Calibration measurement integrated photoacoustic spectroscopy gas detection method and system

Abstract

The application provides a photoacoustic spectrum gas detection method and system integrating calibration and measurement, which adopts two photoacoustic cells with the same structure. When gas monitoring is performed, the two photoacoustic cells are placed in the same physical environment, a first photoacoustic cell is connected with a gas to be detected, and a second photoacoustic cell is connected with a standard gas with a known concentration; the environment temperature and internal pressure of the two photoacoustic cells are the same; the same light source is used to excite photoacoustic spectrum of the two photoacoustic cells; a first microphone and a second microphone are used to collect photoacoustic signals of the first photoacoustic cell and the second photoacoustic cell respectively; the sensing coefficient in the physical environment is calculated by using the photoacoustic signal of the second photoacoustic cell, and the sensing coefficient of the first photoacoustic cell is calibrated according to the sensing coefficient, and then the concentration of the gas to be detected is calculated. The application adopts two photoacoustic cells, one of which is connected with the standard gas for sensing coefficient calibration, and the other of which is connected with the gas to be detected for detection; the calibrated sensing coefficient is used to calculate the concentration of the gas, the gas measurement precision is improved, and the measurement in various physical environments is adapted.

Description

Technical Field

[0001] This invention belongs to the field of photoacoustic spectroscopy technology, specifically relating to a photoacoustic spectroscopy gas detection method and system that integrates calibration and measurement. Background Technology

[0002] Photoacoustic spectroscopy is a highly sensitive detection technique based on the absorption effect of gases on light signals of specific wavelengths. Gas monitoring devices based on this technology are widely used in the analysis of gases in transformer oil.

[0003] Gas concentration sensors fabricated using photoacoustic spectroscopy possess a certain sensing coefficient. The sensing coefficient is the ratio between the measured physical quantity and the target physical quantity. However, the sensing coefficient changes with the detection environment. Therefore, the sensing coefficient needs to be calibrated before measuring the gas to ensure high reliability of the measurement results. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a photoacoustic spectroscopy gas detection method and system that integrates calibration and measurement, thereby improving the accuracy of gas measurement.

[0005] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: a photoacoustic spectroscopy gas detection method integrating calibration and measurement. This method uses two photoacoustic cells with identical structures. The initial sensing coefficient of the first photoacoustic cell is K1, and the initial sensing coefficient of the second photoacoustic cell is K2.

[0006] Data Acquisition: During gas monitoring, two photoacoustic cells are placed in the same physical environment. The gas to be tested is introduced into the first photoacoustic cell, and a standard gas is introduced into the second photoacoustic cell. The ambient temperature and internal pressure of the two photoacoustic cells are the same. The standard gas contains a gas of the same type and concentration as the gas to be tested. A specific wavelength laser is incident on the two photoacoustic cells using the same light source to excite photoacoustic signals. A first microphone collects the photoacoustic signal from the first photoacoustic cell and outputs an electrical signal V1. A second microphone collects the photoacoustic signal from the second photoacoustic cell and outputs an electrical signal V2.

[0007] Sensing coefficient calibration: Sensing coefficient K2 measured under actual physical conditions 实测 =V2 / C 标 C 标 The known concentration of the standard gas; the sensing coefficient after calibration of the first photoacoustic cell.

[0008] Calculation of the concentration of the gas to be measured: Concentration of the gas to be measured C 待测 =V1 / K1 修 .

[0009] According to the above method, the first photoacoustic pool and the second photoacoustic pool are constructed in the following way: a hollow chamber, with a front light-transmitting plate and a middle light-transmitting plate respectively provided at the front end and the middle part of the chamber, which are sealed and connected to the chamber; the front light-transmitting plate and the middle light-transmitting plate form the first photoacoustic pool; and the cavity after the middle light-transmitting plate forms the second photoacoustic pool.

[0010] The same light source comes from a peripheral laser, and the laser emitted by the laser passes sequentially through the front light-transmitting plate, the first photoacoustic cell, the middle light-transmitting plate, and the second photoacoustic cell.

[0011] The first photoacoustic cell is provided with an inlet and an outlet for the gas to be tested. The first microphone is set in the first photoacoustic cell. The electrical signal V1 output by the first microphone is collected when a laser of a certain wavelength is incident.

[0012] The second photoacoustic cell is filled with standard gas and sealed, and the electrical signal V2 output by the second microphone is collected when the laser is incident.

[0013] According to the above method, the second photoacoustic cell is provided with a detachable and sealable vent.

[0014] According to the above method, the first photoacoustic cell and the second photoacoustic cell are formed by sealing and splicing two gas cells with the same structure. The air inlet and outlet of the first photoacoustic cell are connected to the gas to be tested, and the air inlet and outlet of the second photoacoustic cell are sealed.

[0015] According to the above method, the laser is a directly tunable near-infrared semiconductor laser.

[0016] A photoacoustic spectroscopy gas detection system integrating calibration and measurement is disclosed. This system includes a laser, a data processor, two photoacoustic cells, and a microphone; wherein...

[0017] The two photoacoustic cells have identical structures. The initial sensing coefficient of the first photoacoustic cell is K1, and the initial sensing coefficient of the second photoacoustic cell is K2. The first photoacoustic cell is filled with the gas to be tested, and the second photoacoustic cell is filled with a standard gas. The ambient temperature and internal pressure of the two photoacoustic cells are the same. The standard gas contains a gas of the same type as the gas to be tested with a known concentration.

[0018] The laser is used to excite photoacoustic spectra in two photoacoustic cells; the first microphone collects the photoacoustic signal from the first photoacoustic cell and outputs an electrical signal V1; the second microphone collects the photoacoustic signal from the second photoacoustic cell and outputs an electrical signal V2.

[0019] The data processor is used to process the acquired V1 and V2, as well as the known K1, K2, and the known concentration C of the gas of the same type as the gas to be measured in the standard gas. 标 Calculate the sensing coefficient after calibration of the first photoacoustic cell. and the concentration of the gas to be measured, C 待测 =V1 / K1 修 .

[0020] The beneficial effects of this invention are as follows: by employing a dual photoacoustic cell, one of which is used for standard gas calibration and the other for gas to be measured, the gas concentration can be calculated using the calibrated sensor coefficient, thereby improving the accuracy of gas measurement and adapting to various physical environments. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of two photoacoustic cells according to an embodiment of the present invention.

[0022] In the diagram: 1-Laser, 2-1-Front end light-transmitting plate, 2-2-Middle light-transmitting plate, 3-First photoacoustic cell, 4-Second photoacoustic cell, 5-First microphone, 6-Second microphone, 7-Air inlet, 8-Air outlet. Detailed Implementation

[0023] The invention will be further described below with reference to specific examples and accompanying drawings.

[0024] This invention provides a photoacoustic spectroscopy gas detection method and system that integrates calibration and measurement, such as... Figure 1 As shown, the device includes a hollow chamber. A front-end light-transmitting plate 2-1 and a middle light-transmitting plate 2-2, respectively, are respectively provided at the front end and middle of the chamber and are sealed to the chamber. The front-end light-transmitting plate 2-1 and the middle light-transmitting plate 2-2 form a first photoacoustic cell 3, and the cavity after the middle light-transmitting plate 2-2 forms a second photoacoustic cell 4. The laser emitted by the external laser 1 passes sequentially through the front-end light-transmitting plate 2-1, the first photoacoustic cell 3, the middle light-transmitting plate 2-2, and the second photoacoustic cell 4. The initial sensing coefficient of the first photoacoustic cell 3 is K1, and the initial sensing coefficient of the second photoacoustic cell 4 is K2.

[0025] The first photoacoustic cell 3 is provided with an air inlet 7 and an air outlet 8 for passing the gas to be tested. The first microphone 5 is set in the first photoacoustic cell 3, and the electrical signal V1 of the first microphone 5 is collected when a laser of a certain wavelength is incident.

[0026] The second photoacoustic cell 4 is filled with standard gas. A second microphone 6 is placed within the second photoacoustic cell 4. The electrical signal V2 from the second microphone 6 is acquired when the laser 1 scans the wavelength. The standard gas contains a known concentration of the same type of gas as the gas to be tested, and can be a single component or a mixture. The higher the concentration of the same type of gas as the gas to be tested in the standard gas, the stronger the photoacoustic signal and the easier the calibration. However, it cannot be a pure target gas, as pure gas will cause signal distortion. Therefore, we usually select a high-concentration standard gas. The specific concentration varies depending on the gas; for example, an acetylene concentration above 50 ppm is considered high, while an ethane concentration above 4000 ppm is considered high. This value can be a preset value. The standard gas can also be a mixture of gases because when detecting different gases, the operating wavelengths of the light source do not overlap and do not interfere with each other. Introducing a mixture of gases facilitates wavelength calibration for detecting multiple gases. The only requirement is that the second photoacoustic cell 4 contains a high concentration of the same type of gas as the gas to be tested.

[0027] When performing gas monitoring, the two photoacoustic cells are placed in the same physical environment. The gas to be measured is introduced into the first photoacoustic cell 3, and the standard gas is introduced into the second photoacoustic cell 4. The ambient temperature and internal air pressure of the two photoacoustic cells are the same.

[0028] The data processor calculates the sensing coefficient K2 under the measured physical environment. 实测 =V2 / C 标 C 标 The known concentration of the standard gas; the sensing coefficient after calibration of the first photoacoustic cell. Then calculate the concentration of the gas to be measured: gas concentration C 待测 =V1 / K1 修 .

[0029] Furthermore, the second photoacoustic cell 4 is equipped with a removable and sealable vent for filling with standard gas. In this way, regardless of the gas being prepared and detected, the process for the device remains the same; only the corresponding high-concentration standard gas needs to be filled for the target gas.

[0030] For ease of manufacturing, the first photoacoustic cell 3 and the second photoacoustic cell 4 are formed by splicing together two gas cells with identical structures after being sealed with a light-transmitting sheet. The air inlet 7 and the air outlet 8 of the first photoacoustic cell 3 are connected to the gas to be tested, while the air inlet and the air outlet of the second photoacoustic cell 4 are sealed and used only for filling with standard gas.

[0031] The laser 1 is a directly tunable near-infrared semiconductor laser.

[0032] Regardless of changes in the physical environment, the method of this invention can calibrate the sensing coefficient before calculating the concentration of the gas to be measured, and it is easy to operate and the calculation process is simple and fast.

[0033] The above embodiments are only used to illustrate the design concept and features of the present invention, and their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. The protection scope of the present invention is not limited to the above embodiments. Therefore, all equivalent changes or modifications made based on the principles and design ideas disclosed in the present invention are within the protection scope of the present invention.

Claims

1. A photoacoustic spectroscopy gas detection method of calibration measurement integration, characterized by: The method adopts two photoacoustic cells with the same structure, the initial sensing coefficient of the first photoacoustic cell is K1, and the initial sensing coefficient of the second photoacoustic cell is K2; Data acquisition: when gas monitoring is performed, the two photoacoustic cells are placed in the same physical environment, the first photoacoustic cell is connected with the gas to be measured, and the second photoacoustic cell is connected with the standard gas, the environmental temperature and the internal gas pressure of the two photoacoustic cells are the same; the standard gas contains the gas with the same type as the gas to be measured and with a known concentration; the same light source is used to excite the photoacoustic spectrum of the two photoacoustic cells; the first microphone collects the photoacoustic signal of the first photoacoustic cell and outputs an electric signal V1; the second microphone collects the photoacoustic signal of the second photoacoustic cell and outputs an electric signal V2; Sensing coefficient calibration: measured sensing coefficient K2 in physical environment 实测 = V2 / C 标 , where C 标 is the known concentration of the same gas species as the gas to be measured in the standard gas; calibrated sensing coefficient K1 of the first photoacoustic cell 修 = ; Calculated concentration of the gas to be measured: C 待测 = V1 / K1 修 ; The first photoacoustic cell and the second photoacoustic cell are formed by a hollow cavity, the front end and the middle part of the cavity are respectively provided with a front end light transmission sheet and a middle part light transmission sheet which are sealingly connected with the cavity, the first photoacoustic cell is formed between the front end light transmission sheet and the middle part light transmission sheet, and the second photoacoustic cell is formed in the cavity behind the middle part light transmission sheet.

2. The method of claim 1, wherein: The same light source is from an external laser, and the laser emitted laser passes through the front end light transmission sheet, the first photoacoustic cell, the middle part light transmission sheet and the second photoacoustic cell in sequence; The first photoacoustic cell is provided with a gas inlet and a gas outlet for connecting the gas to be measured, and the first microphone is arranged in the first photoacoustic cell, and the electric signal V1 output by the first microphone is collected when the laser with a certain wavelength is incident; The second photoacoustic cell is filled with standard gas and is sealed, and the electric signal V2 output by the second microphone is collected when the laser is incident.

3. The method of claim 2, wherein: The second photoacoustic cell is provided with a detachable air vent.

4. The method of claim 2, wherein: The first photoacoustic cell and the second photoacoustic cell are sealingly spliced by two gas cells with the same structure, the gas inlet and the gas outlet of the first photoacoustic cell are connected with the gas to be measured, and the gas inlet and the gas outlet of the second photoacoustic cell are sealed.

5. The method of claim 2, wherein: The laser is a directly tunable near-infrared semiconductor laser.

6. A photoacoustic spectroscopy gas detection system integrated with calibration measurement, characterized in that: The system comprises a laser, a data processor, and two photoacoustic cells and microphones; wherein, The two photoacoustic cells have the same structure, the initial sensing coefficient of the first photoacoustic cell is K1, and the initial sensing coefficient of the second photoacoustic cell is K2; the first photoacoustic cell is connected with the gas to be measured, and the second photoacoustic cell is connected with the standard gas, and the environmental temperature and the internal gas pressure of the two photoacoustic cells are the same; the standard gas contains the gas with the same type as the gas to be measured and with a known concentration; The laser is used to excite the photoacoustic spectrum of the two photoacoustic cells; the first microphone collects the photoacoustic signal of the first photoacoustic cell and outputs an electric signal V1; the second microphone collects the photoacoustic signal of the second photoacoustic cell and outputs an electric signal V2; The data processor is used for calculating the first photoacoustic cell calibrated sensing coefficient K1 标 according to the collected V1 and V2, and known K1, K2 and the known concentration C of the gas with the same kind of the to-be-detected gas in the standard gas 修 = , and the to-be-detected gas concentration C 待测 =V1 / K1 修 .

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