A mesh probe constant flow sampling device and its actual flow feedback regulation method

Abstract

The application discloses a kind of screen mesh probe constant flow sampling device and its actual flow feedback regulation method, belong to environmental monitoring and microorganism sampling technical field.Device includes six levels screen mesh probe, air extraction device and feedback control device.Six levels screen mesh probe is composed of seat layer, multiple screen layers of screen body stacking and cover layer, and measuring nozzle is movably arranged on the air pipe of cover layer, for real-time acquisition of air pressure;Screen body is rotated and clamped between screen layers by fixed groove and screen layer fixing hook, and interlayer sealing is realized in cooperation with sealing ring.Method includes: obtain air leakage coefficient by static airtightness calibration, and judge probe airtightness;Actual air pressure value is measured by measuring nozzle during sampling, and nozzle actual flow is obtained by differential pressure flow conversion formula, and then corrected to probe actual flow in combination with air leakage coefficient;The deviation of probe actual flow and preset standard flow is input into feedback control algorithm, and the power of air extraction device is dynamically adjusted, so that probe actual flow is stabilized at 28.3 L / min.The application realizes accurate flow measurement at probe inlet, quantitative calibration of air leakage and dynamic constant flow control, and is suitable for microorganism sampling in public places and central air conditioning ventilation system.

Description

Technical Field

[0001] This invention belongs to the field of environmental monitoring and microbial sampling technology, and more specifically, relates to a constant flow sampling device with a sieve probe and a method for actual flow feedback control. Background Technology

[0002] Impact microbial samplers are widely used in hygiene testing of public places and centralized air conditioning and ventilation systems. Their principle is to use an air extraction device to create a high-speed airflow through sieve holes, collecting microorganisms onto agar plates for culture and counting. Current national standards (such as GB / T 18883 and WS 10013) clearly stipulate that the sampling flow rate must be stable at 28.3 L / min.

[0003] Existing technologies for sampling devices using six-stage sieve probes suffer from the following shortcomings: First, the flow measurement point is often located at the connection between the extraction device and the probe, failing to accurately reflect the actual sampling flow rate at the probe inlet, resulting in significant measurement errors. Second, the probe consists of multiple stacked sieves sealed between layers by sealing rings. Over time, these sealing rings are prone to aging and deformation, leading to leaks. Existing devices lack leak detection and calibration methods, directly impacting the reliability of the sampling data. Third, in environments with positive air pressure from air conditioning supply, traditional extraction devices employ static calibration and dynamic locking, failing to dynamically maintain a constant flow rate. These deficiencies lead to distorted microbial sampling data and urgently require improvement. Summary of the Invention

[0004] To address the aforementioned deficiencies or improvement needs of existing technologies, this invention provides a constant flow sampling device for a sieve aperture probe and its actual flow feedback control method. The constant flow sampling device comprises a six-stage sieve aperture probe, an air extraction device, and a feedback control device electrically connected to the air extraction device. The six-stage sieve aperture probe includes: The seat layer includes a seat body, on the upper surface of which a seat layer sealing ring is provided, and on one side an exhaust port is provided, wherein the exhaust port is connected to the air extraction device through a pipe; The sieve layer comprises multiple sieve bodies stacked sequentially on the base layer, each sieve body comprising: A groove for the plate is provided inside the screen body, and the horizontal cross-sectional area of ​​the groove is smaller than that of the screen body; A screen layer sealing ring is disposed on the upper surface of the screen body, and the shape of the screen layer sealing ring is a closed shape. The sieve holes are located at the bottom of the groove in the plate. At least three dish pads are disposed on the bottom surface of the groove in the plate; A cover layer, placed on the sieve layer, includes: Cover; A vent pipe is provided on the upper part of the cover to allow gas to enter the cover and be introduced into the gas supply. A metering nozzle is movably mounted on the air duct and electrically connected to the feedback control device for measuring the air pressure of the incoming air.

[0005] In one embodiment of the present invention, each of the sieve bodies further includes: At least two fixing slots, including: a slot body disposed on the surface of the screen body and a cavity disposed on one side of the bottom surface of the slot body, wherein the height of the cavity body is less than the depth of the slot body, and all the fixing slots are centrally symmetrically disposed on the upper surface of the screen body with the center point of the bottom surface of the screen body as the symmetrical point; At least two screen layer fixing hooks are respectively set at the bottom of the screen body in the direction of gravity relative to the screen layer fixing hook, so that the screen layer fixing hooks of the upper screen layer can be inserted into the fixing grooves of the lower screen layer one by one, and the upper and lower screen layers are locked by rotating the screen body.

[0006] In one embodiment of the present invention, the cover further includes at least two cover fixing hooks, which are symmetrically arranged at the lower part of the cover with the center point of the bottom surface of the cover as the symmetrical point.

[0007] In one embodiment of the present invention, each cavity further includes an inclined groove block disposed at the top of the cavity, such that the height of the cavity on the side closer to the groove is greater than the height on the side farther from the groove.

[0008] In one embodiment of the present invention, friction textures are provided on the outer sides of the sieve body, cover body, and seat layer to increase friction.

[0009] In one embodiment of the present invention, the sieve body further includes an air collecting channel disposed at the bottom of the groove of the plate, wherein the diameter of the air collecting channel is smaller than the diameter of the overall area of ​​the sieve holes.

[0010] The present invention also provides a method for actual flow feedback control of a sieve probe constant flow sampling device, the method comprising: The sixth-level sieve probe that meets the airtightness requirements was determined through static airtightness calibration; The actual air pressure value of the metering nozzle is obtained through the metering nozzle of the six-stage sieve probe. The measured flow rate of the nozzle is calculated using the differential pressure flow rate conversion formula. ; Based on the measured flow rate of the nozzle With the aforementioned leakage coefficient The ratio of the actual flow rate of the probe is used as the actual flow rate. ; The actual flow rate of the probe Compared with the preset standard flow rate value The difference between them is used as the flow deviation. ; Utilizing the flow deviation The pumping power of the pumping device is adjusted according to the feedback control algorithm to ensure the actual flow rate of the probe is [adjusted / improved]. Equal to the preset standard flow value .

[0011] In one embodiment of the present invention, the step of determining a level 6 sieve probe that meets the airtightness requirements through static airtightness calibration includes: Seal the metering nozzle and turn on the suction device to the preset standard flow rate. Run the test to obtain the nozzle sealing pressure value. ; The air pressure value is blocked by the nozzle. The leakage flow rate is calculated using the differential pressure flow rate formula. ; According to the aforementioned air leakage flow rate value and preset standard flow value The leakage coefficient is calculated using the leakage coefficient formula. The leakage coefficient formula is as follows: Leakage coefficient formula: .

[0012] When the leakage coefficient is greater than or equal to the air tightness threshold, the six-level sieve probe meets the air tightness requirements. If the leakage coefficient is less than the air tightness threshold, the six-stage sieve probe does not meet the air tightness requirements.

[0013] In one embodiment of the present invention, the differential pressure-flow conversion formula is: ;in, This represents the actual measured flow rate of the nozzle. To preset the outflow coefficient, To measure the cross-sectional area of ​​the nozzle throat, This refers to the actual air pressure value of the nozzle. This refers to air density.

[0014] In one embodiment of the present invention, the feedback control algorithm is a PID algorithm.

[0015] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects: This invention utilizes a metering nozzle movable at the inlet of a six-stage sieve probe to collect differential pressure in real time and accurately calculate the actual flow rate, eliminating errors caused by incorrect measurement positions in traditional pipelines and controlling measurement accuracy within ±2%. Simultaneously, by employing static airtightness calibration to obtain the leakage coefficient, the condition of the sealing ring can be quantitatively determined, ensuring that the probe's airtightness meets standards before sampling, effectively solving the data distortion problem caused by interlayer leakage. Furthermore, a feedback control algorithm is used to adjust the pumping power in real time based on flow deviation, dynamically offsetting fluctuations in the positive pressure of the air conditioning supply and stably maintaining a standard flow rate of 28.3 L / min. In addition, each sieve layer is secured by a fixed hook and a fixed groove with a friction texture design, making disassembly and assembly convenient and ensuring reliable sealing, suitable for mass application in grassroots disease control. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the external structure of a constant flow sampling device with a sieve probe according to an embodiment of the present invention; Figure 2 This is a schematic cross-sectional view of the six-stage sieve probe in an embodiment of the present invention; Figure 3 This is a schematic cross-sectional view of the sieve layer in an embodiment of the present invention; Figure 4 This is a top view of the sieve layer in an embodiment of the present invention; Figure 5 This is a schematic diagram of the clamping process of the fixing hook in area A in an embodiment of the present invention; Figure 6 This is a schematic cross-sectional view of the nozzle in an embodiment of the present invention; Figure 7 This is a top view of the six-stage sieve probe in an embodiment of the present invention; Figure 8 This is a flowchart illustrating the actual flow feedback control method of a constant flow sampling device with a sieve probe according to an embodiment of the present invention.

[0017] In all the accompanying drawings, the same reference numerals denote the same technical features, specifically: 100-sixth-stage sieve probe, 110-sieve layer, 111-sieve body, 1111-friction texture, 112-sieve layer sealing ring, 113-plate groove, 114-gas collection channel, 115-sieve hole, 116-plate pad, 117-sieve layer fixing hook, 1171-corner protrusion, 118-fixing groove, 1181-groove body, 1182 -Cavity, 1183-Notch, 120-Cover, 121-Cover, 122-Ventilation tube, 123-Cover fixing hook, 130-Metering nozzle, 131-Nose body, 132-Nose ring arm, 133-Nose sealing ring, 134-Air pressure connecting pipe, 140-Seat, 141-Seat, 142-Exhaust port, 143-Seat sealing ring, 200-Evacuation device, 300-Feedback control device. Detailed Implementation

[0018] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the present invention.

[0019] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0020] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0022] Impact sampling is widely used in environmental hygiene testing in public places. The "Indoor Air Quality Standard" GB / T 18883-2022 clearly stipulates that impact sampling is used for total indoor air bacterial count. The principle is that air passes through a narrow slit or small hole to create a high-speed airflow, collecting airborne microorganisms onto nutrient agar plates. After incubation at 36℃±1℃ for 48 hours, colonies are counted. The "Hygienic Standard for Centralized Air Conditioning and Ventilation Systems in Public Places" WS 10013-2023 also stipulates that impact sampling must be used for microbial sampling of centralized air conditioning supply air.

[0023] Current standards uniformly require a sampling flow rate of 28.3 L / min, but actual testing suffers from three major technical deficiencies: First, the flow measurement location is incorrect and cannot reflect the true flow rate: the existing method only measures the flow rate at the connection pipe between the air extraction device and the six-stage sieve probe (or other sieve probes), which cannot accurately reflect the actual sampling flow rate at the probe inlet and is not compatible with the impact grading principle. Secondly, the probe leakage was not included in the quality control and the flow deviation was serious: the six-stage sieve probe is composed of a multi-layer tower body, and the layers are sealed by sealing rings. The aging and deformation of the sealing rings caused leakage. The leakage rate is a key factor affecting the flow rate, and the current specifications do not have a calibration method. Finally, static calibration cannot adapt to dynamic wind pressure on site: existing traditional air extraction devices are power-locked and can only be calibrated under static conditions. When there is positive wind pressure in the air conditioning supply, the flow measurement is completely distorted and cannot maintain the standard value of 28.3 L / min.

[0024] In summary, existing technologies cannot solve the problems of inaccurate actual flow rates, unknown impact of air leakage, and inaccurate dynamic wind pressure, which directly leads to unreliable microbial sampling data and a lack of quality control systems.

[0025] To solve the above problems, such as Figures 1-4 As shown, in an embodiment of the present invention, a constant flow sampling device with a 115-mesh sieve probe comprises a six-stage 115-mesh sieve probe 100, an air extraction device 200, and a feedback control device 300 electrically connected to the air extraction device 200. The six-stage 115-mesh sieve probe 100 includes: The seat 140 includes a seat body 141, a sealing ring for the seat 140 is provided on its upper surface, and an exhaust port 142 is provided on one side. The exhaust port 142 is connected to the air extraction device 200 through a pipe. Screen layer 110, comprising multiple screen bodies 111 stacked sequentially on seat layer 140, each screen body 111 comprising: A groove 113 is provided inside the sieve body 111, and the horizontal cross-sectional area of ​​the groove is smaller than the horizontal cross-sectional area of ​​the sieve body 111. A screen layer sealing ring 112 is disposed on the upper surface of the screen body 111, and the shape of the screen layer sealing ring 112 is a closed shape. A sieve hole 115 is provided at the bottom of the groove 113 of the plate; At least three dish pads 116 are disposed on the bottom surface of the groove 113 of the plate; Cover layer 120, placed on the sieve layer 110, includes: Cover 121; A vent pipe 122 is provided on the upper part of the cover 121 for allowing gas to enter the cover 121 and be introduced into the gas supply. A metering nozzle 130 is movably mounted on the air duct 122 and electrically connected to the feedback control device 300, used to meter the air pressure of the incoming air.

[0026] The basic structure of this invention is similar to that of the equipment used in existing impact sampling methods. It consists of a six-stage sieve 115 probe 100 as the sampling probe, an air extraction device 200 that provides air extraction power to the probe, and a feedback control device 300 for implementing control functions. The six-stage sieve 115 probe 100 and the air extraction device 200 are connected through an exhaust port 142 on the seat 140 of the six-stage sieve 115 probe 100. The feedback control device 300 is electrically connected to the six-stage sieve 115 probe 100 and the air extraction device 200. Next, the gas pressure value at the metering nozzle 130 of the six-stage sieve aperture 115 probe 100 is obtained, and a signal for controlling the air flow rate of the air extraction device 200 is calculated and fed back based on this gas pressure value. When the detection starts, the air extraction device 200 extracts the gas from the six-stage sieve aperture 115 probe 100 at a preset flow rate value, thereby realizing the impact detection. By adding the metering nozzle 130, the actual gas flow rate at the first layer of sieve aperture 115 can be controlled. The preset flow rate is usually 28.3 L / min. In addition, the metering nozzle 130 needs to be connected to a pressure sensor to detect air pressure. That is, the pressure sensor is connected to the pressure communication pipe 134 to detect air pressure. Then, the measured value of the pressure sensor is typically connected to the feedback control device 300 to realize the purpose of feeding back the detected air pressure value to the feedback control device 300. Since this is common knowledge to those skilled in the art, the pressure sensor connected to the pressure communication pipe 134 through the pipe is not shown in the figure. Also, since the location of the feedback control device 300 does not affect the effect of the present invention, the location of the feedback control device 300 is not shown in the figure.

[0027] like Figure 3 As shown, in one embodiment of the present invention, each of the sieve bodies 111 further includes: At least two fixing slots 118, including: a slot 1181 disposed on the surface of the screen body 111 and a cavity 1182 disposed on one side of the bottom surface of the slot 1181. The height of the cavity 1182 is less than the depth of the slot 1181. All the fixing slots 118 are centrally symmetrically disposed on the upper surface of the screen body 111 with the center point of the bottom surface of the screen body 111 as the symmetrical point. At least two screen layer fixing hooks 117 are respectively disposed at the bottom of the screen body 111 in the direction of gravity relative to the screen layer fixing hooks 117, so that the screen layer fixing hooks 117 of the upper screen layer 110 can be inserted into the fixing grooves 118 of the lower screen layer 110 one by one, and the upper and lower screen layers 110 are clamped by rotating the screen body 111.

[0028] The existing conventional sieve aperture 115 probe design has an air leakage problem. The main reason is that the existing design sets up multiple sieve layers 110 in a stacked manner, relying on their own weight to seal or adding several springs to apply overall pressure to achieve a sealing effect. Even with the addition of sealing rings, this design cannot achieve good results in practical applications. This is because the upper sieve layer 110 cannot reliably rely solely on its own weight. Deviations in placement, the presence of small dust particles, or even excessive air pressure can significantly reduce the sealing effect. In the design with added springs, the placement of the springs and the different tensions between different springs make it difficult to apply force evenly, causing slight warping between the sieve layers 110, which still cannot solve the sealing problem.

[0029] To address the air leakage problem of the conventional sieve aperture 115 probe in existing designs, in one embodiment of this design, at least two fixing grooves 118 and at least two corresponding sieve fixing hooks 117 are provided on the sieve body 111 of each sieve layer 110. To ensure uniform force application, the fixing grooves 118 and sieve fixing hooks 117 should be centrally symmetrically distributed along the graphic center of the upper and lower surfaces of the sieve layer 110, respectively. The fixing groove 118 and the screen layer fixing hook 117 are one-to-one corresponding in the direction of gravity on the same screen body 111. The fixing groove 118 is a groove 1181 dug out on the upper surface of the screen body 111 and a cavity 1182 set on the same bottom surface as the groove 1181 but below the upper surface of the screen body 111. The screen layer fixing hook 117 is a hook-shaped structure fixedly set on the lower surface of the screen body 111. A preferred shape is "L". The purpose is to allow the screen layer fixing hook 117 to be placed one-to-one in the groove 1181 of the fixing groove 118 when the screen layers 110 are stacked one on top of the other. Then, by rotating, the lower end of the fixing hook of the screen body 111 is inserted into the cavity 1182 of the fixing groove 118. Because when the two screen layers 110 come into contact, the screen layer sealing ring 112 contacts first. The screen layer sealing ring 112 is usually made of elastic material such as rubber. Therefore, due to the elasticity of the sealing ring, the upper and lower screen layers 110 are clamped together. Furthermore, to ensure a good seal, after stacking, the sieve layer sealing ring 112 supports the upper sieve layer 110. Therefore, the length of the sieve layer fixing hook 117 should be slightly less than the distance between the lower surface of the upper sieve layer 110 and the bottom of the fixing groove 118 of the lower sieve layer 110. This allows the sieve layer fixing hook 117 to be pulled upwards by the elasticity of the sieve layer sealing ring 112. The shape of the fixing groove 118 is similar to that of the sieve layer fixing hook 117, one purpose of which is to allow the sieve layer fixing hook 117 to be inserted into the cavity 1182. This achieves a seal on the sixth-level sieve aperture 115 probe 100, reducing air leakage. The arrows in the figure indicate the direction of airflow.

[0030] Furthermore, in one embodiment of the present invention, the cover 121 further includes at least two cover fixing hooks 123, wherein the cover fixing hooks 123 are centrally symmetrically arranged at the lower part of the cover 121 with the center point of the bottom surface of the cover 121 as the symmetrical point.

[0031] The air leakage problem between the sieve layers 110 is solved. The sealing problem between the cover 121 and the sieve 111 can also be solved by adding a corresponding structure to achieve clamping by rotation. In addition, the same structure can be set between the seat layer 140 and the sieve layer 110 to achieve clamping. For example, a fixing groove 118 can be set on the seat 141 of the seat layer 140, and the sieve fixing hooks 117 of the upper sieve layer 110 can be placed in the fixing groove 118 of the seat 141. Furthermore, since the seat layer 140 is directly connected to the air extraction device 200, and under the weight of the multiple sieve layers 111 and the cover 121, the air leakage here can be ignored. Those skilled in the art can add fixing grooves 118 or similar structures according to actual needs.

[0032] like Figure 4-5 As shown, in one embodiment of the present invention, each cavity 1182 further includes: An inclined groove block is disposed on the top of the cavity 1182, such that the height of the side of the cavity 1182 closer to the groove 1181 is greater than the side farther away from the groove 1181.

[0033] Since the screen layer fixing hook 117 is L-shaped, in actual use, it is necessary to press and rotate it at the same time to insert the screen layer fixing hook 117 into the cavity 1182 to complete the locking. To simplify the use, an inclined groove block is set at the top of each cavity 1182, so that the bottom of the screen layer fixing hook 117 does not need to be pressed to the bottom. When rotating, it can automatically increase the locking pressure downward. Rotating in the opposite direction is a process of releasing force, making it easier to rotate out. In addition, since the screen layer sealing ring 112 is made of rubber with high friction, after being screwed in, the friction between the screen layer sealing ring 112 and the bottom of the upper screen layer 110 can keep the locked structure for a long time without rotating out on its own.

[0034] Furthermore, to better achieve long-term self-holding after the screen layers 110 are locked together, and to improve ease of use, a portion of the "L"-shaped part of the screen layer fixing hook 117 that protrudes into the cavity 1182 can be obliquely cut off, so that the cut-off surface is parallel to the lower surface of the oblique groove block. This structure makes it easier to screw in and out. To ensure locking, a convex angle 1171 with a triangular slope shape is provided at the oblique surface of the screen layer fixing hook 117. Correspondingly, a notch 1183 is provided on the lower surface of the oblique groove block, so that the convex angle 1171 and the notch 1183 can engage and lock together. When tightening, the user can judge the degree of tightening by the displacement vibration generated by the engagement of the convex angle 1171 and the notch 1183. At the same time, the locking effect between the screen layers 110 is better, which further reduces the excessive pressure on the screen layer sealing ring 112 due to misjudgment of the tightening effect, and also protects the screen layer sealing ring 112.

[0035] like Figure 4As shown, in one embodiment of the present invention, the outer sides of the sieve body 111, the cover body 121, and the seat layer 140 are all provided with friction textures 1111 to increase friction.

[0036] The tightening process requires the application of rotational force. To make the rotational tightening process easier, friction is increased by adding friction textures 1111 to the cover layer 120, sieve layer 110 and seat layer 140, thus achieving convenient tightening.

[0037] Meanwhile, since air leakage also exists between the nozzle and the vent pipe 122, in order to further enhance the sealing between the metering nozzle 130 and the vent pipe 122, the present invention provides, as follows: Figure 2 , Figure 6 The metering nozzle 130 structure shown includes: a nozzle body 131, a nozzle ring arm 132 surrounding the outside of the nozzle body 131, a nozzle sealing ring 133 annularly located at the bottom of the nozzle body 131, and a pneumatic connecting pipe 134 located inside the nozzle body 131. The longitudinal cross-section of the nozzle body 131 is a trapezoid with a wider top and a narrower bottom. The diameter of the top of the nozzle body 131 is larger than the inner diameter of the vent pipe 122, and the diameter of the bottom of the nozzle body 131 is smaller than the inner diameter of the vent pipe 122. At the same time, an annular support is provided inside the vent pipe 122, so that when the metering nozzle 130 is installed on the vent pipe 122, the nozzle sealing ring 133 contacts the annular support to achieve a seal. Furthermore, to further increase the sealing between the metering nozzle 130 and the vent pipe 122, threads can be provided on the outside of the vent pipe 122 and the inside of the nozzle ring arm 132. By rotating, the two can be engaged to achieve a further seal. This allows for separate sterilization and convenient assembly and replacement.

[0038] like Figure 3 As shown, in one embodiment of the present invention, the sieve body 111 further includes an air collecting channel 114 disposed at the bottom of the mounting plate groove 113, and the diameter of the air collecting channel 114 is smaller than the diameter of the overall area of ​​the sieve hole 115.

[0039] Because the sieve body 111 of the sieve layer 110 has a placement plate groove 113, during use, a petri dish is placed in the placement plate groove 113 to capture microorganisms in the airflow. After the airflow passes through the sieve holes 115 on the placement plate groove 113 and directly impacts the surface of the petri dish, the airflow becomes turbulent. When flowing to the next sieve layer 110, the effectiveness of the petri dish in capturing microorganisms is affected, which directly affects the final detection result. By setting up the gas collection channel 114, a buffer space can be provided for the turbulent airflow, ensuring that it flows downwards as much as possible before passing through the next sieve hole 115. This allows for the best capture effect when directly impacting the petri dish of the next sieve layer 110. Therefore, the diameter of the gas collection channel 114 should be smaller than the diameter of the sieve hole 115.

[0040] It is worth noting that, in order to enable the six-stage sieve aperture 115 probe 100 to better collect gas from the target location, a pipe can be added at the ventilation pipe 122 to extend to the target location for air collection, or a bracket can be added to raise the six-stage sieve aperture 115 probe 100 to the target location. These are common knowledge to those skilled in the art, and therefore are not shown in the accompanying drawings.

[0041] At this point, the sealing problem of the six-stage sieve aperture 115 probe 100 has been solved. However, in actual use, the six-stage sieve aperture 115 probe 100 is usually placed at the exhaust duct outlet, such as the air conditioning outlet. In this case, the air velocity entering the six-stage sieve aperture 115 probe 100 will be greater than the theoretical ideal condition, which will cause deviations in the measured data. The solution is to reduce the suction power of the extraction device 200 accordingly to balance the air velocity entering the six-stage sieve aperture 115 probe 100. At the same time, the external exhaust rate is not necessarily constant, therefore, the suction power of the extraction device 200 needs to be adjusted in real time.

[0042] like Figure 8 As shown, to solve this problem, the present invention provides a method for actual flow feedback control of a sieve probe constant flow sampling device, the method comprising: The sixth-level sieve probe that meets the airtightness requirements was determined through static airtightness calibration; The actual air pressure value of the nozzle is obtained through the metering nozzle of the six-stage sieve probe. The measured flow rate of the nozzle is calculated using the differential pressure flow rate conversion formula. ; Based on the measured flow rate of the nozzle With the aforementioned leakage coefficient The ratio of the actual flow rate of the probe is used as the actual flow rate. ; The actual flow rate of the probe Compared with the preset standard flow rate value The difference between them is used as the flow deviation. ; Utilizing the flow deviation The pumping power of the pumping device is adjusted according to the feedback control algorithm to ensure the actual flow rate of the probe is [adjusted / improved]. Equal to the preset standard flow value .

[0043] Firstly, in actual use, the six-stage sieve probe mainly relies on various sealing rings for sealing. However, excessive use will exceed its lifespan, leading to a deterioration in sealing performance. Therefore, calibration is necessary to determine whether the six-stage sieve probe meets the airtightness requirements. If it does not, the sealing rings need to be replaced. The steps for determining whether a six-stage sieve probe meets the airtightness requirements through static airtightness calibration include: Seal the metering nozzle and turn on the suction device to the preset standard flow rate. Run the test to obtain the nozzle sealing pressure value. ; The air pressure value is blocked by the nozzle. The leakage flow rate is calculated using the differential pressure flow rate formula. ; According to the aforementioned air leakage flow rate value and preset standard flow value The leakage coefficient is calculated using the leakage coefficient formula. The leakage coefficient formula is as follows: Leakage coefficient formula: .

[0044] When the leakage coefficient is greater than or equal to the air tightness threshold, the six-level sieve probe meets the air tightness requirements. If the leakage coefficient is less than the air tightness threshold, the six-stage sieve probe does not meet the air tightness requirements.

[0045] First, seal the metering nozzle and turn on the suction device to operate at the preset standard flow rate. The operating rate is typically 28.3 L / min, which allows us to obtain the nozzle sealing pressure at the metering nozzle under sealed conditions. Under ideal conditions, the airflow at both the air extraction device and the nozzle sealing pressure value is 0. The air pressure should be equal to the pressure at the extraction device. If a leak occurs, the nozzle should be sealed at the specified pressure. The value will differ significantly from the air pressure at the extraction device. Numerically, this invention converts the air pressure value into a flow rate value using a pressure difference flow rate formula, that is, by sealing the air pressure value through the nozzle. The leakage flow rate value was obtained. The formula for differential pressure flow rate is: ,in, This represents the leakage flow rate (m³ / s or L / min). This is the outflow coefficient, determined by multi-point calibration at the factory, with a value ranging from 0.95 to 0.99. To measure the cross-sectional area (m²) of the nozzle throat. This is the nozzle sealing air pressure value. The density of air (kg / m³) is usually taken as 1.2.

[0046] It should be noted that, under sealed conditions, the minute pressure difference measured by the differential pressure sensor does not originate from the normal flow at the nozzle throat, but rather from the asymmetric flow field along the leakage path. Therefore, the leakage flow rate value calculated using the formula is not the actual physical flow rate, but rather an equivalent flow rate value used to quantify the degree of leakage.

[0047] Then based on the aforementioned air leakage flow rate value and preset standard flow value The leakage coefficient is calculated using the leakage coefficient formula. Leakage coefficient formula: And through the leakage coefficient This serves as a quantitative evaluation standard to further determine whether the six-stage sieve probe meets the airtightness requirements. Specifically, it measures the leakage flow rate when the six-stage sieve probe is leak-free. and preset standard flow value The ratio should be 1. If there is a leak, the leak flow rate should be... The ratio of the two should be closer to 0, as the ratio decreases.

[0048] Ultimately, if the leakage coefficient is greater than or equal to the airtightness threshold, the six-stage sieve probe meets the airtightness requirements and can be used. If the leakage coefficient is less than the airtightness threshold, the six-stage sieve probe does not meet the airtightness requirements and should be recalibrated after replacing the sealing components. The preferred value for the airtightness threshold is 0.9.

[0049] Furthermore, after confirming that the airtightness of the six-stage sieve probe meets the requirements, the six-stage sieve probe is set at the target position, and actual sampling begins. At this time, the actual air pressure value of the metering nozzle is measured. The measured flow rate of the nozzle is calculated using the flow rate-pressure difference formula. .

[0050] To account for minor air leaks at the metering nozzle and vent pipe, the actual measured flow rate of the nozzle needs to be adjusted. The correction is necessary because the airflow measured using the impact method, as stipulated in the relevant regulations, refers to the airflow between the first layer and the cover layer of the sieve probe. Therefore, the flow rate value at this location can be corrected based on the leakage coefficient at the metering nozzle, i.e., according to the actual measured flow rate at the nozzle. With the aforementioned leakage coefficient The ratio of the actual flow rate of the probe is used as the actual flow rate. .

[0051] Then, the actual flow rate of the probe... Compared with the preset standard flow rate value The difference between them is used as the flow deviation. It is used as a basis value for adjusting the power of the air extraction device as feedback data.

[0052] Finally, the flow deviation is utilized. The pumping power of the pumping device is adjusted according to the feedback control algorithm to ensure the actual flow rate of the probe is [adjusted / improved]. Equal to the preset standard flow value This allows for feedback control of the gas flow rate at the target location within the probe. The calculation formula is as follows: ;in, This represents the actual measured flow rate of the nozzle. To preset the outflow coefficient, The cross-sectional area of ​​the throat of the metering nozzle is [missing information]. This refers to the actual air pressure value of the nozzle. The density is the air density, which allows the sampling conditions to reach the most ideal state.

[0053] Preferably, in one embodiment of the present invention, the feedback control algorithm is the PID algorithm. The PID algorithm is a commonly used and mature algorithm in the field of industrial control. In practical use, it has low hardware dependence and requirements, and good performance. Therefore, it is an excellent choice for the feedback control in this solution. Those skilled in the art can also choose other corresponding algorithms based on the flow deviation. Adjustments are made to ensure the actual flow rate of the probe. Equal to the preset standard flow value .

[0054] The above are merely preferred embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application. The above are merely preferred embodiments of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of this application, and these improvements and modifications should also be considered within the protection scope of this application.

Claims

1. A constant flow sampling device with a sieve aperture (115) probe, comprising a six-stage sieve aperture (115) probe (100), an air extraction device (200), and a feedback control device (300) electrically connected to the air extraction device (200), characterized in that, The sixth-level sieve aperture (115) probe (100) includes: The seat layer (140) includes a seat body (141), a seat layer (140) sealing ring is provided on its upper surface, and an exhaust port (142) is provided on one side. The exhaust port (142) is connected to the air extraction device (200) through a pipe. A sieve layer (110), comprising multiple sieve bodies (111) stacked sequentially on the seat layer (140), each sieve body (111) comprising: A groove (113) is provided inside the sieve body (111), and the horizontal cross-sectional area of ​​the groove is smaller than the horizontal cross-sectional area of ​​the sieve body (111). A screen layer sealing ring (112) is disposed on the upper surface of the screen body (111), and the shape of the screen layer sealing ring (112) is a closed shape; A sieve hole (115) is provided at the bottom of the groove (113) of the plate; At least three dish pads (116) are disposed on the bottom surface of the groove (113) of the plate; A cover layer (120), placed on the sieve layer (110), comprising: Cover (121); A vent pipe (122) is provided on the upper part of the cover (121) for allowing gas to enter the cover (121) and vent gas. A metering nozzle (130) is movably mounted on the air duct (122) and electrically connected to the feedback control device (300) for measuring the air pressure of the incoming air.

2. The constant flow sampling device with a sieve aperture (115) probe according to claim 1, characterized in that, Each of the sieve bodies (111) further includes: At least two fixing grooves (118) are provided, including: a groove (1181) disposed on the surface of the screen body (111) and a cavity (1182) disposed on one side of the bottom surface of the groove (1181). The height of the cavity (1182) is less than the depth of the groove (1181). All the fixing grooves (118) are centrally symmetrically disposed on the upper surface of the screen body (111) with the center point of the bottom surface of the screen body (111) as the symmetry point. At least two screen layer fixing hooks (117) are respectively disposed at the bottom of the screen body (111) in the direction of gravity relative to the screen layer fixing hooks (117), so that the screen layer fixing hooks (117) of the upper screen layer (110) can be inserted into the fixing grooves (118) of the lower screen layer (110) one by one, and the upper and lower screen layers (110) are clamped by rotating the screen body (111).

3. The constant flow sampling device with a sieve aperture (115) probe according to claim 2, characterized in that, The cover (121) further includes at least two cover fixing hooks (123), which are symmetrically arranged at the lower part of the cover (121) with the center point of the bottom surface of the cover (121) as the symmetrical point.

4. The constant flow sampling device with a sieve aperture (115) probe according to claim 3, characterized in that, Each of the cavities (1182) further includes: An inclined groove block is disposed on the top of the cavity (1182) such that the height of the cavity (1182) on the side closer to the groove (1181) is greater than the height of the side farther away from the groove (1181).

5. The constant flow sampling device with a sieve aperture (115) probe according to claim 4, characterized in that, The outer sides of the sieve body (111), cover body (121), and seat layer (140) are all provided with friction textures (1111) to increase friction.

6. The constant flow sampling device with a sieve aperture (115) probe according to claim 1, characterized in that, The sieve body (111) also includes an air collection channel (114) disposed at the bottom of the plate groove (113), and the diameter of the air collection channel (114) is smaller than the diameter of the overall area of ​​the sieve hole (115).

7. A method for actual flow feedback control of a sieve probe constant flow sampling device, characterized in that, The method includes: The sixth-level sieve probe that meets the airtightness requirements was determined through static airtightness calibration; The actual air pressure value of the nozzle is obtained through the metering nozzle of the six-stage sieve probe. The measured flow rate of the nozzle is calculated using the differential pressure flow rate conversion formula. ; Based on the measured flow rate of the nozzle With the aforementioned leakage coefficient The ratio of the actual flow rate of the probe is used as the actual flow rate. ; The actual flow rate of the probe Compared with the preset standard flow rate value The difference between them is used as the flow deviation. ; Utilizing the flow deviation The pumping power of the pumping device is adjusted according to the feedback control algorithm to ensure the actual flow rate of the probe is [adjusted / improved]. Equal to the preset standard flow value .

8. A method for actual flow feedback control of a sieve probe constant flow sampling device, characterized in that, The steps for determining whether a Class 6 sieve probe meets the airtightness requirements through static airtightness calibration include: Seal the metering nozzle and turn on the suction device to the preset standard flow rate. Run the test to obtain the nozzle sealing pressure value. ; The air pressure value is blocked by the nozzle. The leakage flow rate is calculated using the differential pressure flow rate formula. ; According to the aforementioned air leakage flow rate value and preset standard flow value The leakage coefficient is calculated using the leakage coefficient formula. The leakage coefficient formula is as follows: Leakage coefficient formula: ; When the leakage coefficient is greater than or equal to the air tightness threshold, the six-level sieve probe meets the air tightness requirements. If the leakage coefficient is less than the air tightness threshold, the six-stage sieve probe does not meet the air tightness requirements.

9. The actual flow feedback control method of the constant flow sampling device with sieve probe according to claim 7, characterized in that, The formula for converting pressure difference to flow rate is: ;in, This represents the actual measured flow rate of the nozzle. To preset the outflow coefficient, The cross-sectional area of ​​the throat of the metering nozzle is [missing information]. This refers to the actual air pressure value of the nozzle. This refers to air density.

10. The actual flow feedback control method of the constant flow sampling device with sieve probe according to claim 7, characterized in that, The feedback control algorithm is the PID algorithm.

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