagnostic function of the TDLAS gas detection device can promptly detect device malfunctions, preventing hazardous gas leaks caused by device failure and ensuring personnel and public safety. For example, in the production, storage, and transportation of flammable and explosive gases such as chemicals and natural gas, timely detection, repair, or replacement of detector malfunctions can effectively prevent explosions, fires, and other accidents, reducing casualties and property damage. Attached Figure Description

[0027] Figure 1 is a schematic diagram of the gas detection device of the present invention.

[0028] Figure label:

[0029] 1-Laser, 2-Gas channel to be tested, 3-Laser receiver, 4-Signal processing unit, 5-Fault detection and self-calibration module, 6-Standard gas chamber, 7-Gas inlet. Detailed Implementation

[0030] The claims of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but this does not constitute any limitation on the present invention. Any limited modifications made by any person within the scope of protection of the claims of the present invention shall still be within the scope of protection of the claims of the present invention.

[0031] A TDLAS gas detection device with a built-in standard gas chamber, as shown in Figure 1, includes a laser 1, a gas channel 2, a laser receiver 3, a signal processing unit 4, and a fault detection and self-calibration module 5. The laser 1 emits laser light of a specific wavelength, and a sealed standard gas chamber 6 is installed inside the laser 1. The standard gas chamber 6 is sealed with a fixed concentration of X. 标准 The standard gas (usually methane) standard gas chamber 6 is detachably installed inside the laser 1 for easy replacement; the gas to be tested channel 2 is connected to the laser output end of the laser 1, and has a gas inlet 7 for introducing the gas to be tested or calibration gas (a calibration gas of known concentration is introduced during calibration); the laser receiver 3 is set opposite to the laser output end of the gas to be tested channel 2, and is used to receive the laser signal passing through the standard gas chamber 6 and the gas to be tested channel 2, convert it into an electrical signal and transmit it; the signal processing unit 4 is connected to the signal output end of the laser receiver 3, and performs signal processing (such as filtering, spectral feature extraction, etc.), concentration calculation, accuracy judgment and other functions; the control end of the fault detection and self-calibration module 5 is connected to the signal processing unit 4, and the output end is connected to the parameter adjustment end of the laser 1, and is used to receive the concentration data transmitted by the signal processing unit in real time, and determine whether there is a situation where there is no standard gas absorption signal (core fault). When there is no standard gas absorption signal, a fault prompt is triggered, and a control signal is sent to the laser to adjust the laser's emission parameters, correct the measurement deviation caused by adjustable factors such as laser aging and environmental interference, and realize the self-calibration function.

[0032] In this embodiment, the signal processing unit uses an STM32 series microcontroller, and the laser receiver uses an InGaAs photodetector to ensure signal processing accuracy and response speed; the standard gas chamber is made of sealed ceramic material to effectively prevent gas leakage and ensure the standard gas concentration X. 标准 Long-term stability.

[0033] The specific work process is as follows:

[0034] Accuracy calibration (generally performed every six months or one year to ensure the device's measurement accuracy meets requirements): Introduce a known concentration of X into the gas channel to be measured. 标定 The calibration gas (externally introduced, used only for this calibration) is first passed through a fixed concentration of X sealed inside the laser after the laser emits a laser of a specific wavelength. 标准 The standard gas is then introduced into the gas channel to be tested, passing through a concentration of X. 标定 The calibration gas is finally received by the laser receiver; the laser receiver converts the received laser signal into an electrical signal and transmits it to the signal processing unit; the signal processing unit, based on the Lambert-Beer Law, calculates the total gas concentration X that causes the laser intensity attenuation by measuring the intensity changes of the incident and emitted light. 总 Theoretically, X 总 It should be equal to X 标准 +X 标定 If the calculated X 总 With X 标准 +X 标定 If the difference ΔX is within the preset error range (±5 ppm), the device measurement is considered normal, and the difference ΔX is taken as the device's detection accuracy. For example, in a calibration, the methane gas concentration X in standard gas chamber 6... 标准 =100 ppm, the concentration X of the calibration gas methane introduced into the gas channel 2 is 100 ppm. 标定 =50 ppm. Theoretically, the total concentration X corresponding to the laser signal calculated by signal processing unit 4 is... 总 It should be 150 ppm; the actual total gas concentration X calculated by signal processing unit 4 总 The concentration is 148 ppm. When compared with the theoretical value of 150 ppm, the difference ΔX is 2 ppm. If it is within the preset error range of ±5 ppm, the device is considered to be measuring normally. The measurement accuracy of the device is 2 ppm. The output corrected gas concentration X=48+2=50 ppm is taken as the measured gas concentration.

[0035] Under normal detection conditions, processing unit 4 receives the standard gas (concentration X) transmitted by laser receiver 3. 标准 The laser signals from the absorption of the target gas twice (after being converted into electrical signals) are analyzed and processed based on the TDLAS (Tunable Semiconductor Laser Absorption Spectroscopy) principle (e.g., filtering, spectral feature extraction), and the total gas concentration X that causes the laser intensity attenuation is calculated. 总 Based on the total gas concentration X 总 Compared with standard gas concentration X 标准 and the concentration of the gas to be measured X 待测Based on the theoretical relationship, calculate the concentration of the gas to be measured, X. 待测 =X 总 -X 标准， The calculated results are then corrected based on the device's detection accuracy ΔX, and finally, the corrected gas concentration X=X is output. 待测 +ΔX, and trigger an alarm when the gas concentration exceeds a preset concentration threshold (e.g., 100ppm) to alert that a gas leak has occurred.

[0036] During the detection process, theoretically, since the concentration of the gas to be tested is ≥0, the total gas concentration X 总 =X 标准 +X 待测 ≥X 标准 If the fault detection and self-calibration module detects X 总 <X 标准 If no standard gas absorption signal is detected (this may be due to adjustable factors such as laser emission power attenuation or wavelength drift causing the standard gas to be ineffectively absorbed, leakage in the standard gas chamber leading to standard gas loss, or a malfunction of a component in the device resulting in the inability to detect the gas absorption signal), then it is determined that there is no standard gas signal, triggering a fault indication and activating the self-calibration function. The fault detection and self-calibration module corrects the measurement deviation caused by adjustable factors by adjusting the laser emission parameters (such as wavelength or power) until the device returns to normal operating status (X). 总 ≥X 标准 This ensures the accuracy of subsequent measurements. If adjusting the laser emission parameters still cannot eliminate the fault, there may be non-automatic situations such as gas leakage in the standard gas chamber or device detection failure, requiring manual intervention to troubleshoot the fault (such as replacing the standard gas chamber or replacing the laser).

[0037] The self-test method includes the following steps:

[0038] S1. Introduce the gas to be tested into the gas channel through the gas inlet;

[0039] S2. Start the device; the laser emits a specific wavelength of laser light, which passes sequentially through a concentration of X. 标准 The standard gas and the gas to be tested both exhibit two characteristic absorptions.

[0040] S3. The laser receiver receives the laser signal after two characteristic absorptions, converts it into an electrical signal, and transmits it to the signal processing unit.

[0041] S4. The signal processing unit calculates the total gas concentration X based on the TDLAS principle. 总 Calculate and output the concentration of the gas to be measured, X=X, after calibration by the device. 总 -X 标准 -ΔX;

[0042] S5, the fault detection and self-calibration module receives the detection data transmitted by the signal processing unit in real time, and calculates the total gas concentration X. 总 Compared with standard gas concentration X 标准 Determine the presence of a standard gas absorption signal based on the relationship between X and X: 总 ≥X 标准 If X 总 <X 标准 If no standard gas signal is detected, a fault message will be triggered and the self-calibration function will be activated. The device will then be restored to normal measurement status by adjusting the laser's emission parameters (emission wavelength or emission power).

[0043] For example, during the detection process, when the calculated total gas concentration X 总 =48 ppm, less than 100 ppm, therefore it is determined that no absorption signal of the standard gas was detected (due to leakage of the standard gas, X). 标准 =0), triggering a fault indication to avoid misjudgment of hazardous gas leaks due to device malfunction; at the same time, a control signal is sent to the laser to activate the self-calibration function by adjusting the key emission parameters of the laser (such as laser wavelength and emission power), correcting measurement deviations caused by factors such as laser aging and environmental interference, restoring the device to normal detection status, and ensuring the accuracy of subsequent detection results without relying on external calibration equipment or manual intervention; only when self-calibration cannot eliminate the fault is manual intervention required to investigate the cause of the fault (such as leakage in the standard gas chamber or laser failure).

[0044] The monitoring device of the present invention can utilize methane gas of a fixed concentration sealed in a standard gas chamber 6 and a fault detection and self-calibration module 5 to calibrate and compensate the detection results in real time during the detection process, eliminate measurement errors caused by environmental changes, equipment aging and other factors, and improve the accuracy and precision of gas concentration detection; at the same time, it can detect faults to avoid misjudgment of dangerous gas leaks due to device failure.

[0045] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them; those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the protection scope of the present invention.

Claims

1. A TDLAS gas detection device with a built-in standard gas chamber, comprising: A laser emits laser light of a specific wavelength and has a sealed standard gas chamber containing a standard gas of a fixed concentration. A test gas channel is connected to the laser output of the laser and has a gas inlet for introducing the test gas or calibration gas. A laser receiver is positioned opposite the laser output of the test gas channel to receive the laser signal and convert it into an electrical signal. A signal processing unit is electrically connected to the laser receiver and analyzes the electrical signal, performing signal processing, concentration calculation, and accuracy determination. A fault detection and self-calibration module is electrically connected to both the signal processing unit and the laser. It receives detection data transmitted by the signal processing unit in real time, determines the presence of a standard gas absorption signal, triggers a fault indication when no standard gas absorption signal is present, and simultaneously sends control signals to the laser to adjust its emission parameters, thus achieving self-calibration.

2. The TDLAS gas detection device with a built-in standard gas chamber according to claim 1, characterized in that: The standard gas mentioned is methane.

3. The TDLAS gas detection device with a built-in standard gas chamber according to claim 1, characterized in that: The transmission parameters include the transmission wavelength and the transmission power.

4. A self-testing method for the device according to any one of claims 1 to 3, characterized in that, Includes the following steps: S1. Introduce the gas to be tested into the gas channel through the gas inlet; S2. Start the device, the laser emits a specific wavelength of laser light, and the laser light passes sequentially through the concentration of X. 标准 The standard gas and the gas to be tested undergo two characteristic absorptions; S3, the laser receiver receives the laser signal after the two characteristic absorptions, converts it into an electrical signal and transmits it to the signal processing unit; S4. The signal processing unit calculates the total gas concentration X based on the TDLAS principle. 总 The system calculates and outputs the concentration of the gas to be tested, corrected for device detection accuracy. S5, the fault detection and self-calibration module, receives the detection data transmitted by the signal processing unit in real time during the detection process, and calculates the concentration based on the total gas concentration X. 总 Compared with standard gas concentration X 标准 The system determines whether a standard gas absorption signal is present. If no standard gas absorption signal is present, a fault prompt is triggered and the self-calibration function is activated. The device is then restored to normal measurement status by adjusting the laser's emission parameters.

5. The self-testing method of the TDLAS gas detection device with a built-in standard gas chamber according to claim 4, characterized in that: Step S5, determining whether a standard gas absorption signal exists, specifically involves: if X 总 ≥X 标准 If X 总 <X 标准 If the signal is not found, it is determined that there is no standard gas signal.

6. The self-testing method of the TDLAS gas detection device with a built-in standard gas chamber according to claim 4, characterized in that: The transmission parameters include the transmission wavelength and the transmission power.

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