CN112858457A - Photoionization sensor for distinguishing gas types - Google Patents
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Abstract
The application discloses a photo-ionization sensor for distinguishing gas types, which is used for improving the classification capability of the photo-ionization sensor in detecting gases with different ionization energies. The application includes: the device comprises an ultraviolet lamp module, a sensor main body, an ion current receiving electrode pair, an amplifying circuit and an output module; the sensor main body is provided with a gas circulation area and an information processing area; the ultraviolet lamp module is arranged in the gas circulation area and is used for emitting ultraviolet light after the ultraviolet lamp module generates an ultraviolet light source; at least two ion current receiving electrode pairs are arranged in the gas circulation area; at least two amplifying circuits are arranged in the information processing area, and the ion current receiving electrode pairs are connected with the amplifying circuits; the output module is arranged in the information processing area and is connected with the amplifying circuit.
Description
Technical Field
The embodiment of the application relates to the field of detection, in particular to a photoionization sensor for distinguishing gas types.
Background
Photo-ionization sensors are an important sensor currently detecting gaseous substances. The working principle is as follows: the gas to be measured absorbs photons emitted by the ultraviolet lamp and is ionized into positive ions and electrons, wherein gas molecules are successfully ionized, and the ultraviolet photon energy (calculated according to E ═ h ν) is required to be larger than the ionization energy of the gas molecules. Under the action of an external electrode, ions move in space to form a weak current which is photoionization current and are collected. The generated ionization current is typically set 10 by9And finally, carrying out logic analysis and calculation through an output module to obtain data of whether the gas to be detected is ionized.
However, in the gas detection process, the gas to be detected may have not only one kind of gas but also a mixture of a plurality of kinds of gases. During the detection process. Because the ultraviolet lamp module on the traditional photoionization sensor only has one ultraviolet light source and one ultraviolet light window, and the photoionization sensor only has one amplifying circuit and an output module, the ionization energy of the ultraviolet light emitted by each ultraviolet light window is fixed, only the gas to be detected with the ionization energy smaller than the ultraviolet light ionization energy can be ionized, and the gas to be detected with the ionization energy larger than the ultraviolet light ionization energy cannot be ionized. That is, only the analysis data of the gas type with ionization energy smaller than the ionization energy of the ultraviolet light can be obtained, and the gas type in the gas to be detected cannot be further analyzed, so that more analysis data about the gas type can be obtained.
Currently, by adding another ultraviolet lamp module capable of emitting ultraviolet light with different energy and adding a new amplifying circuit, the photoionization sensor can continue to further analyze the gas type of the gas to be detected and obtain more analysis data about the gas type.
However, in the method of adding the ultraviolet lamp modules, the gas to be detected is respectively acted by the two ultraviolet lamp modules, that is, the gas to be detected does not share the same ultraviolet light source, uncontrollable differences exist in various aspects such as gas concentration and purity of the ultraviolet light sources, the attenuation speeds of light intensity may also be different in the long-term use process, and in the use process, the accuracy of analysis data of different gas types can be reduced, so that the classification capability of the conventional photoionization sensor in detecting gases with different ionization energies is reduced.
Disclosure of Invention
The embodiment of the application provides a photoionization sensor for distinguishing gas type, which is characterized by comprising:
the device comprises an ultraviolet lamp module, a sensor main body, an ion current receiving electrode pair, an amplifying circuit and an output module;
the sensor body is provided with a gas circulation area and an information processing area;
the ultraviolet lamp module is arranged in the gas circulation area and is used for emitting ultraviolet light after the ultraviolet lamp module generates an ultraviolet light source;
at least two ion current receiving electrode pairs are arranged in the gas circulation area, the ion current receiving electrode pairs are placed in front of the ultraviolet light window, and the ion current receiving electrode pairs are used for receiving signals generated when gas to be detected is ionized;
at least two amplifying circuits are installed in the information processing area, the ion current receiving electrode pairs are connected with the amplifying circuits, and the amplifying circuits are used for processing signals collected by the ion current receiving electrode pairs;
the output module is arranged in the information processing area, connected with the amplifying circuit and used for receiving and generating analysis data for distinguishing the gas to be detected based on the ionization energy threshold according to the signals processed by the amplifying circuit.
Optionally, the ultraviolet lamp module includes an ac voltage module, an ultraviolet light window, an ultraviolet excitation electrode pair, an ultraviolet lamp main body, and a working gas;
the ultraviolet lamp main body contains the working gas and emits ultraviolet light under the excitation of the ultraviolet excitation electrode pair;
the ultraviolet lamp main body is provided with at least two ultraviolet light windows, and after the ultraviolet light emitted by the working substance passes through the ultraviolet light windows, the spectral components emitted by each ultraviolet light window are different;
the ultraviolet excitation electrode pair is arranged on the ultraviolet lamp main body and used for exciting the working gas to generate an ultraviolet light source;
the alternating voltage module is connected with the ultraviolet excitation electrode pair and used for providing high-voltage alternating voltage for the ultraviolet excitation electrode pair.
Optionally, the alternating voltage module includes a high voltage power supply module and a high voltage power supply conversion module;
the high-voltage power supply module is connected with the high-voltage power supply conversion module;
the high-voltage power supply conversion module is connected with the ultraviolet excitation electrode pair and used for providing electric energy for the ultraviolet excitation electrode pair.
Optionally, the ultraviolet lamp module further comprises a gas adsorbent;
the ultraviolet lamp module comprises the gas adsorbent, and the gas adsorbent is used for adsorbing impurity gas in the ultraviolet lamp module.
Optionally, the gas flow-through region comprises a gas inlet, a gas outlet and an ionization region;
the gas inlet is arranged on the sensor main body, the gas to be detected enters the ionization region through the gas inlet, and the gas to be detected is ionized in the ionization region;
the gas vent set up in on the sensor main part, the gas vent is used for with the gas that awaits measuring is taken out ionization region.
Optionally, the gas flow-through region further includes a suction pump for pumping the gas to be measured into the ionization region.
Optionally, the gas flow-through region further comprises an exhaust pump for exhausting the gas to be measured out of the ionization region.
Optionally, the ion current receiving electrode pair is disposed parallel to the ultraviolet light window.
Optionally, the ion current receiving electrode pair is disposed perpendicular to the ultraviolet light window.
Optionally, the output module includes a logic judgment module and an information output module;
the logic judgment module is connected with the amplifying circuit and is used for analyzing the signal processed by the amplifying circuit;
the logic judgment module is connected with the information output module, and the information output module is used for generating gas type analysis data indicating the gas to be detected.
According to the technical scheme, the embodiment of the application has the following advantages:
the ultraviolet lamp module is provided with a plurality of ultraviolet light windows simultaneously, each ultraviolet light window ionizes gas to be detected by emitting ultraviolet light, signals generated when the gas to be detected is ionized are received through a plurality of ion current receiving electrode pairs, the signals are transmitted to the amplifying circuit by the ion current receiving electrode pairs to be subjected to information processing, the output module receives the information transmitted by the amplifying circuits to perform logic analysis and calculation, whether the gas to be detected is ionized on the ultraviolet light window is judged, and therefore gas type analysis data are increased. Due to the fact that the ultraviolet windows are made of different materials, the spectral components of ultraviolet light emitted by the ultraviolet windows are different, data received by the amplifying circuit are different, the output module can conduct logic analysis and calculation on the difference between the data, and analysis data for distinguishing the gas to be detected based on the ionization energy threshold value are obtained. In the embodiment of the application, a plurality of ultraviolet light windows made of different materials are arranged on the same ultraviolet lamp module, so that the ultraviolet light windows share one ultraviolet light source, the gas concentration, the purity and the like of each ultraviolet light window are almost the same, and the classification capability of the photoionization sensor in the process of detecting gases with different ionization energies is improved.
Drawings
FIG. 1 is a schematic diagram of one embodiment of a photoionization sensor for distinguishing between gas types;
FIG. 2 is a schematic structural view of one embodiment of the UV lamp module;
FIG. 3 is a schematic view of an embodiment of a UV lamp module;
FIG. 4 is a schematic view of another embodiment of the UV lamp module;
FIG. 5 is a schematic diagram of another embodiment of a photoionization sensor for distinguishing between gas types;
FIG. 6 is a schematic structural diagram of an embodiment of a positional relationship between an ultraviolet lamp and an ion current receiving electrode pair;
FIG. 7 is a schematic structural diagram of another embodiment of the positional relationship between the UV lamp and the ion current receiving electrode pair;
FIG. 8 is a graph of the response of a photoionization sensor with dual UV lamp windows to measure IBE gas;
FIG. 9 is a graph of the response of a photoionization sensor with a double UV lamp window to ammonia gas measurement;
FIG. 10 is a graph of the response of a photoionization sensor with dual UV lamp windows to measure ammonia and IBE gas mixtures.
Detailed Description
The technical solutions in the present application will be described clearly and completely with reference to the accompanying drawings in the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
The embodiment of the application discloses a photoionization sensor for distinguishing gas types, which is used for improving the classification capability of the photoionization sensor in the process of detecting gases with different ionization energies.
Referring to fig. 1, an embodiment of the present application provides a photoionization sensor for distinguishing gas types, including:
the device comprises an ultraviolet lamp module 1, a sensor main body 2, an ion current receiving electrode pair 3, an amplifying circuit 4 and an output module 5;
the sensor body 2 is provided with a gas flow area and an information processing area;
the ultraviolet lamp module 1 is provided with at least two ultraviolet light windows, the ultraviolet light spectrum components emitted by each ultraviolet light window are different, the ultraviolet lamp module 1 is arranged in the gas circulation area, and the ultraviolet light windows are used for emitting ultraviolet light after the ultraviolet lamp module generates an ultraviolet light source;
at least two ion current receiving electrode pairs 3 are arranged in the gas circulation area, the ion current receiving electrode pairs 3 are placed in front of the ultraviolet light window, and the ion current receiving electrode pairs 3 are used for receiving signals generated when gas to be detected is ionized;
at least two amplifying circuits 4 are installed in the information processing area, the ion current receiving electrode pairs 3 are connected with the amplifying circuits 4, and the amplifying circuits 4 are used for processing signals collected by the ion current receiving electrode pairs 3;
the output module 5 is arranged in the information processing area, the output module 5 is connected with the amplifying circuit 4, and the output module 5 is used for receiving and generating analysis data based on an ionization energy threshold value for distinguishing the gas to be detected according to the signal processed by the amplifying circuit 4.
Fig. 1 illustrates a photoionization sensor with two uv windows, and first, the structure of the photoionization sensor with two uv windows and the operation of the structure will be described.
The photoionization sensor with double ultraviolet windows has a sensor body 2, and the sensor body 2 is a sensor housing for mounting other detecting elements and providing a detecting space for gas to be detected. The sensor main body 2 can be divided into a gas circulation area and an information processing area, an ultraviolet lamp module 1 and an ion current receiving electrode pair 3 are arranged in the gas circulation area, and an amplifying circuit 4 and an output module 5 are arranged in the information processing area.
In practical application, gas to be detected is introduced into a gas flowing region, and the gas to be detected is ionized through the ultraviolet lamp module 1. The information processing area is used for processing and outputting information data detected in the gas circulation area.
The ultraviolet lamp module 1 is a device for emitting ultraviolet light, and on the photoionization sensor with double ultraviolet windows, the ultraviolet lamp module 1 is provided with two ultraviolet light windows 7, the materials of the two ultraviolet light windows are different, and the wavelength and the energy of the ultraviolet light which can penetrate through are also different, so that the components of the emitted ultraviolet light spectrum are different. Since the uv lamp module 1 only generates one uv light source, the two uv windows 7 share the same uv light source. The two ultraviolet light windows 7 share the same ultraviolet light source, so that the difference of the ultraviolet light source, the gas concentration, the purity and the like can be reduced. Compared with a photoionization sensor using a plurality of ultraviolet lamp modules, the photoionization sensor with double ultraviolet windows only uses one ultraviolet light source, and the acquired data error is smaller.
The ion current receiving electrode pairs 3 are formed by combining two electrode plates, and two groups of ion current receiving electrode pairs 3 are arranged in the photoionization sensor with double ultraviolet windows and are used for respectively collecting gas ions ionized by the two ultraviolet windows 7 so as to form a weak current signal. The ion current receiving electrode pair 3 transmits the collected weak current signal to the amplifying circuit 4.
In the photoionization sensor with double ultraviolet windows, two amplifying circuits 4 are arranged, and the two amplifying circuits 4 are respectively connected with two ion current receiving electrode pairs 3. The two amplifying circuits 4 are used for respectively receiving weak current signals formed by the two ion current receiving electrode pairs 3 and amplifying the weak current signals into analog output of a low-resistance voltage signal, and the analog output is finally transmitted to the output circuit 5 by the amplifying circuits 4.
An output module 5 is arranged in the photoionization sensor with double ultraviolet windows, and the output module 5 is used for receiving the analog output transmitted by the two amplifying circuits 4, performing logic analysis and calculation, and generating analysis data based on an ionization energy threshold value for distinguishing the gas to be detected.
The ultraviolet lamp module generates ultraviolet light by exciting rare gas to generate plasma emission, the emission spectrum of the ultraviolet lamp module comprises ultraviolet spectrum with specific wavelength, the plasma emission wavelength of specific atoms depends on the electronic structure of the inner shell layer of the ultraviolet lamp module, although more emission wavelengths exist, each emission wavelength is basically a fixed value, and the ultraviolet lamp module is difficult to change after packaged working substances are selected. Another way is to achieve the selection of the uv wavelength by making the uv window 7 of a material with different transmittances for uv light of different wavelengths. For example: the strong ultraviolet wavelengths in the spectrum line of the common working substance Kr gas are 116.5nm and 123.6nm, which correspond to photon energies of 10.6eV and 10.0eV, so that the wavelengths can be selected to pass through none, one or both of them by using a proper ultraviolet window material.
In this embodiment, according to the method for generating the ultraviolet light source, two ultraviolet light windows 7 made of different materials are installed on the same ultraviolet lamp module, so that the two ultraviolet light windows 7 have different transmittances for ultraviolet light with different wavelengths, resulting in a difference in gases that can be ionized by the two ultraviolet light windows 7, thereby realizing detection of different gas types.
Under the condition that an ultraviolet lamp module is not added, ultraviolet lamp windows can transmit ultraviolet light with different energies, and an ultraviolet light source, gas concentration, purity and the like of each ultraviolet lamp window are almost the same, so that detection of different gas types is realized, and the classification capability of the photoionization sensor in detection of gases with different ionization energies is improved.
Secondly, there are many initial matching problems, calibration problems and extra maintenance problems when multiple sensors are used together without consideration in the detection process. Because this embodiment uses same ultraviolet lamp module, the ultraviolet light source only has one, has reduced cost and the volume of photoionization sensor.
Referring to fig. 2, an embodiment of the present application provides a method, including:
optionally, the ultraviolet lamp module 1 includes an ac voltage module 6, an ultraviolet light window 7, an ultraviolet excitation electrode pair 8, an ultraviolet lamp main body 9, and a working gas 10;
at least two ultraviolet light windows are arranged on the ultraviolet lamp main body 9, and the ultraviolet light spectrum components emitted by each ultraviolet light window 7 are different;
the ultraviolet lamp main body 9 contains the working gas, and emits ultraviolet light under the excitation of the ultraviolet excitation electrode pair 8;
the ultraviolet excitation electrode pairs 8 are arranged on the ultraviolet lamp main body 9, and the ultraviolet excitation electrode pairs 8 are used for exciting the working gas 10 to generate an ultraviolet light source;
the alternating voltage module 6 is connected with the ultraviolet excitation electrode pair 8, and the alternating voltage module 6 is used for providing high-voltage alternating voltage for the ultraviolet excitation electrode pair 8.
In this embodiment, the structure of the ultraviolet lamp module 1 will be described by taking an ultraviolet lamp module with two ultraviolet windows as an example.
The ultraviolet lamp main body 9 is a frame of the ultraviolet lamp module 1, and in this embodiment, the ultraviolet lamp main body 9 of the ultraviolet lamp module with the double ultraviolet windows is cylindrical. Two ultraviolet lamp mounting ports are formed in the ultraviolet lamp main body 9 and used for mounting the ultraviolet light window 7.
In this embodiment, the material of the uv window 7 may be MgF2，CaF2LiF, etc., without limitation. However, the materials of the ultraviolet light windows 7 on the same ultraviolet lamp module 1 are different, so that the ultraviolet light windows 7 emit ultraviolet light with different energies.
The ultraviolet light source needs to be introduced into the ultraviolet lamp main body 9, in the embodiment of the present application, the working gas 10 is injected into the ultraviolet lamp main body 9, the working gas 10 is a gas substance that can be excited under a certain condition to generate the ultraviolet light source, and the working gas used in the embodiment is the rare gas Kr. In theory, there are other noble gases that can act as working gases, and are not limited herein. Since the plasma state of the working gas 10 is easily quenched by other impurity gases, the ultraviolet lamp module 1 is manufactured in a low-pressure sealed state.
The ultraviolet lamp module with the double ultraviolet windows is also provided with an ultraviolet excitation electrode pair 8, each ultraviolet excitation electrode pair 8 is provided with two electrodes, and the ultraviolet excitation electrode pair 8 is used for exciting the working gas 10, so that the working gas 10 is excited out of an ultraviolet light source. The ultraviolet excitation electrode pairs 8 are connected with the alternating voltage module 6, the alternating voltage module 6 connects high-voltage alternating voltage to the ultraviolet excitation electrode pairs 8, so that alternating electric field environments are generated, the working gas 10 can excite ultraviolet light sources under the electric field environments, and the ultraviolet light sources are emitted through the two ultraviolet light windows 7.
In this embodiment, the material of the ultraviolet excitation electrode pair 8 may be a metal such as Cu or Au, or other material with a conductive plating layer, which is not limited herein.
In the embodiment of the present application, an ultraviolet lamp module with two ultraviolet windows is taken as an example, and a manufacturing process of the ultraviolet lamp module 1 is described.
In the ultraviolet lamp module with double ultraviolet windows, an ultraviolet lamp main body 9 is a cylindrical glass tube, an ultraviolet lamp mounting port of the cylindrical glass tube is firstly bonded with an ultraviolet window 7 by using substances such as low-temperature glass powder and the like at high temperature, a semi-open and semi-closed structure is realized, and the ultraviolet window 7 is made of magnesium fluoride. Then, adding substances such as low-temperature glass powder and the like into the other ultraviolet lamp mounting port of the cylindrical glass tube, sealing the device in a low-pressure environment filled with working gas 10, wherein the working gas 10 is Kr gas and the pressure is about 300pa, and then heating to the working temperature of the low-temperature glass powder to paste the glass powder, so that the sealing of the working gas 10 and the bonding of an ultraviolet light window are realized. And then cooling, connecting the air in parallel, and installing the ultraviolet excitation electrode pair 8 to finish the manufacture of the vacuum ultraviolet lamp module 1 with double windows.
Please refer to fig. 3 and fig. 4, it should be noted that, besides the photoionization sensors with two uv windows, theoretically, the photoionization sensors with more uv windows can be manufactured, fig. 3 is a structural diagram of an uv lamp module with three uv windows, fig. 4 is a structural diagram of an uv lamp module with four uv windows, theoretically, by manufacturing uv lamp modules with multiple uv windows, a corresponding photoionization sensor can be manufactured, and the detection fineness of the photoionization sensors when the gas type analysis data is increased is improved.
Referring to fig. 5, the structure of the photo-ionization sensor is described in detail as follows:
optionally, the alternating voltage module 6 includes a high voltage power supply module 11 and a high voltage power supply conversion module 12;
the high-voltage power supply module 11 is connected with the high-voltage power supply conversion module 12;
the high-voltage power supply conversion module 12 is connected to the ultraviolet excitation electrode pair 8, and the high-voltage power supply conversion module 12 is used for supplying electric energy to the ultraviolet excitation electrode pair 8.
In this embodiment, the ac voltage module 6 is divided into two parts, one is a high voltage power supply module 11, the high voltage power supply module 11 provides high voltage electric energy during the operation, the other is a high voltage power supply conversion module 12, the high voltage power supply conversion module 12 converts the high voltage power supply provided by the high voltage power supply module 11 into high voltage ac voltage, so that the ultraviolet excitation electrode pair 8 obtains the high voltage ac voltage.
Optionally, the ultraviolet lamp module 1 further comprises a gas adsorbent;
the ultraviolet lamp module comprises the gas adsorbent, and the gas adsorbent is used for adsorbing impurity gas in the ultraviolet lamp module.
In this embodiment, the gas adsorbent may be an alloy material of Zr, Al, and V, which is not limited herein. During the manufacturing process or the using process of the ultraviolet lamp module 1, impurity gas may permeate into the working gas, and the gas adsorbent can adsorb the impurity gas inside the ultraviolet lamp module 1.
Optionally, the gas flow-through region comprises a gas inlet 13, a gas outlet 14 and an ionization region 15;
the gas inlet 13 is arranged on the sensor main body 1, the gas to be detected enters the ionization region through the gas inlet 13, and the gas to be detected is ionized in the ionization region 15;
the exhaust port 14 is disposed on the sensor body 1, and the exhaust port 14 is used for pumping the gas to be measured away from the ionization region 15.
The gas flow area is provided with a gas inlet 13 and a gas outlet 14, and the gas inlet 13 and the gas outlet 14 introduce the detected gas into an ionization area 15. The method for introducing the detected gas into the ionization region 15 is mainly an active pumping method or a passive diffusion method. The passive diffusion mode is that the detected gas is expanded to the ionization region 15 through the gas inlet 13 by changing the concentration gradient difference of the inner side and the outer side of the gas inlet 13, and after the detection is finished, the detected gas is expanded to the outside from the ionization region 15 through the gas outlet 14 by changing the concentration gradient difference of the inner side and the outer side of the gas outlet 14. The active pumping method is to install an air pump on the air outlet 14 or the air inlet 13, and the air pump is used to realize the entrance of the detected gas into the ionization region 15 and the exit of the detected gas out of the ionization region 15. The flow rate is 50-1000mL/min by adopting diffusion detection or pump suction detection, and the preferable range is 100-400 mL/min.
The following describes the active pumping mode:
optionally, the gas flow-through region further comprises a suction pump 16 for pumping the gas to be measured into the ionization region 15.
Optionally, the gas flow-through region further comprises an exhaust pump 17 for exhausting the gas to be measured out of the ionization region 15.
In this embodiment, the air pump can be divided into an air pump 16 and an air exhaust pump 17 according to the installation position, the air pump 16 is used for pumping the gas to be measured into the ionization region 15, and the air exhaust pump 17 is used for exhausting the gas to be measured out of the ionization region 15. On the same photoionization sensor, the purpose of an active pumping mode can be achieved only by arranging one of the suction pump 16 and the exhaust pump 17, and the suction pump 16 and the exhaust pump 17 can also be installed at the same time, which is not limited herein.
Optionally, the output module 5 includes a logic judgment module 18 and an information output module 19;
the logic judgment module 18 is connected to the amplifying circuit 4, and the logic judgment module 18 is configured to analyze a signal processed by the amplifying circuit 4;
the logic judgment module 18 is connected to the information output module 19, and the information output module 19 is configured to generate gas type analysis data indicating the gas to be detected.
In this embodiment, the logic determination module 18 and the information output module 19 are mainly used for performing logic determination on the electrical signal sent by the amplifying circuit 4.
Referring to fig. 6 and 7, the following describes the placement positions of the ion current receiving electrode pair 3 and the uv window 7:
optionally, the ion current receiving electrode pair 3 is disposed in parallel with the ultraviolet light window 7.
Optionally, the ion current receiving electrode pair 3 is disposed perpendicular to the ultraviolet light window 7.
Currently, in the photoionization sensor, the ion current receiving electrode pair 3 and the ultraviolet light window 7 are installed in different positions. Fig. 6 shows the design that the positive and negative electrodes are parallel to the ultraviolet light emitting direction, fig. 7 shows the design that the positive and negative electrodes are perpendicular to the ultraviolet light emitting direction, and when the design mode of fig. 7 is adopted, the electrode close to the ultraviolet light window 7 is provided with a light through hole, so that the ultraviolet light can reach between the two electrodes through the electrodes. In fig. 6 and 7, the uv light source is sent through the uv window 7, emitting uv light in a direction parallel upwards. The ultraviolet light source of the common photoionization sensor is realized by plasma luminescence of rare gas, the ultraviolet light is emitted through a transparent layer of the ultraviolet light source, and the light source of the common photoionization sensor is cylindrical at the end of the ultraviolet transparent layer. The purpose of the external light source is to ionize the gas molecules to be measured between the ionization regions 15. In fig. 6 and 7, the ion current receiving electrode pair 3 has positive and negative poles for generating an electric field to collect ionized gas molecular ions to be measured. In fig. 6, the direction of the gas flow in the ionization region 15 may be perpendicular to the paper surface, may enter the ionization region 15 through micro-pores on the ion current receiving electrode pair 3, may be perpendicular to the positive and negative electrodes of the ion current receiving electrode pair 3, or may flow from top to bottom or from bottom to top parallel to the direction of the ultraviolet light. In fig. 7, the positive and negative electrodes of the ionization region 15 may flow in parallel to the ion current receiving electrode pair 3, or in the paper, or in the ultraviolet direction, perpendicularly to the positive and negative electrode plates of the ion current receiving electrode pair 3.
In this embodiment, after it is measured that the ionization energy in the gas to be measured is smaller than the energy of the ultraviolet light emitted from a certain ultraviolet light window 7, the gas concentration of the type of gas to be measured can be calculated. The following description is made of the implementation steps:
when the high voltage power supply module 11 inputs a voltage V to the high voltage power supply conversion module 12, an ac signal is generated through an oscillation circuit in the high voltage power supply conversion module 12, and the signal is amplified by hundreds of times by a boost circuit in the high voltage power supply conversion module 12. The high-frequency ac voltage may excite the ultraviolet lamp module 1 filled with rare gas to emit ultraviolet light of a certain intensity. The ultraviolet light penetrates through an ultraviolet light window 7 made of different materials to emit ultraviolet light with different energies, organic and inorganic gas molecules are partially ionized by the ultraviolet light with different energies to generate ions, and the ions are collected by an ion current receiving electrode near a light source to form a weak current through a positive electrode plate and a negative electrode plate of the electrode 3. The current is amplified by the amplifying circuit 4 to finally generate analog output of a low-resistance voltage signal, the output module 5 analyzes, calculates and outputs data of the analog output of the low-resistance voltage signal, and therefore detection of gas molecules is completed, and gas molecular ions generated by ultraviolet light excitation are approximately in direct proportion to the concentration of the gas molecules, so that the concentration of the gas molecules can be determined under the condition of known gas types. From the steps, the photoionization sensor can detect the type of the gas in the gas to be detected and can calculate the concentration of the gas to be detected to a certain degree.
The specific steps of the photoionization sensor will be described in detail, and for the sake of example, a photoionization sensor using a dual uv window is taken as an example.
Referring to fig. 8 to 10, when the photoionization sensor using the dual uv windows is used, CaF is used respectively2Ultraviolet window and MgF of material2The ultraviolet light window of (1). CaF2Ultraviolet window and MgF of material2The ultraviolet light windows all generate an output voltage respectively corresponding to VcAnd VmSince the spectral components of the ultraviolet light are different on both sides (the wavelength and intensity are different, and even if the wavelength is the same, the transmittance of the ultraviolet light is different). The photoionization sensor generally uses Isobutene (IBE) to calibrate the relationship between the output voltage and the gas concentration, and for other gases, calibration Coefficients (CF) are used for conversion, and for the same gas, the CF values are different when the same gas is excited by different ultraviolet wavelengths, and the specific conversion method is as follows:
Cgas to be measured＝CFGas to be measured×CIBE equivalent concentrationFormula one
For a certain gas to be detected, CaF2Window-side IBE equivalent concentration, i.e., IBE equivalent gas concentration (C) with ionization energy (IP) not exceeding 10.0eVc) And the output voltage (V)c) The calibration relation is as follows:
Cc＝fc(Vc) Formula two
For a certain gas to be detected, MgF2Window side IBE equivalent concentration, i.e., IBE equivalent gas concentration (C) with IP not exceeding 10.6eVm) With calibration of the output voltage (V)m) The relationship is as follows:
Cm＝fm(Vm) Formula three
If there are multiple gases in the gas to be measured, then in CaF2The CF of the gas with IP larger than 10.0eV is 0, the gas concentration less than or equal to 10.0eV and the C in the formula IIcThe relationship of (1) is:
similarly, at MgF2Concentration of gases having an IP per side of not more than 10.6eV and CmThe relationship of (1) is:
is when VcAnd VmWhen the maximum output voltage is not exceeded, the concentration of the substance with IP not higher than 10.0eV is calculated as Vc by using a formula II:
if the detected gas is known to be one, the CF value CF may be usedc1To CcCorrecting to calculate the concentration (C) of the measured substanceTarget) The concrete formula is as follows:
CTarget＝Cc·CFc1formula six
Combining the second formula with the seventh formula, the calculation formula of the gas concentration with the IP not higher than 10.0eV is:
CTarget＝Fc(Vc)·CFc1formula seven
IP concentration of 10.0-10.6 eV is expressed as VcAnd VmTaken together, when a gas having an IP higher than 10.0eV but not higher than 10.6eV is one and a gas concentration having an IP not higher than 10.0eV is also one, the formula is calculated in accordance with the above formula:
CTarget＝(Fm(Vm)-Fc(Vc)·CFc1/CFm1)·CFm2equation eight
Due to MgF2The side contains UV light of 10.0eV and 10.6eV, so VmThe value should be greater than or equal to VcThe value is obtained. When one side voltage output value is saturated, it should be VmValue saturation VcThe values are not saturated. At this time, the concentration of the substance having IP not higher than 10.0eV is still VcCalculated, while MgF2Side saturation indicates that the concentration of the IP in the material of 10.0-10.6 eV exceeds MgF2Lateral maximal detectable equivalent IBE concentration and corresponding CaF2And measuring the converted difference of the gas. When the voltage output values at two sides are saturated, the concentration of the substance with IP not higher than 10.0eV exceeds CaF2The maximum detectable equivalent IBE concentration, and the material concentration of IP at 10.0-10.6 eV can not be calculated.
Referring to FIG. 8, the IBE is detected by the double UV window photoionization sensor, and the IP value of isobutylene is 9.43eV, so CaF2And MgF2The windows may all enable IBE to generate ions. FIG. 8 shows the response of a dual UV window photoionization sensor to 25ppm IBE (balance gas nitrogen) due to MgF2The lateral ultraviolet light transmission capacity is larger, the energy is stronger, so the same IBE concentration MgF2The ion current generated by the side is larger, and the signal is stronger. The ratio of signal intensities on both sides of IBE of the same concentration is about 4.5 times.
Referring to FIG. 9, the photo-ionization sensor with two UV windows detects ammonia with an IP value of 10.18V, so MgF is only used2The window can make ammonia gas produce ions, and CaF2The window is not effective in generating ions. FIG. 9 shows the response of a dual window PID device to 20ppm ammonia (balance gas is nitrogen) due to MgF2The side UV light contains 10.6eV UV light, so MgF2The side generates a significant response signal, and CaF2The side does not generate any signal. It was thus assumed that the gas to be measured did not contain a gas having an IP value lower than 10.0eV, and contained a gas having an ionization energy exceeding 10.0eV and not exceeding 10.6 eV.
Referring to FIG. 10, the double UV window photoionization sensor detects a mixture of ammonia and Isobutylene (IBE) having an IP value of 9.43eV and an IP value of 10.18V, so that only MgF is present2The window can make ammonia and IBE produce ions, while CaF2The window is only effective for IBE to generate ions. FIG. 10 shows the response of a dual window PID device to a mixture of 20ppm ammonia and 25ppm IBE (balance nitrogen), due to MgF2The side UV light contains 10.6eV UV light, so MgF2The side generates a significant response signal, and CaF2The signal of the IBE only side, the ratio of the signals of both sides was observed to be 6.2, which is more than the ratio of the IBE only side (4.5 according to fig. 8), and it was considered that the gas mixture contained the gas having the IP value exceeding 10.0 eV. It was thus assumed that the gas to be measured contained a gas having an IP value of less than 10.0eV (isobutylene) and a gas having an ionization energy of more than 10.0eV and not more than 10.6eV (ammonia).
From the above examples, it can be seen that in the photoionization sensor with double ultraviolet windows, multiple gases in the gas to be detected can be detected, and the classification information of the gas to be detected based on the ionization energy is increased. And the ultraviolet light source is shared, the ultraviolet light source, the gas concentration, the purity and the like of each ultraviolet light window are almost the same, so that the detection of different gas types is realized, and the classification capability of the photoionization sensor in the detection of gases with different ionization energies is improved.
In the present application, the terms "upper", "lower", "left", "right", "front", "rear", "top", "bottom", "inner", "outer", "middle", "vertical", "horizontal", "lateral", "longitudinal", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are used only for explaining relative positional relationships between the respective members or components, and do not particularly limit specific mounting orientations of the respective members or components.
Moreover, some of the above terms may be used to indicate other meanings besides the orientation or positional relationship, for example, the term "on" may also be used to indicate some kind of attachment or connection relationship in some cases. The specific meaning of these terms in this application will be understood by those of ordinary skill in the art as appropriate.
Furthermore, the terms "mounted," "disposed," "provided," "connected," and "connected" are to be construed broadly. For example, it may be a fixed connection, a removable connection, or a unitary construction; can be a mechanical connection, or an electrical connection; may be directly connected, or indirectly connected through intervening media, or may be in internal communication between two devices, elements or components. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art as appropriate.
In addition, the structures, the proportions, the sizes, and the like, which are illustrated in the accompanying drawings and described in the present application, are intended to be considered illustrative and not restrictive, and therefore, not limiting, since those skilled in the art will understand and read the present application, it is understood that any modifications of the structures, changes in the proportions, or adjustments in the sizes, which are not necessarily essential to the practice of the present application, are intended to be within the scope of the present disclosure without affecting the efficacy and attainment of the same.
Claims (10)
1. A photoionization sensor for differentiating gas types, comprising:
the device comprises an ultraviolet lamp module, a sensor main body, an ion current receiving electrode pair, an amplifying circuit and an output module;
the sensor body is provided with a gas circulation area and an information processing area;
the ultraviolet lamp module is arranged in the gas circulation area and is used for emitting ultraviolet light after the ultraviolet lamp module generates an ultraviolet light source;
at least two ion current receiving electrode pairs are arranged in the gas circulation area, the ion current receiving electrode pairs are placed in front of the ultraviolet light window, and the ion current receiving electrode pairs are used for receiving signals generated when gas to be detected is ionized;
at least two amplifying circuits are installed in the information processing area, the ion current receiving electrode pairs are connected with the amplifying circuits, and the amplifying circuits are used for processing signals collected by the ion current receiving electrode pairs;
the output module is arranged in the information processing area, connected with the amplifying circuit and used for receiving and generating analysis data for distinguishing the gas to be detected based on the ionization energy threshold according to the signals processed by the amplifying circuit.
2. The photoionization sensor of claim 1 wherein the ultraviolet lamp module includes an alternating voltage module, an ultraviolet light window, a pair of ultraviolet excitation electrodes, an ultraviolet lamp body, and a working gas;
the ultraviolet lamp main body contains the working gas and emits ultraviolet light under the excitation of the ultraviolet excitation electrode pair;
the ultraviolet lamp main body is provided with at least two ultraviolet light windows, and after the ultraviolet light emitted by the working substance passes through the ultraviolet light windows, the spectral components emitted by each ultraviolet light window are different;
the ultraviolet excitation electrode pair is arranged on the ultraviolet lamp main body and used for exciting the working gas to generate an ultraviolet light source;
the alternating voltage module is connected with the ultraviolet excitation electrode pair and used for providing high-voltage alternating voltage for the ultraviolet excitation electrode pair.
3. The photoionization sensor of claim 2 wherein the alternating voltage module comprises a high voltage power module and a high voltage power conversion module;
the high-voltage power supply module is connected with the high-voltage power supply conversion module;
the high-voltage power supply conversion module is connected with the ultraviolet excitation electrode pair and used for providing electric energy for the ultraviolet excitation electrode pair.
4. The photoionization sensor of claim 2 wherein the ultraviolet lamp module further includes a gas adsorbent;
the ultraviolet lamp module comprises the gas adsorbent, and the gas adsorbent is used for adsorbing impurity gas in the ultraviolet lamp module.
5. The photoionized photoionization sensor of any one of claims 1 to 4 wherein the gas flow region includes a gas inlet, a gas outlet, and an ionization region;
the gas inlet is arranged on the sensor main body, the gas to be detected enters the ionization region through the gas inlet, and the gas to be detected is ionized in the ionization region;
the gas vent set up in on the sensor main part, the gas vent is used for with the gas that awaits measuring is taken out ionization region.
6. The photoionization sensor of claim 5 wherein the gas flow region further includes a suction pump for drawing the gas to be measured into the ionization region.
7. The photoionization sensor of claim 5 wherein the gas flow region further includes an exhaust pump for exhausting the gas to be measured from the ionization region.
8. The photoionization sensor of any one of claims 1 to 4 wherein the pair of ion current receiving electrodes is positioned parallel to the UV window.
9. The photoionization sensor of any one of claims 1 to 4 wherein the pair of ion current receiving electrodes are positioned perpendicular to the UV window.
10. The photoionization sensor of any one of claims 1 to 4 wherein the output module includes a logic determination module and an information output module;
the logic judgment module is connected with the amplifying circuit and is used for analyzing the signal processed by the amplifying circuit;
the logic judgment module is connected with the information output module, and the information output module is used for outputting and distinguishing analysis data of the gas to be detected based on an ionization energy threshold.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114487190A (en) * | 2022-01-25 | 2022-05-13 | 南京信息工程大学 | Medical human body exhaled VOC gas detection device based on optical PID sensor |
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2021
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114487190A (en) * | 2022-01-25 | 2022-05-13 | 南京信息工程大学 | Medical human body exhaled VOC gas detection device based on optical PID sensor |
| CN114487190B (en) * | 2022-01-25 | 2023-10-03 | 南京信息工程大学 | Medical human body exhale VOC gas detection device based on light PID sensor |
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