Laser methane sensor and detection alarm device

Abstract

The utility model provides a kind of laser methane sensor, comprising: laser emission unit, including first laser, second laser and third laser, respectively for emitting laser that can be absorbed by methane gas at normal temperature, high temperature and low temperature environment;Optical path assembly is used to guide the laser emitted by three lasers to pass through a common reaction cavity;Detector is used to receive laser after passing through the reaction cavity, and convert optical signal into electrical signal;Signal processing unit is electrically connected with the detector, for processing the electrical signal.The utility model integrates multiple specific wavelength lasers, and uses the wavelength drift characteristics with temperature, to ensure that the laser wavelength covers the absorption peak of methane gas in the entire temperature range, thereby eliminating the need for expensive DFB laser and complex TEC temperature control system in the traditional scheme, under the premise of ensuring the continuity and reliability of detection in the entire working temperature range, reduce system complexity and manufacturing cost.

Description

Technical Field

[0001] This utility model relates to the field of methane monitoring technology, and in particular to a laser methane sensor and detection alarm device. Background Technology

[0002] Currently, laser methane sensors are mainly based on the absorption principle of methane gas by infrared light of a specific wavelength (1653.7nm), combined with tunable laser absorption spectroscopy technology and harmonic detection methods to monitor gas concentration. Methane gas in the measured environment enters the absorption chamber of the sensor probe through diffusion. The laser emits infrared laser light at a fixed frequency. After passing through the chamber, the beam is received by a photodiode, converted into an electrical signal, and then processed through filtering, amplification, and temperature compensation to finally calculate the methane concentration and achieve display and alarm functions.

[0003] In existing technologies, to ensure detection accuracy, DFB lasers with a relatively narrow wavelength range are typically used in conjunction with thermoelectric coolers (TECs) for constant temperature control of the laser to prevent its output wavelength from drifting with temperature changes. However, DFB lasers are expensive, and the introduction of TEC systems further increases the complexity and manufacturing cost of the equipment, limiting the widespread adoption of this type of sensor in low-cost applications.

[0004] Therefore, the current field of methane detection urgently needs a solution that can significantly reduce system costs and simplify structural design while ensuring detection accuracy, so as to improve the practicality and market competitiveness of products. Utility Model Content

[0005] This invention proposes a laser methane sensor and detection alarm device, which solves the problems of complex system structure and high cost caused by the use of DFB laser and TEC system in the existing laser methane sensor to overcome temperature drift.

[0006] The technical solution of this utility model is implemented as follows: The first aspect of this utility model provides a laser methane sensor, comprising: The laser emitting unit includes a first laser, a second laser, and a third laser, which are used to emit laser light that can be absorbed by methane gas under normal temperature, high temperature, and low temperature environments, respectively; the center wavelengths of the first laser, the second laser, and the third laser are respectively... , and And satisfy: ,in, The absorption center wavelength of methane gas at room temperature; Optical path assembly, used to guide the lasers emitted by three lasers through a common reaction cavity; A detector is used to receive the laser light after it passes through the reaction cavity and convert the optical signal into an electrical signal; A signal processing unit, electrically connected to the detector, is used to process the electrical signal.

[0007] Specifically, the normal temperature range is 15℃~35℃, the high temperature range is 35℃~65℃, and the low temperature range is -15℃~15℃; The center wavelength of the first laser The wavelength is 1653.7 nm, which is suitable for the aforementioned room temperature range; The center wavelength of the second laser With a wavelength of 1650.7 nm, it is suitable for the high temperature range. When the ambient temperature rises to the high temperature range, its emission wavelength shifts to the long wavelength direction and enters the effective absorption bandwidth of methane gas. The center wavelength of the third laser With a wavelength of 1656.7 nm, it is suitable for the aforementioned low-temperature range. When the ambient temperature drops to the low-temperature range, its emission wavelength shifts towards shorter wavelengths and enters the effective absorption bandwidth of methane gas.

[0008] Furthermore, the first, second, and third lasers are all FP lasers, with a wavelength temperature drift coefficient of 0.1 nm / ℃ and an effective absorption bandwidth of 1653.7 ± 1 nm for methane gas.

[0009] Specifically, the optical path assembly includes a first lens and a second lens. The first lens and the second lens are respectively installed on the openings at the front and rear ends of the reaction cavity. The first lens is used to guide the laser emitted by the three lasers to the front end of the second lens, and the second lens is used to guide the laser passing through the reaction cavity to the detector.

[0010] Furthermore, the first lens and / or the second lens are focusing lenses.

[0011] Specifically, the outer front end and outer rear end of the reaction cavity are respectively provided with a transmitting cavity and a receiving cavity. The first laser, the second laser and the third laser are fixedly installed on the inner wall of the reaction cavity by a support, and the detector is installed on the inner wall of the receiving cavity.

[0012] Preferably, the reaction chamber has an air inlet and an air outlet on opposite side walls, and both the air inlet and the air outlet are equipped with filter components for removing impurities, and the air inlet or the air outlet is equipped with a fan for accelerating air circulation.

[0013] The second aspect of this utility model provides a methane detection alarm device, including an alarm and a laser methane sensor. The alarm is electrically connected to a signal processing unit, which is configured to control the alarm to respond with an audible and visual alarm when the laser energy received by the detector is lower than a set threshold.

[0014] Optionally, the alarm device further includes a display, which is electrically connected to the signal processing unit. The signal processing unit calculates the methane gas concentration based on the laser energy received by the detector and displays the concentration value on the display.

[0015] The third aspect of this utility model provides a methane detection alarm method, comprising the following steps: Three lasers with different center wavelengths can be controlled to emit lasers simultaneously or at different times, with their center wavelengths adapted to normal temperature, high temperature and low temperature environments, respectively. The lasers emitted by the three lasers are guided through a common reaction cavity by an optical path assembly. The lasers after passing through the reaction cavity are received by a detector and converted into electrical signals. The signal processing unit monitors changes in electrical signals. When the value of the electrical signal is lower than the alarm threshold, the alarm is triggered to respond with an audible and visual alarm. The alarm threshold is set based on the total light energy received by the detector or the light energy of each channel in a methane-free environment. Throughout the entire operating temperature range, at least one laser's emission wavelength falls within the effective absorption bandwidth of methane gas, ensuring continuous detection.

[0016] Compared with the prior art, the advantages of this utility model are as follows: By integrating multiple ordinary lasers with specific wavelengths and utilizing their wavelength drift characteristics with temperature, this utility model ensures that the laser wavelength covers the absorption peak of methane gas throughout the entire temperature range from high temperature to low temperature. This eliminates the need for expensive DFB lasers and complex TEC temperature control systems required in traditional solutions. While ensuring the continuity and reliability of detection throughout the entire operating temperature range, it greatly reduces the complexity of the system structure and manufacturing costs. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. 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 internal structure of a laser methane sensor according to this utility model.

[0019] Figure 2 The images show the spectra of three lasers at room temperature in this embodiment of the invention.

[0020] Figure 3 The images show the spectra of three lasers under extreme high temperatures in this embodiment of the invention.

[0021] Figure 4 The images show the spectra of three lasers operating at extremely low temperatures in this embodiment of the invention.

[0022] In the diagram: 1. First laser; 2. Second laser; 3. Third laser; 4. Reaction cavity; 5. Detector; 6. First lens; 7. Second lens; 8. Emitting cavity; 9. Receiving cavity; 10. Support; 11. Filter assembly; 12. Fan. Detailed Implementation

[0023] The technical solution of this utility model will be clearly and completely described below with reference to its embodiments. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0024] Reference Figure 1 The first aspect of this utility model provides a laser methane sensor, comprising: The laser emitting unit includes a first laser 1, a second laser 2, and a third laser 3, which are used to emit lasers that can be absorbed by methane gas at room temperature, high temperature, and low temperature environments, respectively. The center wavelengths of the first laser 1, the second laser 2, and the third laser 3 are λ1, λ2, and λ3, respectively, and satisfy: λ2 < λ1 < λ3, where λ1 is the absorption center wavelength of methane gas at room temperature. The core function of this wavelength configuration is that, by using the inherent wavelength temperature drift characteristics of the lasers through the preset wavelength difference, the three lasers can respectively cover the methane absorption peaks in a wide temperature range, realizing continuous detection of the entire temperature range without a TEC (thermoelectric cooler), fundamentally reducing the system complexity and cost. The optical path assembly is used to guide the laser beams emitted by the three lasers through a common reaction cavity 4. Its function is to integrate and guide the beams of the three lasers from different physical locations so that they pass together through the gas region to be measured (i.e., reaction cavity 4). This simplifies the optical structure, avoids setting up a separate gas chamber and detector 5 for each laser, and improves the system integration and consistency. Detector 5 is used to receive the laser light after passing through the reaction chamber 4 and convert the optical signal into an electrical signal. Its function is to sense the change in light intensity, which directly reflects the degree of absorption of the methane gas by a specific wavelength of laser light. It converts the optical information into a processable electrical signal to provide data for subsequent concentration calculation and alarm judgment. The signal processing unit is electrically connected to the detector 5 and is used to process the electrical signal, including filtering, amplifying, and analog-to-digital conversion of the electrical signal, and executing a preset algorithm (such as calculating the light intensity attenuation rate) to determine the methane gas concentration or to determine whether the alarm threshold is exceeded, so as to realize accurate signal analysis and intelligent decision-making, and control subsequent alarm and display behaviors.

[0025] This invention integrates multiple ordinary lasers with specific wavelengths and utilizes their wavelength-temperature-shifting characteristics to ensure that the laser wavelength covers the absorption peak of methane gas throughout the entire temperature range from high to low. This eliminates the need for expensive DFB lasers and complex TEC temperature control systems required in traditional solutions. While ensuring continuous and reliable detection throughout the entire operating temperature range, it greatly reduces the complexity of the system structure and manufacturing costs.

[0026] Specifically, the normal temperature range is 15℃~35℃, the high temperature range is 35℃~65℃, and the low temperature range is -15℃~15℃; like Figure 2 As shown, the center wavelength λ1 of the first laser 1 is 1653.7 nm, which is suitable for the ambient temperature range. Within this range, the wavelength of the first laser 1 is within the effective absorption bandwidth of methane gas. For example, at 25°C, λ1 is approximately 1653.7 nm, and the first laser 1 operates at its optimal sensitivity; at 15°C, λ1 is approximately 1652.7 nm, and at 35°C, λ1 is approximately 1654.7 nm, both within the effective absorption bandwidth of methane.

[0027] like Figure 3 As shown, the center wavelength λ2 of the second laser 2 is 1650.7 nm, which is suitable for the high-temperature range. When the ambient temperature rises to the high-temperature range, for example, reaching 50°C, the wavelength of the first laser 1 shifts towards longer wavelengths due to temperature drift, deviating from the absorption peak. At this time, the wavelength of the second laser 2, initially centered at 1650.7 nm, will drift to approximately 1653.2 nm, taking over the detection task. At 65°C (the upper limit temperature), its center wavelength drifts to approximately 1654.7 nm, which is still within the effective absorption bandwidth of methane.

[0028] like Figure 4As shown, the center wavelength λ3 of the third laser 3 is 1656.7 nm, which is suitable for the low-temperature range. When the ambient temperature drops to the low-temperature range, for example, to 0°C, the wavelengths of the first laser 1 and the second laser 2 both drift towards shorter wavelengths and become ineffective. At this time, the wavelength of the third laser 3, which initially has a center wavelength of 1656.7 nm, will drift to approximately 1654.2 nm and take over the detection task. At -15°C (lower limit temperature), its wavelength drifts to approximately 1652.7 nm, which is still within the effective absorption bandwidth of methane.

[0029] Furthermore, the first laser 1, the second laser 2, and the third laser 3 are all FP lasers. The wavelength temperature drift coefficient of the FP laser is 0.1 nm / ℃. The absorption of methane gas near 1653.7 nm is not an infinitely narrow line, but has a certain width, and its effective absorption bandwidth is usually not less than 2 nm (i.e., approximately 1653.7 nm ± 1 nm). The function of using FP lasers is to take advantage of their low cost and the characteristic of wavelength drift with temperature. By combining them with a preset center wavelength and a known temperature drift coefficient, the detection requirements of the entire temperature range can be accurately predicted and covered, thereby achieving the performance level of a high-cost DFB laser combined with a TEC system using low-cost components.

[0030] Specifically, the optical path assembly includes a first lens 6 and a second lens 7. The first lens 6 and the second lens 7 are respectively mounted on the openings at the front and rear ends of the reaction cavity 4. The first lens 6 guides the laser beams emitted by the three lasers to the front end of the second lens 7, and the second lens 7 guides the laser beams passing through the reaction cavity 4 to the detector 5. The function of the first lens 6 is to collimate or converge the emitted beams from the three lasers, enabling them to be efficiently coupled into the reaction cavity 4. The function of the second lens 7 is to collect and converge the beams emitted from the reaction cavity 4, which may have been attenuated by methane absorption, and efficiently focus them onto the photosensitive surface of the detector 5, thereby maximizing light energy utilization, improving the signal-to-noise ratio, and ensuring the stability and consistency of the multi-path optical system.

[0031] Furthermore, the first lens 6 and / or the second lens 7 are focusing lenses (in this embodiment, both lenses are focusing lenses). The function of using a focusing lens is to reduce the beam divergence angle and improve the beam spot quality. This enhances the intensity of the light signal received by the detector 5 and reduces measurement errors caused by beam scattering, thereby improving the sensitivity and accuracy of the detection.

[0032] Specifically, the outer front end and outer rear end of the reaction cavity 4 are respectively provided with a transmitting cavity 8 and a receiving cavity 9. The first laser 1, the second laser 2, and the third laser 3 are fixedly mounted on the inner wall of the reaction cavity 4 via a support 10, and the detector 5 is mounted on the inner wall of the receiving cavity 9. The function of setting up independent transmitting cavities 8 and receiving cavities 9 is to provide physical protection and a stable installation environment for the lasers and detector 5, avoiding external mechanical stress and stray light interference. Its technical effect is to improve the mechanical stability of the sensor and the long-term reliability of optical measurements.

[0033] Preferably, the reaction chamber 4 has an air inlet and an air outlet on opposite sidewalls. Both the air inlet and outlet are equipped with filter components 11 for removing impurities, and a fan 12 for accelerating airflow is installed at either the air inlet or outlet. By providing air inlets and outlets with filters and a fan 12 in the reaction chamber 4, airflow is accelerated to improve response speed, while dust and other impurities are filtered out, preventing optical window contamination and airflow blockage, thereby ensuring long-term monitoring accuracy and extending the sensor's lifespan.

[0034] A second aspect of this invention provides a methane detection alarm device, including an alarm and a laser methane sensor. The alarm is electrically connected to a signal processing unit, which is configured to control the alarm to respond with an audible and visual alarm when the laser energy received by the detector is below a set threshold. By setting the alarm, the sensor's detection results are converted into intuitive and urgent audiovisual warnings. This ensures that in the event of a methane gas leak, on-site personnel can be promptly alerted, effectively preventing safety accidents.

[0035] Optionally, the alarm device further includes a display, which is electrically connected to the signal processing unit. The signal processing unit calculates the methane gas concentration based on the laser energy received by the detector 5 and displays the concentration value on the display.

[0036] The methane detection alarm method of this utility model includes the following steps: System initialization and calibration: In a methane-free environment, control the three lasers to work sequentially or simultaneously, and record the reference electrical signal value (i.e., "total optical energy" or "optical energy of each channel") corresponding to detector 5. Set this as the basis for calculating the system reference and alarm threshold.

[0037] Normal monitoring cycle: Control three lasers with different center wavelengths to emit lasers simultaneously or at different times. Their center wavelengths are adapted to normal temperature, high temperature and low temperature environments, respectively. The lasers emitted by the three lasers are guided through a common reaction cavity 4 by an optical path component.

[0038] Signal detection and conversion: The laser light passing through the reaction cavity 4 is received by the detector 5 and converted into a combined or time-division electrical signal.

[0039] Signal processing and judgment: The signal processing unit continuously monitors the changes in the electrical signal and compares the currently received light energy signal with the alarm threshold set in the initialization stage. The alarm threshold is set based on the total light energy or the light energy of each channel received by the detector 5 in a methane-free environment.

[0040] Alarm Trigger: When the value of the electrical signal (reflecting the received light energy) is lower than the alarm threshold, it indicates that methane gas has absorbed a specific wavelength of laser light, and the signal processing unit immediately triggers the alarm to respond with an audible and visual alarm.

[0041] High-temperature range (35℃ ~ 65℃) adaptive switching: When the ambient temperature rises and exceeds the upper limit of the core ambient temperature range (approximately 35℃), the emission wavelength of the first laser 1 shifts towards longer wavelengths, gradually deviating from the absorption peak center. Simultaneously, the emission wavelength of the second laser 2 also shifts towards longer wavelengths, entering the effective absorption bandwidth of methane. At 65℃, its center wavelength reaches 1654.7nm, still within the absorption peak range. The system, through its signal processing unit, identifies the significant attenuation of the light intensity signal from the second laser 2 channel due to methane absorption and uses this channel for alarm judgment, achieving adaptive switching to the high-temperature range.

[0042] Low-temperature range (-15℃ ~ 15℃) adaptive: When the ambient temperature drops below the lower limit of the core ambient temperature range (approximately 15℃), the emission wavelength of the first laser 1 shifts towards shorter wavelengths, deviating from the center of the absorption peak. At this time, the emission wavelength of the third laser 3 also shifts towards shorter wavelengths as the temperature decreases, entering the effective absorption bandwidth of methane. At -15℃, its center wavelength shifts to 1652.7nm, located in the core region of the absorption peak. The system, through its signal processing unit, identifies that the light intensity signal of the third laser 3 channel is sensitive to methane at low temperatures and automatically switches to this channel as the alarm basis, thereby ensuring the continuity and reliability of detection throughout the defined low-temperature range.

[0043] This invention employs three FP lasers with specific center wavelengths and determines their optimal operating temperature range (-15℃ to 65℃) based on rigorous physical calculations. Within this range, utilizing the temperature drift characteristics of the lasers, the system can always ensure that the emission wavelength of at least one laser completely covers the effective absorption bandwidth of methane gas, thereby achieving continuous and reliable detection within a wide temperature range of 80℃ without the need for a DFB laser and a TEC temperature control system.

[0044] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A laser-driven methane sensor, characterized in that, include: The laser emitting unit includes a first laser (1), a second laser (2), and a third laser (3), which are used to emit lasers that can be absorbed by methane gas in normal temperature, high temperature, and low temperature environments, respectively; the center wavelengths of the first laser (1), the second laser (2), and the third laser (3) are λ1, λ2, and λ3, respectively, and satisfy: λ2<λ1<λ3, where λ1 is the absorption center wavelength of methane gas at normal temperature; Optical path assembly for guiding the lasers emitted by the three lasers through a common reaction cavity (4); The detector (5) is used to receive the laser light after it passes through the reaction cavity (4) and convert the optical signal into an electrical signal; The signal processing unit is electrically connected to the detector (5) and is used to process the electrical signal.

2. The laser methane sensor as described in claim 1, characterized in that, The normal temperature range is 15℃~35℃, the high temperature range is 35℃~65℃, and the low temperature range is -15℃~15℃; The center wavelength λ1 of the first laser (1) is 1653.7nm, which is suitable for the normal temperature range; The center wavelength λ2 of the second laser (2) is 1650.7nm, which is suitable for the high temperature range. When the ambient temperature rises to the high temperature range, its emission wavelength drifts to the long wavelength direction and enters the effective absorption bandwidth of methane gas. The center wavelength λ3 of the third laser (3) is 1656.7nm, which is suitable for the low temperature range. When the ambient temperature drops to the low temperature range, its emission wavelength shifts to the short wave direction and enters the effective absorption bandwidth of methane gas.

3. A laser methane sensor as described in claim 2, characterized in that, The first laser (1), the second laser (2) and the third laser (3) are all FP lasers. The wavelength temperature drift coefficient of the FP laser is 0.1 nm / ℃ and the effective absorption bandwidth of methane gas is 1653.7±1nm.

4. A laser methane sensor as described in claim 1, characterized in that, The optical path assembly includes a first lens (6) and a second lens (7). The first lens (6) and the second lens (7) are respectively installed on the openings at the front and rear ends of the reaction cavity (4). The first lens (6) is used to guide the laser emitted by the three lasers to the front end of the second lens (7). The second lens (7) is used to guide the laser passing through the reaction cavity (4) to the detector (5).

5. A laser methane sensor as described in claim 4, characterized in that, The first lens (6) and / or the second lens (7) are focusing lenses.

6. A laser methane sensor as described in claim 1, characterized in that, The front outer side and the rear outer side of the reaction cavity (4) are respectively provided with a transmitting cavity (8) and a receiving cavity (9). The first laser (1), the second laser (2) and the third laser (3) are fixedly installed on the inner wall of the reaction cavity (4) by a support (10). The detector (5) is installed on the inner wall of the receiving cavity (9).

7. A laser methane sensor as described in claim 1, characterized in that, The reaction chamber (4) has an air inlet and an air outlet on opposite side walls. Both the air inlet and the air outlet are equipped with filter components (11) for filtering out impurities. The air inlet or the air outlet is equipped with a fan (12) for accelerating air circulation.

8. A methane detection alarm device, characterized in that, The device includes an alarm and a laser methane sensor as described in any one of claims 1 to 7, wherein the alarm is electrically connected to a signal processing unit, and the signal processing unit is configured to control the alarm to respond to an audible and visual alarm when the laser energy received by the detector (5) is lower than a set threshold.

9. A methane detection alarm device as described in claim 8, characterized in that, The alarm device also includes a display, which is electrically connected to the signal processing unit. The signal processing unit calculates the methane gas concentration based on the laser energy received by the detector (5) and displays the concentration value on the display.

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