A PID sensor and a VOCs concentration measurement method

Abstract

The present invention discloses a PID sensor and a method for measuring the concentration of VOCs, wherein the PID sensor includes a violet light source and a measuring chamber, wherein the violet light source is arranged above a light-transmitting hole at the top of the measuring chamber. An air inlet is arranged on one side of the ionization region, and an air outlet is arranged on the other opposite side; a plurality of positive and negative electrode pairs are arranged at the bottom of the measuring chamber, and the positive and negative electrode pairs are respectively connected to a signal amplifier and a pre-charge power supply. The embodiment of the present application uses a plurality of positive and negative electrode pairs to absorb ions ionized in the ionization region, and determines the degree of ionization of the ions and the concentration of VOCs by detecting the potential difference between the positive electrode and the negative electrode; and identifies ions of different masses and ions with different charges through the potential difference between the positive and negative electrode pairs in the upstream region and the downstream region, thereby determining the compound ion components of VOCs. The present application can effectively improve the measurement accuracy of VOCs and improve the material differentiation during measurement, and the present application is applicable to the field of gas optical detection.

Description

Technical Field

[0001] The present application relates to the field of gas optical detection, and in particular to a PID sensor and a VOCs concentration measurement method. Background Art

[0002] As people's safety awareness and environmental awareness are further enhanced, the monitoring of atmospheric environment has become an important topic. Among them, VOCs (volatile organic compounds) monitoring is an important part. Since the volatilization of some toxic VOCs can cause serious harm to animals and plants, the VOCs content has become an important indicator for evaluating air quality. In the related art, large-scale VOCs detection machines are expensive and troublesome to arrange. Therefore, in actual air monitoring work, small PID (Photo Ionization Detectors) sensors are often used to measure VOCs concentration. PID sensors have the advantages of fast detection speed and no damage to the detection gas. However, at present, most PID sensors can only measure the total amount of VOCs in the gas. However, VOCs is a general term for a class of volatile organic compounds. The PID sensors in the related art cannot record the characteristics of VOCs in the gas, and it is difficult to distinguish different types of VOCs. This is undoubtedly unfavorable for subsequent atmospheric data analysis and even atmospheric environmental governance. Summary of the invention

[0003] The present application aims to solve at least one of the technical problems in the related art to a certain extent. To this end, the present application proposes a PID sensor and a VOCs concentration measurement method. The PID sensor proposed in the present application is used for gas detection to determine the concentration of VOCs and the compound ion components of VOCs.

[0004] In the first aspect, the embodiment of the present application provides a PID sensor, comprising: an ultraviolet light source, a measuring chamber; a light-transmitting hole is provided on the top of the measuring chamber, and the ultraviolet light source is provided above the light-transmitting hole; an air inlet is provided on one side of the ionization region of the measuring chamber, and an air outlet is provided on the other side opposite to the ionization region; a plurality of positive and negative electrode pairs are provided at the bottom of the upstream region, the bottom of the ionization region, and the bottom of the downstream region, and the positive and negative electrode pairs are connected to a signal amplifier; the positive and negative electrode pairs include a positive electrode and a negative electrode, the positive electrode is connected to the positive input terminal of the signal amplifier, and the negative electrode is connected to the negative input terminal of the signal amplifier; the positive electrode is connected to the positive electrode of the pre-charge power supply, and the negative electrode is connected to the negative electrode of the pre-charge power supply. Wherein, the ionization region is located below the light-transmitting hole, and the ionization region is the maximum region that the ultraviolet light source in the measuring chamber can irradiate; wherein, the upstream region refers to the region between the ionization region and the air inlet; wherein, the downstream region refers to the region between the ionization region and the air outlet.

[0005] Optionally, the positive and negative electrode pairs are arranged on a substrate; a constant voltage electrode plate is also arranged on the substrate; the constant voltage electrode plate includes a positive plate and a negative plate; the positive plate is connected to the positive electrode of the constant voltage power supply; the negative plate is connected to the negative electrode of the constant voltage power supply.

[0006] Optionally, a movable light shielding plate is arranged above the light-transmitting hole.

[0007] Optionally, the gas inlet is provided with a gas controller, and the gas controller is used to control the gas flow rate.

[0008] Optionally, the air inlet is further provided with a gas filter, and the gas filter is connected to the gas controller.

[0009] Optionally, the ultraviolet light source is a vacuum ultraviolet light source, and the power of the ultraviolet light source is 30W to 200W.

[0010] In the second aspect, an embodiment of the present application provides a VOCs concentration measurement method, comprising: using the pre-charging power supply to pre-charge the positive and negative electrode pairs, and cutting off the pre-charging power supply after the pre-charging is completed; when the ultraviolet light source is preheated, introducing test gases with different flow rates from the air inlet to the measuring chamber multiple times; obtaining the voltage difference of the signal amplifier corresponding to each of the positive and negative electrode pairs; determining the change in the potential difference of the positive and negative electrode pairs during the discharge process based on the voltage difference; performing algorithmic analysis on the change in the potential difference to determine the VOCs concentration in the test gas and the compound ion components of the VOCs.

[0011] Optionally, the voltage difference change process data is subjected to an algorithmic analysis to determine the compound ion components and VOCs concentration in the test gas, including: determining the natural discharge curve of any of the positive and negative electrode pairs at different gas flow rates; determining the irradiated discharge curve of any of the positive and negative electrode pairs at different gas flow rates; and determining the VOCs concentration and the content of different compound ion components in the test gas based on the natural discharge curve and the irradiated discharge curve.

[0012] Optionally, the algorithm analysis of the voltage difference to determine the compound ion components and VOCs concentration in the test gas includes: sampling signals of a number of the signal amplifiers according to the spatial distribution of the signal amplifiers to determine a number of signal sampling values; obtaining calibrated sampling values ​​of the VOCs; determining ion mass and charge information according to a number of signal sampling values ​​in the downstream area and the calibrated sampling values; and determining the compound ion components of the VOCs according to the ion mass and charge information.

[0013] The beneficial effects of the embodiments of the present application are as follows: the PID sensor provided in the embodiments of the present application includes a violet light source and a measuring chamber, a light-transmitting hole is provided on the top of the measuring chamber, and the violet light source is provided above the light-transmitting hole; the ionization area is located below the light-transmitting hole, and the ionization area is the maximum area that the violet light source in the measuring chamber can irradiate. An air inlet is provided on one side of the ionization area, and an air outlet is provided on the other side opposite to the ionization area; a plurality of positive and negative electrode pairs are provided at the bottom of the upstream area, the bottom of the ionization area, and the bottom of the downstream area, and the positive and negative electrode pairs are connected to the signal amplifier; the positive and negative electrode pairs include a positive electrode and a negative electrode, the positive electrode is connected to the positive input terminal of the signal amplifier, and the negative electrode is connected to the negative input terminal of the signal amplifier; the positive electrode is connected to the positive electrode of the pre-charge power supply, and the negative electrode is connected to the negative electrode of the pre-charge power supply. The embodiment of the present application uses multiple positive and negative electrode pairs to absorb the ions ionized in the ionization area, and determines the degree of ionization and the concentration of VOCs by detecting the potential difference between the positive electrode and the negative electrode; and identifies ions of different masses and ions with different charges through the potential difference between the positive and negative electrode pairs in the upstream and downstream areas, thereby determining the compound ion components of VOCs. The embodiment of the present application can not only collect signals from multiple positive and negative electrode pairs to improve the measurement accuracy of VOCs concentration, but also determine the compound ion components of VOCs, effectively improving the material discrimination of VOCs measurement, and has a positive impact on subsequent atmospheric data processing and even atmospheric environmental governance. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The accompanying drawings are used to provide further understanding of the technical solution of the present application and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the technical solution of the present application and do not constitute a limitation on the technical solution of the present application.

[0015] Figure 1 is a first schematic diagram of a PID sensor provided in an embodiment of the present application;

[0016] Figure 2 is a second schematic diagram of a PID sensor provided in an embodiment of the present application;

[0017] Figure 3 is a schematic diagram of a substrate provided in an embodiment of the present application;

[0018] Figure 4 A flowchart of the steps of the VOCs concentration measurement method provided in the embodiment of the present application;

[0019] Figure 5 A potential difference variation diagram of a positive and negative electrode pair is provided for an embodiment of the present application. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0021] It should be noted that, although the functional modules are divided in the system schematic diagram and the logical order is shown in the flowchart, in some cases, the steps shown or described may be performed in a different order than the module division in the system or the order in the flowchart. The terms "first", "second", etc. in the specification, claims and the above drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence.

[0022] The embodiments of the present application are further described below in conjunction with the accompanying drawings.

[0023] refer to Figure 1 , Figure 1It is the first schematic diagram of the PID sensor provided in the embodiment of the present application. The PID sensor 100 includes a violet light source 110 and a measuring chamber 120. A light-transmitting hole 121 is provided on the top of the measuring chamber. The violet light source is provided above the light-transmitting hole. When the violet light source is turned on, ultraviolet rays are irradiated from the light-transmitting hole to the inside of the measuring chamber. The maximum area in the measuring chamber irradiated by the violet light source is called the ionization area 130. On one side of the ionization area, the measuring chamber is provided with an air inlet 122, and on the other side opposite to the ionization area, an air outlet 123 is provided. Based on the ionization area, the area between the ionization area and the air inlet is the upstream area, which is indicated by the reference numeral 140; the area between the ionization area and the air outlet is the downstream area, which is indicated by the reference numeral 150. A plurality of positive and negative electrode pairs 160 are arranged at the bottom of the upstream area, the bottom of the ionization area and the bottom of the downstream area, and the positive and negative electrode pairs are connected to the signal amplifier; the positive and negative electrode pairs include a positive electrode and a negative electrode, the positive electrode is connected to the positive input terminal of the signal amplifier, and the negative electrode is connected to the negative input terminal of the signal amplifier; the positive electrode is connected to the positive electrode of the pre-charging power supply, and the negative electrode is connected to the negative electrode of the pre-charging power supply. Figure 1 The positive electrode, negative electrode signal amplifier and pre-charging power supply are not drawn in the figure, and the connection of the positive and negative electrode pairs will be explained in detail below in conjunction with other drawings.

[0024] In the related art, low-power PID sensors use weak ultraviolet light to ionize the test gas. Because of its low light emission and weak ionization effect, the sensor can easily stop working due to contamination. In the embodiment of the present application, a vacuum ultraviolet light source with a power of 30W to 2000W is used as the ultraviolet light source. The power is relatively large, which can ensure that the vacuum ultraviolet light flux with a photon energy of 10.6eV is large enough, so that it will not fail due to slight contamination and cannot stop working, which is conducive to improving the life of the PID sensor.

[0025] like Figure 1 As shown in the direction, there is an air inlet on the left side of the ionization area and an air outlet on the right side. The flow direction of the gas in the measurement chamber is from left to right. The gas to be tested enters the measurement chamber from the air inlet. Since the PID sensor is a non-destructive detection device for gas, after the gas is ionized, the ions can also combine with positive or negative charges to be reduced to gas, and the reduced gas is discharged from the measurement chamber through the air outlet. If the gas flow process in the PID sensor is described from the perspective of the three areas in the measurement chamber, it is: the test gas enters the measurement chamber from the air inlet, passes through the upstream area, is ionized in the ionization area, and then the ions are reduced to gas in the ionization area or the downstream area, and discharged from the measurement chamber through the air outlet.

[0026] It is understandable that the embodiment of the present application does not impose any specific restrictions on the shape of the light-transmitting hole, nor does it impose any specific restrictions on the distance from the ultraviolet light source to the light-transmitting hole. Figure 1The region labeled 130 in the figure represents the ionization region, but the ionization region in the actual PID sensor may also have other shapes.

[0027] The PID sensor provided in the embodiment of the present application uses multiple positive and negative electrode pairs to absorb ions ionized in the ionization area, and determines the degree of ionization and the concentration of VOCs by detecting the potential difference between the positive electrode and the negative electrode; and identifies ions of different masses and different charges through the potential difference between the positive and negative electrode pairs in the upstream and downstream areas, thereby determining the compound ion components of VOCs. The embodiment of the present application can not only collect signals from multiple positive and negative electrode pairs to improve the measurement accuracy of VOCs concentration, but also determine the compound ion components of VOCs, effectively improving the material discrimination of VOCs measurement, and has a positive impact on subsequent atmospheric data processing and even atmospheric environmental governance.

[0028] In some embodiments, Figure 1 As shown, the PID sensor is also provided with a movable shading plate 170, which is arranged above the light-transmitting hole. The shading plate can open or cover the light-transmitting hole by means of rotation, translation, or other moving methods. When the sensor is not performing gas testing, the shading plate is used to cover the light-transmitting hole. When the sensor needs to be used, the preheating of the ultraviolet light source is completed first. When the ultraviolet light source can provide stable light, the shading plate is removed to allow the light to enter the measuring room. The movable shading plate helps to maintain a stable measuring environment in the measuring room, and also helps to maintain a stable light source, reducing the inconsistency of ionization caused by unstable light and the reduction of data reliability.

[0029] In some embodiments, Figure 1 As shown, the PID sensor is also provided with a substrate 180, and the positive and negative electrode pairs mentioned above are arranged on the substrate. The signal sensor and the pre-charging power supply can also be arranged on the substrate to facilitate the layout of multiple lines and the collection of signals.

[0030] In some embodiments, Figure 1 As shown, the PID sensor is also provided with a gas controller 190, which is provided at the inlet of the measuring chamber. The gas controller controls the gas flow rate entering the measuring chamber, and the ion drift speed is controlled by controlling the gas flow rate, thereby helping to calculate the compound ion components of VOCs. The content of controlling the gas flow rate will be explained in more detail below.

[0031] In some embodiments, Figure 1As shown, the PID sensor is also provided with a gas filter 1100, which is connected to a gas controller. The test gas first passes through the gas filter to filter out impurities such as dust, and the filtered test gas is transported to the measurement chamber at a speed controlled by the gas controller. Since the test gas has been filtered, large particles such as dust are unlikely to enter the measurement chamber and cause pollution; in addition, the gas discharged from the measurement chamber can also be directly used for subsequent other analysis and detection without filtering, which helps to simplify the operation process of gas detection.

[0032] The flexible combination of the components in the above embodiments helps to improve at least one of the measurement accuracy and service life of the PID sensor in the embodiments of the present application. Figure 2 , Figure 2 This is a second schematic diagram of the PID sensor provided in an embodiment of the present application. Figure 2 and Figure 1 All represent the PID sensors proposed in the embodiments of the present application, so Figure 2 Used in Figure 1 The labels of the various components in . Figure 2 As shown, the test gas passes through the gas filter 1100 and the gas controller 190 and enters the measurement chamber from the air inlet 121. When the gas passes through the ionization area 130, the gas is ionized under ultraviolet light, and the ions are adsorbed by the positive and negative electrode pairs 160 arranged on the bottom substrate 180. The ions are then combined with the positive or negative charges on the positive and negative electrode pairs, reduced to gas, and discharged from the measurement chamber through the air outlet to complete the gas measurement.

[0033] In some embodiments, Figure 2 As shown, the sensor PID is also provided with a constant voltage electrode plate, which includes a positive plate 210 and a negative plate 220; the positive plate is connected to the positive electrode of the constant voltage power supply; and the negative plate is connected to the negative electrode of the constant voltage power supply. Figure 2 The constant voltage power supply is not shown in the figure. The connection method of the constant voltage electrode plate will be described in the following with other figures. The constant voltage motor plate adds a high voltage bias electric field to the measurement chamber, such as Figure 2 As shown in the direction, the positive electrode and negative electrode in the positive and negative electrode pair are arranged in parallel, and the direction in the positive and negative electrode pair is that the positive electrode is at the top and the negative electrode is at the bottom. Then the positive plate is arranged at the top, in the same direction as the positive electrode, so that as many negatively charged ions as possible are attracted to the positive electrode after ionization. Similarly, the negative plate is arranged at the bottom, in the same direction as the negative electrode. Then the ions generated after the gas is ionized are attracted by the bias electric field generated by the constant voltage motor plate, and move to the positive plate and the negative plate respectively, and are adsorbed by the positive electrode and the negative electrode.

[0034] In some embodiments, Figure 2As shown, the positive and negative electrode pairs are arranged in a matrix on the substrate. In the process of ions being adsorbed by the positive and negative electrode pairs and detecting signals, the signals of the signal amplifiers connected to the multiple positive and negative electrode pairs at symmetrical positions on the substrate can be collected as much as possible, so that the collected data can be used as a reference for each other, which helps to improve the reliability of the data. In addition, since the gas flows in the measurement chamber, the regularly arranged positive and negative electrode pairs can minimize the impact of the positive and negative electrode pairs on the gas flow, which also helps to improve the reliability of the collected data.

[0035] Reference Figure 3 , Figure 3 is a schematic diagram of a substrate provided in an embodiment of the present application, such as Figure 3 As shown, a constant voltage electrode plate, a positive and negative electrode pair, a signal amplifier 300, a constant voltage power supply 310 and a pre-charge power supply 320 are provided on the substrate. The positive pole of the pre-charge power supply is connected to the positive electrode 330, and the negative pole of the pre-charge power supply is connected to the negative electrode 340. The positive input terminal of the signal amplifier is connected to the positive electrode, and the negative input terminal of the signal amplifier is connected to the negative electrode. The positive pole of the constant voltage power supply is connected to the positive plate 210, and the negative pole of the constant voltage power supply is connected to the negative plate 220. After the pre-charge power supply is charged, the power supply will be disconnected. The constant voltage power supply is always powered on when the PID sensor is working. When the PID sensor is working, the signal is collected from the input end of each signal sensor for data analysis.

[0036] Reference Figure 4 , Figure 4 The following is a flow chart of the method for measuring VOCs concentration provided in an embodiment of the present application, which includes but is not limited to steps S400-S430:

[0037] S400, pre-charging the positive and negative electrode pairs using a pre-charging power supply, and cutting off the pre-charging power supply after the pre-charging is completed;

[0038] Specifically, the positive and negative electrode pairs are charged with a pre-charge power supply before the gas test. After the charging is completed, the positive and negative electrode pairs can better maintain the potential. In addition, by monitoring the potential of the positive and negative electrode pairs, the charging and discharging process of the pre-charge power supply can be fully measured, which helps to more accurately reflect the ionization process.

[0039] S410, when the purple light source is preheated, a test gas with different flow rates is introduced into the measuring chamber from the air inlet for multiple times;

[0040] Specifically, in order to provide stable light, the ultraviolet light source needs to be preheated. When the ultraviolet light source is preheated, the test gas is introduced into the measurement chamber from the air inlet. If a gas filter is provided at the air inlet, the filtered test gas is introduced into the measurement chamber.

[0041] In addition, in some embodiments, if the PID sensor used includes a gas controller, the flow rate of the test gas can be adjusted according to the gas controller. By changing the test gas flow rate multiple times, multiple sets of test data can be obtained, which helps to reduce test errors and improve the test accuracy of the VOCs concentration testing method of the embodiment of the present application.

[0042] S420, obtaining the voltage difference of the signal amplifier corresponding to each positive and negative electrode pair, and determining the change of the potential difference of the positive and negative electrode pairs during the discharge process according to the voltage difference;

[0043] Specifically, when the gas passes through the ionization area, it is ionized by ultraviolet light. Part of the ionized ions reach the upstream area in the upwind direction due to thermal diffusion, part is adsorbed by the positive and negative electrode pairs in the ionization area, and part drifts to the downstream area in the downwind direction with the airflow. The adsorption of the ions by the positive and negative electrode pairs will cause the voltage difference between the positive electrode and the negative electrode to change, and the signal amplifier will amplify the voltage difference. Therefore, the signal of each signal amplifier can be collected to obtain the voltage difference of each positive and negative electrode pair.

[0044] Furthermore, it can be understood that during the entire test process, the positive and negative electrode pairs are discharged, and the voltage difference of the positive electrode pairs can be collected multiple times, thereby obtaining the change in the potential difference of each positive and negative electrode pair during the discharge process.

[0045] S430, performing algorithm analysis on the change of the potential difference to determine the VOCs concentration and the compound ion components of the VOCs in the test gas;

[0046] Specifically, the voltage difference data of multiple signal amplifiers are obtained, and the changes in these potential differences are analyzed by algorithms, so that the concentration of VOCs in the test gas and the compound ion components of VOCs can be determined.

[0047] First, the concentration of VOCs in the test gas can be determined by the change in potential difference. Figure 5 , Figure 5 A potential difference change diagram of a positive and negative electrode pair is provided for the embodiment of the present application, such as Figure 5 As shown, the curve indicated by reference numeral 500 is the pre-charge curve of the current positive and negative electrode pair, reference numeral 510 indicates the irradiation discharge curve of the current positive and negative electrode pair under ultraviolet light irradiation at a certain fixed gas flow rate when the PID sensor is working normally, and reference numeral 520 indicates the natural discharge curve of the current positive and negative electrode pair without ultraviolet light irradiation. It can be understood that Figure 5 The three curves can be obtained by detecting the signals of the signal amplifier connected to the positive and negative electrode pairs. Figure 5The shaded area 530 between the natural discharge curve and the irradiated discharge curve is the charge integral of the charged ions reaching the current positive and negative electrode pairs. Based on the principle of PID sensor, volatile organic compounds such as VOCs will be ionized under the irradiation of ultraviolet light source, but relatively stable gas components such as oxygen and nitrogen will not be ionized. Therefore, it can be understood that the charge integral represented by the shaded area is positively correlated with the total amount of VOCs in the test gas. After more analysis and calibration of the signal amplifier output signal, the VOCs concentration in the test gas can be determined.

[0048] It is understandable that in order to obtain multiple sets of test data, the gas flow rate can be adjusted multiple times through the gas controller to obtain multiple irradiation discharge curves of the same positive and negative electrode pair at different gas flow rates, thereby obtaining multiple sets of test data, which is conducive to improving the accuracy of the test.

[0049] Secondly, the compound ion components of VOCs in the test gas can be determined by the change in potential difference. Figure 4 Step S420 in the method mentioned that part of the ions ionized by the test gas reaches the upstream area in the upwind direction with thermal diffusion, part of them is adsorbed by the positive and negative electrode pairs in the ionization area, and part of them drifts to the downstream area in the downwind direction with the airflow. Under the premise of similar charge, the greater the mass of the ion, the greater the momentum, and it will reach farther in the downstream area along the airflow. Moreover, the charge carried by different ions is also different, and the change in the potential difference of the corresponding positive and negative electrode pairs will also be different. Therefore, according to the spatial distribution of the signal amplifier, signal sampling is performed on several signal amplifiers in the upstream and downstream areas to determine several signal sampling values; according to the signal sampling value and the pre-acquired calibration sampling value, the voltage difference of the positive and negative electrode pairs in the upstream area and the voltage difference of the positive and negative electrode pairs in the downstream area are combined to obtain the ion mass information related to pure momentum; and the ion ion degree can be determined by combining the voltage difference of the positive and negative electrode pairs in the ionization area to determine the charge information of the ion, and the measurement value of each type of compound in VOCs can be obtained after the calibration algorithm is processed, that is, the compound ion component of VOCs can be determined.

[0050] It can be understood that the calibration sampling value mentioned in the embodiment of the present application is the standard sampling value of the signal of the index gas in the PID sensor provided in the embodiment of the present application. The standard gas contains VOCs of various components, and the accurate components of each type of VOCs are known. During factory calibration, the standard gas is passed into the PID sensor of the embodiment of the present application, and the standard gas is measured by the VOCs concentration measurement method provided in the embodiment of the present application. The test data is analyzed by an algorithm and the standard sampling values ​​collected by each positive and negative electrode pair are obtained. These standard sampling values ​​reflect the specific ionization conditions of different types of VOCs in the PID sensor of the present application, and the specific positions where they will be adsorbed by the positive and negative electrode pairs. Therefore, the standard sampling values ​​can be used as reference data for the signal sampling values ​​collected during normal use of the PID sensor.

[0051] It should be noted that the embodiment of the present application does not impose any specific restrictions on the algorithm for analyzing and processing the data collected from the PID sensor, and the data can be analyzed and processed using a suitable algorithm in the relevant technology.

[0052] In some embodiments, if the PID sensor in the embodiment of the present application is provided with an airflow controller, the airflow speed can be changed by the airflow controller to measure the test gas multiple times. In the related art, the PID sensor for VOCs measurement can measure diffuse or flowing airflows, and in order to achieve controllable ion drift speed, the embodiment of the present application sets an airflow controller to control the speed of the test gas. By changing the airflow speed and measuring repeatedly multiple times, the reliability of the collected data is improved, which helps to improve the accuracy of distinguishing the ion components of VOCs compounds.

[0053] In summary, the PID sensor provided in the embodiment of the present application includes a violet light source and a measuring chamber, a light-transmitting hole is provided on the top of the measuring chamber, and the violet light source is provided above the light-transmitting hole; the ionization area is located below the light-transmitting hole, and the ionization area is the maximum area that the violet light source in the measuring chamber can irradiate. An air inlet is provided on one side of the ionization area, and an air outlet is provided on the other side opposite to the ionization area; a plurality of positive and negative electrode pairs are provided at the bottom of the upstream area, the bottom of the ionization area, and the bottom of the downstream area, and the positive and negative electrode pairs are connected to the signal amplifier; the positive and negative electrode pairs include a positive electrode and a negative electrode, the positive electrode is connected to the positive input terminal of the signal amplifier, and the negative electrode is connected to the negative input terminal of the signal amplifier; the positive electrode is connected to the positive electrode of the pre-charge power supply, and the negative electrode is connected to the negative electrode of the pre-charge power supply. In different embodiments, the PID sensor proposed in the embodiment of the present application also includes at least one or a combination of multiple components such as a substrate, a gas filter, a gas controller, and a constant voltage electrode plate.

[0054] The VOCs concentration measurement method provided in the embodiment of the present application uses the PID sensor provided in the embodiment of the present application, uses multiple positive and negative electrode pairs to absorb ions ionized in the ionization area, and determines the degree of ionization of the ions and the concentration of VOCs by detecting the potential difference between the positive electrode and the negative electrode; and identifies ions of different masses through the potential difference between the positive and negative electrode pairs in the upstream and downstream areas, thereby determining the compound ion components of VOCs.

[0055] Therefore, the embodiments of the present application can not only collect signals from multiple positive and negative electrode pairs to improve the measurement accuracy of VOCs concentration, but also determine the compound ion components of VOCs, effectively improve the material differentiation of VOCs measurement, and have a positive impact on subsequent atmospheric data processing and even atmospheric environment governance.

[0056] The above is a specific description of the preferred implementation of the present application, but the present application is not limited to the above-mentioned implementation mode. Technical personnel familiar with the field can also make various equivalent deformations or substitutions without violating the spirit of the present application. These equivalent deformations or substitutions are all included in the scope defined by the claims of the present application.

Claims

1. A method for measuring VOCs concentration, characterized in that: The VOCs concentration measurement method is implemented by a PID sensor; The PID sensor comprises: an ultraviolet light source and a measuring chamber; A light-transmitting hole is provided on the top of the measuring chamber, and the ultraviolet light source is arranged above the light-transmitting hole; An air inlet is provided on one side of the ionization region of the measuring chamber, and an air outlet is provided on the other side opposite to the ionization region; A plurality of positive and negative electrode pairs are arranged at the bottom of the upstream region, the bottom of the ionization region and the bottom of the downstream region, and the positive and negative electrode pairs are connected to a signal amplifier; The positive and negative electrode pair includes a positive electrode and a negative electrode, the positive electrode is connected to the positive input terminal of the signal amplifier, and the negative electrode is connected to the negative input terminal of the signal amplifier; The positive electrode is connected to the positive electrode of the pre-charging power supply, and the negative electrode is connected to the negative electrode of the pre-charging power supply; Wherein, the ionization area is located below the light-transmitting hole, and the ionization area is the maximum area that can be irradiated by the ultraviolet light source in the measuring chamber; Wherein, the upstream region refers to the region between the ionization region and the air inlet; Wherein, the downstream region refers to the region between the ionization region and the gas outlet; The VOCs concentration measurement method comprises the following steps: Using the pre-charging power supply to pre-charge the positive and negative electrode pairs, and cutting off the pre-charging power supply after the pre-charging is completed; When the ultraviolet light source is preheated, the test gas with different flow rates is introduced into the measuring chamber from the air inlet for multiple times; Acquire the potential difference of the signal amplifier corresponding to each of the positive and negative electrode pairs, and determine the change of the potential difference of the positive and negative electrode pairs during the discharge process according to the potential difference; Performing algorithm analysis on the potential difference change to determine the VOCs concentration and the compound ion components of the VOCs in the test gas; Determining the compound ion components of VOCs includes the following steps: Obtaining the calibrated sampling value of the VOCs; According to the spatial distribution of the signal amplifiers, signal sampling is performed on a plurality of signal amplifiers in an upstream area and a downstream area to determine a plurality of signal sampling values; According to the signal sampling value and the calibration sampling value, combined with the potential difference of the positive and negative electrode pairs in the upstream region and the potential difference of the positive and negative electrode pairs in the downstream region, the ion mass information related to pure momentum is obtained; The degree of ionization of the ions is determined based on the potential difference between the positive and negative electrode pairs in the ionization region, and the charge information of the ions is obtained; The compound ion components of the VOCs are determined based on the ion mass information and the charge information after being processed by a calibration algorithm.

2. The VOCs concentration measurement method according to claim 1, characterized in that: The positive and negative electrode pairs are arranged on a substrate; A constant voltage electrode plate is also provided on the substrate; The constant voltage electrode plate includes a positive electrode plate and a negative electrode plate; The positive plate is connected to the positive electrode of the constant voltage power supply; The negative electrode plate is connected to the negative electrode of the constant voltage power supply.

3. The VOCs concentration measurement method according to claim 1, characterized in that: A movable light shielding plate is arranged above the light transmission hole.

4. The VOCs concentration measurement method according to claim 1, characterized in that: The gas inlet is provided with a gas controller, and the gas controller is used to control the gas flow rate.

5. The VOCs concentration measurement method according to claim 4, characterized in that: The air inlet is also provided with a gas filter, and the gas filter is connected to the gas controller.

6. The VOCs concentration measurement method according to claim 1, characterized in that: The ultraviolet light source is a vacuum ultraviolet light source, and the power of the ultraviolet light source is 30W to 200W.

7. The VOCs concentration measurement method according to claim 1, characterized in that: The algorithm analysis of the potential difference change to determine the VOCs concentration and the compound ion components of the VOCs in the test gas includes: Determining a natural discharge curve of any of the positive and negative electrode pairs; Determining the irradiation discharge curve of any of the positive and negative electrode pairs at different gas flow rates; The VOCs concentration and the contents of different compound ion components in the test gas are determined according to the natural discharge curve and the irradiation discharge curve.

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