Laser methane gas sensor with reference light path

Abstract

The utility model provides a laser methane gas sensor with a reference light path, which comprises a sensor body, the sensor body is provided with a laser, a detector, a reference gas chamber and a detection gas chamber communicated with the outside, and the reference gas chamber is filled with target gas with fixed gas concentration; wherein the detection gas chamber, the reference gas chamber, the laser and the detector are matched to form a target gas detection and laser wavelength calibration light path, or form a target gas detection light path and a laser wavelength calibration light path. The laser methane gas sensor with the reference light path has the advantages that the reference light path is integrated in the sensor, so that real-time tracking and calibration of the output central wavelength of the laser are realized, and the accuracy of a laser gas detection system for detecting target gas is further improved; and the correlation light path is selected, so that compared with a reflective light path, the water vapor interference resistance of the laser gas detection system is further enhanced.

Description

TECHNICAL FIELD

[0001] The utility model relates to a kind of laser methane sensors, specifically, a kind of laser methane gas sensor with reference light path is involved. BACKGROUND

[0002] Methane is the main component of natural gas, and its lower explosive limit is 5% VOL. In addition, methane is also a greenhouse gas, and the greenhouse effect of the same amount of methane is more than 20 times that of carbon dioxide. Therefore, from the perspective of reducing safety accidents or controlling greenhouse effect, we should strictly monitor the concentration of methane.

[0003] Although traditional electrochemical and semiconductor methane sensors have the advantage of low price, they have the disadvantages of poor gas selectivity and easy interference. Compared with them, laser methane gas detection systems have strong advantages, strong anti-interference performance and rapid response.

[0004] At present, in order to realize low cost, the first probe and reference gas chamber are not used in household laser methane gas detection devices, such as a household laser flammable gas sensor disclosed in Chinese utility model patent CN202420119404.1. When such household / commercial laser methane gas detection devices detect target gas under changing conditions of external environment temperature, etc., they cannot determine whether the center wavelength of the laser output drifts. In order to realize high-precision measurement of the laser, it is necessary to ensure that the center wavelength of the laser light source in the laser system is exactly aligned with the absorption wavelength of the measured gas. However, factors such as driving current and environmental temperature of the laser light source will cause the wavelength of the laser chip to drift, resulting in inaccurate detection of target gas or false alarm of the laser methane gas detection device.

[0005] In order to solve the above problems, people have been seeking an ideal technical solution. CONTENT OF THE UTILITY MODEL

[0006] The utility model aims at the deficiency of prior art, and provides a laser methane gas sensor with reference light path.

[0007] In order to achieve the above purpose, the utility model adopts the technical scheme of: including sensor body, laser, detector, reference gas chamber and detection gas chamber communicating with the outside on the sensor body, the reference gas chamber is filled with target gas with fixed gas concentration;

[0008] The output light beam of the laser passing through the detection gas chamber and the reference gas chamber cooperates with the detector to form a target gas detection and laser wavelength calibration light path; or the output light beam of the laser passing through only the detection gas chamber cooperates with the detector to form a target gas detection light path, and the output light beam of the laser passing through the detection gas chamber and the reference gas chamber cooperates with the detector to form a laser wavelength calibration light path.

[0009] Based on the above, the detector includes a composite detector, and the output light beam of the laser passing through the detection gas chamber and the reference gas chamber is detected by the composite detector to form the target gas detection and laser wavelength calibration light path, which is used for detecting the target gas concentration in the detection gas chamber and calibrating the wavelength of the output light beam of the laser.

[0010] Based on the above, the laser outputs a focused laser beam, and the laser and the composite detector are arranged at opposite ends of the detection gas chamber.

[0011] Based on the above, the reference gas chamber is integrally integrated into the light entrance side of the composite detector to form a photoelectric detector with a reference gas chamber.

[0012] Based on the above, the detector includes a detection detector and a reference detector, the output light beam of the laser passing through only the detection gas chamber is detected by the detection detector to form the target gas detection light path, which is used for detecting the target gas concentration in the detection gas chamber; and the output light beam of the laser passing through the detection gas chamber and the reference gas chamber in sequence is detected by the reference detector to form the laser wavelength calibration light path, which is used for calibrating the wavelength of the output light beam of the laser.

[0013] Based on the above, the laser outputs a focused laser beam, and a beam splitter is arranged in the detection gas chamber, and after the focused laser beam passes through the beam splitter, part of the focused laser beam is detected by the detection detector after passing through only the detection gas chamber, and the other part of the focused laser beam is detected by the reference detector after passing through the detection gas chamber and the reference gas chamber in sequence.

[0014] Based on the above, the laser outputs a divergent laser beam, and part of the divergent laser beam is detected by the detection detector after passing through only the detection gas chamber, and the other part of the divergent laser beam is detected by the reference detector after passing through the detection gas chamber and the reference gas chamber in sequence.

[0015] Based on the above, the laser and the detection probe are arranged at opposite ends of the detection gas chamber, and the reference gas chamber and the reference probe are arranged on the side wall or bottom wall of the detection gas chamber between the laser and the detection probe.

[0016] Based on the above, the reference gas chamber and the reference probe are arranged in the mounting groove of the side wall or bottom wall of the detection gas chamber, the bottom of the detection gas chamber is provided with a circuit board, and a chamfer is arranged at the communication position of the mounting groove and the detection gas chamber.

[0017] Based on the above, the reference gas chamber is integrally integrated into the light inlet side of the reference probe to form a photoelectric detector with a reference gas chamber.

[0018] Based on the above, the side wall and the bottom wall of the detection gas chamber are blackened.

[0019] Based on the above, the laser adopts a TO package, and the laser adopts a TEC type laser or a heating type laser.

[0020] The utility model discloses relative prior art has substantial feature and progress, specifically speaking, the laser methane gas sensor with reference light path of the utility model has the advantages that: by integrating reference light path in household laser methane gas sensor, namely using reference gas chamber and corresponding photoelectric detector, the real -time tracking and calibration of laser output center wavelength are realized, and the accuracy of laser gas detection system detecting target gas is further improved, and the selected light path is compared with the reflection type light path, and the water vapor interference performance of laser gas detection system is further enhanced. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 It is the whole structure schematic diagram of embodiment 1 of the utility model;

[0022] Figure 2 It is another structure schematic diagram of embodiment 1 in the utility model;

[0023] Figure 3 It is the whole structure schematic diagram of embodiment 2 in the utility model;

[0024] Figure 4 It is the whole structure schematic diagram of embodiment 3 in the utility model;

[0025] Figure 5 It is another structure schematic diagram (without chamfer) of embodiment 3 in the utility model;

[0026] Figure 6 It is another structure schematic diagram (with chamfer) of embodiment 3 in the utility model;

[0027] In the drawing, the reference signs are:

[0028] Sensor body 10; laser 1; detector 2, composite detector 21, detection detector 22, reference detector 23, photodetector 24 with reference gas chamber; detection gas chamber 3; reference gas chamber 4; beam splitter 5; chamfer 6. Detailed Implementation

[0029] The technical solution of this utility model will be further described in detail below through specific embodiments.

[0030] Example 1

[0031] like Figure 1 , Figure 2 As shown, the laser methane gas sensor with a reference optical path in this embodiment includes a sensor body 10. The sensor body 10 is also equipped with a laser 1 and a detector 2. The detector 2 is a photodetector to detect the laser beam emitted by the laser 1. The sensor body 10 is equipped with a detection chamber 3, which is connected to the outside to allow the target gas (such as methane gas) to enter smoothly, facilitating the detection of the target gas in conjunction with the laser 1 and the detector 2. The sensor body 10 is also equipped with a reference chamber 4. The interior of the detection chamber 3 is connected to the optical path of the reference chamber 4. The reference chamber 4 is filled with a target gas of a fixed concentration. The reference chamber 4 is used to calibrate the laser wavelength in conjunction with the laser 1 and the detector 2. Of course, the sensor body 10 is also equipped with related circuits, such as circuits for sending / receiving signals to the laser 1 and the detector 2 and a microcontroller for processing signals. Generally, the related circuits are set on a circuit board, which is set at the bottom of the sensor body 10 (opposite to the side where the detection chamber 3 is set, i.e., the detection chamber 3 is set at the top of the sensor body 10).

[0032] In this embodiment, the detector 2 is equipped with only one composite detector 21. The composite detector 21 is a photodetector. The reference gas chamber 4 is located inside the detection gas chamber 3. The detection gas chamber 3 and the reference gas chamber 4 are located between the laser 1 and the composite detector 21. The laser beam emitted by the laser 1 will be detected by the composite detector 21 after passing through the detection gas chamber 3 and the reference gas chamber 4.

[0033] In this embodiment, the laser 1 outputs a focused laser beam, that is, the output beam of the single-path laser 1 is detected by the composite detector 21.

[0034] In this embodiment, the composite detector 21 is used to detect the concentration of the target gas in the detection chamber 3 and to calibrate the wavelength of the output beam of the laser 1; specifically, the output beam of the laser 1 passing through the detection chamber 3 and the reference chamber 4 in turn is detected by the composite detector 21, forming a target gas detection and laser wavelength calibration optical path, that is, the laser 1, the composite detector 21, the detection chamber 3 and the reference chamber 4 are used for target gas detection together, and the laser 1, the composite detector 21, the detection chamber 3 and the reference chamber 4 are also used for laser wavelength calibration, providing calibration and tracking of the laser wavelength for the laser 1.

[0035] In the target gas detection and laser wavelength calibration optical path, the laser 1 outputs a laser beam, and the composite detector 21 detects a laser signal; when the target gas from the outside enters the detection chamber 3, the detection signal changes; when the center wavelength of the laser emitted by the laser 1 drifts, the detection signal changes differently.

[0036] The principle is as follows: in the tunable diode laser absorption spectroscopy (hereinafter referred to as TDLAS) technology, when the concentration of the target gas changes or the emission wavelength of the laser changes, the detection signal (hereinafter referred to as PD signal) of the photodetector will change accordingly, and the change occurs in the depth and position of the notch (hereinafter referred to as notch depth and notch position) in the PD signal; specifically, when the concentration of the target gas increases, the absorption intensity of the gas to the laser will increase, which is usually manifested as an increase in the notch depth corresponding to the gas absorption line in the PD signal in the TDLAS technology, and the increase in the notch depth directly reflects the increase in the gas concentration, and vice versa; therefore, by measuring the change in the notch depth, the concentration of the target gas can be accurately measured.

[0037] In addition, in the TDLAS technology, the notch position in the PD signal is usually related to the emission wavelength of the laser; when the concentration of the target gas changes, although the notch depth changes, the notch position usually remains relatively stable, because the emission wavelength of the laser and the absorption line position of the gas to be measured are determined by physical laws and are independent of the concentration of the gas. Therefore, during the measurement process, the stability of the notch position can be ensured by maintaining the stability of the emission wavelength of the laser; conversely, when the emission wavelength of the laser drifts, the notch position of the PD signal usually changes.

[0038] In summary, when the notch depth changes, i.e. the target gas is detected, an alarm signal needs to be sent; when the notch position changes, i.e. the wavelength of the laser drifts, measures such as adjusting the operating temperature of the laser need to be taken to correct the drift of the laser wavelength.

[0039] Based on the above, the laser 1 and the composite detector 21 are arranged at opposite ends of the detection gas chamber 3, that is, the selected light path is compared with the reflection type light path, and the water vapor interference performance of the laser gas detection system is further enhanced.

[0040] Based on the above, as shown in Figure 2 The reference gas chamber 4 is integrally formed into the light inlet side of the composite detector 21 to form a photoelectric detector with a reference gas chamber 24; the reference gas chamber, the photoelectric detector, and the photoelectric detector with the reference gas chamber are all prior art, and will not be described here.

[0041] Based on the above, the side wall and the bottom wall of the detection gas chamber 3 are blackened to prevent stray light from reflecting inside the detection gas chamber 3 and causing optical interference noise.

[0042] Based on the above, the laser 1 adopts TO packaging, and the laser 1 can adopt a TEC type laser or a heating type laser according to actual needs.

[0043] Embodiment 2

[0044] As shown in Figure 3 The laser methane gas sensor with a reference light path of the present embodiment is similar to that of embodiment 1, and based on embodiment 1, the present embodiment and embodiment 1 have the following differences: first, the detector 2 includes a detection detector 22 and a reference detector 23, and no longer includes a composite detector 21; second, the detection detector 22 and the laser 1 are arranged at opposite ends of the detection gas chamber 3, and the reference gas chamber 4 and the reference detector 23 are arranged on the side wall or the bottom wall of the detection gas chamber 3 between the laser 1 and the detection detector 22; third: the detection gas chamber 3 is also provided with a beam splitter 5.

[0045] In the present embodiment, the detector 2 is provided with one detection detector 22 and one reference detector 23, and the detection detector 22 and the reference detector 23 are both photoelectric detectors, the beam splitter 5 is arranged in the detection gas chamber 3, and the reference gas chamber 4 is arranged between the beam splitter 5 and the reference detector 23.

[0046] In the present embodiment, the laser 1 outputs a focused laser beam, that is, the output beam of the single-path laser 1 is split by the beam splitter 5 into two parts.

[0047] In this embodiment, the detection probe 22 is used to detect the target gas concentration in the detection chamber 3, and the reference probe 23 is used to calibrate the wavelength of the output light beam of the laser 1. Specifically, the laser 1 outputs a laser beam towards the beam splitter 5, and the laser beam is split by the beam splitter 5 into two parts. One part is detected by the detection probe 22 after only passing through the detection chamber 3, forming a target gas detection light path. The other part passes through the detection chamber 3 and the reference chamber 4 in turn and is detected by the reference probe 23, forming a laser wavelength calibration light path. That is, the laser 1, the detection probe 22, the detection chamber 3, and the beam splitter 5 together form the target gas detection light path, and the laser 1, the reference probe 23, the detection chamber 3, the reference chamber 4, and the beam splitter 5 together form the laser wavelength calibration light path, providing calibration and tracking of the laser wavelength for the laser 1.

[0048] In the target gas detection light path, the laser 1 outputs a laser beam, and the detection probe 22 detects the laser signal. When the target gas from the outside enters the detection chamber 3, the detection signal of the detection probe 22 changes. In the laser wavelength calibration light path, the laser 1 outputs a laser beam, and the reference probe 23 detects the laser signal. When the center wavelength of the laser emitted by the laser 1 drifts, the detection signal of the reference probe 23 changes differently.

[0049] The principles of the target gas detection light path and the laser wavelength calibration light path of this embodiment are similar to those in Embodiment 1. When the detection signal of the detection probe 22 changes in the depth of the recess, it indicates that the target gas has been detected, and an alarm signal needs to be sent. When the detection signal of the reference probe 23 changes in the position of the recess, it indicates that the wavelength of the laser has drifted, and measures such as adjusting the operating temperature of the laser need to be taken to correct the drift of the laser wavelength.

[0050] Using the detection probe 22 and the reference probe 23 for detection respectively can make the detection of the target gas and the calibration of the laser wavelength more rapid and accurate.

[0051] Based on the above, the laser 1 and the detection probe 22 are arranged at opposite ends of the detection chamber 3, and the same is selected for the light path; the reference chamber 4 and the reference probe 23 are arranged on the side wall or the bottom wall of the detection chamber 3 between the laser 1 and the detection probe 22; in this way, the target gas detection light path has a longer path than the laser wavelength calibration light path, thereby improving the accuracy of target gas detection.

[0052] Based on the above, the reference chamber 4 and the reference probe 23 are arranged in the mounting groove of the side wall or the bottom wall of the detection chamber 3; Figure 3The reference gas chamber 4 and the reference detector 23 are arranged in the mounting groove of the side wall of the detection gas chamber 3; the reference gas chamber 4 and the reference detector 23 arranged in the mounting groove of the bottom wall of the detection gas chamber 3 are similar to the arrangement in the mounting groove of the side wall, that is, the Figure 3 spectrometer 5, the reference gas chamber 4 and the reference detector 23 in the above embodiment are all rotated by 90 degrees (the sensor body 10 is not changed) to the bottom wall of the sensor body 10; in general, the related circuit of the sensor body 10 is arranged on a circuit board, the circuit board is arranged at the bottom end of the sensor body 10, and the reference detector 23 is arranged on the bottom wall of the detection gas chamber 3, so that the reference detector 23 is arranged vertically on the circuit board.

[0053] Based on the above, the reference gas chamber 4 is integrally integrated into the light-incident side of the reference detector 23 to form a photoelectric detector 24 with a reference gas chamber.

[0054] Based on the above, the laser 1 adopts a TO package; the laser 1 can adopt a TEC type laser or a heating type laser according to actual needs; the side wall and the bottom wall of the detection gas chamber 3 are blackened.

[0055] Embodiment 3

[0056] As shown in Figure 4 , Figure 5 , Figure 6 , the laser methane gas sensor with a reference light path in the embodiment is similar to the scheme in Embodiment 2, and the difference between the embodiment and Embodiment 2 is that the laser 1 outputs a divergent laser beam, and the spectrometer 5 is no longer arranged.

[0057] In the embodiment, the laser 1 outputs a divergent laser beam, the detection gas chamber 3 is arranged between the laser 1 and the detection detector 22, and a part of the divergent laser beam is detected by the detection detector 22 after passing through the detection gas chamber 3 only, forming a target gas detection light path; the reference gas chamber 4 is arranged between the laser 1 and the reference detector 23, and another part of the divergent laser beam is detected by the reference detector 23 after passing through the detection gas chamber 3 and the reference gas chamber 4 in sequence, forming a laser wavelength calibration light path.

[0058] The principle of the target gas detection light path and the laser wavelength calibration light path in the embodiment is consistent with that in Embodiment 2, and will not be described here.

[0059] In the embodiment, as shown in Figure 4 , Figure 5 , Figure 6 , the reference gas chamber 4 and the reference detector 23 are arranged in the mounting groove of the side wall or the bottom wall of the detection gas chamber 3 between the laser 1 and the detection detector 22, Figure 4 is a schematic view of being arranged in the side wall, Figure 5 , Figure 6is a schematic view of the bottom wall; in addition, as shown in Figure 4 、 Figure 6 The installation groove is provided with a chamfer 6 at the communication position with the detection gas chamber 3, and the chamfer 6 is used for avoiding the divergent laser beams so that more divergent laser beams reach the reference gas chamber 4.

[0060] In the embodiment, the photoelectric detector 24 with the reference gas chamber is preferably adopted, and compared with the split type reference gas chamber 4 and the reference detector 23, more divergent laser beams can be received.

[0061] According to the laser methane gas sensor with the reference light path according to the embodiments 1-3, by integrating the reference light path in the household laser methane gas sensor, that is, using the reference gas chamber and the corresponding photoelectric detector, the real-time tracking and calibration of the central wavelength of the laser output are realized, and the accuracy of the laser gas detection system in detecting the target gas is further improved; and the selected opposite light path further enhances the water vapor interference resistance of the laser gas detection system compared with the reflective light path.

[0062] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application rather than limit them; although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that: the specific implementation of the present application can still be modified or some technical features can be replaced by equivalent; without departing from the spirit of the technical solutions of the present application, they should be covered in the technical solution range of the present application claimed.

Claims

1. A laser-based methane gas sensor with a reference optical path, characterized in that: The sensor body (10) includes a laser (1), a detector (2), a reference gas chamber (4) and a detection gas chamber (3) connected to the outside world. The reference gas chamber (4) is filled with a target gas of a fixed gas concentration. In this process, the output beam of the laser (1) passing through the detection gas chamber (3) and the reference gas chamber (4) cooperates with the detector (2) to form a target gas detection and laser wavelength calibration optical path; or, only the output beam of the laser (1) passing through the detection gas chamber (3) cooperates with the detector (2) to form a target gas detection optical path, and the output beam of the laser (1) passing through the detection gas chamber (3) and the reference gas chamber (4) cooperates with the detector (2) to form a laser wavelength calibration optical path.

2. The laser methane gas sensor with reference optical path according to claim 1, characterized in that: The detector (2) includes a composite detector (21). The output beam of the laser (1) that passes through the detection gas chamber (3) and the reference gas chamber (4) in sequence is detected by the composite detector (21) to form the target gas detection and laser wavelength calibration optical path. The target gas detection and laser wavelength calibration optical path is used to detect the target gas concentration in the detection gas chamber (3) and to calibrate the wavelength of the output beam of the laser (1).

3. The laser methane gas sensor with reference optical path according to claim 2, characterized in that: The laser (1) outputs a focused laser beam, and the laser (1) and the composite detector (21) are respectively located at opposite ends of the detection gas chamber (3).

4. The laser methane gas sensor with a reference optical path according to claim 2 or 3, characterized in that: The reference chamber (4) is integrated into the light-inlet side of the composite detector (21) to form a photodetector (24) with a reference chamber.

5. The laser methane gas sensor with reference optical path according to claim 1, characterized in that: The detector (2) includes a detection detector (22) and a reference detector (23). The output beam of the laser (1) passing only through the detection chamber (3) is detected by the detection detector (22) to form the target gas detection optical path, which is used to detect the target gas concentration in the detection chamber (3). The output beam of the laser (1) passing sequentially through the detection chamber (3) and the reference chamber (4) is detected by the reference detector (23) to form the laser wavelength calibration optical path, which is used to calibrate the wavelength of the output beam of the laser (1).

6. The laser methane gas sensor with a reference optical path according to claim 5, characterized in that: The laser (1) outputs a focused laser beam. The detection chamber (3) is equipped with a beam splitter (5). After the focused laser beam passes through the beam splitter (5), part of it passes only through the detection chamber (3) and is then detected by the detection detector (22). The other part passes through the detection chamber (3) and the reference chamber (4) in sequence and is then detected by the reference detector (23).

7. The laser methane gas sensor with reference optical path according to claim 5, characterized in that: The laser (1) outputs a diverging laser beam, wherein a portion of the diverging laser beam is detected by the detection detector (22) after passing only through the detection gas chamber (3), and the other portion of the diverging laser beam is detected by the reference detector (23) after passing through the detection gas chamber (3) and the reference gas chamber (4) in sequence.

8. The laser methane gas sensor with a reference optical path according to claim 5, 6, or 7, characterized in that: The laser (1) and the detection detector (22) are respectively located at opposite ends of the detection chamber (3), and the reference chamber (4) and the reference detector (23) are located on the side wall or bottom wall of the detection chamber (3) between the laser (1) and the detection detector (22).

9. The laser methane gas sensor with a reference optical path according to claim 8, characterized in that: The reference gas chamber (4) and the reference detector (23) are installed in the mounting groove on the side wall or bottom wall of the detection gas chamber (3). The bottom of the detection gas chamber (3) is provided with a circuit board. The connection between the mounting groove and the detection gas chamber (3) is provided with a chamfer (6).

10. The laser methane gas sensor with a reference optical path according to claim 5, 6, or 7, characterized in that: The reference chamber (4) is integrated into the light-inlet side of the reference detector (23) to form a photodetector (24) with a reference chamber.

11. The laser methane gas sensor with reference optical path according to claim 1, characterized in that: The side walls and bottom walls of the detection chamber (3) are treated with black.

12. The laser methane gas sensor with reference optical path according to claim 1, characterized in that: The laser (1) is packaged in TO and is a TEC type laser or a heated laser.

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