CN114923972A - Mixed gas component detection device and method - Google Patents

Abstract

The invention provides a mixed gas component detection device and a method, the device comprises a box body, a plasma generation device and a Langmuir probe, wherein the plasma generation device comprises a cathode, an anode and a power supply, the cathode and the anode are arranged at intervals, are respectively positioned on the inner top wall and the inner bottom wall of the box body and are respectively connected with the power supply, the Langmuir probe is inserted into the box body and is positioned between the cathode and the anode, and the two opposite side walls of the box body are respectively provided with an air inlet and an air outlet. The invention has the beneficial effects that: the portability of the mixed gas detection device is realized, the detection cost is reduced, and the detection efficiency is improved.

Description

A kind of mixed gas composition detection device and method

technical field

The present invention relates to the technical field of gas analysis, and in particular, to a mixed gas component detection device and method.

Background technique

At present, in order to detect some human body functions, sampling is often required, usually including invasive methods and non-invasive methods. Among them, invasive methods mainly include blood test and urine test, which need to collect human blood and urine samples, and the operation is complicated, while non-invasive methods mainly include exhaled gas detection method.

Exhaled gas detection methods currently mainly use electronic nose or gas chromatography-mass spectrometry to detect the mixed gas exhaled by the human body. Among them, the electronic nose includes different kinds of compounds and an array of different detectors that react with a given kind of compounds, but the sensitivity and selectivity of the detectors are not suitable for analyzing and detecting exhaled gas mixture. The experimental equipment used in gas chromatography-mass spectrometry requires high vacuum requirements, and different detectors are required for different types of detected gases. The detection equipment is expensive, large in size, and low in detection efficiency. At the same time, this type of The equipment requires relevant professional and technical personnel to operate and the equipment needs to be regularly maintained, resulting in a significant increase in testing costs.

SUMMARY OF THE INVENTION

The problem solved by the present invention is how to reduce the detection cost of exhaled mixed gas and how to improve the detection efficiency.

In order to solve the above problems, the present invention provides a mixed gas component detection device and method.

In a first aspect, the present invention provides a mixed gas component detection device, comprising a box body, a plasma generating device and a Langmuir probe, the plasma generating device comprising a cathode, an anode and a power source, the cathode and the anode spaced apart and located on the inner top wall and the inner bottom wall of the box body, and are respectively connected with the power supply, the Langmuir probe is inserted into the box body and located between the cathode and the anode, The opposite two side walls of the box body are respectively provided with an air inlet and an air outlet.

In the mixed gas composition detection device of the present invention, the user can exhale from the air inlet, and the gas will flow out from the air outlet. During this process, powered by the power supply, the cathode and the anode in the box will discharge the mixed gas exhaled by the user. Through the use of Langmuir probe, the plasma parameters generated by ionization can be obtained, and gas composition analysis can be further carried out through, for example, current-voltage relationship. The device has a simple structure, is convenient to carry, can effectively improve the detection efficiency of the mixed gas, and can correspondingly reduce the detection cost.

Further, the cathode includes a molybdenum sheet.

Further, the anode includes a silicon substrate and carbon nanotubes, the silicon substrate is attached to the inner bottom wall of the box body, and the carbon nanotubes are grown on the silicon substrate by chemical vapor deposition. top.

Further, the material of the box body is quartz glass.

Further, the power source includes a battery and a voltage regulating mechanism, the voltage regulating mechanism is connected to the battery and used to regulate the voltage applied to the cathode and the anode.

Further, the mixed gas component detection device further includes a distance adjustment mechanism, and the distance adjustment mechanism is used to adjust the distance between the cathode and the anode.

Further, the mixed gas component detection device further includes a helium gas supply mechanism, and the helium gas supply mechanism is used for communicating with the box body.

In a second aspect, the present invention provides a mixed gas composition detection method, based on the above mixed gas composition detection device, comprising:

Passing the gas to be detected mixed with the calibration gas into the box, wherein the spacing between the cathode and the anode and the applied voltage are determined based on Paschen's law and the calibration gas;

When the gas is ionized, the plasma parameters are obtained by the Langmuir probe;

The composition of the gas to be detected is determined by the plasma parameters.

In the mixed gas detection method of the present invention, the calibration gas can be determined in advance, and an inert gas such as helium is usually selected. Based on the relevant characteristics of the calibration gas, the optimal applied voltage of the cathode and the anode of the mixed gas detection device can be determined according to Paschen's law. and the distance, so that the product of the distance and the atmospheric pressure is located at the right position of the lowest point of the U-shaped Paschen curve, so that when the mixed gas and calibration gas exhaled by the user pass through the box, the air pressure in the box decreases, and the above distance and the current pressure The product of , will drop to the lowest point of the U-shaped Paschen curve, and then the mixed gas will be ionized to generate plasma. Using the Langmuir probe, the plasma parameters can be obtained, and the gas composition can be further analyzed by, for example, the relationship between current and voltage. The method can not only ensure the detection accuracy of the mixed gas, but also effectively improve the detection efficiency and reduce the detection cost accordingly.

Further, the determining the composition of the gas to be detected by the plasma parameters includes:

obtaining a current/voltage curve of the plasma;

The second-order derivative is performed on the current/voltage curve to obtain an electron energy distribution function with characteristic electron peaks;

According to the characteristic electron peak on the electron energy distribution function, the composition of the gas to be detected is determined.

Further, the calibration gas is helium, the range of the distance is 40 to 50 mm, and the applied voltage is 400V.

Description of drawings

1 is a schematic structural diagram of a mixed gas component detection device according to an embodiment of the present invention;

Fig. 2 is the Paschen curve of the helium of the embodiment of the present invention;

3 is a schematic flowchart of a mixed gas component detection method according to an embodiment of the present invention;

FIG. 4 is a plasma electron spectrum of a mixed gas containing N ₂ and CO according to an embodiment of the present invention.

Description of reference numbers:

1-cathode; 2-anode; 21-silicon substrate; 22-carbon nanotubes; 3-power supply; 4-box body; 5-Langmuir probe; 6-inlet hole; 7-outlet hole.

Detailed ways

In order to make the above objects, features and advantages of the present invention more clearly understood, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

Referring to FIG. 1 , a mixed gas component detection device according to an embodiment of the present invention includes a box body 4 , a plasma generating device and a Langmuir probe 5 , and the plasma generating device includes a cathode 1 , an anode 2 and a power source 3 , The cathode 1 and the anode 2 are arranged at intervals and are located on the inner top wall and the inner bottom wall of the box body 4 respectively, and are respectively connected with the power source 3, and the Langmuir probe 5 is inserted into the box body 4 and located between the cathode 1 and the anode 2, the opposite two side walls of the box body 4 are respectively provided with an air inlet 6 and an air outlet 7.

Specifically, the box body 4 has a cavity structure, and its interior can be in the shape of a hollow cuboid, and correspondingly, the outside can also be in the shape of a cuboid, so as to be convenient to carry and use. The plasma generating device comprises a cathode 1, an anode 2 and a power source 3, the anode 2 can be arranged on the inner bottom wall of the box body 4, and can be connected with the negative electrode of the power source 3 through a wire, and the cathode 1 can be arranged on the inner top wall of the box body 4, It can be connected to the positive electrode of the power source 3 through a wire, so as to discharge and break down the mixed gas in the box body 4 to generate plasma. A through hole can be opened on the side wall of the box body 4, so that the Langmuir probe 5 is inserted into the box body 4 from the through hole and its needle is located between the cathode 1 and the anode 2, for obtaining plasma parameters, And further gas impurity analysis. An air inlet 6 can be provided on the left side wall of the box body 4 for introducing the mixed gas to be detected, for example, directly exhaled by the user, and an air outlet is provided on the right side wall of the box body 4 for discharging the detected mixed gas.

During detection, a calibration gas is also introduced into the box body 4 together with the mixed gas. The calibration gas can be determined in advance, and an inert gas such as helium (He) is usually selected. Based on the relevant characteristics of the calibration gas, the optimal applied voltage and distance between the cathode 1 and the anode 2 can be determined according to Paschen's law.

Paschen's law includes:

Among them, the constants A and B represent gas-related parameters. For example, if the calibration gas is helium, it is the related parameter of helium, p represents the pressure of the ionization chamber, that is, the air pressure in the box 4, and V represents the breakdown voltage. , γ represents the cathode secondary electron emission coefficient, which depends on the cathode material, L represents the distance between the cathode 1 and the anode 2, and pL represents the product of the pressure of the ionization chamber and the distance between the cathode and the anode.

It can be seen that both pL and V have minimum values, namely, (pL) _min and (V) _min . As shown in Figure 2, using helium as the calibration gas, the Paschen curve is shown in the figure, the curve is a U-shaped curve, and the breakdown voltage first decreases with the increase of the product of the distance between the anode 2 and the cathode 1 and the gas pressure. The breakdown voltage has a minimum value, and then the breakdown voltage increases with the increase of the product of the distance between the anode 2 and the cathode 1 and the gas pressure. Take the minimum value of the breakdown voltage as the applied voltage of the mixed gas detection device in this embodiment, take the right value of the minimum value of the breakdown voltage, and obtain the corresponding spacing value between the cathode 1 and the anode 2, as the value of the mixed gas detection device in this embodiment. The distance between cathode 1 and anode 2. It can be understood that the detection device is in a stable state at this time. When the user blows gas from the air inlet 6, the air pressure in the box body 4 decreases due to the increase of the air flow, and the product of the air pressure and the distance between the cathode 1 and the anode 3 decreases. The breakdown voltage decreases and reaches the minimum value, and the discharge breakdown between the cathode 1 and the anode 2 of the detection device will generate plasma.

In this embodiment, the user can exhale through the air inlet, and the gas will flow out from the air outlet. During this process, powered by the power supply, the cathode and anode in the box will discharge and break down the mixed gas exhaled by the user. The Muir probe can obtain the plasma parameters generated by ionization, and can further analyze the gas composition through, for example, the current-voltage relationship. The device has a simple structure, is convenient to carry, can effectively improve the detection efficiency of the mixed gas, and can correspondingly reduce the detection cost.

Optionally, the cathode 1 includes a molybdenum sheet.

Specifically, the cathode 1 is made of a metal molybdenum sheet, which has good electrical conductivity, small volume, and low space usage requirements. Using the molybdenum sheet as the cathode 1 can increase the portability of the mixed gas detection device, and the price of the molybdenum sheet is reasonable. , which can effectively reduce the production cost of the mixed gas detection device and increase its practicability. For example, a molybdenum sheet with a thickness of 0.15 mm is selected as the cathode 1 of the mixed gas detection device of this embodiment.

Optionally, the anode 2 includes a silicon substrate 21 and carbon nanotubes 22, the silicon substrate 21 is attached to the inner bottom wall of the box body 4, and the carbon nanotubes 22 are grown by chemical vapor deposition. on the top surface of the silicon substrate 21 .

Specifically, as shown in FIG. 1 , the anode 2 includes a silicon substrate 21 and carbon nanotubes 22. One end of the silicon substrate 21 is attached to the inner bottom wall of the box body 4, and the other end uses a chemical vapor deposition method to grow a layer of carbon nanotubes. The tube 22 is arranged opposite to the cathode 1 . Silicon substrates are widely used and cheap, which effectively increases the feasibility of mixed gas detection devices and reduces production costs; carbon nanotubes have high electrical conductivity and heat resistance, and as one-dimensional nanomaterials, they are light in weight, stable in structure, and stable in structure. High hardness. Using the silicon substrate 21 and the carbon nanotubes 22 as the anode 2 can effectively improve the portability of the mixed gas detection device, at the same time, it has strong stability and low price, reduces the maintenance and replacement of the equipment, etc., so that the service life of the mixed gas detection device is longer. long, effectively reducing the detection cost.

Optionally, the material of the box body 4 is quartz glass.

Specifically, the box body 4 is made of quartz glass into a hollow cuboid shape. Since quartz glass has the advantages of high hardness and high temperature resistance, the box body 4 is made of quartz glass, so that the mixed gas detection device has a strong structure, increases the service life, and at the same time , Quartz glass also has high electrical insulation, which avoids leakage when the monitoring device performs mixed gas ionization, and increases the safety of mixed gas detection. In addition, the size of the box body 4 can be set to a size that is convenient to hold, so that it is convenient to carry and use.

In this embodiment, as shown in FIG. 1, the good electrical conductivity of molybdenum sheets and carbon nanotubes are used as cathode 1 and anode 2, respectively, to ionize the mixed gas to generate plasma, which effectively increases the detection efficiency. At the same time, quartz glass is used. As the box body 4, the internal structure is protected, the portability and service life of the monitoring device are increased, and the quartz glass has high electrical insulation, which greatly improves the safety of the monitoring device.

Optionally, the power source 3 includes a battery and a voltage regulating mechanism, the voltage regulating mechanism is connected to the battery and used to regulate the voltage applied to the cathode 1 and the anode 2 .

Specifically, the power source 3 includes a battery and a voltage adjustment mechanism, the battery is connected to the voltage adjustment mechanism, the battery is used to provide an applied voltage to the cathode 1 and the anode 2, and the voltage adjustment mechanism is used to adjust the applied voltage provided by the battery, so that the applied voltage meets the detection device. required breakdown voltage. For example, a lithium battery is selected as the battery of the mixed gas detection device. As can be seen from Figure 2, when helium is used as the calibration gas to detect the composition of the mixed gas, the required applied voltage is 400V, and the maximum safe voltage of the battery is 36V. The voltage adjustment mechanism amplifies the applied voltage to 400V, which meets the voltage required for detection. The voltage adjustment mechanism can choose a micro voltage power amplifier. In addition, if the required applied voltage is less than the maximum safe voltage of the lithium battery, 36V, a lithium battery with a suitable voltage can be selected to meet the detection requirements.

In this embodiment, a voltage adjustment mechanism is set to adjust the voltage provided by the battery, so that the applied voltage meets the voltage required by the mixed gas detection device, so as to prevent the cathode 1 and the anode 2 from being unable to discharge and break down normally due to insufficient applied voltage to generate plasma, ensuring that the Check the normal operation of the device.

Optionally, the mixed gas component detection device further includes a distance adjustment mechanism, and the distance adjustment mechanism is used to adjust the distance between the cathode 1 and the anode 2 .

Specifically, the mixed gas detection device further includes a distance adjustment mechanism, which is used to adjust the distance between the cathode 1 and the anode 2 . Exemplarily, a rack and pinion mechanism can be used as the spacing adjustment structure. By rotating the gear, the rack moves linearly to drive the connected cathode 1 and anode 2 to approach or move away from each other, thereby adjusting the spacing between the two.

In this embodiment, since different types of calibration gases can be selected according to the actual situation, the required electrode spacing and applied voltage in the mixed gas detection device are also different. The distance between the electrodes is then adjusted by the distance adjustment mechanism, so that the detection device can operate normally while maintaining the detection accuracy after the calibration gas is replaced. .

Optionally, the mixed gas component detection device further includes a helium gas supply mechanism, and the helium gas supply mechanism is used to communicate with the box body 4 .

The mixed gas detection device also includes a helium gas supply mechanism, which communicates with the box body 4 and is used for the detection of mixed gas components by introducing helium gas as a calibration gas for mixed gas detection. In addition, due to the similar properties of the inert gas, other inert gases, such as neon gas, argon gas, etc., can also be selected as the calibration gas, and a neon gas supply mechanism or an argon gas supply mechanism and the like are correspondingly provided.

In this embodiment, a helium gas supply mechanism is provided, and helium gas is introduced as a calibration gas to detect the composition of the mixed gas, which can quickly complete the composition analysis of the mixed gas, reduce the time and cost of detection, and improve the detection efficiency.

Referring to FIG. 3 , a mixed gas composition detection method according to another embodiment of the present invention is based on the above-mentioned mixed gas composition detection device; the method includes:

Step S1, pass the gas to be detected mixed with the calibration gas into the box body 4, wherein, the distance between the cathode 1 and the anode 2 and the applied voltage are determined based on Paschen's law and the calibration gas;

Step S2, when the gas is ionized, obtain plasma parameters through the Langmuir probe 5;

Step S3, determining the composition of the gas to be detected by the plasma parameters.

Specifically, when using the mixed gas composition detection device for gas composition analysis, first determine the calibration gas, and then determine the required applied voltage and the distance between the cathode 1 and the anode 2 according to Paschen's law. In this embodiment, helium is selected as the calibration gas, and it can be seen from FIG. 2 that the required applied voltage of helium is 400V. During detection, the user blows air into the air inlet 6 while using the helium supply device to introduce helium, and applies a voltage of 400V to the cathode 1 and the anode 2 through the power supply 3, so that the mixed gas achieves discharge breakdown and generates plasma. Among them, the metastable atomic energy based on helium is sufficient to ionize almost all gases exhaled by the human body. In addition, different voltages can be applied to the Langmuir probe 5 in contact with the plasma, so as to obtain the current generated by the plasma under different voltages, and realize the composition analysis of the mixed gas according to the obtained current and voltage data.

In this embodiment, the calibration gas can be determined in advance, and an inert gas such as helium is usually selected. Based on the relevant characteristics of the calibration gas, the optimal applied voltage and distance between the cathode and the anode of the hybrid detection device can be determined according to Paschen's law. , so that the product of the distance and the atmospheric pressure is located to the right of the lowest point of the U-shaped Paschen curve, so that when the mixed gas and the calibration gas exhaled by the user pass through the box, the product of the above distance and the current pressure will be reduced due to the decrease of the pressure in the box. It will drop to the lowest point of the U-shaped Paschen curve, and then ionize the mixed gas to generate plasma. The plasma parameters can be obtained by using the Langmuir probe, and the gas composition can be further analyzed by, for example, the relationship between current and voltage. The method can not only ensure the detection accuracy of the mixed gas, but also effectively improve the detection efficiency and reduce the detection cost accordingly.

Optionally, the determining the composition of the gas to be detected by the plasma parameter includes:

obtaining a current/voltage curve of the plasma;

The second-order derivative is performed on the current/voltage curve to obtain an electron energy distribution function with characteristic electron peaks;

According to the characteristic electron peak on the electron energy distribution function, the composition of the gas to be detected is determined.

Specifically, the cathode 1 and the anode 2 are powered by the power supply 3 to realize the discharge breakdown to generate plasma, and the Langmuir probe 5 is used to apply a certain voltage to the plasma to obtain the current change of the plasma under a certain voltage to generate The current/voltage curve of the plasma, the second-order derivation of the probe current of the current/voltage curve relative to the probe voltage is performed to obtain the electron energy distribution function with characteristic electron peaks, and the plasma electron energy spectrum is generated, as shown in Figure 4. As shown, by fitting the area ratio of each characteristic electron peak (the area corresponding to the dotted line part), the proportions of components such as N ₂ and CO in the mixed gas can be obtained, and the analysis of the components of the mixed gas can be realized.

In this embodiment, the current/voltage curve is collected by the Langmuir probe, and then the plasma electron energy spectrum is generated. According to the area ratio in the plasma electron energy spectrum, the quantitative analysis of the mixed gas is performed to complete the detection of the mixed gas composition. The quantitative analysis of the detected gas is carried out by the plasma electron energy spectrum, which makes the detection result more intuitive, and at the same time, the method is simple to operate and improves the detection efficiency of the mixed gas composition.

It can be understood that the plasma electron energy spectrum contains the energy of atoms and molecules of the components in the detected gas, and the ionization energy of each component is obtained according to the initial kinetic energy of different characteristic electron peaks on the plasma electron energy spectrum and the excitation energy of excited atoms. Furthermore, the composition of impurities (that is, the mixed gas to be detected) can be determined, and the qualitative analysis of impurities can be realized. For example, according to the Penning ionization reaction: A ^* +M→A+M ⁺ +e{E _f }, since the impurity atoms (molecules) have different ionization potentials E _i , Penning electrons have different The initial kinetic energy E _f . The ionization potential (E _i =E _m -E _f ) of gas atoms (molecules) is determined by analyzing the energy of these different electrons, so as to achieve the purpose of identifying gas components. Usually, the transport gas (that is, the calibration gas) can be helium. The initial kinetic energy of different characteristic electron peaks on the plasma electron energy spectrum and the excitation energy of excited atoms (He) are known to obtain the ionization energy of impurities. This further determination of the composition of the impurity enables qualitative analysis of the impurity. Since the energy of the metastable He atom is E _m =19.8eV, which is sufficient to ionize any (except Ne) gas atoms (molecules), helium is often used as the transport gas for qualitative analysis and detection of gas atoms (molecules). In this way, the quantitative analysis of the detected gas can be quickly completed, the time cost of detection can be reduced, and the detection efficiency can be improved.

Optionally, the calibration gas is helium. According to Paschen's law, the distance between the cathode 1 and the anode 2 can be calculated to be in the range of 40 to 50 mm, and the minimum applied voltage is 400V. Helium is used as the calibration gas, and a detection device is set up to detect the mixed gas composition according to the obtained data, which can improve the detection efficiency and reduce the detection cost while ensuring the accuracy of the detection results.

Although the present invention is disclosed above, the protection scope of the present invention is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and these changes and modifications will all fall within the protection scope of the present invention.

Claims (10)

1. A mixed gas composition detection device, characterized in that, comprising a box (4), a plasma generating device and a Langmuir probe (5), the plasma generating device comprising a cathode (1), an anode (2) and power supply (3), the cathode (1) and the anode (2) are arranged at intervals and are respectively located on the inner top wall and the inner bottom wall of the box body (4), and are respectively connected with the power supply (3) , the Langmuir probe (5) is inserted into the box body (4) and is located between the cathode (1) and the anode (2), and the opposite two side walls of the box body (4) An air inlet (6) and an air outlet (7) are respectively provided. 2 . The mixed gas component detection device according to claim 1 , wherein the cathode ( 1 ) comprises a molybdenum sheet. 3 . 3 . The mixed gas component detection device according to claim 1 , wherein the anode ( 2 ) comprises a silicon substrate ( 21 ) and carbon nanotubes ( 22 ), and the silicon substrate ( 21 ) is attached to the On the inner bottom wall of the box body (4), the carbon nanotubes (22) are grown on the top surface of the silicon substrate (21) by chemical vapor deposition. 4 . The mixed gas component detection device according to claim 1 , wherein the material of the box body ( 4 ) is quartz glass. 5 . 5 . The mixed gas composition detection device according to claim 1 , wherein the power source ( 3 ) comprises a battery and a voltage regulating mechanism, and the voltage regulating mechanism is connected to the battery and used to regulate the voltage applied to the battery. 6 . The voltage of the cathode (1) and the anode (2). 6 . The mixed gas component detection device according to claim 1 , further comprising a distance adjustment mechanism, the distance adjustment mechanism is used to adjust the distance between the cathode ( 1 ) and the anode ( 2 ). 7 . 7 . The mixed gas component detection device according to claim 1 , further comprising a helium gas supply mechanism, the helium gas supply mechanism being used for communicating with the box body ( 4 ). 8 . 8. A mixed gas composition detection method, characterized in that, based on the mixed gas composition detection device according to any one of claims 1 to 7, comprising: Passing the gas to be detected mixed with the calibration gas into the box body (4), wherein the distance between the cathode (1) and the anode (2) and the applied voltage are determined based on Paschen's law and the calibration gas; When the gas is ionized, the plasma parameters are obtained by the Langmuir probe (5); The composition of the gas to be detected is determined by the plasma parameters. 9 . The method for detecting a mixed gas composition according to claim 8 , wherein the determining the composition of the gas to be detected by the plasma parameter comprises: 10 . obtaining a current/voltage curve of the plasma; The second-order derivative is performed on the current/voltage curve to obtain an electron energy distribution function with characteristic electron peaks; According to the characteristic electron peak on the electron energy distribution function, the composition of the gas to be detected is determined. 10 . The method for detecting mixed gas components according to claim 8 , wherein the calibration gas is helium gas, the range of the distance is 40 to 50 mm, and the applied voltage is 400V. 11 .

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