Particulate matter detection device and detection method

Abstract

The present application relates to the technical field of environment detection equipment, and more particularly to a particulate matter detection device, which comprises an illumination system, a scattered light collection system and an air path system; the illumination system comprises a laser module, a lens mounting seat and a lens, the laser module is fixed to the outer side of the lens mounting seat, the lens is mounted on the inner side of the lens mounting seat and corresponds to the laser module; the scattered light collection system comprises a scattering cavity, a first photodetector, a second photodetector and a PCB board, the lens mounting seat is fixed to the side of the scattering cavity, the lower end opening of the scattering cavity is used for mounting the PCB board, and the first photodetector and the second photodetector are respectively mounted on the fixing plate; the air path system comprises an air inlet, an air outlet and an air pump, the air inlet is fixed to the upper surface of the scattering cavity, and the air outlet is fixed to the PCB board. The present application changes the problems that the state of the photodetector in the existing particulate matter detection device cannot be checked, the accuracy of long-term application data cannot be guaranteed and the like, and improves the measurement data precision.

Description

Technical Field

[0001] The present invention relates to the technical field of environmental detection equipment, and in particular to a particle detection device and a detection method. Background Art

[0002] In recent years, the detection device for measuring atmospheric particulate matter using the laser scattering method has made great progress. Its main principle is to use laser to illuminate the particles in the atmosphere to produce scattering, and then collect the scattered light through the scattered light collection system, and calculate the number and mass of the particles based on the collected signals.

[0003] In the practical application of laser scattering particulate matter sensors, the design of the detection device's lighting system, gas flow system, and scattered light collection system all affect the device's measurement accuracy. Uneven light intensity distribution in the lighting system can lead to misjudgment of particle size, resulting in low measurement results. Some particles in the gas flow system settle into the photosensitive area, gradually degrading the detection device's performance. Improper design of the scattered light collection system leads to weak collected signals, making it difficult to simultaneously detect small (D < 1 μm) and large (10 μm < D < 100 μm) particles. Furthermore, the photodetector's status cannot be verified, and abnormalities in the photodetector cannot be detected promptly. These problems hinder the further development of particulate matter detection devices. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies of the above-mentioned technologies and to provide a particle detection device and a detection method.

[0005] In order to achieve the above-mentioned objectives, the present invention adopts the following technical solutions: a particle detection device, characterized in that it includes an illumination system, a scattered light collection system, an air path system and an analysis and processing unit; the illumination system includes a laser module, a lens mount and a lens, the laser module is fixed to the outside of the lens mount, and the lens is installed on the inside of the lens mount and corresponds to the laser module; the scattered light collection system includes a scattering cavity, a first photodetector, a second photodetector and a PCB board, the lens mount is fixed to the side of the scattering cavity, the lower end opening of the scattering cavity is used to install the PCB board and seal the cavity, the PCB board has a fixing plate for installing and positioning the photodetector, and the first photodetector and the second photodetector are respectively installed on the fixing plate; the air path system includes an air inlet, an air outlet, an air pump and a filter, the air inlet is fixed to the upper surface of the scattering cavity, the air outlet is fixed to the PCB board, the filter is connected to the air outlet, and the air pump is connected to the filter through a sampling tube.

[0006] Preferably, the scattering cavity is a circular or rectangular cavity.

[0007] Preferably, the inner wall of the scattering cavity is surface-treated with matte paint.

[0008] Preferably, the first photodetector and the second photodetector are respectively located on both sides of the photosensitive area.

[0009] Preferably, the first photodetector and the second photodetector are fixed on a fixing plate and are located on the same side of the photosensitive area.

[0010] Preferably, the first photodetector and the second photodetector are installed on the same side of a line connecting the air inlet and the air outlet.

[0011] Preferably, the air inlet adopts an outer circle and inner square pattern, that is, the end connected to the sampling tube is round, and the end connected to the scattering cavity is square, and the deformation part is determined through experimental optimization and the corners are chamfered at this part.

[0012] A detection method for a particulate matter detection device, characterized in that: in this method, a first photodetector corresponds to a first signal detection circuit and a first analysis and processing unit, detecting particulate matter with a particle size of 2.5-100 μm, and a second photodetector corresponds to a second signal detection circuit and a second analysis and processing unit, detecting particulate matter with a particle size of 0.3-5 μm, wherein the first photodetector and the second photodetector have overlapping detection ranges between 2.5-5 μm in particle size, and each other's states are verified, so that the same detection device can simultaneously detect particulate matter with a particle size range of less than 1 μm and particulate matter with a particle size range of greater than 10 μm and less than 100 μm, and the state verification includes the following steps:

[0013] Step 1: When the detection device is working for the first time, start from step 2; otherwise, start from step 3;

[0014] Step 2: calibrating the first analysis and processing unit and the second analysis and processing unit of the particulate matter detection device;

[0015] Step 3: Perform formal measurement to calculate the number and mass concentration of particles of different sizes within the particle size range corresponding to the first analysis and processing unit and the second analysis and processing unit;

[0016] Step 4: extract the number and mass concentration of particles between 2.5 μm and 5 μm from the calculation results of the first analysis processing unit and the second analysis processing unit, and calculate their ratio X;

[0017] Step 5: Record the number N of times X> set value A within a continuous period of time (such as one hour or one day), where A can be set according to the measurement accuracy, such as A can be 0.95-1.05;

[0018] Step 6. If N> set value B, it is determined that the photoelectric detector is in poor condition and needs to be repaired or replaced. The value B can be optimally set according to the experiment. Depending on the continuous time, B can take different values, such as 10 for one hour and 200 for one day.

[0019] During the formal measurement in step 3 above, a signal peak correction algorithm is used to correct the peak value of the collected particulate matter pulse signal. The particle size partitioning and mass concentration calculation are performed based on the corrected signal peak value, including the following steps:

[0020] Step 1: When the detection device is working for the first time, start from step 2, otherwise, start from step 3;

[0021] Step 2: Based on the Gaussian beam characteristics of the laser light source and the design of the illumination system, calculate and save the proportional coefficient K of the light intensity at different positions in the photosensitive area to the central light intensity;

[0022] Step 3: The analysis and processing unit extracts the peak value of the particle pulse signal and calculates the position of the particle when it passes through the photosensitive area based on probability;

[0023] Step 4: Read the proportional coefficient K between the corresponding light intensity and the central light intensity;

[0024] Step 5: Correct the peak value of the pulse signal of the analysis and processing unit using the coefficient K;

[0025] Step 6: Compare the corrected pulse signal peak value with the threshold value of each partition that has passed the calibration, and place it in the corresponding partition, while counting the number of pulse signal peak values ​​in the partition;

[0026] Step 7: Calculate the number of particles and volume concentration per unit sampling volume;

[0027] Step 8: Calculate the mass concentration of particulate matter.

[0028] The present invention has the following beneficial effects: Compared to existing technologies, this invention addresses the problem of reflected light from common right-angle scattering systems reaching the photodetector multiple times, interfering with measurement, by optimizing the scattered light collection system. The use of dual photodetectors and their optimized relative positioning enable mutual verification, ensuring accuracy. This dual photodetector design increases the detection efficiency of small-sized particles and provides detailed grading of particles of varying sizes, resulting in more accurate mass concentration calculations. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is an exploded view of the present invention;

[0030] Figure 2 is a perspective view of the present invention;

[0031] Figure 3 This is a schematic diagram of the installation position of the photoelectric detector and the direction of airflow movement in the present invention;

[0032] Figure 4 Schematic diagram of the position of the light-shielding aperture of the lighting system of the present invention;

[0033] Figure 5a This is an installation structure diagram of the photoelectric detector in the present invention;

[0034] Figure 5b This is another installation structure diagram of the photoelectric detector in the present invention;

[0035] Figure 6 Schematic diagram of the air inlet structure of the present invention;

[0036] Figure 7 Flowchart of this method. DETAILED DESCRIPTION

[0037] The specific implementation of the present invention is described in detail below with reference to the accompanying drawings and preferred embodiments. Figure 1 and Figure 2 As shown, a particle detection device includes an illumination system, a scattered light collection system, an air path system, and an analysis and processing unit; the illumination system includes a laser module 1, a lens mount 2, and a lens 3, the laser module is fixed to the outside of the lens mount, specifically, a cylinder is provided on the outside of the lens mount, which is communicated with the inside, the laser module is installed in the cylinder, the lens is installed on the inside of the lens mount and corresponds to the laser module, and the laser generated by the laser module is focused in one dimension on the photosensitive area through the lens. In this device, the length of the lens mount is less than 20 mm, and the focal length of the lens is less than 25 mm, thereby reducing the size of the particle detection device and facilitating installation and integration. A vertical light-shielding diaphragm 11 and a horizontal light-shielding diaphragm 12 are added behind the lens 3 as shown. Figure 4 As shown, a portion of the illumination light beam with higher uniformity is intercepted to reach the photosensitive area, and the light spot width of the entire photosensitive area remains consistent, thereby improving the accuracy of the measurement.

[0038] The scattered light collection system includes a scattering cavity 4, a first photodetector 5, a second photodetector 6, and a PCB board 7. The inner wall of the scattering cavity is surface-treated with matte paint to minimize stray light and improve measurement accuracy. The lens mount is fixed to the side of the scattering cavity. The lower end opening of the scattering cavity is used to install the PCB board and seal the cavity. The PCB board has a fixing plate 8 for installing and positioning the photodetectors. The first photodetector and the second photodetector are respectively installed on the fixing plate. The dual photodetector design improves the scattered light collection capability, effectively detects small-sized particulate matter, and improves detection efficiency.

[0039] The air path system includes an air inlet 9, an air outlet 10, an air pump and a filter. The air inlet is fixed on the upper surface of the scattering cavity, the air outlet is fixed on the PCB board, the filter is connected to the air outlet, and the air pump is connected to the filter through a sampling tube. The air inlet is specially designed to adopt an outer circle and inner square pattern, that is, the end connected to the sampling tube is circular with a diameter of 4mm. The end connected to the scattering cavity is a flat rectangle with a size of 1.5×3mm, and the deformation part is determined through experiments and is chamfered to reduce the sedimentation and accumulation of particles. The circular entrance of the air inlet is convenient for connection to the circular sampling tube, and the rectangular outlet can constrain the running area of ​​the particles to be rectangular when they reach the photosensitive area, ensuring that all particles in the sampling air flow are illuminated by the main light beam, while allowing the particles to pass through the photosensitive area one by one, reducing the phenomenon of multiple particles passing through in a cluster and being misjudged.

[0040] There are many possibilities for the relative positions of the photodetectors in the present invention, such as Figure 5a As shown, the first photodetector 5 and the second photodetector 6 are separated on both sides of the photosensitive area 13, and the two photodetectors respectively receive scattered light 14 with different scattering angle ranges, and the collected signals of the two photodetectors are mutually verified. In order to ensure the accuracy of the measurement, the first photodetector is close to the photosensitive area, close to right-angle scattering, and detects large-sized particles; the second photodetector is far away from the photosensitive area, so it is closer to forward scattering, with a high scattered light intensity, and detects small-sized particles. Or as Figure 5b As shown, the first and second photodetectors 5 and 6 are fixed to a fixed plate and located on the same side of the photosensitive area 13. Each photodetector receives scattered light 14 at different angles. To ensure measurement accuracy, the first photodetector is positioned closer to the photosensitive area, scattering light at near right angles, and detecting large particles. The second photodetector is positioned further away from the photosensitive area, resulting in closer forward scattering and higher scattered light intensity, allowing it to detect small particles. The placement of the photodetectors avoids reflected light at right angles, effectively preventing light from reaching the photodetectors after multiple reflections, which could interfere with measurement.

[0041] The installation position of the photoelectric detector in the present invention forms a certain distance from the direction of air flow, such as Figure 3 As shown, the boundary of the airflow and the boundary of the photodetector are separated from each other by a certain distance (greater than 5 mm) to ensure that the particles move with the airflow to the outside of the scattering cavity after being detected, thereby preventing the particles from being deposited on the photodetector and interfering with the measurement.

[0042] In the present invention, the first photodetector 5 and the second photodetector 6 verify each other's status. Specifically, the first photodetector 5 detects particle sizes of 2.5-100 μm, while the second photodetector 6 detects particle sizes of 0.3-5 μm. The two perform repeated detection within the particle size range of 2.5-5 μm. When the deviation of the detection result is too large, it is considered that there is a problem with the detection device and it needs to be repaired.

[0043] This embodiment provides a detection method for a particle detection device. In this method, a first photodetector corresponds to a first signal detection circuit and a first analysis and processing unit, and detects particles with a particle size of 2.5-100 μm. A second photodetector corresponds to a second signal detection circuit and a second analysis and processing unit, and detects particles with a particle size of 0.3-5 μm. The first photodetector and the second photodetector have overlapping detection ranges between 2.5-5 μm in particle size, and their states are verified. The same detection device can simultaneously detect particles with a particle size of less than 1 μm and particles with a particle size of greater than 10 μm and less than 100 μm. The state verification includes the following steps:

[0044] Step 1: When the detection device is working for the first time, start from step 2; otherwise, start from step 3;

[0045] Step 2: calibrating the first analysis and processing unit and the second analysis and processing unit of the particulate matter detection device;

[0046] Step 3: Perform formal measurement to calculate the number and mass concentration of particles of different sizes within the particle size range corresponding to the first analysis and processing unit and the second analysis and processing unit;

[0047] Step 4: extract the number and mass concentration of particles between 2.5 μm and 5 μm from the calculation results of the first analysis processing unit and the second analysis processing unit, and calculate their ratio X;

[0048] Step 5: Record the number N of times X> set value A within a continuous period of time (such as one hour or one day), where A can be set according to the measurement accuracy, such as A can be 0.95-1.05;

[0049] Step 6. If N> set value B, it is determined that the photoelectric detector is in poor condition and needs to be repaired or replaced. The value B can be optimally set according to the experiment. Depending on the continuous time, B can take different values, such as 10 for one hour and 200 for one day.

[0050] like Figure 7 As shown, when performing formal measurement in step 3 above, a signal peak correction algorithm is used to correct the peak value of the collected particulate matter pulse signal. The particle size partitioning and mass concentration calculation are performed based on the corrected signal peak value, including the following steps:

[0051] Step 1: When the detection device is working for the first time, perform step 2 first and then step 3, otherwise directly perform step 3;

[0052] Step 2: Based on the Gaussian beam characteristics of the laser light source and the design of the illumination system, calculate and save the proportional coefficient K of the light intensity at different positions in the photosensitive area to the central light intensity;

[0053] Step 3: The analysis and processing unit extracts the peak value of the particle pulse signal and calculates the position of the particle when it passes through the photosensitive area based on probability;

[0054] Step 4: Read the proportional coefficient K between the corresponding light intensity and the central light intensity;

[0055] Step 5: Correct the peak value of the pulse signal of the analysis and processing unit using the coefficient K;

[0056] Step 6: Compare the corrected pulse signal peak value with the threshold value of each partition that has passed the calibration, and place it in the corresponding partition, while counting the number of pulse signal peak values ​​in the partition;

[0057] Step 7: Calculate the number of particles and volume concentration per unit sampling volume;

[0058] Step 8: Calculate the mass concentration of particulate matter.

[0059] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A detection method for a particulate matter detection device, characterized in that: In this method, a first photodetector corresponds to a first signal detection circuit and a first analysis and processing unit, and detects particles with a particle size of 2.5-100 μm. A second photodetector corresponds to a second signal detection circuit and a second analysis and processing unit, and detects particles with a particle size of 0.3-5 μm. The first photodetector and the second photodetector have overlapping detection ranges between particle sizes of 2.5-5 μm, and the states of each other are verified. The state verification includes the following steps: Step 1: When the detection device is working for the first time, start from step 2; otherwise, start from step 3; Step 2: calibrating the first analysis and processing unit and the second analysis and processing unit of the particulate matter detection device; Step 3: Perform formal measurement to calculate the number and mass concentration of particles of different sizes within the particle size range corresponding to the first analysis and processing unit and the second analysis and processing unit; Step 4: extract the number and mass concentration of particles between 2.5 μm and 5 μm from the calculation results of the first analysis processing unit and the second analysis processing unit, and calculate their ratio X; Step 5: Record the number N of times X> set value A within a continuous period of time, where A can be set according to the measurement accuracy; Step 6: If N > the set value B, the photoelectric detector is judged to be in poor condition and needs to be repaired or replaced. The value B can be set according to the experiment; The particle detection device includes an illumination system, a scattered light collection system, an air path system and an analysis and processing unit; the illumination system includes a laser module, a lens mount and a lens, the laser module is fixed to the outside of the lens mount, and the lens is mounted on the inside of the lens mount and corresponds to the laser module; the scattered light collection system includes a scattering cavity, a first photodetector, a second photodetector and a PCB board, the lens mount is fixed to the side of the scattering cavity, the lower end opening of the scattering cavity is used to install the PCB board and seal the cavity, the PCB board has a fixing plate for installing and positioning the photodetectors, and the first photodetector and the second photodetector are respectively installed on the fixing plate; the air path system includes an air inlet, an air outlet, an air pump and a filter, the air inlet is fixed to the upper surface of the scattering cavity, the air outlet is fixed to the PCB board, the filter is connected to the air outlet, and the air pump is connected to the filter through a sampling tube; the scattering cavity is a circular or rectangular cavity.

2. The detection method of the particle detection device according to claim 1, characterized in that: The inner wall of the scattering cavity is surface-treated with matte paint.

3. The detection method of the particle detection device according to claim 1, characterized in that: The first photodetector and the second photodetector are respectively located on two sides of the photosensitive area.

4. The detection method of the particle detection device according to claim 1, characterized in that: The first photodetector and the second photodetector are fixed on a fixing plate and are located on the same side of the photosensitive area.

5. The detection method of the particle detection device according to claim 1, characterized in that: The first photodetector and the second photodetector are installed on the same side of a line connecting the air inlet and the air outlet.

6. The detection method of the particle detection device according to claim 1, characterized in that: The end of the air inlet connected to the sampling tube is circular, while the end connected to the scattering cavity is square, and the deformed part is designed with rounded corners.

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