Gas concentration detection device

Abstract

The utility model discloses a gas concentration detection device. The gas concentration detection device comprises a shell and a detection assembly, an optical air cavity is defined by the shell and provided with a first side and a second side which are opposite in the preset direction, the first side is provided with a first side face and a second side face, the second side is provided with a third side face opposite to the second side face in the preset direction, and a fourth side face is arranged between the second side face and the third side face. The third side surface extends from the second side to the first side along the second side and is gradually close to the top surface of the optical air cavity, and the fourth side surface extends from the bottom surface of the optical air cavity along the first side to the second side and is gradually far away from the bottom surface of the optical air cavity. The detection assembly comprises a light source and a light detector, the light source and the first side face are spaced in the preset direction, and the light detector is located on the side, facing the bottom face of the optical air cavity, of the third side face and located on the side, deviating from the second side face, of the fourth side face. According to the gas concentration detection device disclosed by the embodiment of the utility model, the incidence rate of the light beam entering the optical detector can be improved.

Description

Technical Field

[0001] This utility model relates to the field of gas concentration detection technology, and in particular to a gas concentration detection device. Background Technology

[0002] A gas sensor is a device that converts information such as the composition and concentration of a gas into information that can be used by personnel, instruments, computers, etc. A common gas concentration detection device is the NDIR (Non-Dispersive Infrared) gas sensor, which mainly consists of a light source for emitting a light beam, an optical cavity for reflecting the light beam, and a photodetector for receiving infrared light. Its working principle is that the light beam emitted by the light source is reflected multiple times within the optical cavity before entering the photodetector. Because the concentration of the gas being detected varies within the optical cavity, the intensity of the light beam detected by the photodetector will also vary. Therefore, by converting the detected light beam intensity into a digital signal, the concentration of the gas being detected can be obtained.

[0003] In related technologies, the light beam undergoes multiple reflections within the optical cavity. When the light beam is reflected to the location of the photodetector, some of the beam will be directed towards the bottom surface of the optical cavity at the location of the photodetector. This results in a portion of the beam not being reflected to the photodetector and received by it. Therefore, the incident rate of the light beam onto the photodetector is low. Utility Model Content

[0004] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention proposes a gas concentration detection device that can improve the incident rate of a light beam onto a photodetector.

[0005] The gas concentration detection device of this utility model embodiment includes:

[0006] The outer shell defines an optical cavity for containing the gas to be detected. The optical cavity has a first side and a second side opposite to each other along a preset direction. The first side is provided with a first side surface and a second side surface. The second side is provided with a third side surface opposite to the second side surface along a preset direction. A fourth side surface is provided between the second side surface and the third side surface. The third side surface extends from the second side surface in a direction pointing from the second side surface to the first side surface and gradually approaches the top surface of the optical cavity. The fourth side surface extends from the bottom surface of the optical cavity in a direction pointing from the first side surface to the second side surface and gradually moves away from the bottom surface of the optical cavity.

[0007] The detection assembly includes a light source and a photodetector, which are housed within an optical cavity. The light source and a first side are spaced apart along a predetermined direction. The photodetector is located on the third side facing the bottom surface of the optical cavity, and on a fourth side opposite to the second side.

[0008] A portion of the light beam emitted by the light source can be reflected sequentially through the first side, the second side, and the third side before being received by the photodetector. Another portion of the light beam emitted by the light source can be reflected sequentially through the first side, the second side, the fourth side, and the third side before being received by the photodetector.

[0009] The support structure according to the embodiments of this utility model has at least the following beneficial effects:

[0010] By setting a third and a fourth side, and placing the photodetector on the side of the third side facing the bottom of the optical cavity, and the photodetector on the side of the fourth side away from the second side, when a portion of the light beam emitted by the light source is reflected to the bottom of the optical cavity where the photodetector is located, the fourth side can reflect this portion of the light beam so that it can be reflected to the third side and then reflected by the third side to the photodetector for reception. Through this design, the incident rate of the light beam to the photodetector is increased, thereby improving the detection accuracy of the concentration of the gas to be measured by the gas concentration detection device.

[0011] According to some embodiments of the present invention, the distance between the first side and the second side gradually increases along the direction from the first side to the second side.

[0012] According to some embodiments of the present invention, the second side is further provided with a fifth side surface. The first side surface and the fifth side surface are opposite each other along a preset direction. Along the direction from the second side to the first side, the distance between the two ends of the fifth side surface gradually increases. The light source is located on the side of the fifth side surface facing the first side surface. The fifth side surface is used to converge and reflect the light beam emitted by the light source to the second side to the first side surface.

[0013] According to some embodiments of the present invention, the inner surface of the optical cavity is provided with a reflective layer for reflecting light beams.

[0014] According to some embodiments of the present invention, a light-blocking structure is provided inside the optical air cavity. The light-blocking structure is located between the light source and the photodetector, and the optical air cavity is separated to form a first cavity and a second cavity. The first cavity and the second cavity are connected at one end near the first side.

[0015] According to some embodiments of the present invention, the outer shell defines at least two air inlets, which are distributed on opposite sides of the light-blocking structure, and each air inlet is connected to the optical air cavity.

[0016] According to some embodiments of the present invention, the outer shell defines an air inlet, which is connected to the optical air cavity;

[0017] The gas concentration detection device also includes a breathable membrane that covers at least two air inlets.

[0018] According to some embodiments of the present invention, the outer shell includes a first shell and a second shell, the first shell and the second shell are connected, and the first shell and the second shell together define an optical air cavity; the first shell is provided with a first positioning structure, the second shell is provided with a second positioning structure, and the first positioning structure and the second positioning structure are positioned and cooperated.

[0019] According to some embodiments of the present invention, the gas concentration detection device further includes a circuit board connected to the housing, and a light source and a photodetector electrically connected to the circuit board respectively; the housing defines a first mounting port and a second mounting port, both of which are connected to the optical gas cavity, and the light source and the photodetector extend into the optical gas cavity through the first mounting port and the second mounting port respectively.

[0020] According to some embodiments of the present invention, the circuit board defines a clearance hole, the portion of the light source extending out of the first mounting port is received in the clearance hole, and the pins of the light source pass through the clearance hole and are connected to the side of the circuit board facing away from the housing.

[0021] Additional aspects and advantages of this invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0022] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein:

[0023] Figure 1 This is an exploded view of the gas concentration detection device according to an embodiment of the present invention;

[0024] Figure 2 for Figure 1 A three-dimensional structural view of the first shell of the outer casing shown;

[0025] Figure 3 for Figure 1 A three-dimensional structural view of the second shell of the outer casing shown;

[0026] Figure 4 for Figure 1 The diagram shows a top view of the second housing and the light source, where the dashed lines represent the optical path of the light beam emitted by the light source within the optical cavity.

[0027] Figure 5 for Figure 1 The diagram shows a partial optical path within the optical cavity, where the dashed line represents the propagation path of the light beam emitted by the light source within the optical cavity.

[0028] Figure 6 for Figure 1 The diagram shows the structural assembly of the gas concentration detection device.

[0029] Figure label:

[0030] Gas concentration detection device 100;

[0031] Outer shell 10; First side 110; Second side 120; Optical air cavity 101; First side 1011; Second side 1012; Third side 1013; Fourth side 1014; Fifth side 1015; Light-blocking structure 102; Air inlet 103; First mounting port 104; Second mounting port 105; First housing 11; First positioning structure 111; Second housing 12; Second positioning structure 121;

[0032] Detection component 20; light source 21; pin 211; photodetector 22;

[0033] Breathable membrane 30;

[0034] Circuit board 40; clearance hole 401;

[0035] Preset direction X. Detailed Implementation

[0036] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this utility model, and should not be construed as limiting this utility model.

[0037] In the description of this utility model, it should be understood that the directional descriptions, such as up, down, front, back, left, right, etc., indicate the directional or positional relationships based on the directional or positional relationships shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0038] In the description of this utility model, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0039] In the description of this utility model, unless otherwise explicitly defined, terms such as "setting," "installation," and "connection" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this utility model in conjunction with the specific content of the technical solution.

[0040] In the description of this utility model, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this utility model. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0041] Please see Figures 1 to 6 This utility model provides a gas concentration detection device 100 for detecting the concentration of gases such as carbon dioxide in the air.

[0042] The gas concentration detection device 100 includes a housing 10 and a detection component 20. The housing 10 defines an optical cavity 101 for containing the gas to be detected. The optical cavity 101 has a first side 110 and a second side 120 opposite to each other along a preset direction X. The first side 110 is provided with a first side surface 1011 and a second side surface 1012. The second side 120 is provided with a third side surface 1013 opposite to the second side surface 1012 along the preset direction X. A fourth side surface 1014 is provided between the second side surface 1012 and the third side surface 1013. The third side surface 1013 extends from the second side 120 in a direction pointing from the second side 120 toward the first side 110 and gradually approaches the top surface of the optical cavity 101. The fourth side surface 1014 extends from the bottom surface of the optical cavity 101 in a direction pointing from the first side 110 toward the second side 120 and gradually moves away from the bottom surface of the optical cavity 101. The detection component 20 includes a light source 21 and a photodetector 22, which are housed in an optical cavity 101. The light source 21 and the first side surface 1011 are spaced apart along a preset direction X. The photodetector 22 is located on the side of the third side surface 1013 facing the bottom surface of the optical cavity 101, and the photodetector 22 is located on the side of the fourth side surface 1014 away from the second side surface 1012.

[0043] Among them, such as Figure 4 and Figure 5 As shown, a portion of the light beam emitted by the light source 21 can be reflected sequentially by the first side 1011, the second side 1012 and the third side 1013 and then received by the photodetector 22. Another portion of the light beam emitted by the light source 21 can be reflected sequentially by the first side 1011, the second side 1012, the fourth side 1014 and the third side 1013 and then received by the photodetector 22.

[0044] During use, the gas to be tested can enter the optical gas cavity 101. The gas to be tested entering the optical gas cavity 101 can absorb part of the light beam emitted by the light source 21. Since the absorption degree of the light beam is different for different concentrations of the gas to be tested, the gas concentration detection device 100 can calculate the concentration of the gas to be tested by measuring the light intensity of the remaining unabsorbed light beam.

[0045] The gas concentration detection device 100 of this utility model embodiment, by setting a third side 1013 and a fourth side 1014, and placing the photodetector 22 on the side of the third side 1013 facing the bottom surface of the optical cavity 101, and the photodetector 22 on the side of the fourth side 1014 away from the second side 1012, can improve the detection accuracy of the gas concentration detection device 100 by setting a third side 1013 and a fourth side 1014 facing the bottom surface of the optical cavity 101 where the photodetector 22 is located. When a portion of the light beam emitted by the light source 21 is reflected to the bottom surface of the optical cavity 101 where the photodetector 22 is located, the fourth side 1014 can reflect the portion of the light beam so that it can be reflected to the third side 1013 and then reflected by the third side 1013 to the photodetector 22 for reception. Through the above design, the incident rate of the light beam to the photodetector 22 is improved, thereby improving the detection accuracy of the gas concentration detection device 100.

[0046] like Figure 3 As shown, in some embodiments, the third side surface 1013 is an arc surface.

[0047] In other embodiments, the third side 1013 is a plane.

[0048] like Figure 2 As shown, in some embodiments, the fourth side 1014 is a plane.

[0049] In other embodiments, the fourth side surface 1014 is curved.

[0050] like Figure 4 As shown, in some embodiments, the distance between the first side 1011 and the second side 1012 gradually increases along the direction from the first side 110 to the second side 120. This allows the light beam emitted by the light source 21 to have a better optical path extension and be reflected by the first side 1011 and the second side 1012 to the photodetector 22, thereby forming two reflections in different directions.

[0051] In some embodiments, the angle between the first side 1011 and the second side 1012 is 90°. This allows the light beam's propagation direction to be reversed after reflection from the first side 1011 and the second side 1012, increasing the uniformity of the light beam's propagation within the optical cavity 101. When the light beam from the light source 21 is incident on the first side 1011 along a preset direction X, the incident angle and exit angle of the light beam on the first side 1011 are both 45° and 45°. When the light beam is reflected from the first side 1011 and incident on the second side 1012, the incident angle and exit angle of the light beam on the second side 1012 are both 45° and 45°. That is, the light beam emitted by the light source 21 along the preset direction X (specifically, the direction from the second side 120 to the first side 110) continues to be incident on the location of the photodetector 22 along the preset direction X (specifically, the direction from the first side 110 to the second side 120) after two reflections by the first side 1011 and the second side 1012.

[0052] like Figure 1 As shown, in some embodiments, both the first side 1011 and the second side 1012 are planar.

[0053] In other embodiments, both the first side surface 1011 and the second side surface 1012 are curved surfaces.

[0054] like Figure 4 As shown, in some embodiments, the second side 120 is further provided with a fifth side 1015. The first side 1011 and the fifth side 1015 are opposite each other along a preset direction X. In the direction from the second side 120 to the first side 110, the distance between the two ends of the fifth side 1015 gradually increases. The light source 21 is located on the side of the fifth side 1015 facing the first side 1011. The fifth side 1015 is used to converge and reflect the light beam emitted by the light source 21 to the second side 1012 back to the first side 1011. By providing the fifth side 1015, the light beam emitted by the light source 21 to the second side 1012 can be substantially reflected back to the first side 1011, improving the light extraction efficiency of the light source 21 towards the first side 1011, thereby improving the utilization rate of the light beam emitted by the light source 21.

[0055] The two ends of the fifth side 1015 are the two ends of the fifth side 1015 along the direction parallel to the bottom surface of the optical gas cavity 101. When the gas concentration detection device 100 is placed flat, the two ends of the fifth side 1015 are the two ends of the fifth side 1015 along the horizontal direction.

[0056] In some embodiments, the fifth side surface 1015 is a parabolic surface.

[0057] In other embodiments, the fifth side 1015 is an isosceles trapezoid with an opening, and the light source 21 is located between the openings of the two waistlines of the isosceles trapezoid.

[0058] In some embodiments, the inner surface of the optical cavity 101 is provided with a reflective layer for reflecting the light beam. By providing the reflective layer, the light beam emitted by the light source 21 can be better reflected, which is beneficial to the propagation of the light beam in the optical cavity 101 and reduces the light loss during the propagation process.

[0059] In some embodiments, the reflective layer may be a reflective photocoating layer.

[0060] like Figure 4 As shown, in some embodiments, a light-blocking structure 102 is provided inside the optical cavity 101. The light-blocking structure 102 is located between the light source 21 and the photodetector 22, and the optical cavity 101 is separated to form a first cavity 101a and a second cavity 101b. The first cavity 101a and the second cavity 101b are connected at the ends near the first side 110, thereby forming a "maze" inside the optical cavity 101. The light beam emitted by the light source 21 needs to pass through the first cavity 101a to be directed to the first side 1011. The light beam reflected by the first side 1011 needs to pass through the connection between the first cavity 101a and the second cavity 101b to be directed to the second side 1012. The light beam reflected by the second side 1012 needs to pass through the second cavity 101b to be directed to the location of the photodetector 22, ensuring that the light beam emitted by the light source 21 has a long optical path inside the optical cavity 101. By setting the light-blocking structure 102, stray light emitted by the light source 21 can be blocked, preventing stray light from directly entering the photodetector 22 through the second cavity 101b and affecting the gas concentration detection device 100's detection of the concentration of the gas to be tested.

[0061] Specifically, one end of the light-blocking structure 102 is connected to the second side 120, and the other end of the light-blocking structure 102 extends toward the first side 110. A gap is defined between the other end of the light-blocking structure 102 and the first side 110 so that the first cavity 101a and the second cavity 101b can communicate through the gap.

[0062] like Figure 1 and Figure 4 As shown, in some embodiments, the housing 10 defines at least two air inlets 103, which are distributed on opposite sides of the light-blocking structure 102. Each air inlet 103 is connected to the optical air cavity 101. This allows the air inlets 103 located on opposite sides of the light-blocking structure 102 to form an air channel with the optical air cavity 101. The gas to be tested can freely circulate and diffuse within this air channel, which is beneficial for the gas to be tested to quickly enter and exit the optical air cavity 101 through the air inlet 103, thereby improving the rapid response capability of the gas concentration detection device 100.

[0063] like Figure 1As shown, in some embodiments, the housing 10 defines an air inlet 103, which communicates with the optical air cavity 101. The gas concentration detection device also includes a breathable membrane 30 that covers the air inlet 103. By providing the breathable membrane 30, impurities such as moisture and dust from the external environment can be prevented from entering the optical air cavity 101 through the air inlet 103, ensuring that only the gas to be measured can pass through the breathable membrane 30 into the optical air cavity 101, thereby reducing the influence of the external environment on the gas concentration detection device 100.

[0064] like Figures 1 to 3 As shown, in some embodiments, the outer casing 10 includes a first casing 11 and a second casing 12, which are connected and together define the aforementioned optical cavity 101. The first casing 11 is provided with a first positioning structure 111, and the second casing 12 is provided with a second positioning structure 121. The first positioning structure 111 and the second positioning structure 121 are positioned and engaged, thus facilitating the positioning of the first casing 11 and the second casing 12 during assembly, thereby simplifying assembly and preventing misalignment between the first casing 11 and the second casing 12 during installation, which could affect the propagation of light within the optical cavity 101.

[0065] In some embodiments, the first positioning structure 111 is disposed on the end face of the first housing 11 opposite to the second housing 12, and the second positioning structure 121 is disposed on the end face of the second housing 12 opposite to the first housing 11.

[0066] In some embodiments, the first positioning structure 111 and the second positioning structure 121 are both positioning holes, and the positioning holes on the first housing 11 correspond to and communicate with the positioning holes on the second housing 12. In specific implementation, screws can be threaded into the corresponding positioning holes of the first housing 11 and the second housing 12 to achieve connection and fixation between the first housing 11 and the second housing 12.

[0067] In some other embodiments, the first positioning structure 111 and the second positioning structure 121 may also be other structures that can achieve positioning of the first housing 11 and the second housing 12. For example, one of the first positioning structure 111 and the second positioning structure 121 may be a positioning hole, and the other of the first positioning structure 111 and the second positioning structure 121 may be a positioning post. The positioning post is inserted into the positioning hole to achieve positioning between the first housing 11 and the second housing 12.

[0068] In other embodiments, the first housing 11 and the second housing 12 can also be connected and fixed in other ways. For example, one of the first housing 11 and the second housing 12 is provided with a male buckle, and a female buckle is provided between the first housing 11 and the second housing 12. The male buckle and the female buckle are engaged to fix the first housing 11 and the second housing 12. Alternatively, the first housing 11 and the second housing 12 can be fixed by adhesive or welding.

[0069] In some embodiments, the opposite end faces of the first housing 11 and the second housing 12 have the same profile.

[0070] like Figures 1 to 3 As shown, the first housing 11 and the second housing 12 together form the first side 1011 and the second side 1012 of the optical cavity 101 on the inner wall of the first side 110. That is, the first side 1011 is divided into two opposing parts, one part located in the first housing 11 and the other part located in the second housing 12. The second side 1012 is similarly divided into two opposing parts. The second housing 12 together forms the third side 1013 of the optical cavity 101 on the inner wall of the second side 120. The inner bottom wall of the first housing 11 forms the fourth side 1014 of the optical cavity 101. The first housing 11 and the second housing 12 together form the fifth side 1015 of the optical cavity 101 on the inner wall of the second side 120. That is, the fifth side 1015 is divided into two opposing parts, one part located in the first housing 11 and the other part located in the second housing 12. The light-blocking structure 102 is also divided into two opposing parts, one part located in the first housing 11 and the other part located in the second housing 12.

[0071] The bottom surface of the optical cavity 101 is the inner bottom wall of the first housing 11, and the top surface of the optical cavity 101 is the inner top wall of the second housing 12.

[0072] In some embodiments, the light source 21 is an infrared light source 21, which can emit an infrared beam. The carbon dioxide and other gas to be measured can absorb the infrared beam in the optical gas cavity 101. The photodetector 22 is a photoelectric sensor, which can receive the infrared beam that has not been absorbed by the carbon dioxide and other gas to be measured, so as to measure the concentration of the gas to be measured.

[0073] like Figure 2 and Figure 6 As shown, in some embodiments, the gas concentration detection device 100 further includes a circuit board 40, which is connected to the housing 10. The light source 21 and the photodetector 22 are electrically connected to the circuit board 40, respectively. The housing 10 defines a first mounting port 104 and a second mounting port 105, both of which are connected to the optical gas cavity 101. The light source 21 and the photodetector 22 extend into the optical gas cavity 101 through the first mounting port 104 and the second mounting port 105, respectively.

[0074] In some embodiments, a central processing unit (CPU), a signal transmitter, and a signal conditioner are disposed on the circuit board 40. The CPU is electrically connected to the signal transmitter and the signal conditioner, and the photodetector 22 is electrically connected to the signal transmitter. When a light beam emitted by the light source 21 that is not absorbed by the analyte gas such as carbon dioxide is incident on the measurement area of ​​the photodetector 22, the photodetector 22 generates an electrical signal and transmits it to the CPU via the signal transmitter. The CPU converts the received analog electrical signal into a digital electrical signal, and the signal conditioner processes the digital electrical signal to measure the concentration of the analyte gas such as carbon dioxide.

[0075] like Figure 5 As shown, in some embodiments, the circuit board 40 defines a clearance hole 401, the portion of the light source 21 extending out of the first mounting port 104 is received in the clearance hole 401, and the pins 211 of the light source 21 protrude through the clearance hole 401 and are connected to the side of the circuit board 40 facing away from the housing 10. By providing the clearance hole 401, the portion of the light source 21 extending out of the first mounting port 104 can be cleared, that is, the light source 21 is basically received by the optical cavity 101, the first mounting port 104 and the clearance hole 401, thereby reducing the overall height of the gas concentration detection device 100 and making the structure of the gas concentration detection device 100 more compact.

[0076] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. A gas concentration detecting device characterized by comprising: include: The housing defines an optical cavity for containing a gas to be detected. The optical cavity has a first side and a second side opposite to each other along a preset direction. The first side is provided with a first side surface and a second side surface. The second side is provided with a third side surface opposite to the second side surface along the preset direction. A fourth side surface is provided between the second side surface and the third side surface. The third side surface extends from the second side surface in a direction pointing from the second side surface to the first side surface and gradually approaches the top surface of the optical cavity. The fourth side surface extends from the bottom surface of the optical cavity in a direction pointing from the first side surface to the second side surface and gradually moves away from the bottom surface of the optical cavity. A detection component includes a light source and a photodetector, the light source and the photodetector being housed within an optical cavity. The light source and the first side are spaced apart along a predetermined direction. The photodetector is located on the side of the third side facing the bottom surface of the optical cavity, and the photodetector is located on the side of the fourth side opposite to the second side. A portion of the light beam emitted by the light source can be reflected sequentially by the first side, the second side, and the third side before being received by the photodetector. Another portion of the light beam emitted by the light source can be reflected sequentially by the first side, the second side, the fourth side, and the third side before being received by the photodetector.

2. The gas concentration detecting apparatus according to claim 1, characterized by Along the direction from the first side to the second side, the distance between the first side and the second side gradually increases.

3. The gas concentration detecting apparatus according to claim 1, wherein The second side is also provided with a fifth side surface. The first side surface and the fifth side surface are opposite each other along the preset direction. Along the direction from the second side to the first side, the distance between the two ends of the fifth side surface gradually increases. The light source is located on the side of the fifth side surface facing the first side surface. The fifth side surface is used to converge and reflect the light beam emitted by the light source to the second side to the first side surface.

4. The gas concentration detecting apparatus according to claim 1, wherein The inner surface of the optical cavity is provided with a reflective layer for reflecting light beams.

5. The gas concentration detecting apparatus according to claim 1, wherein A light-blocking structure is provided inside the optical cavity. The light-blocking structure is located between the light source and the photodetector, and separates the optical cavity to form a first cavity and a second cavity. The first cavity and the second cavity are connected at their ends near the first side.

6. The gas concentration detecting device according to claim 5, wherein The outer casing defines at least two air inlets, which are distributed on opposite sides of the light-blocking structure, and each air inlet is connected to the optical air cavity.

7. The gas concentration detecting apparatus according to claim 1, wherein The outer casing defines an air inlet, which is in communication with the optical cavity; The gas concentration detection device also includes a breathable membrane that covers at least two of the air inlets.

8. The gas concentration detecting apparatus according to claim 1, wherein The outer casing includes a first housing and a second housing, the first housing and the second housing are connected, and the first housing and the second housing together define the optical air cavity; the first housing is provided with a first positioning structure, the second housing is provided with a second positioning structure, and the first positioning structure and the second positioning structure are positioned and cooperate.

9. The gas concentration detecting apparatus according to claim 1, wherein The gas concentration detection device further comprises a circuit board connected with the shell, and the light source and the light detector are electrically connected with the circuit board respectively; the shell defines a first mounting opening and a second mounting opening, both of which are in communication with the optical air cavity, and the light source and the light detector respectively extend into the optical air cavity through the first mounting opening and the second mounting opening.

10. The gas concentration detecting apparatus according to claim 9, wherein The circuit board defines a relief hole, the part of the light source extending out of the first mounting opening is accommodated in the relief hole, and the pin of the light source penetrates through the relief hole and is connected with the side of the circuit board away from the shell.

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