A resonant gas sensor

Abstract

The present invention relates to the technical field of gas sensors, and particularly relates to a resonant gas sensor, comprising: an integrated light source, a photoacoustic cell, an acoustic detector, and a circuit layer substrate. The integrated light source and the acoustic detector are arranged on the circuit layer substrate. A filter is arranged on the integrated light source. The photoacoustic cell is a semi-closed cavity, and the shape and structure of the photoacoustic cell are adapted to those of the circuit layer substrate and they jointly form a closed cavity with holes. The integrated light source, the photoacoustic cell, and the acoustic detector arranged on the circuit layer substrate are enclosed within the cavity of the photoacoustic cell. The photoacoustic cell includes a support framework and a plurality of resonant surfaces. The support framework and the resonant surfaces are adhesively combined to form a semi-closed cavity. At least one of the resonant surfaces is thinner. One or more smaller air holes are provided on any one or more of the resonant surfaces. A waterproof and breathable membrane or a waterproof and sound-permeable membrane is arranged outside the air holes. The resonant gas sensor of the present invention has higher sensitivity, higher measurement accuracy, and higher resolution.

Description

Technical Field

[0001] The present invention relates to the technical field of gas sensors, and particularly to a resonant gas sensor. Background Art

[0002] Gas sensors are widely used in fields such as smart cities, healthcare, and industrial control. With the rapid development of emerging industries such as the Internet of Things and the increasing attention of people to air environmental quality, the application demand for gas sensors has grown rapidly. Gas sensors mainly include types such as semiconductor type, catalytic combustion type, electrochemical type, and non-dispersive infrared (NDIR) type. Among them, the biggest problem in the use of semiconductor type, catalytic combustion type, electrochemical type and other gas sensors is the poor selectivity to gases, and there is cross-interference between different gases. Infrared gas sensors work based on the principle of selective absorption of specific wavelength infrared light by gas molecules. The NDIR type infrared gas sensor has good selectivity and can achieve fingerprint feature recognition of gases, but has problems such as low integration, large volume, and low measurement accuracy.

[0003] Photoacoustic spectroscopy technology, as an optical technology, is widely used in trace gas detection and has the advantages of high sensitivity generated by zero background characteristics, convenient output signal, and strong selectivity. In recent years, with the development of semiconductor technology and microelectronics technology, miniaturized photoacoustic gas sensors are expected to become the mainstream technology for gas sensors in the future.

[0004] Currently, photoacoustic gas sensors still have problems such as low sensitivity and large volume. For example, the Chinese patent "Integrated Infrared Light Source and Acoustic Detector for Photoacoustic Gas Sensor" (201110184435.2) provides a photoacoustic gas sensor including an integrated light source, an infrared filter, an acoustic sensor, and a TO package. The Chinese patent "Photoacoustic Gas Sensor Package" (201910635660.X) provides a photoacoustic gas sensor with a ceramic cavity package including core components such as a light source and a photoacoustic detector. Since the acoustic signal released after the measured gas absorbs light in a specific spectral band is relatively weak, the above sensors do not consider the acoustic signal enhancement technology, so the sensitivity of the sensors is relatively low. Summary of the Invention

[0005] In order to solve the problems existing in the above-mentioned existing photoacoustic sensors, the present invention provides a resonant gas sensor, which is a miniaturized gas sensor with higher measurement accuracy.

[0006] A resonant gas sensor includes: an integrated light source, a photoacoustic cell, an acoustic detector, and a circuit layer substrate. The integrated light source and the acoustic detector are disposed on the circuit layer substrate. A filter is provided on the integrated light source. The photoacoustic cell is a semi-closed cavity, and the shape and structure of the photoacoustic cell are adapted to those of the circuit layer substrate, and they jointly form a closed cavity with holes. The integrated light source, the photoacoustic cell, and the acoustic detector disposed on the circuit layer substrate are wrapped in the cavity of the photoacoustic cell. The photoacoustic cell includes a support skeleton and multiple resonant surfaces. The support skeleton and the resonant surfaces are adhesively combined to form a semi-closed cavity. At least one of the resonant surfaces is relatively thin, and one or more small air holes are provided on any one or more of the resonant surfaces. A waterproof breathable membrane or a waterproof sound transmission membrane is provided outside the air holes.

[0007] Further, the photoacoustic cell is in the shape of a cuboid and includes 1 hexahedron support skeleton and 5 resonant surfaces (the resonant surfaces are flexible surfaces). One or more small air holes are provided on any one or more of the 5 resonant surfaces (the air holes ensure that the target gas to be measured can quickly enter the interior of the photoacoustic cell); a waterproof breathable membrane or a waterproof sound transmission membrane is provided outside the air holes.

[0008] Further, the photoacoustic cell is in the shape of a cylinder and includes 1 cylindrical frame and 2 resonant surfaces (including a top surface and a cylindrical surface). One or more small air holes are provided on any one or more of the 2 resonant surfaces (the air holes ensure that the target gas to be measured can quickly enter the interior of the photoacoustic cell); a waterproof breathable membrane or a waterproof sound transmission membrane is provided outside the air holes, forming a semi-closed cavity with air holes.

[0009] Further, the support skeleton is made of a metal or alloy material with strong stiffness, a large Young's modulus, and easy processing, or made of silicon, resin, or acrylic material.

[0010] Further, the resonant surface is made of a flexible thin film material with a low Young's modulus.

[0011] Advantages of the present invention:

[0012] Compared with the traditional photoacoustic gas sensor, the miniaturized resonant photoacoustic gas sensor provided by the present invention adopts a new type of rectangular and circular resonant photoacoustic cell. After the object to be measured absorbs the periodically modulated light, heat is released in the form of periodic sound waves. The resonant photoacoustic cell can amplify the periodic sound waves, improve the output signal intensity of the acoustic detector, so that the photoacoustic sensor can be smaller in volume, higher in sensitivity, higher in measurement accuracy, and higher in resolution. Description of the Drawings

[0013] The following further describes the present invention in detail with reference to the drawings and specific embodiments.

[0014] Figure 1Schematic diagram of the overall structure of a rectangular miniaturized resonant photoacoustic gas sensor provided by the present invention;

[0015] Figure 2 Schematic diagram of the structure of a circular miniaturized resonant photoacoustic gas sensor provided by the present invention;

[0016] Figure 3 Schematic diagram of the structure of a photoacoustic cell with a single resonant surface provided by the present invention;

[0017] Figure 4 Schematic diagram of the structure of a photoacoustic cell with multiple resonant surfaces provided by the present invention;

[0018] Figure 5 Schematic diagram of the diagonal cross-section of the structure of a photoacoustic cell with a single resonant surface provided by the present invention. Detailed implementation manner

[0019] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0020] The resonant gas sensor mentioned in this embodiment is a miniaturized resonant photoacoustic gas sensor. Compared with the prior art, the miniaturized resonant photoacoustic gas sensor of the present invention has higher sensitivity, higher measurement accuracy, and higher resolution compared with traditional photoacoustic gas sensors.

[0021] This embodiment provides a resonant gas sensor, as Figure 1 and Figure 5 shown, its structure includes: an integrated light source, a photoacoustic cell, an acoustic detector, and a circuit layer substrate. The integrated light source and the acoustic detector are arranged on the circuit layer substrate. A filter is arranged on the integrated light source. The photoacoustic cell is a semi-closed cavity. The shape and structure of the photoacoustic cell are adapted to those of the circuit layer substrate and are combined together by adhesion to form a closed cavity with holes. The integrated light source, the photoacoustic cell, and the acoustic detector arranged on the circuit layer substrate are enclosed in the cavity of the photoacoustic cell.

[0022] The integrated light source can adopt a narrowband light source that can cover the characteristic absorption spectrum lines of the target gas; or a broadband light source that can cover the characteristic absorption spectrum lines of the target gas.

[0023] In a preferred implementation manner, the integrated light source and the filter are used in combination. The filter is used to filter out the light of non-target gas characteristic absorption spectrum lines. By modulating the driving frequency of the integrated light source, a photoacoustic signal corresponding to the frequency can be generated for the sensor.

[0024] The photoacoustic cell is designed to be cuboid, cylindrical or other shapes, and there is a space inside the photoacoustic cell for the interaction between gas and light.

[0025] The photoacoustic cell includes a support skeleton and multiple resonant surfaces. The support skeleton and the resonant surfaces are adhesively combined into a semi-closed cavity. One or more smaller air holes are opened on any one or more of the resonant surfaces, and a waterproof breathable membrane or a waterproof sound-permeable membrane is arranged outside the air holes. Therefore, the photoacoustic cell is a cavity with air holes, and by selecting appropriate materials and thicknesses, the sound signal emitted after the gas absorbs the characteristic spectral line light can be enhanced and amplified.

[0026] The support skeleton is made of a metal or alloy material with strong stiffness, large Young's modulus and easy processing, or made of silicon, resin, acrylic material.

[0027] The resonant surface of the photoacoustic cell is made of a flexible thin film material with a lower Young's modulus, such as polyimide film, metal film, acrylic film, etc. Using a flexible thin film material with a lower Young's modulus can achieve resonance in a suitable frequency range.

[0028] In the photoacoustic cell structure, at least one resonant surface is thinner and can resonate with the modulation frequency of the light source, thereby enhancing the intensity of the sound signal emitted after the target gas absorbs light.

[0029] In a preferred embodiment, the photoacoustic cell is in the shape of a cuboid, as Figure 1 , Figure 3 and Figure 4 shown, including a hexahedron support skeleton and 5 rectangular resonant surfaces (the resonant surfaces are flexible surfaces). One or more smaller air holes are opened on any one or more of the 5 rectangular resonant surfaces, and the air holes ensure that the target gas to be measured can quickly enter the interior of the photoacoustic cell; a waterproof breathable membrane or a waterproof sound-permeable membrane (which can be selected according to the use scenario of the sensor) is arranged outside the air holes.

[0030] In the cuboid photoacoustic cell, the 5 rectangular resonant surfaces adopt a structure of 4 side surfaces + 1 top surface, and one or more smaller air holes can be opened on the top surface or the 4 side surfaces to ensure that the target gas to be measured can quickly enter the interior of the photoacoustic cell.

[0031] Furthermore, the 4 side surfaces of the photoacoustic cell cavity can be made of a metal or alloy, silicon, resin, acrylic, etc. with strong stiffness, large Young's modulus and easy processing. Common materials are aluminum alloy, stainless steel, kovar alloy, etc.

[0032] Further, one top surface of the photoacoustic cell can be made of a flexible thin film material with a low Young's modulus, such as polyimide film, metal film, acrylic film, etc. The flexible thin film material with a low Young's modulus can achieve resonance in a suitable frequency range.

[0033] In another alternative embodiment, the photoacoustic cell is in the shape of a cylinder, as Figure 2 shown, including a cylindrical frame and two resonant surfaces. One or more smaller air holes are provided on any one or more of the two resonant surfaces. The air holes ensure that the target gas to be measured can quickly enter the interior of the photoacoustic cell. According to the usage scenario of the sensor, a waterproof and breathable membrane or a waterproof and sound-permeable membrane can be provided outside the air holes to form a semi-closed cavity with air holes.

[0034] In the cylindrical photoacoustic cell, the two resonant surfaces adopt a structure of one cylindrical surface + one top surface. One or more smaller air holes can be provided on the top surface or the cylindrical surface to ensure that the target gas to be measured can quickly enter the interior of the photoacoustic cell.

[0035] Further, one cylindrical surface of the photoacoustic cell cavity can be made of materials with strong stiffness, large Young's modulus, and easy processing, such as metals or alloys, silicon, resin, acrylic, etc. Common materials can include aluminum alloy, stainless steel, kovar alloy, etc.

[0036] Further, one top surface of the photoacoustic cell can be made of a flexible thin film material with a low Young's modulus, such as polyimide film, metal film, acrylic film, etc. The flexible thin film material with a low Young's modulus can achieve resonance in a suitable frequency range.

[0037] Further, in some preferred embodiments, the inner wall of the photoacoustic cell is made of a material that has a reflective effect on the light of the characteristic absorption spectral lines of the target gas. For example, the photoacoustic cell can be made of a metal material with strong light reflection ability such as gold, silver, etc. In some other embodiments, the photoacoustic cell can also be made of materials such as silicon, resin, acrylic, etc., and then a layer of material with strong light reflection ability can be integrated on the inner wall of the photoacoustic cell by methods such as evaporation plating, electroplating, sputtering, etc. to increase the propagation optical path of the light and enhance the absorption amount of the target gas to be measured for the light.

[0038] In this embodiment, the matching problem between the light source driving frequency and the resonance frequency of the flexible thin film material in the photoacoustic cell is the key to realizing the enhancement of the photoacoustic signal.

[0039] The acoustic detector can adopt a MEMS microphone or other gas acoustic detection devices that can pick up the acoustic signal released after the target gas absorbs the characteristic spectral line light, such as a barometric pressure sensor, a pressure sensor, etc.

[0040] The circuit layer substrate is used to integrate the integrated light source, the photoacoustic cell, the acoustic detector and the circuit for acoustic signal processing. The substrate can be made of PCB, ceramic, silicon or other materials.

[0041] Furthermore, the circuits used for acoustic signal processing include but are not limited to functions such as amplification, digital-to-analog conversion, processing and data transmission.

[0042] The shape and structure of the circuit layer substrate are adapted to the shape and structure of the photoacoustic cell. When the photoacoustic cell is in the shape of a cuboid, the shape of the circuit layer substrate is a rectangular structure adapted to the structural size of the rectangular photoacoustic cell; when the photoacoustic cell is in the shape of a cylinder, the shape of the circuit layer substrate is a circular structure matching the structure of the photoacoustic cell; when the photoacoustic cell is in other shapes, the shape of the circuit layer substrate is other shapes matching the structural size of the photoacoustic cell.

[0043] The miniaturized resonant photoacoustic gas sensor provided in the embodiment of the present invention can detect gases including but not limited to: carbon dioxide CO2, carbon monoxide CO, methane CH4, nitrogen oxides NO x wait.

[0044] The working principle of the resonant gas sensor of the embodiment of the present invention includes: driving the integrated light source through a tuning circuit to emit periodic light containing characteristic absorption lines of the target gas; the light is reflected multiple times inside the photoacoustic cell, and the measured gas selectively absorbs the characteristic spectrum line light during the light propagation process, and the position of the integrated light source and the structure of the photoacoustic cell are preferably arranged to ensure that the light has a reasonable optical path length in the photoacoustic cell, thereby enhancing the absorption rate of the light; after the measured gas absorbs the characteristic spectrum line light, it releases energy in the form of an acoustic signal. Since the light emitted by the integrated light source is periodic, the measured gas absorbs the periodic characteristic spectrum line light. After the characteristic spectral line light is absorbed, an acoustic signal of the same frequency will also be generated; by adjusting the material and structural parameters of the photoacoustic cell, it is ensured that at least one surface of the photoacoustic cell can form a resonance near the luminous frequency of the integrated light source. Therefore, the amplitude of the acoustic signal generated by the measured gas after absorbing the periodic characteristic spectral line light can be enhanced through the resonance surface of the photoacoustic cell, thereby improving the sensitivity of the sensor; the acoustic signal generated by the measured gas after absorbing the periodic characteristic spectral line light can be detected by the acoustic detector to form an electrical signal, and then the electrical signal is analyzed by the signal processing circuit to obtain the concentration of the measured target gas, thereby realizing the quantitative detection of the measured gas. By selecting an integrated light source with different luminous wavelengths, quantitative detection of different types of gases to be measured can be realized.

[0045] When introducing elements of various embodiments of the present application, the articles "a," "an," "the," and "said" are intended to mean that there are one or more elements. The words "comprising," "including," and "having" are all inclusive and mean that there may be additional elements in addition to the listed elements.

[0046] In the description of this embodiment, it should be understood that the orientation or positional relationship indicated by terms such as "bottom", "top", "upper", "one side", "top", "inner", "center", "two ends", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing this embodiment and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation on the present invention.

[0047] Each embodiment in this specification is described in a progressive manner. For the same or similar parts among the embodiments, reference can be made to each other. The key point of each embodiment is to illustrate the differences from other embodiments. The device embodiments described above are merely illustrative. The units and modules described as separate components may or may not be physically separated. Additionally, some or all of the units and modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment. A person of ordinary skill in the art can understand and implement it without creative efforts.

[0048] The above are only the specific implementation manners of this application. It should be noted that for those of ordinary skill in the art, various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirits of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A resonant gas sensor, comprising: Integrated light source, photoacoustic cell, acoustic detector, circuit layer substrate. The integrated light source and the acoustic detector are arranged on the circuit layer substrate, and a filter is arranged on the integrated light source. It is characterized in that the photoacoustic cell is a semi-closed cavity, and the shape and structure of the photoacoustic cell are adapted to those of the circuit layer substrate and jointly form a closed cavity with holes. The integrated light source, photoacoustic cell, and acoustic detector arranged on the circuit layer substrate are wrapped in the cavity of the photoacoustic cell; the photoacoustic cell includes a support skeleton and multiple resonant surfaces. The support skeleton and the resonant surfaces are adhesively combined to form a semi-closed cavity. At least one of the resonant surfaces is relatively thin, and one or more smaller air holes are provided on any one or more of the resonant surfaces. A waterproof breathable membrane or a waterproof sound-permeable membrane is arranged outside the air holes; The resonant surface is made of a flexible thin film material with a low Young's modulus.

2. The resonant gas sensor according to claim 1, characterized in that, The photoacoustic cell is in the shape of a cuboid and includes a hexahedron support skeleton and five resonant surfaces. One or more smaller air holes are provided on any one or more of the five resonant surfaces.

3. A resonant gas sensor according to claim 1, characterized in that, The photoacoustic cell is in the shape of a cylinder and includes a cylindrical frame and two resonant surfaces. One or more smaller air holes are provided on any one or more of the two resonant surfaces, forming a semi-closed cavity with air holes.

4. A resonant gas sensor according to any one of claims 1 to 3, characterized in that The support skeleton is made of a metal or alloy material with strong stiffness, large Young's modulus, and easy processing, or made of silicon, resin, or acrylic material.

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