CN108593511B - Dual wavelength formula PM2.5 check out test set - Google Patents

Abstract

The invention discloses a dual-wavelength PM2.5 detection device, comprising a casing, characterized in that a detection cavity is formed inside the casing, an incident light channel is communicated with one side of the detection cavity, and the incident light channel is far from the detection cavity. One end is provided with a two-color light generating mechanism to generate a two-color light beam that is incident to the detection position in the detection cavity, and the two-color light beam includes a first color beam with a circular cross-section and a cross-section adjacent to the first color beam. The annular second color light column, the diameter of the cross-sectional circle of the first color light column is 2.5 microns, the detection cavity is also provided with a ventilation channel that communicates with the outside world, and the inner wall of the detection cavity is also provided with a color sensor, and the sensing direction of the color sensor is facing the detection. Location settings. The invention can well shield the interference of large particles to realize the detection of PM2.5, and has the advantages of simple implementation, convenience and speed, accurate and reliable detection results, and the like.

Description

A dual-wavelength PM2.5 detection equipment

technical field

The invention relates to the technical field of air quality detection; in particular, it relates to a dual-wavelength PM2.5 detection device.

Background technique

Fine particles are also called fine particles , fine particles, and PM2.5 . Refers to the particles in the ambient air with an aerodynamic equivalent diameter of less than or equal to 2.5 microns . It can be suspended in the air for a long time, and the higher its concentration in the air, the more serious the air pollution is. Although PM2.5 is only a very small component in the composition of the earth's atmosphere, it has important effects on air quality and visibility. Compared with coarser atmospheric particles, PM2.5 has smaller particle size, larger area, stronger activity, and is prone to carry toxic and harmful substances (such as heavy metals , microorganisms , etc.), and has a long residence time in the atmosphere and a long transportation distance. , and thus have a greater impact on human health and the quality of the atmospheric environment.

At present, with the development of society and the improvement of people's living standards, people pay more and more attention to environmental health and air quality. The PM2.5 content is a very important indicator parameter to characterize urban air quality. PM2.5 not only causes large-scale haze disasters, resulting in serious air pollution, but also easily causes diseases such as asthma and respiratory tract infections. At the same time, it may also contain carcinogenicity and endanger human health. Therefore, the detection of PM2.5 is very necessary for people to go out.

At present, the detection methods for PM2.5 at home and abroad include gravimetric method, micro-oscillation balance method, β-ray absorption method, and single-wavelength light scattering method. At present, the portable PM2.5 detector mainly adopts single-wavelength scattering method. The key component of the single-wavelength scattering method, the PM2.5 cutter, adopts the oil adsorption method to absorb large interfering particles to achieve the purpose of eliminating interference. However, the cutter has the disadvantages of being difficult to clean and high maintenance costs, which may easily cause the detector to reduce the efficiency of the cutting machine. And the phenomenon of increasing error.

Therefore, how to design a PM2.5 detection technology that can better shield the interference of large particles, improve the accuracy of PM2.5 detection, and is simple to implement, convenient and quick, and the detection results are accurate and reliable, has become a problem to be considered by those skilled in the art. question.

SUMMARY OF THE INVENTION

In view of the deficiencies of the above-mentioned prior art, the technical problem to be solved by the present invention is: how to provide a dual-wavelength PM2. .

In order to solve the above-mentioned technical problems, the present invention adopts the following technical solutions:

A dual-wavelength PM2.5 detection device includes a housing, and is characterized in that a detection cavity is formed inside the housing, an incident light channel is communicated with one side of the detection cavity, and an end of the incident light channel away from the detection cavity is provided with a two-color detection cavity. A light generating mechanism, the two-color light generating mechanism is used to generate a two-color light beam that is incident to the detection position in the detection cavity, and the two-color light beam includes a first color beam with a circular cross-section and a cross-section connected to the first color. An annular second color light column outside the cross-sectional circle of the light column, the diameter of the cross-sectional circle of the first color light column is 2.5 microns, and the detection cavity is also provided with a ventilation channel that communicates with the outside world, and a ventilation device is arranged in the ventilation channel. The detection position in the detection cavity forms a stable wind flow, and a color sensor is also arranged on the inner wall of the detection cavity.

The working principle of this equipment is that when the PM2.5 concentration in the air is fixed and the wind speed is fixed, the number of PM2.5 particles passing through a unit space volume with a cross-section of 2.5 microns per unit time is also fixed, so that the detection of the The amount of PM2.5 particulate matter is converted to obtain the corresponding air PM2.5 concentration. When the device is used, it relies on the ventilation device to form a stable airflow at the detection position in the detection cavity, and relies on the bi-color light generating mechanism to generate a bi-color light beam that is incident at the detection position. The first color beam and the second color beam are different in color. When solid particles in the air pass through the first color light column, scattering occurs, and particles of different sizes scatter light with different intensities. The light signal is captured and collected by the color sensor, and then according to the collected color signal, it can be determined whether there is PM2.5 particles passing in the first color light column, and finally the value of PM2.5 particles passing in a single cycle can be calculated. The concentration of PM2.5 in the current test environment. The second color light column is used to filter out particles with a diameter greater than 2.5 microns when judging, that is, when the collected particles only scatter the first color light, it can be judged that the particles are PM2.5, if the particles also scatter the first color. light and the second color light, you can judge whether the particle is larger than 2.5 microns according to the ratio of the two colors of light. When calculating, first delete the solid particles with a diameter larger than 2.5 microns, so that the large particles of solid matter can be perfectly shielded. The detection interference greatly improves the detection accuracy. Among them, the specific calculation method can be directly calculated by relying on the conversion formula preset in the computer according to the above-mentioned principle; or under the condition of constant wind flow, the air with different PM2. It can be measured and preset into the computer. In actual detection, the detection result can be obtained by matching the corresponding PM2.5 concentration according to the measurement data of the color sensor.

Further, the ventilation channel includes an air inlet channel and an air outlet channel that communicate with the detection cavity, and the ventilation device is an air suction pump and is arranged in the air outlet channel. In this way, the air flow is formed by means of air extraction, and it is avoided that the lubricating oil in the ventilation device is easily brought into the detection chamber by means of blowing air, which affects the detection accuracy.

Further, the air inlet channel and the air outlet channel are arranged horizontally through the casing along the direction perpendicular to the incident light channel, and a calibration channel is also arranged along the direction facing the incident light channel. In this way, the wind flow can be better guaranteed to flow in the direction perpendicular to the incident light, which is beneficial to detection. The calibration channel set at the same time can realize the inspection and calibration of the incident light to ensure accurate and reliable detection. The inspection and calibration can be realized by using a microscope. After the inspection and calibration is completed, the calibration channel can be closed to reduce the interference to the wind flow direction.

Further, the inner wall of the detection cavity is provided with a black material layer. In this way, the interference caused by the reflected light from the inner wall of the detector to the detection can be reduced, and the detection accuracy can be improved.

Further, the shell is made of metal material, and the black material layer is obtained by black anodic oxidation. In this way, the strength of the casing can be ensured, and the arrangement of the black material layer is facilitated. The housing material is more preferably aluminum alloy. Excellent processing performance, excellent weldability, extrudability and electroplating, good corrosion resistance, toughness, easy to polish, color film, excellent anodizing effect.

Further, one side of the casing is provided with a color sensor insertion opening for installing the color sensor, which facilitates the installation and fixation of the color sensor.

Further, the installation direction of the color sensor is perpendicular to the incident direction of the incident light beam, and a baffle plate perpendicular to the incident direction of the incident light beam is disposed on each side of the detection head of the color sensor. In this way, the detection of the number of particles in a unit space volume can be better realized, the interference of the scattered light of particles passing through other spatial positions of the light column to the detection can be avoided, and the detection accuracy is greatly improved.

Further, the cross-sectional circle diameter of the second color light beam is 10 microns. This diameter can better ensure the detection accuracy, because if the diameter of the cross-sectional circle of the second color beam is too small, it is difficult to reflect the scattering situation of the large solid particles. If it is too large, the detection is easily disturbed by the small solid particles in the second color light column.

Further, the two-color light generating mechanism includes a first incident channel set perpendicular to the incident light channel, and a beam splitter at an angle of 45 degrees is provided at the intersection of the first incident channel and the incident light channel, and the first incident channel A first laser is arranged at the outer end, and the first laser emits laser light through the beam splitter to form a first color beam or a second color beam. A second laser is arranged at the outer end of the incident channel, and the laser light emitted by the second laser is refracted by the beam splitter to form a second color beam or a first color beam.

In this way, the bichromatic beam can be generated stably and reliably.

Further, the first incident channel is formed in a first incident member, one end of the first incident member is fixed on the housing, and the other end is fixed with a first laser mount for installing the first laser, the second incident The channel is formed in a second incident tube, the second incident tube is detachably fixed on the housing through a connecting piece, and the outer end of the second incident tube is fixed with a second laser mounting seat for installing the second laser.

In this way, it has the advantages of simple structure, convenient disassembly and assembly, and favorable cleaning.

Further, the connecting piece and the fixed end of the second incident tube are provided with elongated holes along the length direction of the second incident tube and are fixed by bolts. In this way, the front and rear directions of the second incident tube can be easily adjusted, thereby achieving focus alignment.

Further, a black shielding block is provided at the center of the lens of the laser emitting end lens for generating the second color beam, and the black shielding block is used to form a shielding range with a diameter of 2.5 microns at the detection position. In this way, it is avoided that the first color light beam at the detection position is actually a mixed light of two colors, which makes it more difficult for the color sensor to identify, and the detection accuracy can be better improved. The first color light beam may be blue light, and the second color light beam may be red light, because the red and blue light is easier to be collected and distinguished by the color sensor.

In implementation, the laser can use a laser diode and focus it through a collimating lens to obtain the desired beam. Low cost and easy to implement. Specifically, in order to expand the discrimination of different light scattering, 650nm (5mw) red laser diodes and 405nm (5mw) polarized violet laser diodes are selected. The reason why the selected laser diodes are all 5mw is to avoid that because the power is too high, after the emitted light is focused by the collimating lens, the light intensity of the focus is too large, which will cause the vaporization of particles and affect the test results.

Therefore, the present invention can well shield the interference of large particles to realize the detection of PM2.5, and has the advantages of simple implementation, convenience and speed, accurate and reliable detection results, and the like.

Description of drawings

FIG. 1 is a front view of the structure of a detection device according to an embodiment of the present invention.

FIG. 2 is a top view of FIG. 1 .

FIG. 3 is a perspective view of FIG. 1 .

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings. 1-3 are schematic diagrams of the structure of the detection device according to the embodiment of the present invention, but the ventilation device, the color sensor and the laser are not shown in the figures.

Example: Referring to Figures 1-3, a dual-wavelength PM2.5 detection device includes a casing 1, a detection cavity 2 is formed inside the casing, and an incident light channel 3 is connected to one side of the detection cavity 2, and the incident light One end of the channel 3 away from the detection cavity is provided with a bichromatic light generating mechanism, which is used to generate a bichromatic light beam that is incident to the detection position in the detection cavity, and the bichromatic light beam includes a first color with a circular cross-section. The light column and the cross section are in the form of an annular second color light column that is connected to the cross-sectional circle of the first color light column. The diameter of the cross-sectional circle of the first color light column is 2.5 microns. A ventilation device is arranged in the channel. The ventilation device is used to form a stable air flow at the detection position in the detection cavity. A color sensor is also arranged on the inner wall of the detection cavity.

The working principle of this equipment is that when the PM2.5 concentration in the air is fixed and the wind speed is fixed, the number of PM2.5 particles passing through a unit space volume with a cross-section of 2.5 microns per unit time is also fixed, so that the detection of the The amount of PM2.5 particulate matter is converted to obtain the corresponding air PM2.5 concentration. When the device is used, it relies on the ventilation device to form a stable airflow at the detection position in the detection cavity, and relies on the bi-color light generating mechanism to generate a bi-color light beam that is incident at the detection position. The first color beam and the second color beam are different in color. When solid particles in the air pass through the first color light column, scattering occurs, and particles of different sizes scatter light with different intensities. The light signal is captured and collected by the color sensor, and then according to the collected color signal, it can be determined whether there is PM2.5 particles passing in the first color light column, and finally the value of PM2.5 particles passing in a single cycle can be calculated. The concentration of PM2.5 in the current test environment. The second color light column is used to filter out particles with a diameter greater than 2.5 microns when judging, that is, when the collected particles only scatter the first color light, it can be judged that the particles are PM2.5, if the particles also scatter the first color. light and the second color light, you can judge whether the particle is larger than 2.5 microns according to the ratio of the two colors of light. When calculating, first delete the solid particles with a diameter larger than 2.5 microns, so that the large particles of solid matter can be perfectly shielded. The detection interference greatly improves the detection accuracy. Among them, the specific calculation method can be directly calculated by relying on the conversion formula preset in the computer according to the above-mentioned principle; or under the condition of constant wind flow, the air with different PM2. It can be measured and preset into the computer. In actual detection, the detection result can be obtained by matching the corresponding PM2.5 concentration according to the measurement data of the color sensor.

When implemented, the color sensor is a mature existing technology, and the core component can use TCS230 color recognition chip, through which color recognition can be realized, and then the color of scattered light can be judged. TCS230 is a programmable color light and frequency converter. By integrating a configurable silicon photodiode and a current-to-frequency converter on a CMOS circuit, and integrating three red, green and blue (RGB) filters on a single chip, it is the industry's first RGB with a digitally compatible interface. color sensor. The output signal of TCS230 is a digital quantity, which can drive standard TTL or CMOS logic input, so it can also be directly connected with a microprocessor or other logic circuits; the details are not described in detail here.

Wherein, the ventilation channel 4 includes an air inlet channel and an air outlet channel that communicate with the detection cavity, and the ventilation device is an air suction pump and is arranged in the air outlet channel. In this way, the air flow is formed by means of air extraction, and it is avoided that the lubricating oil in the ventilation device is easily brought into the detection chamber by means of blowing air, which affects the detection accuracy.

Wherein, the air inlet channel and the air outlet channel are arranged horizontally through the casing 1 along the direction perpendicular to the incident light channel, and a calibration channel is also arranged along the direction facing the incident light channel. In this way, the wind flow can be better guaranteed to flow in the direction perpendicular to the incident light, which is beneficial to detection. The calibration channel set at the same time can realize the inspection and calibration of the incident light to ensure accurate and reliable detection. The inspection and calibration can be realized by using a microscope. After the inspection and calibration is completed, the calibration channel can be closed to reduce the interference to the wind flow direction.

Wherein, the inner wall of the detection cavity 2 is provided with a black material layer. In this way, the interference caused by the reflected light from the inner wall of the detector to the detection can be reduced, and the detection accuracy can be improved.

The shell 1 is made of metal material, and the black material layer is obtained by black anodizing. In this way, the strength of the casing can be ensured, and the arrangement of the black material layer is facilitated. The housing material is more preferably aluminum alloy. Excellent processing performance, excellent weldability, extrudability and electroplating, good corrosion resistance, toughness, easy to polish, color film, excellent anodizing effect.

Wherein, one side of the housing 1 is provided with a color sensor insertion opening 5 for installing the color sensor, which facilitates the installation and fixation of the color sensor.

Among them, the setting direction of the color sensor is perpendicular to the incident direction of the incident light beam, and a baffle plate (not shown in the figure) perpendicular to the incident direction of the incident light beam is arranged on each side of the detection head of the color sensor. In this way, the detection of the number of particles in a unit space volume can be better realized, the interference of the scattered light of particles passing through other spatial positions of the light column to the detection can be avoided, and the detection accuracy is greatly improved.

Wherein, the diameter of the cross-section circle of the second color beam is 10 microns. This diameter can better ensure the detection accuracy, because if the diameter of the cross-sectional circle of the second color beam is too small, it is difficult to reflect the scattering situation of the large solid particles. If it is too large, the detection is easily disturbed by the small solid particles in the second color light column.

Wherein, the two-color light generating mechanism includes a first incident channel 6 arranged perpendicular to the incident light channel, and a beam splitter 7 at an angle of 45 degrees is provided at the intersection of the first incident channel 6 and the incident light channel 3. A first laser is arranged at the outer end of the incident channel 6. The first laser emits laser light through the beam splitter to form a first color beam or a second color beam. The incident channel is provided with a second laser at the outer end of the second incident channel, and the laser light emitted by the second laser is refracted by the beam splitter to form a second color beam or a first color beam.

In this way, the bichromatic beam can be generated stably and reliably.

The first incident channel is formed in a first incident member 8, one end of the first incident member 8 is fixed on the casing 1, and the other end is fixed with a first laser mounting seat 9 for installing the first laser, so The second incident channel is formed in a second incident tube 10, the second incident tube 10 is detachably fixed on the housing through a connecting piece 11, and the outer end of the second incident tube 10 is fixed with a second laser mounting seat and used for. Install the second laser. During implementation, the lower end of the second incident tube is fixed on the mounting table, and the mounting table is detachably fixed on the casing through the connecting piece. This makes it easier to install and fix.

In this way, it has the advantages of simple structure, convenient disassembly and assembly, and favorable cleaning.

Wherein, the connecting piece 11 and the fixed end of the second incident tube are provided with a long hole along the length direction of the second incident tube 10 and are fixed by bolts. In this way, the front and rear directions of the second incident tube can be easily adjusted, thereby achieving focus alignment.

Wherein, a black shielding block is provided at the center of the lens of the laser emitting end lens for generating the second color beam, and the black shielding block is used to form a shielding range of a 2.5-micron cross-sectional circle at the detection position. In this way, it is avoided that the first color light beam at the detection position is actually a mixed light of two colors, which makes it more difficult for the color sensor to identify, and the detection accuracy can be better improved. The first color light beam may be blue light, and the second color light beam may be red light, because the red and blue light is easier to be collected and distinguished by the color sensor.

In implementation, the laser can use a laser diode and focus it through a collimating lens to obtain the desired beam. Low cost and easy to implement. Specifically, in order to expand the discrimination of different light scattering, 650nm (5mw) red laser diodes and 405nm (5mw) polarized violet laser diodes are selected. The reason why the selected laser diodes are all 5mw is to avoid that because the power is too high, after the emitted light is focused by the collimating lens, the light intensity of the focus is too large, which will cause the vaporization of particles and affect the test results.

In order to actually test the test accuracy of the above-mentioned detection equipment to determine whether the dual-wavelength method can be practically used for PM2.5 monitoring, the applicant has carried out relevant tests. The specific experimental process is as follows:

(1) Experimental equipment: the above testing equipment, a certain type of high-precision PM2.5 detector.

(2) Experimental location: a school in Zhengzhou

(3) Operation method:

At each time point, three groups of data were tested at 5-minute intervals and the average value was taken into the results. The results obtained are shown in Table 1

Table 1 Test results of two different PM2.5 test methods

The average value of this testing equipment Contrast Detector Average 37 31.5 39 34.8 37 32.6 37 33.1 39 35.4

Since the average concentration of PM2.5 in each district is the average of all districts and counties in Zhengzhou, there are certain differences in the actual value of PM2.5 in different regions. The allowable error range of general PM2.5 concentration testers on the market is 25%. In order to facilitate the measurement, we purchased a certain type of PM2.5 detector. The test report shows that its accuracy error is within ±10%, which is the highest accuracy tester that the experimenter can buy. Here, the test process of the dual-wavelength method is compared with the results of this type of detector. The error rate obtained is shown in Table 2:

Table 2 Comparison of the results of the detection equipment of the dual-wavelength light scattering method of the present application and a certain type of high-precision PM2.5 detector

PM2.5 average concentration value Deviation ratio of this testing equipment 31.5 17.46% 34.8 12.07% 32.6 13.50% 33.1 11.78% 35.4 10.17%

It can be seen from Table 2 that when the air quality is good, the error of measuring the PM2.5 concentration by the dual-wavelength light scattering method is less than 25%, which is in line with the allowable error range of the general PM2.5 concentration tester on the market.

Therefore, in an environment with good air quality, the detection device based on the dual-wavelength light scattering method of the present application can be used for PM2.5 detection, and can meet the national requirements for detection accuracy, so the dual-wavelength light scattering method can also be applied to PM2.5 concentration detection, the experiment was successful.

Claims (10)

1. A dual-wavelength PM2.5 detection device comprises a shell and is characterized in that a detection cavity is formed in the shell, an incident light channel is communicated with one side of the detection cavity, a bicolor light generating mechanism is arranged at one end, far away from the detection cavity, of the incident light channel and used for generating a bicolor light column incident to a detection position in the detection cavity, the bicolor light column comprises a first color light column with a circular section and a second color light column with an annular section, the second color light column is connected with the outer side of the section of the first color light column in a connected mode, the diameter of the section circle of the first color light column is 2.5 micrometers, a ventilation channel communicated with the outside is further arranged on the detection cavity, a ventilation device is arranged in the ventilation channel and used for forming stable air flow at the detection position in the detection cavity, a color sensor is further arranged on the inner wall of the detection cavity, the sensing direction of the color sensor is just opposite to the detection, the color sensor is in communication connection with the computer.

2. The apparatus of claim 1, wherein the ventilation channel comprises an air inlet channel and an air outlet channel, the air inlet channel and the air outlet channel are communicated with the detection chamber, and the ventilation device is a suction pump and is disposed in the air outlet channel.

3. The apparatus of claim 1, wherein the air inlet channel and the air outlet channel are horizontally disposed through the housing along a direction perpendicular to the incident light channel, and a calibration channel is disposed along a direction opposite to the incident light channel.

4. The dual wavelength PM2.5 detection apparatus of claim 1 wherein the detection chamber interior walls are provided with a layer of black material.

5. The apparatus of claim 4, wherein the housing is made of a metal material, and the black material layer is formed by black anodizing.

6. The dual wavelength PM2.5 sensing apparatus as claimed in claim 1, wherein a color sensor insertion opening is provided at one side of the housing for mounting said color sensor.

7. The dual wavelength PM2.5 detection apparatus of claim 1 wherein the second color light cylinder has a cross-sectional circle diameter of 10 microns.

8. The apparatus according to claim 1, wherein the dual-wavelength PM2.5 detection device includes a first incident channel disposed perpendicular to the incident light channel, a splitter disposed at an intersection of the first incident channel and the incident light channel and forming an included angle of 45 degrees with the first incident channel and the incident light channel, a first laser disposed at an outer end of the first incident channel, the first laser emitting laser light to form the first color light column or the second color light column through emission of the splitter, a second incident channel disposed at a side of the splitter away from the incident light channel along the direction of the incident light channel, a second laser disposed at an outer end of the second incident channel, and the laser emitting laser light from the second laser being refracted by the splitter to form the second color light column or the first color light column.

9. The dual wavelength PM2.5 detection apparatus as claimed in claim 8, wherein said first incident channel is formed in a first incident member having one end fixed to the housing and the other end fixed with the first laser mount for mounting the first laser, said second incident channel is formed in a second incident pipe detachably fixed to the housing by a connecting piece, the second incident pipe having the second laser mount fixed to the outer end thereof for mounting the second laser.

10. The dual wavelength PM2.5 detecting apparatus as claimed in claim 9, wherein the connecting piece and the fixed end of the second incident pipe are provided with a long hole along the length direction of the second incident pipe and fixed by a bolt.

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