CN217766213U - Ionization chamber device for photoionization sensor - Google Patents

Abstract

An object of the utility model is to provide an ionization chamber structure improves photoionization sensor's sensitivity, stability, accuracy. The utility model discloses an ionization chamber device for photoionization sensor, including ultraviolet source and main part, the main part includes: the negative and positive plates are sequentially provided with a first insulating sheet, a capture plate and a second insulating sheet; the negative plate and the positive plate in the shell are arranged in a direction parallel to the irradiation direction of the ultraviolet light source, and the shell is provided with an air inlet which is intersected with the irradiation direction of the ultraviolet light source. The utility model has the advantages that: the light path direction of the ultraviolet lamp is parallel to the arrangement direction of the electrode plates, so that the problem of poor electric field uniformity caused by the fact that the areas of the positive and negative electrode plates need to be cut off is solved; 2, the positive and negative electrode plates only provide electric fields and do not participate in the capture of ions and electrons, thereby physically eliminating the interference of power supply signals.

Description

Ionization chamber device for photoionization sensor

Technical Field

The utility model relates to an environmental detection technical field specifically is gas detection surveys device for environmental detection.

Background

The photoionization sensor (PID) can detect volatile organic compounds or other toxic and harmful gases, can be embedded into a gas chromatograph to directly measure hydrocarbon compounds in the atmosphere, has wide application in the fields of indoor air quality detection, industrial process detection, drug and explosive detection, fire protection, counter terrorism, aerospace and the like, and also becomes a powerful tool for detecting pollution, environmental protection and the like in real time.

Photoionization sensors (PID) operate by photoionizing volatile organic compounds in an ionization chamber with a vacuum ultraviolet lamp. In practical operation, the sensitivity of the photoionization sensor is greatly limited by the performance of the ionization chamber, and therefore, the design quality of the ionization chamber of the PID is often the core problem of primary consideration in system design.

A portable photoionization sensor (PID) is a detection instrument that operates at normal temperature and pressure. The principle is as follows: two parallel electrodes are placed in the ionization chamber, and the electrodes are insulated from each other and are respectively connected to the positive and negative ends of a power supply high voltage. Gas is pumped into the ionization chamber through a vacuum pump or enters the ionization chamber in a diffusion mode, ultraviolet light is emitted by a detection lamp in the ionization chamber to bombard gas molecules, so that the gas molecules are ionized into positively charged ions and negatively charged electrons, and under the action of an electric field with an electrode plate, the ions and the electrons drift and impact towards two electrodes respectively to cause the induced charge quantity of the electrode plate to change, so that weak current capable of being detected is formed.

The existing commonly used photoionization sensor (PID) ultraviolet lamp light path direction is perpendicular to the electrode plate, and in order to ensure that a gas channel is smooth, a part needs to be cut off on the motor plate so as to allow gas to pass through, the uniformity of an electric field is damaged to a certain extent, at the moment, sensor data is obtained by detecting ionic current, and the sensitivity of the sensor is restricted. Secondly, the electric field polar plate participates in ion capture at the same time, and the I/U conversion resistor is easy to break down by the high voltage applied by the polar plate. Thirdly, in order to prevent the gas from oxidizing the electrode plates, all the electrode plates generally need to be plated with gold, which greatly increases the cost of the electrode plates and the complexity of the manufacturing process. Fourthly, the leading relationship between the voltage signal and the concentration of a photoionization sensor (PID) is influenced by the temperature and humidity, wherein the humidity has a large influence on the linearity.

SUMMERY OF THE UTILITY MODEL

An object of the utility model is to provide an ionization chamber structure improves photoionization sensor's sensitivity, stability, accuracy to reduction in production cost.

In order to solve the technical problem, the utility model discloses a realize through following technical scheme: an ionization chamber apparatus for a photoionization sensor, comprising an ultraviolet light source and a body, the body comprising: the negative and positive plates are sequentially provided with a first insulating sheet, a capture plate and a second insulating sheet; the negative plate and the positive plate in the shell are arranged in a direction parallel to the irradiation direction of the ultraviolet light source, and the shell is provided with an air inlet which is intersected with the irradiation direction of the ultraviolet light source.

Preferably, the capture plate is disposed closer to the negative or positive electrode plate.

Preferably, the air inlet is provided with a waterproof membrane.

Preferably, the capture board is provided with a data connection.

Preferably, a temperature sensor and a humidity sensor are arranged on the shell.

Compared with the prior art, the utility model has the advantages that:

the light path direction of the ultraviolet lamp is parallel to the arrangement direction of the electrode plates, so that the problem of poor electric field uniformity caused by the fact that the areas of the positive and negative electrode plates need to be cut off is solved;

2, the positive and negative electrode plates are separated by the insulating sheet, and only provide an electric field without participating in the capture of ions and electrons, thereby physically eliminating the interference of power signals. The positive and negative plates are completely isolated from the gas to be measured, so that oxidation resistance treatment is not needed, good corrosion resistance is also not needed, the performance is improved, and the cost is reduced.

3, the utility model discloses catch the board and can hug closely negative plate or the insulating separation blade of positive plate, can not catch the electron that the opposite side removed because of the electric field effect, further promote the ionization chamber sensitivity.

And 4, the direction of the air inlet is crossed and staggered with the irradiation direction of the ultraviolet light source, so that the air inlet and outlet directions can be flexibly designed, and the method can also be used for designing diffusion type and power air supply type photoionization sensors.

Drawings

FIG. 1 is a schematic diagram of the structure of positive and negative plates of the present invention;

fig. 2 is a schematic structural diagram of the external power type photoionization sensor of the present invention.

1-negative plate, 2-first insulating plate, 3-capture plate, 31-data connection, 4-second insulating plate, 5-positive plate, 6-ultraviolet light source light path direction, 7-air inlet direction, 8-ultraviolet light source, 9-shell, 91-air inlet, 92-temperature sensor, 93-humidity sensor.

Detailed Description

The embodiments of the present invention will be further explained with reference to the accompanying drawings:

as shown in fig. 1-2, the ionization chamber device for the photoionization sensor comprises an ultraviolet light source 8, a main body and a housing 9, wherein the main body comprises: the negative plate 1 and positive plate 5 are equipped with first insulating sheet 2, capture board 3 and second insulating sheet 4 between negative plate and the positive plate in proper order. The arrangement directions of the negative plate and the positive plate in the shell are parallel to the irradiation direction 6 of the ultraviolet light source, namely the light path direction of the ultraviolet lamp is parallel to the arrangement directions of the positive plate and the negative plate, so that the problem of poor electric field uniformity caused by the fact that the areas of the positive plate and the negative plate need to be cut off is solved. An air inlet 91 is formed in the shell, and the direction 7 of the air inlet is intersected with the irradiation direction of the ultraviolet light source. The design of the air inlet and outlet directions can be flexible, and the design method can also be used for designing diffusion type and power air supply type photoionization sensors.

The capture plate is disposed closer to the negative or positive electrode plate. Electrons on the other side moving under the action of the electric field cannot be captured, and the sensitivity of the ionization chamber is further improved. The air inlet is provided with a waterproof membrane, so that the function of well removing liquid water and other impurities is achieved. The capture board is equipped with data link portion, is equipped with temperature sensor 92 and humidity transducer 93 on the shell, and the relation of photoionization sensor's voltage signal and concentration presents better linearity when lower concentration, and has comparatively serious nonlinear problem when the high concentration, the utility model discloses a curve that the fitting corresponds when the high concentration, this is high to the requirement of removing the interference of ionization signal, and secondly because ionization chamber theory of operation limits, ionization signal detection can be influenced by temperature and humidity. The utility model discloses arrange temperature sensor and humidity transducer in the ionization chamber, do temperature and humidity compensation when actual measurement, increase that can be very big detects the accuracy.

In one embodiment, the positive and negative plates are symmetrically arranged in the ionization chamber, the thickness of the positive and negative plates is 0.5mm, and the distance between the positive and negative plates is 1.2mm. The insulating baffle plate is made of PTFE and has the thickness of 0.1mm. The capture plate participates in charge capture, is directly irradiated by ultraviolet light, and adopts stainless steel gold plating with the thickness of 0.1mm. The measured gas enters the ionization chamber from the right side, the ionization chamber is an external power type photoionization sensor, and the gas enters from the right side and exits from the left side. If the sensor is externally connected with a diffusion type photoionization sensor, the left outlet is sealed. Ultraviolet light irradiates from top to bottom, 250v of voltage is applied to the positive electrode and the negative electrode, and an electric field is formed between the positive electrode plate and the negative electrode plate. Organic matter gas in the gas to be detected can be excited and ionized, the excited ions move towards two stages of an electric field, the ions are captured by the capture plate, a voltage signal is obtained after I/U conversion, and the voltage signal is in direct proportion to the concentration of the organic matter in the gas, so that the concentration detection of the gas to be detected is realized.

The above description is only for the specific embodiment of the present invention, but the technical features of the present invention are not limited thereto, and any person skilled in the art can make changes or modifications within the scope of the present invention.

Claims (6)

1. An ionization chamber apparatus for a photoionization sensor, comprising an ultraviolet light source and a body, wherein the body comprises:

the negative and positive plates are sequentially provided with a first insulating sheet, a capture plate and a second insulating sheet;

the negative plate and the positive plate in the shell are arranged in a direction parallel to the irradiation direction of the ultraviolet light source, and the shell is provided with an air inlet, wherein the direction of the air inlet is intersected with the irradiation direction of the ultraviolet light source.

2. The ionization chamber arrangement for photoionization sensors of claim 1, wherein the capture plate is disposed closer to the negative or positive electrode plate.

3. The ionization chamber arrangement for photoionization sensors of claim 1, wherein the capture plate is provided in two pieces to form a dual circuit.

4. The ionization chamber device for photoionization sensors of claim 1, wherein the air inlet is provided with a waterproof diaphragm.

5. An ionization chamber arrangement for a photoionization sensor of claim 1, wherein the capture plate is provided with a data connection.

6. The ionization chamber assembly of claim 1 wherein said housing has a temperature sensor and a humidity sensor.

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