Gas sensor and gas detection equipment

Abstract

The invention discloses a gas sensor and gas detection equipment, and is applied to the technical field of gas detection. The photoacoustic detection unit comprises a sound pressure detection module and a light source module, the sound pressure detection module comprises a sound pressure detector and a shell covering the sound pressure detector, an acoustic cavity is formed in the shell, and the acoustic cavity is provided with a gas hole used for leading in external environment gas; the light source module is used for emitting light with a preset wavelength into the acoustic cavity so as to generate a photoacoustic signal in the acoustic cavity, and the sound pressure detector is used for generating an electric signal based on the photoacoustic signal. The photoacoustic signals are directly generated in the acoustic cavity, a back cavity in an existing sound pressure detector can be integrated with a photoacoustic cell, the photoacoustic cell does not need to be additionally arranged, and therefore the size of the gas sensor is further reduced.

Description

Technical Field

[0001] The present application relates to the field of gas detection technology, and in particular to a gas sensor and a gas detection device. Background Art

[0002] Gas sensors based on photoacoustic spectroscopy (PAS), such as CO2 sensors, are already in use in production. They detect gas concentrations by exploiting the acoustic pressure generated by gases like CO2 absorbing infrared light of a specific wavelength. They typically consist of an infrared light source such as a blackbody, a filter, an acoustic pressure detector such as a microphone, an ASIC (Application Specific Integrated Circuit) controller, and a corresponding non-resonant photoacoustic cell. In operation, a controller drives the infrared light source to emit broad-spectrum infrared light at a specific frequency. This light is then filtered by a filter, and the specific wavelength of infrared light is directed toward the target gas. The target gas absorbs the infrared light and generates a corresponding acoustic pressure, which is detected by the acoustic pressure detector. The signal is then processed by the controller, where it is then retrieved using an established algorithm or a calibrated lookup table (LUT). Compared to other types of gas sensors, such as electrochemical gas sensors and NDIR (Non-Dispersive InfraRed) gas sensors, they offer advantages such as small size, light weight, low cost and power consumption, and relatively accurate measurement. Therefore, they are expected to have a wide range of applications. Since gas sensors are primarily used in miniaturized devices, finding a miniaturized gas sensor is an urgent challenge for those skilled in the art. Summary of the Invention

[0003] The purpose of this application is to provide a gas sensor with a smaller volume; further, this application proposes another gas detection device with an even smaller volume.

[0004] To solve the above technical problems, the present application provides a gas sensor comprising a photoacoustic detection unit;

[0005] The photoacoustic detection unit includes a sound pressure detection module and a light source module. The sound pressure detection module includes a sound pressure detector and a shell covering the sound pressure detector. An acoustic cavity is formed inside the shell, and the acoustic cavity is provided with air holes for introducing external environmental gas; the light source module is used to emit light of a preset wavelength into the acoustic cavity to generate a photoacoustic signal in the acoustic cavity, and the sound pressure detector is used to generate an electrical signal based on the photoacoustic signal.

[0006] Optionally, the gas sensor also includes a PCB board and a detector control chip, the photoacoustic detection unit is arranged on the surface of the PCB board, and the electrical signal generated by the sound pressure detector is transmitted to the detector control chip through the PCB board; the shell is arranged on the surface of the PCB board and forms the acoustic cavity together with the PCB board.

[0007] Optionally, the air holes are covered with a breathable membrane.

[0008] Optionally, the air pores are an air pore array formed by a plurality of micro air pores distributed in an array, and a support wall is formed between adjacent micro air pores; the air permeable membrane covers the air pore array and is in contact with the support wall.

[0009] Optionally, the sound pressure detector includes a diaphragm, the acoustic cavity accommodates the diaphragm, and the diaphragm generates the electrical signal based on the photoacoustic signal; wherein the air hole is arranged in an area corresponding to where the diaphragm is located.

[0010] Optionally, a first reflective layer having reflectivity to the light is provided on the surface of the diaphragm facing the side where the photoacoustic signal is generated;

[0011] And / or, a second reflective structure that is reflective to the light is provided on a surface of the microphone chip of the sound pressure detector that faces the side where the photoacoustic signal is generated.

[0012] Optionally, a light through hole is provided on one side of the shell, and the light source module is provided on the side of the sound pressure detection module where the light through hole is provided, and emits the light to the acoustic cavity through the light through hole.

[0013] Optionally, the light source module includes a MEMS blackbody light source module with a filter, or a MEMS blackbody light source with a metasurface structure that directly generates infrared light of a specific wavelength, or an LED light source with a filter, or a laser that generates the required wavelength.

[0014] Optionally, the sound pressure detector and the light source module are arranged in the acoustic cavity, and the detector control chip is arranged outside the acoustic cavity;

[0015] Alternatively, the sound pressure detector, the light source module and the detector control chip are all arranged in the acoustic cavity.

[0016] Optionally, the pores are provided in a region of the PCB board corresponding to the diaphragm, and / or the pores are provided on a side of the housing facing away from the PCB board.

[0017] Optionally, the light source module includes a light source chip and a filter, wherein the light source chip is located in a groove preset in the PCB board, and the light source chip is connected to a heat sink in the PCB board; the filter is located at an opening of the groove and connected to the PCB board;

[0018] Alternatively, the light source module includes a light source chip and a filter, the light source chip is located on the surface of the PCB board, and the light source chip is connected to the heat sink in the PCB board; the filter is in a cover shape covering the light source chip and is connected to the PCB board.

[0019] The present invention also provides a gas detection device, characterized in that it includes any of the gas sensors described above.

[0020] A gas sensor provided in the present application includes a photoacoustic detection unit; the photoacoustic detection unit includes a sound pressure detection module and a light source module, the sound pressure detection module includes a sound pressure detector and a shell covering the sound pressure detector, an acoustic cavity is formed inside the shell, and the acoustic cavity is provided with air holes for introducing external environmental gas; the light source module is used to emit light of a preset wavelength into the acoustic cavity to generate a photoacoustic signal in the acoustic cavity, and the sound pressure detector is used to generate an electrical signal based on the photoacoustic signal.

[0021] By directly generating photoacoustic signals in the acoustic cavity, the back cavity in the existing sound pressure detector can be integrated with the photoacoustic cell, eliminating the need for an additional photoacoustic cell, thereby further reducing the volume of the gas sensor.

[0022] Another object of the present application is to provide a gas detection device, which also has the above-mentioned beneficial effects and will not be described in detail here. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present application or the technical solutions of the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0024] Figure 1 A schematic diagram of the structure of a gas sensor provided in an embodiment of the present application;

[0025] Figure 2 Schematic diagram of the structure of the air hole array;

[0026] Figure 3 A schematic structural diagram of a first specific photoacoustic detection unit provided in an embodiment of the present application;

[0027] Figure 4A schematic structural diagram of a second specific photoacoustic detection unit provided in an embodiment of the present application;

[0028] Figure 5 for Figure 4 Schematic diagram of the structure of the corresponding gas sensor;

[0029] Figure 6 This is a structural diagram of the first light source module;

[0030] Figure 7 Schematic diagram of the structure of the second light source module;

[0031] Figure 8 A schematic structural diagram of a third specific gas sensor provided in an embodiment of the present application;

[0032] Figure 9 A schematic structural diagram of a fourth specific gas sensor provided in an embodiment of the present application;

[0033] Figure 10 A schematic structural diagram of a fifth specific gas sensor provided in an embodiment of the present application;

[0034] Figure 11 This is a schematic structural diagram of the sixth specific gas sensor provided in an embodiment of the present application.

[0035] In the figure: 1. Photoacoustic detection unit, 2. PCB board, 3. Detector control chip, 4. Sound pressure detector, 41. Diaphragm, 42. Acoustic cavity, 43. Air hole, 431. Air hole array, 44. Breathable membrane, 45. Optical through hole, 46. Housing, 47. Microphone chip, 48. Substrate, 5. Light source module, 51. Light source chip, 52. Filter. DETAILED DESCRIPTION

[0036] The core of this application is to provide a gas sensor. In the prior art, a gas sensor is usually composed of the following parts: an infrared light source, a sound pressure detector, an ASIC controller and a corresponding non-resonant photoacoustic cell. The non-resonant photoacoustic cell is used to store the target gas, and the sound pressure generated when the gas sensor is working is also generated in the non-resonant photoacoustic cell. The sound pressure will be transmitted from the non-resonant photoacoustic cell to the sound pressure detector to generate a corresponding electrical signal. During operation, the controller drives the infrared light source to emit broad-spectrum infrared light at a specific frequency, which is then filtered by a filter and irradiated onto the target gas in the non-resonant photoacoustic cell. The target gas absorbs the infrared light and generates a corresponding sound pressure. The sound pressure will be converted into an electrical signal by the sound pressure detector, and the signal will be sent to the controller for processing to obtain the concentration of the detected gas.

[0037] The gas sensor provided in the present application includes a photoacoustic detection unit; the photoacoustic detection unit includes a sound pressure detection module and a light source module, the sound pressure detection module includes a sound pressure detector and a shell covering the sound pressure detector, an acoustic cavity is formed inside the shell, and the acoustic cavity is provided with air holes for introducing external environmental gas; the light source module is used to emit light of a preset wavelength into the acoustic cavity to generate a photoacoustic signal in the acoustic cavity, and the sound pressure detector is used to generate an electrical signal based on the photoacoustic signal.

[0038] By directly generating photoacoustic signals in the acoustic cavity, the back cavity in the existing sound pressure detector can be integrated with the photoacoustic cell, eliminating the need for an additional photoacoustic cell, thereby further reducing the volume of the gas sensor.

[0039] In order to enable those skilled in the art to better understand the present application, the present application is further described in detail below in conjunction with the accompanying drawings and specific embodiments. Obviously, the embodiments described are only a part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making any creative efforts are within the scope of protection of the present application.

[0040] Please refer to Figure 1 as well as Figure 2 , Figure 1 A schematic diagram of the structure of a gas sensor provided in an embodiment of the present application; Figure 2 Schematic diagram of the structure of the air hole array.

[0041] See also Figure 1 In the embodiment of the present application, the gas sensor includes a photoacoustic detection unit 1, a PCB board 2 and a detector control chip 3.

[0042] The photoacoustic detection unit 1 includes a sound pressure detection module and a light source module 5. The sound pressure detection module includes a sound pressure detector 4 and a shell 46 covering the outside of the sound pressure detector. An acoustic cavity 42 is formed inside the shell 46. The acoustic cavity 42 is provided with an air hole 43 for introducing external environmental gas; the light source module 5 is used to emit light of a preset wavelength into the acoustic cavity 42 to generate a photoacoustic signal in the acoustic cavity 42, and the sound pressure detector is used to generate an electrical signal based on the photoacoustic signal.

[0043] The above-mentioned sound pressure detection module can convert the detected sound pressure into an electrical signal. In this embodiment, the sound pressure detector 4 of the sound pressure detection module can detect the weak sound pressure generated by the photoacoustic signal and convert it into an electrical signal. The above-mentioned photoacoustic detection unit 1 generates a photoacoustic signal, and the photoacoustic signal is converted into an electrical signal within the photoacoustic detection unit 1. The electrical signal is ultimately transmitted to the control chip of the gas sensor, namely the detector control chip 3. The detector control chip 3 determines the target gas concentration based on the acquired electrical signal: the concentration of the gas to be detected is determined by an existing algorithm or a calibrated LUT table. The specific structure of the detector control chip 3 can be set according to actual conditions and is not specifically limited here. Typically, in the embodiment of the present application, the gas sensor also includes a PCB board 2, and the photoacoustic detection unit 1 is specifically arranged on the surface of the PCB board 2. The electrical signal generated by the above-mentioned sound pressure detector 4 based on the photoacoustic signal is transmitted to the detector control chip 3 through the PCB board 2. The detector control chip 3 can also be specifically arranged directly on the surface of the PCB board 2. In this case, the detector control chip 3 and the photoacoustic detection unit 1 can be directly electrically connected through the PCB board 2 to transmit electrical signals. The photoacoustic detection unit 1 includes an acoustic pressure detection module and a light source module 5. The light source module 5 is used to generate light of a specific wavelength. This specific wavelength is absorbed by the gas to be detected, producing a photoacoustic effect and a corresponding photoacoustic signal. This photoacoustic signal is essentially an acoustic signal. Therefore, the wavelength of the light emitted by the light source module 5 needs to correspond to the type of gas to be detected, and this is not specifically limited here.

[0044] In this embodiment, the sound pressure detection module also includes a housing 46, which is specifically arranged to cover the outside of the sound pressure detector 4, and an acoustic cavity 42 is formed inside the housing 46. In this embodiment, the above-mentioned photoacoustic effect will specifically occur in the acoustic cavity 42, and the photoacoustic signal generated based on the photoacoustic effect will be directly received by the sound pressure detector 4 in the acoustic cavity 42 to be converted into an electrical signal and finally transmitted to the detector control chip 3. Specifically, the above-mentioned housing 46 can be provided on the surface of the PCB board 2 and form the above-mentioned acoustic cavity 42 together with the PCB board 2. Therefore, in this embodiment, the above-mentioned PCB board 2 can not only be used to transmit electrical signals, but also be used to form a part of the acoustic cavity 42.

[0045] In this embodiment, the sound pressure detection module generates a corresponding electrical signal for detection based on the photoacoustic signal generated by the photoacoustic effect. Specifically, in this embodiment of the present invention, the sound pressure detection module typically includes a sound pressure detector 4, which is typically a microphone module including a diaphragm 41. The acoustic cavity 42 houses the diaphragm 41, which generates the electrical signal based on the photoacoustic signal. Specifically, the diaphragm 41 is specifically used to detect the weak sound pressure generated by the photoacoustic signal and convert it into an electrical signal.

[0046] The above-mentioned sound pressure detector 4 includes at least one diaphragm 41, and the above-mentioned acoustic cavity 42 is used to accommodate the above-mentioned diaphragm 41. The diaphragm 41 is used to receive the above-mentioned photoacoustic signal and convert the received photoacoustic signal into an electrical signal. The above-mentioned diaphragm 41 is usually provided with a pressure relief hole, and another function of the above-mentioned acoustic cavity 42 is to provide a space for the diaphragm 41 to vibrate. In an embodiment of the present application, the above-mentioned acoustic cavity 42 is provided with an air hole 43 for introducing external environmental gas, and the external gas, including the gas to be detected, can enter the acoustic cavity 42 through the air hole 43 and the pressure relief hole on the diaphragm 41. The above-mentioned light source module 5 can specifically emit light of a preset wavelength into the acoustic cavity 42. At the same time, since the gas to be detected will be introduced into the acoustic cavity 42 through the air hole 43, the acoustic cavity 42 can play the role of a photoacoustic pool, and directly generate a photoacoustic effect in the acoustic cavity 42. At this point, the diaphragm 41 within the acoustic cavity 42 generates a corresponding electrical signal based on the photoacoustic signal, which is then transmitted to the detector control chip 3 for final processing, thereby generating a detection result for the target gas concentration. The specific process by which the detector control chip 3 determines the target gas concentration based on the electrical signal can be referenced in the prior art and is not specifically limited here.

[0047] In this embodiment, the above-mentioned air holes 43 can be set corresponding to the area where the diaphragm 41 is located, so that the gas entering the acoustic cavity 42 through the air holes 43 during operation can produce a photoacoustic effect near the diaphragm 41, which facilitates the diaphragm 41 to receive a larger photoacoustic signal, thereby improving the detection sensitivity of the gas sensor.

[0048] Specifically, in the embodiment of the present application, the air hole 43 is covered with a breathable membrane 44. The breathable membrane 44 generally allows gas to pass through, thereby enabling gas exchange between the acoustic cavity 42 and the external environment; while blocking other substances, such as liquids, water vapor, foreign matter, etc. from entering the acoustic cavity 42. At the same time, the breathable membrane 44 can semi-close the acoustic cavity 42 to form a semi-closed cavity. Since the generation of the photoacoustic signal and the vibration of the diaphragm 41 are both carried out in the acoustic cavity 42, semi-sealing the acoustic cavity 42 by the breathable membrane 44 can effectively prevent energy loss in the acoustic cavity 42.

[0049] See also Figure 2Furthermore, the air holes 43 may be an air hole array 431 formed by a plurality of micro air holes distributed in an array, and a support wall is formed between adjacent micro air holes; the air permeable membrane 44 covers the air hole array 431 and is in contact with the support wall. The air hole array 431 is usually composed of a plurality of micro air holes distributed in an array of smaller sizes. In this case, a support wall is formed between the micro air holes. In this case, the air permeable membrane 44 may specifically cover the air hole array 431 and be in contact with the support wall. By supporting the air permeable membrane 44 with the support wall, the vibration of the air permeable membrane 44 can be avoided, thereby preventing the sound in the external environment from being transmitted into the acoustic cavity 42 through the air hole 43, that is, isolating the sound in the external environment.

[0050] A gas sensor provided in an embodiment of the present application directly generates a photoacoustic signal in an acoustic cavity 42 , and can integrate the back cavity in the existing sound pressure detector 4 with the photoacoustic cell, eliminating the need for an additional photoacoustic cell, thereby further reducing the volume of the gas sensor.

[0051] The specific contents of the gas sensor provided by this application will be described in detail in the following application examples.

[0052] Please refer to Figure 3 , Figure 3 This is a schematic structural diagram of the first specific photoacoustic detection unit provided in an embodiment of the present application.

[0053] Different from the above-mentioned embodiment, the present embodiment further defines the structure of the photoacoustic detection unit 1 based on the above-mentioned embodiment. The rest of the contents have been introduced in detail in the above-mentioned embodiment and will not be repeated here.

[0054] See also Figure 3 In the embodiment of the present application, a light through hole 45 is provided on the side of the housing 46 facing away from the PCB board 2, and the light source module 5 is provided on the side of the sound pressure detector 4 facing away from the PCB board 2, and emits the light to the acoustic cavity 42 through the light through hole 45.

[0055] The aforementioned sound pressure detection module can be an existing, pre-packaged conventional sound pressure detection module. Conventional sound pressure detection modules typically include the aforementioned housing 46 forming the acoustic cavity 42, and the sound pressure detector 4 located within the housing 46. A diaphragm 41 and a microphone chip 47 are located within the housing 46. The acoustic cavity 42 is divided into a back cavity by the diaphragm 41. The microphone chip 47 and diaphragm 41 are typically mounted on a substrate 48. In this embodiment, the diaphragm 41 detects the weak sound pressure generated by the photoacoustic effect and converts it into an electrical signal. The signal is then typically transmitted to the microphone chip 47 for pre-processing and ultimately to the detector control chip 3 for processing, thereby generating a detection result for the target gas concentration. The microphone chip 47 is typically an ASIC chip. The specific structure of the microphone chip 47 is not specifically limited in this embodiment of the present invention and depends on the specific situation. Of course, the microphone chip 47 can also be omitted in this embodiment. In this case, the diaphragm 41 can directly transmit the generated electrical signal to the detector control chip 3 for unified processing.

[0056] A light through hole 45 is provided on one side of the above-mentioned shell 46, and the light source module 5 is provided on the side of the sound pressure detection module provided with the light through hole 45, and emits light to the acoustic cavity 42 through the light through hole 45. That is, the above-mentioned light source module 5 and the sound pressure detector 4 are not located in the same packaging structure, but are stacked. Specifically, a through hole will be opened on one side of the shell 46 as the light through hole 45, and the light source module 5 will be specifically located on the side of the sound pressure detection module provided with the light through hole 45, and the opening of the light source module 5 is usually arranged toward the sound pressure detection module, and light of a preset wavelength can be emitted into the acoustic cavity 42 through the above-mentioned light through hole 45. At this time, a photoacoustic signal can be directly generated in the acoustic cavity 42 and directly collected by the diaphragm 41, and the corresponding electrical signal is first processed by its own microphone chip 47 and then transmitted to the detector control chip 3 to measure the target gas concentration.

[0057] The above-mentioned light source module 5 can specifically be a MEMS blackbody light source module with a filter 52, or a MEMS blackbody light source with a metasurface structure that directly generates infrared light of a specific wavelength, or an LED light source with a filter 52, or a laser that generates the required wavelength. That is, it can also be other light sources that can generate the required infrared wavelength, such as LED lights, lasers, etc. The above-mentioned blackbody light source module 5 can specifically be a packaged blackbody light source module 5, which usually includes a slot-shaped bracket, a light source chip 51 is arranged in the slot, and a filter 52 is arranged at the opening of the slot-shaped blackbody to filter out infrared light of other wavelengths and only emit light of a preset wavelength of a specific wavelength. The above-mentioned blackbody light source module 5 is usually arranged toward the above-mentioned light through hole 45, so as to directly emit light into the acoustic cavity 42.

[0058] Specifically, the above-mentioned optical through hole 45 can be set towards the area of ​​the sound pressure detector 4 where the diaphragm 41 is not set, that is, the optical through hole 45 can be set specifically towards the microphone chip 47 in the sound pressure detector 4, so that the light transmitted into the acoustic cavity 42 does not directly illuminate the diaphragm 41. Because the diaphragm 41 is transparent to certain wavelengths, the light passing through the diaphragm 41 may generate photoacoustic signals on both sides of the diaphragm 41 at the same time, which will weaken the output of the sound pressure detector 4. When the optical through hole 45 is set towards the area of ​​the sound pressure detector 4 where the diaphragm 41 is not set, the light usually does not undergo multiple reflections in the acoustic cavity 42. At this time, the photoacoustic signal is only generated inside the back cavity on one side of the diaphragm 41, and the sound pressure detector 4 has a stronger output. Of course, according to the specific structural design, in the embodiment of the present application, a larger optical through hole can also be opened on the entire surface of one side of the shell 46 of the entire sound pressure detector 4 to allow more light to enter the acoustic cavity 42, thereby generating a stronger photoacoustic signal. Even if light strikes diaphragm 41, a photoacoustic signal is generated on the other side of diaphragm 41. However, since a stronger photoacoustic signal is generated on the side of diaphragm 41 near optical aperture 45, this offsets the photoacoustic signal generated on the other side of diaphragm 41, resulting in a relatively strong detectable signal. The blackbody light source module 5 and the analog or digital signal generated by sound pressure detector 4 are both driven and processed by detector control chip 3.

[0059] When the housing 46 is disposed on the surface of the PCB board 2, that is, the sound pressure detector 4 is directly disposed on the surface of the PCB board 2 to form an acoustic cavity 42, the air hole 43 corresponding to the acoustic cavity 42 can be specifically disposed in the area of ​​the PCB board 2 corresponding to the diaphragm 41, that is, the air hole 43 is disposed in the area of ​​the PCB board 2 corresponding to the diaphragm 41. In this case, the air hole 43 and the optical through hole 45 are respectively disposed on both sides of the diaphragm 41. However, the gas to be measured entering the acoustic cavity 42 from the air hole 43 can be transmitted to the other side of the diaphragm 41 through the pressure relief hole in the diaphragm 41, and generate a photoacoustic signal with the light transmitted into the acoustic cavity 42 from the optical through hole 45. In this embodiment, since the sound pressure detectors 4 used are all packaged sound pressure detectors 4, the sound pickup hole of the sound pressure detector 4 can be used as the air hole 43. In order to increase the volume of the back cavity in the sound pressure detector 4, the air hole 43 is usually disposed on the surface of the sound pressure detector 4 facing away from the light source module 5.

[0060] It should be noted that in this embodiment, the packaging structure can be stacked up and down, so that the light source module 5 can be connected to the PCB board 2 through the large solder pad at the bottom for heat dissipation, and the upper sound pressure detection module can be connected to the contacts on the surface of the PCB board 2 through the side of the light source module 5; or the entire packaging structure can be rotated 90 degrees, and the light source module 5 and the sound pressure detector 4 are both connected to the PCB board 2 through the side contacts.

[0061] In this embodiment and the following embodiments, the surface of the diaphragm 41 facing the photoacoustic signal generation side is provided with a first reflective layer that is reflective of the light; and / or the surface of the microphone chip 47 of the sound pressure detector facing the photoacoustic signal generation side is provided with a second reflective structure that is reflective of the light. These first reflective layer and second reflective structure are primarily used to reflect the light generated by the light source module 5, typically by reflecting the light back into the acoustic cavity 42, thereby preventing absorption of the light by the diaphragm 41 and the microphone chip 47.

[0062] Specifically, the first reflective layer is disposed on the surface of the diaphragm 41. Based on the structure of the diaphragm 41, the first reflective layer is typically a coating plated on the surface of the diaphragm 41. The first reflective layer may be a metal coating, so that the light emitted by the light source module 5 and irradiated to the diaphragm 41 is reflected back to the acoustic cavity 42 by virtue of the metal's own reflectivity to light. The second reflective structure is used to reflect the light irradiated to the microphone chip 47 back to the acoustic cavity 42. Based on the structure of the microphone chip 47, the second reflective structure may be a coating plated on the surface of the microphone chip 47. The material of the coating may be metal, that is, the second reflective structure may be a metal coating, so that the light emitted by the light source module 5 and irradiated to the microphone chip 47 is reflected back to the acoustic cavity 42 by virtue of the metal's own reflectivity to light. The above-mentioned second reflective structure can also be a packaging shell covering the microphone chip 47. The material of the packaging shell can be metal, that is, the above-mentioned second reflective structure can be a metal shell, so that the light emitted by the light source module 5 and irradiated to the microphone chip 47 can be reflected back to the acoustic cavity 42 through the metal's own reflectivity to light.

[0063] A gas sensor provided in the present application uses an existing packaged sound pressure detector 4 and a light source module 5, which can reduce production costs; and the light source module 5 is arranged outside the acoustic cavity 42, and a low thermal conductivity filter 52 is used to thermally isolate the light source chip 51 and the acoustic cavity 42, which can prevent the heat generated by the light source chip 51 during operation from being transferred to the acoustic cavity 42, thereby preventing temperature changes from interfering with the photoacoustic signal.

[0064] The specific contents of the gas sensor provided by this application will be described in detail in the following application examples.

[0065] Please refer to Figures 4 to 7 , Figure 4 A schematic structural diagram of a second specific photoacoustic detection unit 1 provided in an embodiment of the present application; Figure 5 for Figure 4 Schematic diagram of the structure of the corresponding gas sensor; Figure 6 Schematic diagram of the structure of the first light source module 5; Figure 7 Schematic diagram of the structure of the second light source module 5.

[0066] Different from the above-mentioned embodiment, the present embodiment further defines the structure of the photoacoustic detection unit 1 based on the above-mentioned embodiment. The rest of the contents have been introduced in detail in the above-mentioned embodiment and will not be repeated here.

[0067] See also Figure 4 In the embodiment of the present application, the sound pressure detector 4 and the light source module 5 can be arranged in the acoustic cavity 42, and the detector control chip 3 can be arranged outside the acoustic cavity 42. The diaphragm 41 and the light source module 5, which are usually the light-emitting structures in the light source module 5, such as the light source chip 51, the filter 52, etc., can be arranged in the housing 46, that is, the light source chip 51 and the filter 52 are placed inside the sound pressure detection module, and the microphone chip 47 is removed. In the embodiment of the present application, the light source chip 51 and the above-mentioned diaphragm 41 are directly arranged in the same cavity. After the light source chip 51 is powered on and emits light, the photoacoustic signal will be directly generated in the acoustic cavity 42 in the housing 46. Therefore, the acoustic cavity 42 is also equivalent to a photoacoustic pool. By directly generating a photoacoustic signal in the acoustic cavity 42 for detection, there is no need to set up an additional photoacoustic pool, thereby further reducing the volume of the gas sensor and also reducing the microphone chip 47.

[0068] In the embodiment of the present application, the diaphragm 41 is usually mounted in the housing 46, and the light source chip 51 is usually arranged on the surface of the PCB board 2. Specifically, since the light source chip 51 generates relatively high heat when working. In order to avoid the temperature change in the acoustic cavity 42 caused by the heat, which interferes with the photoacoustic signal, the above-mentioned light source module 5, usually specifically the light source chip 51, needs to be connected to the heat sink in the PCB board 2. By connecting the heat sink to the light source chip 51, the heat generated by the light source chip 51 is promptly conducted out of the cavity through the heat sink in the PCB board 2, thereby avoiding the heat generated when the light source module 5 is working to affect the photoacoustic signal. Normally, the light source chip 51 can be connected to the heat sink in the PCB board 2 through a solder pad.

[0069] In the embodiment of the present application, the diaphragm 41 and the light source chip 51 are uniformly packaged, which can further reduce the volume and power consumption of the gas sensor. Compared with the existing conventional sound pressure detector 4, the microphone chip 47 can be removed in the present application, and the electrical signal generated by the diaphragm 41 can be directly processed by the detector control chip 3. At this time, compared with the existing conventional sound pressure detector 4, the above-mentioned light source chip 51 can replace the position of its microphone chip 47, so that the volume of the packaged photoacoustic detection unit 1 in the present application is roughly the same as that of the conventional sound pressure detector 4, thereby forming a smaller photoacoustic detection unit 1.

[0070] Specifically, the air holes 43 can be provided in the area of ​​the PCB board 2 corresponding to the diaphragm 41, and / or the air holes 43 can be provided on the side of the housing 46 facing away from the PCB board 2. When the air holes 43 are provided in the area of ​​the PCB board 2 corresponding to the diaphragm 41, the position where the gas to be measured enters and the position where the photoacoustic signal is generated are respectively on both sides of the diaphragm 41. In this case, the diaphragm 41 needs to have a pressure relief hole; and when the air holes 43 are provided on the side of the housing 46 facing away from the PCB board 2, the position where the gas to be measured enters and the position where the photoacoustic signal is generated are on the same side of the diaphragm 41. In this case, it can be ensured that the gas in the acoustic cavity 42 has a faster exchange speed with the external environment, and a diaphragm 41 without a pressure relief hole can be used. In this case, the air holes 43 are usually provided in the area of ​​the housing 46 facing away from the PCB board 2 corresponding to the diaphragm 41, so that the photoacoustic signal with the maximum energy is generated near the diaphragm 41.

[0071] See also Figure 5 In this embodiment, the detector control chip 3 is specifically located outside the aforementioned housing 46. In this case, the detector control chip 3 needs to be separately packaged, and signals are transmitted between the detector control chip 3 and the photoacoustic detection unit 1 via the PCB board 2. The detector control chip 3 can be used to acquire and analyze the electrical signals generated by the diaphragm 41 in the photoacoustic detection unit 1, as well as to control the light source chip 51. Placing the detector control chip 3 outside the photoacoustic detection unit 1 prevents heat generated during operation from interfering with the photoacoustic signals generated within the housing 46.

[0072] In this embodiment, two packaging structures of the light source module 5 are specifically provided. Please refer to Figure 6 In the first packaging structure of the light source module 5, the light source module 5 includes a light source chip 51 and a filter 52. The light source chip 51 is located in a recess pre-set in the PCB board 2 and connected to a heat sink in the PCB board 2. The filter 52 is located at the opening of the recess and connected to the PCB board 2. Specifically, in this structure, a recess is provided in the PCB board 2 to accommodate the light source chip 51, which is configured to output light across a wide wavelength range. The filter 52 is located at the opening of the recess and seals the opening, enclosing the light source chip 51 in a sealed environment. Only light of a specific wavelength passes through the filter 52 and enters the acoustic cavity 42, thereby enabling detection of the gas to be measured. In this case, the filter 52 can be in the form of a flat sheet. In this case, the filter 52 can provide a certain degree of heat insulation, thereby preventing heat generated by the light source chip 51 during operation from interfering with the photoacoustic signal.

[0073] Please refer to Figure 7In the second packaging structure of the light source module 5, the light source module 5 includes a light source chip 51 and a filter 52. The light source chip 51 is located on the surface of the PCB 2 and connected to a heat sink in the PCB 2. The filter 52 is shaped like a cover, enclosing the light source chip 51 and connected to the PCB 2. In other words, in this structure, there is no need to provide a groove in the PCB 2; the light source chip 51 can be directly placed on the flat surface of the PCB 2. However, in this structure, a filter 52 is required to cover the light source chip 51. The filter 52 can be arc-shaped, semicircular, or similar. While covering the light source chip 51, the filter 52 is typically sealed to the PCB, isolating the light source chip 51 from direct contact with the interior of the acoustic cavity 42. This keeps the light source chip 51 in a sealed environment, allowing only light of a specific wavelength to pass through the filter 52 and enter the acoustic cavity 42, thereby enabling detection of the gas to be tested. At this time, the filter 52 can play a role in isolating heat transfer to a certain extent, thereby preventing the heat generated by the light source chip 51 during operation from interfering with the photoacoustic signal.

[0074] A gas sensor provided in an embodiment of the present application integrates the light source chip 51 and the sound pressure detector 4 into an integrated package, which can effectively reduce the volume of the photoacoustic detection unit 1 and further achieve miniaturization of the gas sensor.

[0075] The specific contents of the gas sensor provided by this application will be described in detail in the following application examples.

[0076] Please refer to Figures 8 to 11 , Figure 8 A schematic structural diagram of a third specific gas sensor provided in an embodiment of the present application; Figure 9 A schematic structural diagram of a fourth specific gas sensor provided in an embodiment of the present application; Figure 10 A schematic structural diagram of a fifth specific gas sensor provided in an embodiment of the present application; Figure 11 This is a schematic structural diagram of the sixth specific gas sensor provided in an embodiment of the present application.

[0077] Different from the above-mentioned embodiment, the present embodiment further defines the structure of the photoacoustic detection unit 1 based on the above-mentioned embodiment. The rest of the contents have been introduced in detail in the above-mentioned embodiment and will not be repeated here.

[0078] See also Figure 8In the embodiment of the present application, the sound pressure detector 4, the light source module 5 and the detector control chip 3 can all be arranged in the acoustic cavity 42, that is, the diaphragm 41, the light source chip 51 and the detector control chip 3 are all arranged in the housing 46. In the embodiment of the present application, the light source module 5 is directly arranged, and the light-emitting structure of the light source module 5, such as the light source chip 51, the filter 52, etc., is usually arranged in the same cavity with the diaphragm 41 and the detector control chip 3, that is, the light source chip 51, the diaphragm 41 and the detector control chip 3 are encapsulated in the same structure through the same housing 46. At this time, the cavity in the housing 46 is equivalent to the acoustic cavity 42 and also to the photoacoustic pool. By directly generating the photoacoustic signal for detection in the acoustic cavity 42, there is no need to set up an additional photoacoustic pool, thereby further reducing the volume of the gas sensor.

[0079] In this embodiment, the detector control chip 3 located within the housing 46 can be a bare chip. That is, the unpackaged, bare detector control chip 3 can be packaged within the housing 46, thereby completing the entire detector control chip 3 through a single package. In this embodiment of the present application, the diaphragm 41, light source module 5, and detector control chip 3 are uniformly packaged, which further reduces the size and power consumption of the gas sensor.

[0080] Specifically, in this embodiment, the light source module 5, typically specifically the light source chip 51, needs to be connected to the heat sink in the PCB board 2, and the detector control chip 3 also needs to be connected to the heat sink in the PCB board 2. The heat sink in the PCB board 2 promptly conducts the heat generated by the light source module 5 and the detector control chip 3 out of the cavity, thereby preventing the heat generated by the light source chip 51 and the detector control chip 3 during operation from affecting the photoacoustic signal. Typically, the light source chip 51 and the detector control chip 3 can both be connected to the heat sink in the PCB board 2 via solder pads.

[0081] See also Figure 8 and Figure 9, the PCB board 2 is provided with the air hole 43 in the area corresponding to the diaphragm 41, and / or the housing 46 is provided with the air hole 43 on the side facing away from the PCB board 2. The position of the air hole 43 can be set as the position of the air hole 43 in the above-mentioned application embodiment. For details, please refer to the above-mentioned application embodiment and will not be repeated here. Specifically, two specific structures of the light source module 5 are also provided in the embodiment of the present application. The first one: the light source module 5 includes a light source chip 51 and a filter 52. The light source chip 51 is located in a preset groove of the PCB board 2. The light source chip 51 is connected to the heat sink in the PCB board 2; the filter 52 is located at the opening of the groove and is connected to the PCB board 2. The second one: the light source module 5 includes a light source chip 51 and a filter 52. The light source chip 51 is located on the surface of the PCB board 2. The light source chip 51 is connected to the heat sink in the PCB board 2; the filter 52 is in the shape of a cover and covers the light source chip 51 and is connected to the PCB board 2. The specific structures of the two light source modules 5 have been introduced in the above-mentioned embodiments. The specific structure of the light source module 5 in the embodiments of the present application can refer to the above-mentioned embodiments and will not be described again here.

[0082] Please refer to Figure 10 as well as Figure 11 In this embodiment, the air holes 43 may be a vent array 431 formed by a plurality of micro-vents arranged in an array, with a support wall formed between adjacent micro-vents. The air permeable membrane 44 covers the vent array 431 and contacts the support wall. The details of the vent array 431 have been described in detail in the aforementioned embodiments and will not be repeated here.

[0083] At this stage, there are many options for the light source module 5, but for this application, for the sake of reducing volume, power consumption, cost, etc., a black body manufactured by MEMS technology is selected, and the modulation frequency is within 50Hz, preferably between 10Hz-40Hz. A black body with a metasurface can also be used to directly generate infrared light of a specific wavelength, so that there is no need for a filter 52 to select the wavelength. For the detection of CO2 gas, an infrared narrowband filter 52 with a central wavelength of 4300um can be used. CO2 molecules have a good absorption of light in this band, while other gases including water molecules have basically no absorption in this band, which is the preferred wavelength for CO2 concentration measurement. The measurement of other gases can select a suitable wavelength based on the absorption spectrum.

[0084] The present embodiment proposes a small-volume chip-based gas sensor. Compared with the existing detector, the external photoacoustic pool is eliminated and the back cavity is used as the photoacoustic pool. The pressure relief hole on the diaphragm 41 is used to communicate with the CO2 concentration in the outside world. The infrared light of a specific band emitted by the low-power light source module 5 is absorbed by the CO2 gas molecules inside the sound pressure detection module and directly acts on the diaphragm 41 to generate a strong signal, thereby further reducing the volume while maintaining the gas detection performance; further, only using the sound pressure detector 4 such as the MEMS sound pressure detector 4, the light source module 5 such as the blackbody chip, the detector control chip 3 such as the ASIC control chip and the corresponding packaging can achieve the extremely small volume level of a single chip-level package, which is convenient for promotion and use in various portable devices. The present application uses the acoustic cavity 42 as the photoacoustic pool, eliminates the external photoacoustic pool, reduces the volume and reduces the power consumption, and further encapsulates the light source module 5 and the detector control chip 3 into the sound pressure detection module to achieve an extremely small volume.

[0085] The present application also provides a gas detection device, which specifically includes a gas sensor provided by any of the above embodiments. Other structures of the above gas detection device can refer to the existing technology and will not be described in detail here.

[0086] Since the gas sensor provided in the above embodiment has a smaller volume, the gas detection device in the embodiment of the present application can also have a smaller volume, thereby achieving miniaturization of the device. The specific structure of the gas sensor provided in the present application has been described in detail in the above embodiment of the application and will not be repeated here.

[0087] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0088] Finally, it should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article, or device comprising the element.

[0089] The above is a detailed introduction to a gas sensor and a photoacoustic spectroscopy gas detection device provided by the present application. This article uses specific examples to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method of the present application and its core idea. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present application, several improvements and modifications can be made to the present application, and these improvements and modifications also fall within the scope of protection of the claims of the present application.

Claims

1. A gas sensor, characterized in that: It includes a photoacoustic detection unit (1); The photoacoustic detection unit (1) comprises a sound pressure detection module and a light source module (5), wherein the sound pressure detection module comprises a sound pressure detector (4) and a housing (46) arranged outside the sound pressure detector (4), wherein an acoustic cavity (42) is formed inside the housing (46), and the acoustic cavity (42) is provided with an air hole (43) for introducing external ambient gas; the light source module (5) is used to emit light of a preset wavelength into the acoustic cavity (42) to generate a photoacoustic signal in the acoustic cavity (42), and the sound pressure detector is used to generate an electrical signal based on the photoacoustic signal.

2. The gas sensor according to claim 1, wherein The gas sensor further comprises a PCB board (2) and a detector control chip (3); the photoacoustic detection unit (1) is arranged on the surface of the PCB board (2); the electrical signal generated by the sound pressure detector (4) is transmitted to the detector control chip (3) via the PCB board (2); and the housing (46) is arranged on the surface of the PCB board (2) and forms the acoustic cavity (42) together with the PCB board (2).

3. The gas sensor according to claim 1, wherein The air holes (43) are covered with a breathable membrane (44).

4. The gas sensor according to claim 3, characterized in that The air holes (43) are an air hole array (431) formed by a plurality of micro air holes distributed in an array, and a support wall is formed between adjacent micro air holes; the air permeable membrane (44) covers the air hole array (431) and is in contact with the support wall.

5. The gas sensor according to claim 2, wherein: The sound pressure detector includes a diaphragm (41), the acoustic cavity (42) accommodates the diaphragm (41), and the diaphragm (41) generates the electrical signal based on the photoacoustic signal; wherein the air hole (43) is provided in a region corresponding to the location of the diaphragm (41).

6. The gas sensor according to claim 5, characterized in that The surface of the diaphragm (41) facing the side where the photoacoustic signal is generated is provided with a first reflective layer that is reflective to the light; And / or, a second reflective structure having reflectivity to the light is provided on the surface of the microphone chip (47) of the sound pressure detector (4) facing the side where the photoacoustic signal is generated.

7. The gas sensor according to claim 1, wherein A light through hole (45) is provided on one side of the housing (46), and the light source module (5) is provided on the side of the sound pressure detection module where the light through hole (45) is provided, and emits the light toward the acoustic cavity (42) through the light through hole (45).

8. The gas sensor according to claim 1, wherein The light source module (5) includes a MEMS blackbody light source module with a filter (52), or a MEMS blackbody light source with a metasurface structure that directly generates infrared light of a specific wavelength, or an LED light source with a filter (52), or a laser that generates a required wavelength.

9. The gas sensor according to claim 2, wherein: The sound pressure detector (4) and the light source module (5) are arranged in the acoustic cavity (42), and the detector control chip (3) is arranged outside the acoustic cavity (42); Alternatively, the sound pressure detector (4), the light source module (5), and the detector control chip (3) are all arranged in the acoustic cavity (42).

10. The gas sensor according to claim 9, characterized in that The pores (43) are provided in the area of ​​the PCB board (2) corresponding to the diaphragm (41), and / or the pores (43) are provided on the side of the housing (46) facing away from the PCB board (2).

11. The gas sensor according to claim 9, characterized in that The light source module (5) comprises a light source chip (51) and a filter (52); the light source chip (51) is located in a groove preset in the PCB board (2); the light source chip (51) is connected to a heat sink in the PCB board (2); the filter (52) is located at an opening of the groove and is connected to the PCB board (2); Alternatively, the light source module (5) comprises a light source chip (51) and a filter (52), wherein the light source chip (51) is located on the surface of the PCB board (2), and the light source chip (51) is connected to a heat sink in the PCB board (2); and the filter (52) is in a cover shape, covering the light source chip (51) and connected to the PCB board (2).

12. A gas detection device, characterized in that: The method comprises the gas sensor according to any one of claims 1 to 11.

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