Particulate matter monitoring sensor in air

Abstract

The utility model relates to air particulate matter monitoring sensor, including the casing, the airflow cavity is arranged in the casing, the airflow cavity is connected with the gas supply mechanism, the top wall of airflow cavity is provided with laser emission element, the side wall of airflow cavity is provided with optical detector, the airflow cavity includes air inlet cavity, stratified cavity and detection chamber, the stratified cavity is divided into measured gas cavity and protective gas cavity by vertical first baffle, the protective gas cavity is located in the side wall of optical detector, and the measured gas cavity is divided into multiple horizontal laminar flow channels by multiple horizontal second baffle, the laser emission element and optical detector are located in detection chamber, the air inlet cavity is connected with the gas supply mechanism, the air inlet cavity, measured gas cavity and detection chamber communicate in proper order, the uppermost laminar flow channel and protective gas cavity all are connected with pure air supply mechanism, the utility model can slow down the pollution of optical window, and reduce the cleaning and calibration frequency.

Description

Technical Field

[0001] This invention belongs to the field of air quality detection technology, and in particular to a sensor for monitoring particulate matter in the air. Background Technology

[0002] Monitoring particulate matter (especially PM2.5) in the air can provide timely warnings of health risks, and by monitoring changes in particulate matter concentration and its source distribution, data can be used to assess the effectiveness of pollution control measures.

[0003] Existing particulate matter monitoring sensors are typically laser scattering sensors. These sensors generally include a laser diode, an airflow cavity, an optical detector, a signal processing circuit, and an airflow drive mechanism. The laser diode emits a stable, focused laser beam (usually a red laser with a wavelength of approximately 650 nm) into the airflow cavity, providing the light source for measurement. The optical detector receives the scattered light and converts it into an electrical signal. During detection, the airflow drive mechanism propels the air being measured through the airflow cavity at a constant flow rate. The laser diode emits laser light into the airflow cavity. When the laser encounters particulate matter in the air, it dissipates heat. The optical detector receives this dissipated laser light and generates a pulsed current signal. The more and larger the particulate matter in the air, the stronger the scattered light, and the more pulses, resulting in a stronger current. Therefore, the concentration of particulate matter in the air is determined by the current intensity and the number of pulses.

[0004] When using existing laser scattering sensors, the sensor's optical window gradually becomes contaminated, causing the measurement reference to drift and requiring frequent manual calibration. Utility Model Content

[0005] The technical problem to be solved by this invention is to provide an airborne particulate matter monitoring sensor that reduces the contamination of the optical window and reduces the frequency of cleaning and calibration.

[0006] To solve the above problems, the technical solution adopted by this utility model is as follows: an air particulate matter monitoring sensor, including a housing, an airflow cavity disposed inside the housing, an air supply mechanism connected to the airflow cavity, a laser emitting element disposed on the top wall of the airflow cavity, and an optical detector disposed on the side wall of the airflow cavity.

[0007] The airflow cavity includes an inlet cavity, a stratification cavity, and a detection cavity. The stratification cavity is divided into a test gas cavity and a protective gas cavity by a vertical first partition. The protective gas cavity is located on the side wall where the optical detector is located. The test gas cavity is divided into multiple horizontal laminar flow channels by multiple horizontal second partitions. The laser emitting element and the optical detector are located in the detection cavity. The inlet cavity is connected to the gas supply mechanism. The inlet cavity, the test gas cavity, and the detection cavity are connected in sequence. The uppermost laminar flow channel and the protective gas cavity are both connected to a pure air supply mechanism.

[0008] Furthermore, the clean air supply mechanism includes a HEPA filter mechanism, which is connected to the air supply mechanism through a first pipe, and the air intake chamber is connected to the air supply mechanism through a second pipe. Both the first and second pipes are equipped with flow valves.

[0009] Furthermore, the gas supply mechanism is a fan.

[0010] Furthermore, the laser emitting element is a vertical cavity surface-emitting laser.

[0011] Furthermore, the optical detector is a single-photon avalanche diode.

[0012] Furthermore, a vertical first mounting hole is provided at the top of the airflow cavity, and a first glass window is provided at the lower end of the first mounting hole. The laser emitting element is installed in the first mounting hole, and a first piezoelectric ceramic sheet is provided on the first glass window. A horizontal second mounting hole is provided on the side wall of the airflow cavity, and a second glass window is provided at the opening connecting the first mounting hole and the airflow cavity. A second piezoelectric ceramic sheet is provided on the second glass window, and the optical detector is installed in the second mounting hole.

[0013] The beneficial effects of this invention are as follows: In traditional sensors, air entering the airflow cavity is usually turbulent, and air particles easily adhere to the optical windows of the optical detector and laser emitting element, gradually degrading measurement accuracy. This invention, by setting up a layered cavity, separates multiple horizontal laminar flow channels within the layered cavity. The air to be measured enters the detection cavity horizontally through these laminar flow channels. Since the air is laminar, particles can pass through the laser more orderly, resulting in a clearer pulse signal. Furthermore, by introducing pure air into the uppermost laminar flow channel and the protective gas cavity, the pure air, positioned above and to one side of the air being measured, separates the air from the optical windows of the optical detector and laser emitting element, providing a certain degree of protection. This reduces the number of particles adhering to the optical windows, thereby mitigating contamination and reducing the frequency of cleaning and calibration. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the front sectional view of this utility model;

[0015] Figure 2 yes Figure 1 Schematic diagram of the AA section;

[0016] Figure 3 yes Figure 1 Schematic diagram of the BB section;

[0017] Reference numerals: 1—Housing; 2—Airflow cavity; 21—Inlet cavity; 22—Layered cavity; 23—Detection cavity; 24—Second partition; 3—Gas supply mechanism; 4—Laser emitting element; 5—Optical detector; 6—First partition; 7—Protective gas cavity; 8—HEPA filter mechanism; 9—First pipe; 10—Second pipe; 11—Flow valve; 12—First glass window; 13—First piezoelectric ceramic sheet; 14—Second glass window; 15—Second piezoelectric ceramic sheet. Detailed Implementation

[0018] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0019] The air particulate matter monitoring sensor of this utility model, such as Figures 1 to 3 As shown, it includes a housing 1, an airflow cavity 2 is provided inside the housing 1, an air supply mechanism 3 is connected to the airflow cavity 2, a laser emitting element 4 is provided on the top wall of the airflow cavity 2, and an optical detector 5 is provided on the side wall of the airflow cavity 2.

[0020] The housing 1 can be made of metal or plastic and has an overall rectangular shape. The airflow cavity 2 is used to allow the measured air to pass through, and the air supply mechanism 3 is used to deliver the measured air from the outside into the airflow cavity 2. The air supply mechanism 3 can specifically be a fan, air pump, or other similar equipment. The laser emitting element 4 is used to emit laser light into the airflow cavity 2, and the emission direction of the laser emitting element 4 is downward. The laser emitting element 4 can be an existing laser diode. In a preferred embodiment of this invention, the laser emitting element 4 is a vertical cavity surface emitting laser (VCSEL), which has advantages such as good beam quality (circular spot), low threshold current, low power consumption, fast modulation speed, long lifespan, and ease of two-dimensional integration. The optical detector 5 is used to receive the laser light dissipated by the particles. It can be a photodiode, but traditional photodiodes have extremely weak signals for very low concentrations (such as cleanroom environments). Therefore, this invention uses single-photon avalanche diodes (SPADs). SPADs have single-photon level detection capabilities, which greatly improves the detection limit and sensitivity of the sensor and can be used in special occasions where monitoring of extremely low concentrations of PM2.5 is required.

[0021] In this invention, the airflow cavity 2 includes an inlet cavity 21, a layered cavity 22, and a detection cavity 23 arranged sequentially. The layered cavity 22 is divided into a gas chamber to be measured and a protective gas chamber 7 by a vertical first partition 6. The protective gas chamber 7 is located on the side wall where the optical detector 5 is located. The gas chamber to be measured is divided into multiple horizontal laminar flow channels by multiple horizontal second partitions 24, and the thickness of each laminar flow channel is the same. The laser emitting element 4 and the optical detector 5 are located in the detection cavity 23. The inlet cavity 21 is connected to the gas supply mechanism 3. The inlet cavity 21, the gas chamber to be measured, and the detection cavity 23 are connected in sequence. The uppermost laminar flow channel and the protective gas chamber 7 are both connected to a pure air supply mechanism.

[0022] The clean air supply mechanism provides clean air, which is purified air with low particulate matter content. This air does not cause significant heat dissipation from the laser and does not affect the accuracy of the detection. During detection, the air supply mechanism 3 delivers external air to the air intake chamber 21. The air in the air intake chamber 21 then enters the detection chamber 23 through various laminar flow channels. By stratifying the air to be tested, the air can enter the detection chamber 23 in an orderly manner, forming a laminar flow. Particulate matter in the air can also pass through the laser in an orderly manner, resulting in a clearer pulse signal.

[0023] Simultaneously, purified air is introduced into the uppermost laminar flow channel and protective gas chamber 7 using a pure air supply mechanism. The purified air then enters the detection chamber 23 through the uppermost laminar flow channel and protective gas chamber 7, forming a pure air protective layer above and to one side of the air being measured. This separates the air being measured from the optical windows of the optical detector 5 and the laser emitting element 4, preventing particles in the air from directly contacting the optical windows of the optical detector 5 and the laser emitting element 4. This reduces the number of particles adhering to the optical windows, thus mitigating contamination and reducing the frequency of cleaning and calibration. The uppermost laminar flow channel may not be connected to the air inlet chamber 21.

[0024] In this invention, the pure air supply mechanism includes a HEPA filter 8, which is connected to the air supply mechanism 3 via a first pipe 9. The air intake chamber 21 is connected to the air supply mechanism 3 via a second pipe 10. Both the first pipe 9 and the second pipe 10 are equipped with flow valves 11. The HEPA filter 8 can be located on the upper surface of the housing 1 and connected to the uppermost laminar flow channel and the protective gas chamber 7 via air vents. The air supply mechanism 3 delivers a portion of the external air to the HEPA filter 8. After filtration by the HEPA filter 8, the air becomes pure air and then enters the uppermost laminar flow channel and the protective gas chamber 7. The remaining air directly enters the air intake chamber 21 as the air to be measured. The ratio of the two types of air can be adjusted using the flow valves 11.

[0025] To automatically clean the optical windows of the optical detector 5 and the laser emitting element 4, a vertical first mounting hole is provided at the top of the airflow cavity 2. A first glass window 12 is provided at the lower end of the first mounting hole. The laser emitting element 4 is installed in the first mounting hole, and a first piezoelectric ceramic sheet 13 is provided on the first glass window 12. The first piezoelectric ceramic sheet 13 can be attached to the first glass window 12. A horizontal second mounting hole is provided on the side wall of the airflow cavity 2. A second glass window 14 is provided at the opening connecting the first mounting hole and the airflow cavity 2. A second piezoelectric ceramic sheet 15 is provided on the second glass window 14. The second piezoelectric ceramic sheet 15 can be attached to the second glass window 14, and the optical detector 5 is installed in the second mounting hole.

[0026] At regular intervals, a high-frequency alternating current can be applied to the first piezoelectric ceramic sheet 13 and the second piezoelectric ceramic sheet 15. The first piezoelectric ceramic sheet 13 and the second piezoelectric ceramic sheet 15 generate ultrasonic vibrations, which can shake off particles attached to the first glass window 12 and the second glass window 14, achieving automatic cleaning and reducing the frequency of manual maintenance. During automatic cleaning, air can be introduced using the air supply mechanism 3, and the flowing air can carry the shaken-off particles out of the airflow chamber 2.

[0027] The above description is merely a preferred embodiment of this utility model and is not intended to limit the utility model. Various modifications and variations can be made to this utility model by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. An airborne particulate matter monitoring sensor, comprising a housing (1), wherein an airflow cavity (2) is provided inside the housing (1), the airflow cavity (2) is connected to an air supply mechanism (3), a laser emitting element (4) is provided on the top wall of the airflow cavity (2), and an optical detector (5) is provided on the side wall of the airflow cavity (2), characterized in that: The airflow cavity (2) includes an air inlet cavity (21), a stratification cavity (22), and a detection cavity (23). The stratification cavity (22) is divided into a gas chamber to be measured and a protective gas chamber (7) by a vertical first partition (6). The protective gas chamber (7) is located on the side wall where the optical detector (5) is located. The gas chamber to be measured is divided into multiple horizontal laminar flow channels by multiple horizontal second partitions (24). The laser emitting element (4) and the optical detector (5) are located in the detection cavity (23). The air inlet cavity (21) is connected to the air supply mechanism (3). The air inlet cavity (21), the gas chamber to be measured, and the detection cavity (23) are connected in sequence. The uppermost laminar flow channel and the protective gas chamber (7) are both connected to a pure air supply mechanism.

2. The airborne particulate matter monitoring sensor as described in claim 1, characterized in that: The clean air supply mechanism includes a HEPA filter (8), which is connected to the air supply mechanism (3) through a first pipe (9). The air inlet chamber (21) is connected to the air supply mechanism (3) through a second pipe (10). Both the first pipe (9) and the second pipe (10) are equipped with flow valves (11).

3. The airborne particulate matter monitoring sensor as described in claim 1, characterized in that: The gas supply mechanism (3) is a fan.

4. The airborne particulate matter monitoring sensor as described in claim 1, characterized in that: The laser emitting element (4) is a vertical cavity surface-emitting laser.

5. The airborne particulate matter monitoring sensor as described in claim 1, characterized in that: The optical detector (5) is a single-photon avalanche diode.

6. The airborne particulate matter monitoring sensor as described in claim 1, characterized in that: The airflow cavity (2) has a vertical first mounting hole at the top, and a first glass window (12) is provided at the lower end of the first mounting hole. The laser emitting element (4) is installed in the first mounting hole, and a first piezoelectric ceramic sheet (13) is provided on the first glass window (12). The airflow cavity (2) has a horizontal second mounting hole on its side wall. A second glass window (14) is provided at the opening of the first mounting hole connected to the airflow cavity (2). A second piezoelectric ceramic sheet (15) is provided on the second glass window (14), and the optical detector (5) is installed in the second mounting hole.

Images