Anti-vibration photoacoustic cell and photoacoustic spectroscopy gas detection system

Abstract

This invention discloses a shock-resistant photoacoustic cell and a photoacoustic spectroscopy gas detection system, belonging to the field of gas detection technology. It includes: a photoacoustic cell body; within the photoacoustic cell body, there is a photoacoustic cell chamber, a microphone rear chamber, and a microphone diaphragm; the microphone diaphragm is located between the photoacoustic cell chamber and the microphone rear chamber, separating the gases in the photoacoustic cell chamber and the microphone rear chamber; the center of gravity of the microphone rear chamber is located on the same side of the microphone diaphragm as the center of gravity of the photoacoustic cell chamber, but the center of gravity of the microphone rear chamber is farther from the microphone diaphragm than that of the photoacoustic cell chamber; the distance between the center of gravity of the microphone rear chamber and the center of gravity of the photoacoustic cell chamber matches the material density and thickness of the microphone diaphragm. In a vibration environment, the inertial force of the microphone diaphragm itself is opposite to and cancels out the inertial forces of the gases on both sides, thereby suppressing noise caused by external vibrations and improving the signal-to-noise ratio and detection limit of photoacoustic spectroscopy gas detection.

Description

Technical Field

[0001] This invention belongs to the field of gas detection technology, and more specifically, relates to a shock-resistant photoacoustic cell and a photoacoustic spectroscopy gas detection system. Background Technology

[0002] Photoacoustic spectroscopy is a key technology for detecting trace gases. Photoacoustic gas detection systems can generally be classified into two types based on their operating mode: non-resonant and resonant. Non-resonant photoacoustic gas detection systems typically operate in a low-frequency non-resonant mode, using a broadband thermal radiation infrared light source combined with different passband filters to achieve multi-component gas detection.

[0003] In a non-resonant photoacoustic spectroscopy detection system, the photoacoustic cell is an essential component, serving as a container for the gas that generates photoacoustic signals. In this system, the two main sources of noise are the same-frequency noise absorbed by the cell walls and windows, and mechanical noise caused by external environmental vibrations, both of which need to be suppressed during system design. When operating in a quiet environment, the mechanical noise from the external environment is primarily generated by the mechanical vibrations of the system's own components, such as the chopper and heat sink. In actual operation, depending on the working environment, mechanical noise sources may include vehicle traffic, construction work, and road / bridge construction.

[0004] Non-resonant photoacoustic spectroscopy gas detection systems typically operate under low-frequency conditions, making them highly susceptible to low-frequency noise. Low-frequency mechanical noise further significantly impacts the signal-to-noise ratio of the gas detection system, greatly affecting the minimum detection limit. Furthermore, current vibration damping designs are usually implemented for the chassis enclosure, lacking vibration-resistant design for the photoacoustic cell structure. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a shock-resistant photoacoustic cell and a photoacoustic spectroscopy gas detection system, aiming to solve the problem of noise caused by external environmental vibrations in existing non-resonant photoacoustic spectroscopy systems.

[0006] To achieve the above objectives, in a first aspect, the present invention provides a shock-resistant photoacoustic cell, comprising: a photoacoustic cell body; the photoacoustic cell body is provided with a photoacoustic cell chamber, a microphone rear chamber, and a microphone diaphragm; The microphone diaphragm is located between the photoacoustic cell chamber and the microphone rear chamber, and separates the gas in the two chambers to detect the photoacoustic signal generated in the photoacoustic cell chamber. The center of gravity of the rear cavity of the microphone is located on the same side of the microphone diaphragm as the center of gravity of the photoacoustic pool chamber, and the center of gravity of the rear cavity of the microphone is farther away from the microphone diaphragm than the center of gravity of the photoacoustic pool chamber. The distance between the center of gravity of the microphone's rear cavity and the center of gravity of the photoacoustic cell chamber.d 1 satisfies: ; d 2 represents the microphone diaphragm thickness. r 1 represents the density of the gas on both sides of the microphone diaphragm. r 2 represents the material density of the microphone diaphragm.

[0007] More preferably, the microphone rear cavity includes: a microphone chamber, an additional back cavity, and a pinhole channel; the microphone chamber and the additional back cavity are connected through the pinhole channel; The microphone chamber and the photoacoustic pool chamber are located on both sides of the microphone diaphragm; the additional back cavity and the microphone chamber are located on both sides of the microphone diaphragm. The volume of the additional back cavity is larger than the volume of the microphone chamber, and the distance between the additional back cavity and the microphone diaphragm is greater than the distance between the photoacoustic pool chamber and the microphone diaphragm.

[0008] More preferably, the center of gravity of the microphone rear cavity, the center of gravity of the photoacoustic cell cavity, and the center of mass of the microphone diaphragm are located on the same straight line.

[0009] More preferably, the photoacoustic cell chamber extends through the photoacoustic cell body, and both ends are provided with cells windows for transmitting excitation light.

[0010] More preferably, the photoacoustic pool body is further provided with an air inlet pipe and an air outlet pipe; the side wall of the photoacoustic pool chamber is provided with an air inlet connected to the air inlet pipe and an air outlet connected to the air outlet pipe. The trace gas to be measured enters the photoacoustic cell chamber through the inlet pipe and the inlet port, and is finally discharged through the outlet pipe.

[0011] More preferably, the material of the photoacoustic pool is a metallic material.

[0012] Secondly, the present invention also provides a photoacoustic spectroscopy gas detection system, comprising: a blackbody radiation source, a photoacoustic cell, a chopper, a bandpass filter, and a signal demodulation module; The infrared light emitted from the light source is collimated and then intensity modulated by a chopper. After being filtered by a bandpass filter, it is incident on the photoacoustic cell to generate a photoacoustic signal. The photoacoustic signal is then demodulated by a signal demodulation module to achieve gas detection. The aforementioned photoacoustic cell is the earthquake-resistant photoacoustic cell provided in the first aspect of the present invention.

[0013] In summary, the above-described technical solutions conceived in this invention can achieve the following beneficial effects: 1. This invention provides a vibration-resistant photoacoustic cell, comprising: a photoacoustic cell chamber, a microphone rear chamber, and a microphone diaphragm. The center of gravity of the microphone rear chamber is located on the same side of the microphone diaphragm as the center of gravity of the photoacoustic cell chamber, and the center of gravity of the microphone rear chamber is farther from the microphone diaphragm than the center of gravity of the photoacoustic cell chamber. The distance between the center of gravity of the microphone rear chamber and the center of gravity of the photoacoustic cell chamber is matched with the material density and thickness of the microphone diaphragm, so that in a vibration environment, the inertial force of the microphone diaphragm itself is opposite to the inertial force of the gas on both sides and can cancel each other out, thereby suppressing noise caused by external vibration.

[0014] 2. Furthermore, the shock-resistant photoacoustic cell provided by the present invention includes a microphone chamber, an additional back cavity, and a pinhole pipe connected by a pinhole pipe. The overall structure is simple, so the present invention only requires three chambers: the photoacoustic cell chamber, the microphone chamber, and the additional back cavity. The microphone chamber and the additional back cavity are connected by a pinhole pipe. By selecting a microphone diaphragm with matching material density and thickness, and reasonably adjusting the volume and position of the three chambers, the suppression of external vibration noise can be achieved.

[0015] 3. Furthermore, in the shock-resistant photoacoustic cell provided by the present invention, the center of gravity of the microphone rear cavity, the center of gravity of the photoacoustic cell chamber, and the center of gravity of the microphone diaphragm are located on the same straight line, so as to ensure the best suppression effect on mechanical noise from the external environment.

[0016] 4. Furthermore, the photoacoustic cell provided by the present invention has a cell body made of metal material to achieve better isolation from external sound sources and better heat conduction.

[0017] 5. The photoacoustic spectroscopy gas detection system provided by the present invention, by adopting the shock-resistant photoacoustic cell provided in the first aspect of the present invention, can suppress noise caused by external vibration, and greatly improve the signal-to-noise ratio and detection limit of photoacoustic spectroscopy gas detection. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of a seismic-resistant photoacoustic cell provided in an embodiment of the present invention.

[0019] In the diagram: 1. Back cavity sealing cover; 2. Pool window; 3. Microphone rear cavity; 4. Photoacoustic pool chamber; 5. Microphone diaphragm; 31. Microphone chamber; 32. Pinhole tube; 33. Additional back cavity. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0021] In a first aspect, the present invention provides a shock-resistant photoacoustic cell, comprising: a photoacoustic cell body; the photoacoustic cell body is provided with a photoacoustic cell chamber, a microphone rear chamber and a microphone diaphragm; The microphone diaphragm is located between the photoacoustic cell chamber and the rear microphone chamber, separating the gases in the two chambers and used to detect the photoacoustic signal generated in the photoacoustic cell chamber. Specifically, one side of the microphone diaphragm is adjacent to the photoacoustic cell chamber, and the other side is adjacent to the rear microphone chamber, directly contacting the gases in both chambers and separating them. Furthermore, the photoacoustic cell chamber penetrates the photoacoustic cell body and has windows at both ends for transmitting excitation light. The center of gravity of the microphone's rear cavity is located on the same side of the microphone diaphragm as the center of gravity of the photoacoustic cell chamber, but the center of gravity of the rear cavity is farther from the microphone diaphragm than that of the photoacoustic cell chamber. This results in the microphone diaphragm experiencing opposite directions of its own inertial force and the inertial forces of the gases on both sides when vibration occurs. Simultaneously, the distance between the center of gravity of the rear cavity and the center of gravity of the photoacoustic cell chamber... d 1 satisfies: ;in, d 2 represents the microphone diaphragm thickness. r 1 represents the density of the gas on both sides of the microphone diaphragm (i.e., the gas in the photoacoustic cell chamber and the rear cavity of the microphone; the gas types in the photoacoustic cell chamber and the rear cavity of the microphone are the same, generally air, but not limited to air, and can also be methane, ethane, ethylene, acetylene, carbon monoxide, carbon dioxide, hydrogen sulfide, etc.). r 2 represents the material density of the microphone diaphragm, which ensures that when vibration occurs, the inertial force of the gas surrounding the microphone diaphragm can counteract the inertial force acting on the microphone diaphragm itself.

[0022] In one optional embodiment, the microphone rear cavity includes: a microphone chamber, an additional back cavity, and a pinhole channel; the microphone chamber and the additional back cavity are connected through the pinhole channel. The microphone chamber and the photoacoustic pool chamber are located on both sides of the microphone diaphragm; the additional back cavity and the microphone chamber are located on both sides of the microphone diaphragm. The volume of the additional back cavity is larger than the volume of the microphone chamber, and the distance between the additional back cavity and the microphone diaphragm is greater than the distance between the photoacoustic pool chamber and the microphone diaphragm.

[0023] To further explain, in order to facilitate the manufacturing of the additional back cavity structure, the additional back cavity also penetrates the photoacoustic cell body, and both ends of it are sealed by sealing caps.

[0024] Preferably, the center of gravity of the microphone's rear cavity, the center of gravity of the photoacoustic cell, and the center of mass of the microphone diaphragm are located on the same straight line, so as to more accurately cancel out the inertial force of the microphone diaphragm itself and the inertial force of the surrounding gas.

[0025] Furthermore, the aforementioned photoacoustic pool is also equipped with an air inlet pipe and an air outlet pipe; the side wall of the photoacoustic pool chamber is provided with an air inlet connected to the air inlet pipe and an air outlet connected to the air outlet pipe. The trace gas to be measured enters the photoacoustic cell chamber through the inlet pipe and the inlet port, and is finally discharged through the outlet pipe.

[0026] It should be noted that the material of the photoacoustic pool can be metal, resin, etc.; metal materials such as Al, Cu, and stainless steel are preferred.

[0027] To further illustrate the shock-resistant photoacoustic cell provided by the present invention, a specific embodiment is described in detail below: like Figure 1 As shown, this embodiment of the invention provides a shock-resistant photoacoustic pool, including a photoacoustic pool body, which is a cuboid structure (it should be noted that the cuboid structure is only for illustration and is not limited to cuboid structures; cube structures, columnar structures, etc. are also acceptable); the photoacoustic pool body is provided with a back cavity sealing cover 1, a pool window 2, a microphone rear cavity 3, a photoacoustic pool chamber 4, and a microphone diaphragm 5; In this embodiment, the microphone rear cavity 3 is composed of three parts: a microphone chamber 31, a pinhole pipe 32, and an additional back cavity 33. Both the photoacoustic pool chamber 4 and the additional back cavity 33 are cylindrical; however, the specific shapes are for illustrative purposes only and are not limited to cylindrical shapes. The additional back cavity 33 is placed horizontally and penetrates the photoacoustic pool body, with both ends sealed by two back cavity sealing caps 1. The photoacoustic pool chamber 4 is placed vertically and penetrates the photoacoustic pool body, with both ends using pool windows 2 for light transmission. The additional back cavity 33 and the microphone chamber 31 are connected through the pinhole pipe 32, together forming the microphone rear cavity 3. The microphone diaphragm 5 is located between the photoacoustic pool chamber 4 and the microphone chamber 31, separating the gas (air in this embodiment) in the two chambers, and is used to detect the photoacoustic signal generated within the photoacoustic pool chamber 4. The center of gravity of the rear cavity 3 of the microphone and the center of gravity of the photoacoustic cell 4 are both located on the left side of the microphone diaphragm 5. Compared with the microphone diaphragm 5, the center of gravity of the rear cavity 3 of the microphone is farther away from the microphone diaphragm 5. Specifically, the additional back cavity 33 and the microphone chamber 31 are located on both sides of the microphone diaphragm 5, and the volume of the additional back cavity 33 is larger than the volume of the microphone chamber 31.

[0028] When the photoacoustic cell is placed in a vibrating environment, due to the inertia of objects with mass, the microphone diaphragm 5 will be subjected to its own inertial force as well as the inertial force of the surrounding gas in the microphone rear cavity 3 and the photoacoustic cell chamber 4. When the center of gravity of the microphone rear cavity 3 and the center of gravity of the photoacoustic cell chamber 4 are located on the same side of the microphone diaphragm, and the center of gravity of the microphone rear cavity 3 is farther away from the microphone diaphragm 5, the inertial force on the microphone diaphragm 5 and the inertial force of the surrounding gas act in opposite directions. The distance between the center of gravity of the microphone rear cavity 3 and the center of gravity of the photoacoustic cell 4 is matched with the material and thickness of the microphone diaphragm 5. The center of gravity of the microphone rear cavity 3, the center of gravity of the photoacoustic cell 4, and the center of mass of the microphone diaphragm 5 are located on the same horizontal line. This achieves the effect of mutual cancellation of the inertial force of the microphone diaphragm 5 and the inertial force of the surrounding gas, thereby reducing the response of the photoacoustic cell to external vibration noise, obtaining higher detection accuracy, and achieving anti-vibration effect.

[0029] Secondly, the present invention also provides a photoacoustic spectroscopy gas detection system, comprising: a blackbody radiation source, a photoacoustic cell, a chopper, a bandpass filter, and a signal demodulation module; The infrared light emitted from the light source is collimated and then intensity modulated by a chopper. After being filtered by a bandpass filter, it is incident on the anti-vibration photoacoustic cell to generate a photoacoustic signal. The photoacoustic signal is acquired by the microphone diaphragm in the photoacoustic cell and then demodulated by the signal demodulation module to achieve gas detection. The aforementioned photoacoustic cell is the earthquake-resistant photoacoustic cell provided in the first aspect of the present invention.

[0030] The relevant technical solutions are the same as those provided in the first aspect of this invention, and will not be described in detail here.

[0031] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A seismic-resistant photoacoustic cell, characterized in that, include: The photoacoustic pool body; the photoacoustic pool body is equipped with a photoacoustic pool chamber, a microphone rear chamber and a microphone diaphragm; The microphone diaphragm is located between the photoacoustic cell chamber and the microphone rear chamber, and separates the gas in the photoacoustic cell chamber from the gas in the microphone rear chamber, for detecting the photoacoustic signal generated in the photoacoustic cell chamber; The center of gravity of the rear cavity of the microphone is located on the same side of the microphone diaphragm as the center of gravity of the photoacoustic pool chamber, and the center of gravity of the rear cavity of the microphone is farther away from the microphone diaphragm than the center of gravity of the photoacoustic pool chamber. The distance between the center of gravity of the microphone rear cavity and the center of gravity of the photoacoustic cell chamber d 1 satisfies: ; d 2 represents the thickness of the microphone diaphragm. ρ 1 represents the density of the gas on both sides of the microphone diaphragm. ρ 2 represents the material density of the microphone diaphragm; The rear cavity of the microphone It includes: a microphone chamber, an additional back cavity, and a pinhole channel; the microphone chamber and the additional back cavity are connected through the pinhole channel; The microphone chamber and the photoacoustic pool chamber are located on both sides of the microphone diaphragm; the additional back cavity and the microphone chamber are located on both sides of the microphone diaphragm, the volume of the additional back cavity is larger than the volume of the microphone chamber, and the distance between the additional back cavity and the microphone diaphragm is greater than the distance between the photoacoustic pool chamber and the microphone diaphragm.

2. The earthquake-resistant photoacoustic cell according to claim 1, characterized in that, The center of gravity of the microphone rear cavity, the center of gravity of the photoacoustic cell cavity, and the center of mass of the microphone diaphragm are located on the same straight line.

3. The earthquake-resistant photoacoustic cell according to any one of claims 1-2, characterized in that, The photoacoustic cell chamber runs through the photoacoustic cell body, and both ends are equipped with cells windows for transmitting excitation light.

4. The earthquake-resistant photoacoustic cell according to any one of claims 1-2, characterized in that, The photoacoustic pool is also equipped with an air inlet pipe and an air outlet pipe; the side wall of the photoacoustic pool chamber is provided with an air inlet connected to the air inlet pipe and an air outlet connected to the air outlet pipe. The trace gas to be measured enters the photoacoustic cell chamber through the air inlet via the air inlet pipe, and is finally discharged through the air outlet via the air outlet pipe.

5. The earthquake-resistant photoacoustic cell according to any one of claims 1-2, characterized in that, The photoacoustic pool is made of metal.

6. A photoacoustic spectroscopy gas detection system, characterized in that, include: Blackbody radiation source, photoacoustic cell, chopper, bandpass filter and signal demodulation module; The infrared light emitted from the light source is collimated and then intensity-modulated by the chopper. After being filtered by the bandpass filter, it is incident on the photoacoustic cell to generate a photoacoustic signal. The photoacoustic signal is then demodulated by the signal demodulation module to achieve gas detection. The photoacoustic cell is the earthquake-resistant photoacoustic cell according to any one of claims 1-5.

Images