Photoacoustic spectrum detection device and detection method

Abstract

The invention discloses a photoacoustic spectrum detection device and a detection method. The photoacoustic spectrum detection device comprises a light source module, a photoacoustic cell structure and a gas path module, the light source module is used for emitting a light source; the photoacoustic cell structure comprises a first photoacoustic cell, a second photoacoustic cell, a first window, a second window and a condensing lens. The method has the advantages that the concentration of the background gas and the concentration of the to-be-detected gas can be measured at the same time, the concentration of the two gases does not need to be detected separately, the detection process is simplified, and the detection efficiency is remarkably improved. And the vacuum isolation layer and the condensing lens are arranged to converge the light beams dispersed by the first photoacoustic cell and then emit the light beams into the second photoacoustic cell, so that the light loss is reduced to the maximum extent, the interference is reduced, and the detection sensitivity and accuracy are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of gas detection, in particular to a photoacoustic spectrum detection device and a detection method. Background Art

[0002] In recent years, with the sustained and rapid development of the national economy, my country has become the country with the fastest growing power industry in the world. Safe, high-quality and economical power supply are the three major elements of modern large power grid operation, and safety is the most important among them. However, with the increase of operating time, the reduction of insulation caused by material aging will significantly increase the probability of electrical equipment failure. In order to ensure the safe operation of the power grid, it is necessary to continuously monitor, analyze and control the equipment during operation. If the signs of failure can be discovered in time and corresponding measures can be taken, major accidents can be avoided. The detection and analysis of the type and content of dissolved gas in transformer oil is an effective means to monitor the operating status of oil-using equipment and judge the type and energy of equipment failure. The real-time nature of gas analysis and detection data is crucial. Some faults that could have been discovered and solved in time at the early stage of the fault, due to the lack of effective monitoring guidance, the faults further develop and expand, and eventually evolve into accidents such as tripping or even damage.

[0003] At present, the photoacoustic spectrometer mainly adopts a single photoacoustic cell structure. The gas in the environment is input into the photoacoustic cell through the air inlet pipeline. The light source is transmitted through the filter and the window to the photoacoustic cavity to produce a photoacoustic effect. The microphone converts the weak pressure signal inside the photoacoustic cavity into an electrical signal, which is transmitted to the computer through the phase-locked amplifier and the data acquisition card for signal processing, and the background signal is calculated; the gas to be tested is input into the photoacoustic cell again through the air inlet pipeline, and the light source is transmitted through the filter and the window to the photoacoustic cavity to produce a photoacoustic effect. The microphone converts the weak pressure signal inside the photoacoustic cavity into an electrical signal, which is transmitted to the computer through the phase-locked amplifier and the data acquisition card for signal processing, and the entire photoacoustic signal is calculated. By eliminating the interference of the background signal, the concentration information of the gas to be tested is finally obtained. The single photoacoustic cell device has a simple structure, but the detection procedure is complicated and the detection time is long; for time-sensitive equipment, the device cannot meet the requirements, and may even lead to further escalation of the detection device failure due to the long detection time. Summary of the invention

[0004] The technical problem to be solved by the present invention is how to optimize the detection process and improve the detection efficiency.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] A photoacoustic spectrum detection device comprises a light source module, a photoacoustic cell structure and a gas path module;

[0007] The light source module is used to emit light;

[0008] The photoacoustic cell structure comprises a first photoacoustic cell, a second photoacoustic cell, a first window, a second window, and a focusing lens, wherein the first photoacoustic cell is connected to the second photoacoustic cell, an input end of the first photoacoustic cell is arranged close to an emission end of a light source module, an input end and an output end of the first photoacoustic cell are both provided with a first window, an output end of the second photoacoustic cell is provided with a second window, a vacuum isolation layer is further formed between two groups of windows at a connection between the first photoacoustic cell and the second photoacoustic cell, and the focusing lens is arranged in the vacuum isolation layer;

[0009] The first photoacoustic cell is provided with a first air inlet and a first air outlet for passing background gas, and a first microphone for collecting photoacoustic signals of the first photoacoustic cell;

[0010] The second photoacoustic cell is provided with a second air inlet and a second air outlet for passing the gas to be measured and a second microphone for collecting the photoacoustic signal of the second photoacoustic cell;

[0011] The first air inlet and the second air inlet are both connected to the output end of the air circuit module, the first air outlet is connected to the second air inlet, and the second air outlet is connected to the input end of the air circuit module.

[0012] In the present invention, the concentration of the background gas and the gas to be measured can be measured simultaneously, without separately detecting the concentrations of the two gases, thus simplifying the detection process and significantly improving the detection efficiency. In addition, the vacuum isolation layer and the focusing lens are arranged to converge the light beam dispersed by the first photoacoustic pool and then inject it into the second photoacoustic pool, thereby minimizing the design of light loss, thereby reducing interference, improving the sensitivity and accuracy of detection, thereby shortening the warning time of equipment failure, and ensuring the safety and stability of equipment operation.

[0013] Preferably, the light source module comprises a light source, a chopper, a filter disk and a filter. The chopper and the filter disk are sequentially arranged below the light source. A plurality of filters are evenly arranged circumferentially on the filter disk. Rotating the filter disk can make the light source and the filter vertically coaxially arranged.

[0014] Preferably, the light source is an infrared light source.

[0015] Preferably, the chopper adopts a circular disk surface, and fan-shaped holes capable of aligning with the filter are evenly arranged circumferentially on the circular disk surface.

[0016] Preferably, the first photoacoustic cell and the second photoacoustic cell are both regular cubic structures and are arranged vertically coaxially with the light source.

[0017] Preferably, the first air outlet is connected to the second air inlet via a first three-way valve, the first air inlet is connected to the first three-way valve via a second three-way valve, and the second three-way valve is also connected to the input end of the air circuit module.

[0018] Preferably, the first window sheet and the second window sheet are both light-transmitting window sheets.

[0019] Preferably, the first air inlet, the first air outlet, the second air inlet and the second air outlet are all provided with solenoid valves.

[0020] Preferably, the present invention also provides a detection method of a photoacoustic spectroscopy detection device, comprising the following steps:

[0021] Step 1: Vacuum

[0022] The photoacoustic cell structure is evacuated through the gas path module;

[0023] Step 2: Input background gas

[0024] The background gas is input into the first photoacoustic cell from the first air inlet through the gas path module, and then enters the second photoacoustic cell from the first air outlet through the second air inlet, and then the background gas inside the second photoacoustic cell is discharged from the second air outlet, and the purge is continued until all the impurity gases in the two groups of photoacoustic cells are discharged, and the background gas input is completed;

[0025] Step 3: Input the gas to be tested

[0026] The first air inlet and the first air outlet of the first photoacoustic cell are closed, the gas to be measured is input into the second photoacoustic cell through the second air inlet, and the background gas input in step 2 is discharged from the second air outlet, and the purge is continued until all the background gas in the second photoacoustic cell is discharged, thereby completing the input of the gas to be measured into the second photoacoustic cell;

[0027] Step 4: Detection

[0028] After the background gas and the gas to be tested are injected, the light source module emits the light source, which is incident into the first photoacoustic cell after passing through the first window, exciting the background gas to produce a photoacoustic signal, and then the light source is incident into the second photoacoustic cell after passing through the vacuum isolation layer between the first photoacoustic cell and the second photoacoustic cell and focusing by the focusing lens, exciting the gas to be tested to produce a photoacoustic effect, and finally the signals generated in the two groups of photoacoustic cells are collected by the first microphone and the second microphone, respectively, and are recorded as S background and S total ;

[0029] Step 5: Signal Processing

[0030] The microphone converts the sound pressure signal in the photoacoustic cell into an electrical signal. The total signal S total， Background signal S background and the net signal S net The relationship is:

[0031] S net =S total -Sbackground

[0032] Gas concentration to be measured C measured for:

[0033] C measured =f(S net )

[0034] Among them, the function f(S net ) is calibrated and calculated based on the nonlinear response model of photoacoustic spectroscopy, including the gas absorption coefficient α(λ), the light source power P, the photoacoustic cell related geometric factor G, and the photoacoustic conversion coefficient A.

[0035]

[0036] Get the accurate concentration value of the gas to be measured.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] In the present invention, the concentration of the background gas and the gas to be measured can be measured simultaneously, and the concentration of the two gases does not need to be detected separately, which simplifies the detection process and significantly improves the detection efficiency. In addition, the vacuum isolation layer and the focusing lens are set to converge the light beam dispersed by the first photoacoustic pool and then inject it into the second photoacoustic pool, thereby minimizing the design of light loss, thereby reducing interference, improving the sensitivity and accuracy of detection, thereby shortening the warning time of equipment failure and ensuring the safety and stability of equipment operation.

[0039] In addition, the device has a simple structure and is easy to operate, and is suitable for gas detection needs in a variety of industrial applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a structural schematic diagram of an embodiment of the present invention;

[0041] Figure 2 A cross-sectional view of a photoacoustic cell structure according to an embodiment of the present invention;

[0042] Figure 3 The figure is a flow chart of a detection method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0043] In order to facilitate those skilled in the art to understand the technical solution of the present invention, the technical solution of the present invention is further described in conjunction with the accompanying drawings of the specification.

[0044] In this application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or a communication; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0045] In this application, unless otherwise expressly specified and limited, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, "plurality" means two or more, unless otherwise clearly and specifically limited.

[0046] See also Figure 1 and Figure 2 This embodiment discloses a photoacoustic spectroscopy detection device, including a light source module 1, a photoacoustic cell structure 2 and a gas path module (not shown in the figure).

[0047] The light source module 1 is used to emit light. The light source module 1 includes a light source 11, a chopper 12, a filter disk 13 and a filter 14. The chopper 2 and the filter disk 3 are sequentially arranged below the light source 1. A plurality of filters 14 are evenly arranged circumferentially on the filter disk 13. In the present embodiment, the light source 1 is an infrared light source. The chopper 12 adopts a circular disk surface. Sector-shaped holes that can be aligned with the filters 14 are evenly arranged circumferentially on the circular disk surface. Rotating the filter disk 13 can make the light source 11 and the filter 14 vertically coaxially arranged.

[0048] The photoacoustic cell structure 2 includes a first photoacoustic cell 21, a second photoacoustic cell 22, a first window 23, a second window 24, and a focusing lens 25. The first photoacoustic cell 21 is connected to the second photoacoustic cell 22. The input end of the first photoacoustic cell 21 is arranged close to the emission end of the light source module 1. The input end and the output end of the first photoacoustic cell 21 are both provided with the first window 23. The output end of the second photoacoustic cell 22 is provided with the second window 24. A vacuum isolation layer is also formed between the two groups of windows at the connection between the first photoacoustic cell 21 and the second photoacoustic cell 22. The focusing lens 25 is arranged in the vacuum isolation layer, which is used to converge the light beams dispersed by the first photoacoustic cell 21 and then inject them into the second photoacoustic cell 22 to minimize light loss.

[0049] In this embodiment, both the first photoacoustic cell 21 and the second photoacoustic cell 22 are regular cube structures and are arranged vertically coaxially with the light source 11 .

[0050] The first photoacoustic cell 21 is provided with a first air inlet 211 and a first air outlet 212 for passing background gas, and a first microphone 213 for collecting photoacoustic signals of the first photoacoustic cell 21; the second photoacoustic cell 22 is provided with a second air inlet 221 and a second air outlet 222 for passing the gas to be tested, and a second microphone 223 for collecting photoacoustic signals of the second photoacoustic cell 22.

[0051] The first air inlet 211 and the second air inlet 221 are both connected to the output end of the gas circuit module, the first air outlet 212 is connected to the second air inlet 221, and the second air outlet 222 is connected to the input end of the gas circuit module. Specifically, the first air outlet 212 is connected to the second air inlet 221 through the first three-way valve 3, the first air inlet 211 is connected to the first three-way valve 3 through the second three-way valve 4, and the second three-way valve 4 is also connected to the input end of the gas circuit module. Furthermore, the first air inlet 211, the first air outlet 212, the second air inlet 221 and the second air outlet 222 are all provided with solenoid valves.

[0052] For details, see Figure 3 This embodiment also discloses a detection method of a photoacoustic spectroscopy detection device, comprising the following steps:

[0053] Step 1: Vacuum

[0054] The inner cavities of the first photoacoustic cell 21 and the second photoacoustic cell 22 are evacuated through the gas path module;

[0055] Step 2: Input background gas

[0056] Open the solenoid valves provided on the first air inlet 211, the first air outlet 212, the second air inlet 221 and the second air outlet 222, input the background gas from the first air inlet 211 into the first photoacoustic cell 21 through the air path module, then enter the second photoacoustic cell 22 from the first air outlet 212 through the second air inlet 221, and then discharge the background gas from the second photoacoustic cell 22 from the second air outlet 222, and continue to purge until all the impurity gases in the two groups of photoacoustic cells are discharged, completing the background gas input;

[0057] Step 3: Input the gas to be tested

[0058] The electromagnetic valves on the first air inlet 211 and the first air outlet 212 of the first photoacoustic cell 21 are closed, and the gas to be measured is input into the second photoacoustic cell 22 through the second air inlet 221, and then the background gas input in step 2 is discharged from the second air outlet 222, and the purge is continued until all the background gas in the second photoacoustic cell 22 is discharged, thereby completing the input of the gas to be measured into the second photoacoustic cell 22;

[0059] Step 4: Detection

[0060] After the background gas and the gas to be measured are injected, the light source 11 is incident into the first photoacoustic cell 21 after passing through the first window 23, exciting the background gas to generate a photoacoustic signal. The light source 11 is then incident into the second photoacoustic cell 22 after passing through the vacuum isolation layer between the first photoacoustic cell 21 and the second photoacoustic cell 22 and focusing by the focusing lens 25, exciting the gas to be measured to generate a photoacoustic effect. Finally, the signals generated in the two groups of photoacoustic cells are collected by the first microphone 213 and the second microphone 223, respectively, and are recorded as S background and S total ;

[0061] Step 5: Signal Processing

[0062] The microphone converts the sound pressure signal in the photoacoustic cell into an electrical signal. The total signal S total， Background signal S background and the net signal S net The relationship is:

[0063] S net =S total -S background

[0064] Gas concentration to be measured C measured for:

[0065] C measured =f(S net )

[0066] Among them, the function f(S net ) is calibrated and calculated based on the nonlinear response model of photoacoustic spectroscopy, including the gas absorption coefficient α(λ), the light source power P, the photoacoustic cell related geometric factor G, and the photoacoustic conversion coefficient A.

[0067]

[0068] Get the accurate concentration value of the gas to be measured.

[0069] In the present invention, the concentration of the background gas and the gas to be measured can be measured simultaneously, and the concentration of the two gases does not need to be detected separately, which simplifies the detection process and significantly improves the detection efficiency. In addition, the vacuum isolation layer and the focusing lens 25 are arranged to converge the light beam dispersed by the first photoacoustic pool 21 and then inject it into the second photoacoustic pool 22, thereby minimizing the design of light loss, thereby reducing interference, improving the sensitivity and accuracy of detection, thereby shortening the warning time of equipment failure, and ensuring the safety and stability of equipment operation.

[0070] In addition, the device has a simple structure and is easy to operate, and is suitable for gas detection needs in a variety of industrial applications.

[0071] It is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be regarded as exemplary and non-limiting from any point of view, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention, and any reference numerals in the claims should not be regarded as limiting the claims involved.

[0072] The above-described embodiments merely represent implementation methods of the invention. The protection scope of the present invention is not limited to the above-described embodiments. For those skilled in the art, several modifications and improvements may be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A photoacoustic spectroscopy detection device, characterized in that: It includes a light source module, a photoacoustic cell structure and a gas path module; The light source module is used to emit light; The photoacoustic cell structure comprises a first photoacoustic cell, a second photoacoustic cell, a first window, a second window, and a focusing lens, wherein the first photoacoustic cell is connected to the second photoacoustic cell, an input end of the first photoacoustic cell is arranged close to an emission end of a light source module, an input end and an output end of the first photoacoustic cell are both provided with a first window, an output end of the second photoacoustic cell is provided with a second window, a vacuum isolation layer is further formed between two groups of windows at a connection between the first photoacoustic cell and the second photoacoustic cell, and the focusing lens is arranged in the vacuum isolation layer; The first photoacoustic cell is provided with a first air inlet and a first air outlet for passing background gas, and a first microphone for collecting photoacoustic signals of the first photoacoustic cell; The second photoacoustic cell is provided with a second air inlet and a second air outlet for passing the gas to be measured and a second microphone for collecting the photoacoustic signal of the second photoacoustic cell; The first air inlet and the second air inlet are both connected to the output end of the air circuit module, the first air outlet is connected to the second air inlet, and the second air outlet is connected to the input end of the air circuit module.

2. A photoacoustic spectroscopy detection device according to claim 1, characterized in that: The light source module comprises a light source, a chopper, a filter disk and a filter. The chopper and the filter disk are arranged in sequence below the light source. A plurality of filters are evenly arranged circumferentially on the filter disk. The light source and the filter can be arranged vertically coaxially by rotating the filter disk.

3. A photoacoustic spectroscopy detection device according to claim 2, characterized in that: The light source is an infrared light source.

4. A photoacoustic spectroscopy detection device according to claim 2, characterized in that: The chopper adopts a circular disk surface, and fan-shaped holes capable of aligning with the filter are evenly arranged circumferentially on the circular disk surface.

5. A photoacoustic spectroscopy detection device according to claim 2, characterized in that: The first photoacoustic cell and the second photoacoustic cell are both regular cube structures and are arranged vertically coaxially with the light source.

6. A photoacoustic spectroscopy detection device according to claim 1, characterized in that: The first air outlet is connected to the second air inlet via a first three-way valve, the first air inlet is connected to the first three-way valve via a second three-way valve, and the second three-way valve is also connected to the input end of the air path module.

7. A photoacoustic spectroscopy detection device according to claim 1, characterized in that: The first window sheet and the second window sheet are both light-transmitting window sheets.

8. A photoacoustic spectroscopy detection device according to claim 1, characterized in that: The first air inlet, the first air outlet, the second air inlet and the second air outlet are all provided with solenoid valves.

9. A detection method according to any one of claims 1 to 8, characterized in that: The steps include: Step 1: Vacuum The photoacoustic cell structure is evacuated through the gas path module; Step 2: Input background gas The background gas is input into the first photoacoustic cell from the first air inlet through the gas path module, and then enters the second photoacoustic cell from the first air outlet through the second air inlet, and then the background gas inside the second photoacoustic cell is discharged from the second air outlet, and the purge is continued until all the impurity gases in the two groups of photoacoustic cells are discharged, and the background gas input is completed; Step 3: Input the gas to be tested The first air inlet and the first air outlet of the first photoacoustic cell are closed, the gas to be measured is input into the second photoacoustic cell through the second air inlet, and the background gas input in step 2 is discharged from the second air outlet, and the purge is continued until all the background gas in the second photoacoustic cell is discharged, thereby completing the input of the gas to be measured into the second photoacoustic cell; Step 4: Detection After the background gas and the gas to be tested are injected, the light source module emits the light source, which is incident into the first photoacoustic cell after passing through the first window, exciting the background gas to produce a photoacoustic signal, and then the light source is incident into the second photoacoustic cell after passing through the vacuum isolation layer between the first photoacoustic cell and the second photoacoustic cell and focusing by the focusing lens, exciting the gas to be tested to produce a photoacoustic effect, and finally the signals generated in the two groups of photoacoustic cells are collected by the first microphone and the second microphone, respectively, and are recorded as S background and S total ; Step 5: Signal Processing The microphone converts the sound pressure signal in the photoacoustic cell into an electrical signal. The total signal S total， Background signal S background and the net signal S net The relationship is: S net =S total -S background Gas concentration to be measured C measured for: C measured =f(S net ) Among them, the function f(S net ) is calibrated and calculated based on the nonlinear response model of photoacoustic spectroscopy, including the gas absorption coefficient α(λ), the light source power P, the photoacoustic cell related geometric factor G, and the photoacoustic conversion coefficient A. Get the accurate concentration value of the gas to be measured.

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