A microflow sensor

Abstract

This utility model discloses a microflow sensor, including a sensor substrate and a control system. The sensor substrate has a flow channel extending from one side to the other. A heating resistor is located at the center of the flow channel. A first thermistor and a second thermistor are symmetrically arranged on both sides of the heating resistor, closely attached to the outer wall of the flow channel and adjacent to the inlet and outlet of the flow channel, respectively. A square groove is formed in the sensor substrate, and a back release cavity for heat exchange extends below the square groove. A support structure is provided on the side of the square groove near the back release cavity, from top to bottom, where the heating resistor and the heat insulation layer are sequentially placed. A stepped filter structure is provided at the inlet of the flow channel. The control system includes a microcontroller. The first and second thermistors are connected to the microcontroller through a first signal conversion module and a second signal conversion module, respectively. This invention overcomes the problems of easy clogging of microchannels, measurement errors caused by substrate thermal conduction, and long response time, enabling rapid and accurate flow detection and calculation.

Description

Technical Field

[0001] This utility model belongs to the field of liquid detection technology, specifically relating to a microflow sensor. Background Technology

[0002] In existing industrial production, traditional flow meters such as turbine flow meters, Roots flow meters, and Pimometer flow meters are technologically mature and reliable. However, these flow meters are relatively large and heavy, and their sensitivity to detecting minute changes in flow rate is not high. They are unsuitable for micro-scale fluid detection, especially in fields such as biological analysis, liquid biopsy, and drug delivery. Therefore, highly integrated, highly sensitive, and interference-free MEMS microflow sensors are playing an increasingly important role in microfluidic detection.

[0003] However, the manufacturing process of MEMS flow sensors is relatively complex, and the flow channel size is too small, which poses a risk of pipe blockage. Furthermore, in scenarios such as biological analysis and drug detection, replacing pipes is difficult and costly, which poses challenges to the manufacturing of flow channels and product packaging. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this utility model provides a micro-flow sensor, aiming to overcome problems such as flow channel blockage that occur during operation of existing micro-flow sensors, as well as the complex and costly pipe replacement in single-use scenarios.

[0005] The technical solution provided by this utility model is as follows:

[0006] This utility model provides a micro-flow sensor, including a sensor substrate and a control system. The sensor substrate has a flow channel extending from one side to the other. A heating resistor is provided at the center of the flow channel. A first thermistor and a second thermistor are symmetrically arranged on both sides of the heating resistor, closely attached to the outer wall of the flow channel and respectively adjacent to the inlet and outlet of the flow channel. A square groove is formed in the sensor substrate, and a back release cavity for heat exchange extends below the square groove. A support structure is provided on the side of the square groove near the back release cavity, from top to bottom, in which the heating resistor and the heat insulation layer are placed. A stepped filter structure is provided at the inlet of the flow channel. The control system includes a microcontroller. The first thermistor and the second thermistor are connected to the microcontroller through a first signal conversion module and a second signal conversion module, respectively.

[0007] Furthermore, the sensor base includes a detachably connected upper sensor base and a lower sensor base. The upper end face of the lower sensor base has a lower mounting groove extending from one side to the other, and the lower end face of the upper sensor base has an upper mounting groove extending from one side to the other. The flow channel is embedded in the space enclosed by the upper mounting groove and the lower mounting groove. A square groove is provided below the middle part of the lower mounting groove, and the first thermistor and the second thermistor are symmetrically arranged on the left and right ends of the square groove.

[0008] Furthermore, the tiered filtration structure includes an elliptical liquid storage tank perpendicular to the flow channel pipe. The liquid storage tank has a liquid inlet and a liquid outlet connected to the flow channel pipe on its sides near and away from the inlet, respectively. A top cover plate is bonded to the top of the liquid storage tank. Several layers of cylindrical arrays are arranged sequentially between the upper and lower ends of the liquid storage tank along the direction of liquid flow. The number of cylinders in the outermost cylindrical array gradually increases from the innermost cylindrical array to the outermost cylindrical array. The radius of the cylinders in the outermost cylindrical array to the innermost cylindrical array and the spacing between the cylinders in the outermost cylindrical array to the spacing between the cylinders in the innermost cylindrical array both decrease step by step.

[0009] Furthermore, the support structure is a cross-shaped structure located on the side of the square groove near the rear release cavity. The top of the rear release cavity corresponds to the bottom of the square groove and its length gradually increases along the bottom direction of the lower sensor base, and its cross-section is an isosceles trapezoid.

[0010] Furthermore, the upper sensor base is provided with a first disassembly structure and a second disassembly structure, and the lower sensor base is provided with a first disassembly slot and a second disassembly slot corresponding to the first disassembly structure and the second disassembly structure. The first disassembly structure and the first disassembly slot, the second disassembly structure and the second disassembly slot are all connected to the upper sensor base and the lower sensor base by a snap-fit ​​structure.

[0011] Furthermore, it also includes a positioning protrusion and a positioning slot. The positioning protrusion is disposed on the upper sensor base, and the positioning slot is disposed on the lower sensor base. The positioning protrusion is embedded in the positioning slot to achieve positioning alignment between the upper sensor base and the lower sensor base.

[0012] Furthermore, it also includes wire grooves and wire holes provided on the lower sensor substrate, and the heating resistor, the first thermistor and the second thermistor are connected to the control system through wires led out from the wire grooves and wire holes.

[0013] Furthermore, the microcontroller is an STM32 microcontroller, and both the first signal conversion module and the second signal conversion module use MAX31865 modules. Both the first signal conversion module and the second signal conversion module are connected to the STM32 microcontroller through an SPI interface, and both the first thermistor and the second thermistor are connected to the first signal conversion module and the second signal conversion module using a three-wire connection.

[0014] Beneficial effects

[0015] This invention utilizes first and second thermistors symmetrically arranged on both sides of a heating resistor to accurately sense minute temperature differences between the upstream and downstream of the fluid. Combined with signal processing by a microcontroller, it achieves high sensitivity and high precision measurement of micro-flow rates. The tiered filtration structure effectively intercepts impurity particles at the inlet, significantly reducing the risk of flow channel blockage. The rear-side release chamber design, combined with the heat insulation layer within the square groove, significantly optimizes thermal management. On one hand, it concentrates heat in the central region of the flow channel to improve heating efficiency; on the other hand, it reduces ineffective heat dissipation to the substrate, ensuring both measurement sensitivity and energy consumption. The overall structure of this invention is compact, and its thermal design is reasonable, ensuring the stability and accuracy of the sensor in micro-flow rate detection.

[0016] This invention relates to a microflow sensor with a stepped filtration structure in its flow channel, effectively reducing the risk of flow channel blockage. It also incorporates a heat insulation structure and a back-side release cavity, minimizing heat conduction between the heating resistor and the sensor substrate. This significantly reduces measurement errors caused by heat conduction, greatly lowering the sensor's manufacturing cost while enabling accurate and stable flow detection. This invention overcomes the problems of easy blockage in microchannels, measurement errors due to substrate heat conduction, and long response times, achieving reliable, fast, and accurate flow detection and calculation while reducing manufacturing costs. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the lower sensor substrate structure provided by this utility model;

[0018] Figure 2 This is a schematic diagram of the structure of the upper sensor substrate provided by this utility model;

[0019] Figure 3 This is a schematic diagram of the structure of the lower sensor substrate provided by this utility model;

[0020] Figure 4 This is a schematic diagram of the structure of the sensor substrate provided by this utility model;

[0021] Figure 5 This is a schematic diagram of the rear release cavity provided by this utility model;

[0022] Figure 6This is a schematic diagram of the flow channel pipe with a stepped filtration structure provided by this utility model;

[0023] Figure 7 This is an enlarged view of the cascade filter structure provided by this utility model;

[0024] Figure 8 This is a schematic diagram of the structure of the novel micro-flow sensor.

[0025] Explanation of reference numerals in the attached drawings: 1. Heating resistor; 2. Flow channel; 3. Upper sensor base; 4. Lower sensor base; 5. First thermistor; 6. Second thermistor; 7. First disassembly slot; 8. Positioning slot; 9. Second disassembly slot; 10. Step-by-step filter structure; 11. Rear release chamber; 12. Inlet; 13. Outlet; 14. Wire hole; 15. First MAX31865 module; 16. STM32 microcontroller; 17. Second MAX31865 module; 18. Positioning protrusion; 19. First disassembly structure; 20. Second disassembly structure; 21. Support structure; 23. Heat insulation layer; 24. First cylindrical array; 25. Second cylindrical array; 26. Third cylindrical array; 27. Fourth cylindrical array; 28. Top cover plate; 29. ​​Liquid storage tank. Detailed Implementation

[0026] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0027] In the description of this utility model, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this utility model, unless otherwise stated, "a plurality of" means two or more.

[0028] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" 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 utility model based on the specific circumstances.

[0029] Example 1

[0030] like Figures 1 to 8 As shown, this utility model embodiment provides a micro-flow sensor, including a sensor substrate and a control system. The sensor substrate has a flow channel extending from one side to the other. A heating resistor 1 is provided at the center of the flow channel. A first thermistor 5 and a second thermistor 6 are symmetrically arranged on both sides of the heating resistor 1, closely attached to the outer wall of the flow channel 2 and respectively adjacent to the inlet 12 and outlet 13 of the flow channel. A square groove is provided in the sensor substrate, and a back release cavity 11 for heat exchange extends below the square groove. A support structure 21 is provided on the side of the square groove near the back release cavity 11, in which the heating resistor 1 and the heat insulation layer 23 are arranged sequentially from top to bottom. A stepped filter structure 10 is provided at the inlet 12 of the flow channel. The control system includes a microcontroller. The first thermistor 5 and the second thermistor 6 are connected to the microcontroller through a first signal conversion module and a second signal conversion module, respectively.

[0031] This invention utilizes first and second thermistors symmetrically arranged on both sides of a heating resistor to accurately sense minute temperature differences between the upstream and downstream of the fluid. Combined with signal processing by a microcontroller, it achieves high sensitivity and high precision measurement of micro-flow rates. The tiered filtration structure effectively intercepts impurity particles at the inlet, significantly reducing the risk of flow channel blockage. The rear-side release chamber design, combined with the heat insulation layer within the square groove, significantly optimizes thermal management. On one hand, it concentrates heat in the central region of the flow channel to improve heating efficiency; on the other hand, it reduces ineffective heat dissipation to the substrate, ensuring both measurement sensitivity and energy consumption. The overall structure of this invention is compact, and its thermal design is reasonable, ensuring the stability and accuracy of the sensor in micro-flow rate detection.

[0032] Example 2

[0033] like Figures 1 to 8As shown, this utility model provides a micro-flow sensor, including a sensor substrate and a control system. The sensor substrate contains a heating resistor 1, a first thermistor 5, a second thermistor 6, a flow channel 2, a back release chamber 11, and a heat insulation layer 23. The sensor substrate has an inlet 12 and an outlet 13, which are used to connect to an external fluid pipe to achieve fluid conduction between the micro-flow sensor and the external fluid pipe. A stepped filter structure 10 is provided near the inlet end of the flow channel 2. The flow channel 2 extends from one side of the sensor substrate to the other side of the sensor for fluid flow. The heating resistor 1 is located at the center of the flow channel 2 and is used to heat the fluid inside the flow channel 2. The first thermistor 5 and the second thermistor 6 are symmetrically placed on both sides of the heating resistor 1 to detect the fluid temperature inside the flow channel 2. The first thermistor 5 is located near the filter structure in the flow channel 2 and is in close contact with the outer wall of the flow channel 2 to detect the filtered fluid inside the flow channel 2. The temperature of the fluid in the flow channel 2 is measured by the temperature of the fluid in the flow channel 2. The second thermistor 6 is located away from the stepped filter structure 10 and is in close contact with the outer wall of the flow channel 2. It is used to detect the temperature of the fluid in the flow channel 2 after being heated by the heating resistor 1. A square groove is provided in the sensor substrate, and a back release cavity 11 for heat exchange extends below the square groove. A support structure 21 is provided on the side of the square groove near the back release cavity 11, in which the heating resistor 1 and the heat insulation layer 23 are placed sequentially from top to bottom. This is used to reduce the heat conduction between the heating resistor 1 and the sensor substrate. The control system includes an STM32 microcontroller 16, a first MAX31865 module 15 and a second MAX31865 module 17. The first thermistor 5 and the second thermistor 6 are connected to the STM32 microcontroller 16 through the first MAX31865 module 15 and the second MAX31865 module 17, respectively. They are used to detect the change in the resistance of the thermistor and send it to the STM32 microcontroller 16 to calculate the corresponding flow rate in the flow channel 2. Figure 7 ).like Figure 1 As shown, the sensor substrate is made of red wax resin; the first thermistor 5 and the second thermistor 6 are platinum resistors; the heating resistor 1 is a PTC heating resistor; and the heat insulation layer 23 is made of silicon nitride.

[0034] In this embodiment, as Figure 4 As shown, the sensor base includes an upper sensor base 3 and a lower sensor base 4 that are detachably connected. The upper end face of the lower sensor base 4 is provided with a lower mounting groove extending from one side to the other side. The lower end face of the upper sensor base 3 is provided with an upper mounting groove extending from one side to the other side. The flow channel is embedded in the space enclosed by the upper mounting groove and the lower mounting groove. A square groove is provided below the middle part of the lower mounting groove, and the first thermistor 5 and the second thermistor 6 are symmetrically arranged on the left and right ends of the square groove.

[0035] In this embodiment, the tiered filtration structure 10 includes an elliptical liquid storage tank 29 perpendicular to the flow channel pipe. The liquid storage tank 29 has a liquid inlet and a liquid outlet connected to the flow channel pipe on its sides near and away from the inlet 12, respectively. A top cover plate 28 is bonded to the top of the liquid storage tank 29. Several layers of cylindrical arrays are arranged sequentially between the upper and lower ends of the liquid storage tank 29 along the direction of liquid flow. The number of cylinders in the outermost cylindrical array to the innermost cylindrical array gradually increases, and the radius of the cylinders in the outermost cylindrical array to the innermost cylindrical array and the spacing between the cylinders in the outermost cylindrical array to the spacing between the cylinders in the innermost cylindrical array both decrease step by step.

[0036] Specifically, such as Figure 6 and Figure 7 As shown, a first cylindrical array 24, a second cylindrical array 25, a third cylindrical array 26, and a fourth cylindrical array 27 are sequentially arranged between the upper and lower ends of the liquid storage tank 29 along the direction of liquid flow. The first cylindrical array 24 consists of 11 cylinders with a radius of 0.15 mm and a height of 1 mm, with a spacing of 0.15 mm between adjacent cylinders. When the fluid passes through the first cylindrical array 24, solid impurities larger than 0.15 mm will be retained in the liquid storage tank 29. The second cylindrical array 25 consists of 13 cylinders with a radius of 0.13 mm and a height of 1 mm, with a spacing of 0.13 mm between adjacent cylinders. When the fluid passes through the second cylindrical array 25, solid impurities larger than 0.13 mm will be retained in the liquid storage tank 29. The liquid storage tank 29 consists of a third cylindrical array 26, which comprises 15 cylinders with a radius of 0.11 mm and a height of 1 mm, with a spacing of 0.11 mm between adjacent cylinders. When the fluid passes through the third cylindrical array 26, solid impurities larger than 0.11 mm will be retained in the liquid storage tank 29. The fourth cylindrical array 27 consists of 17 cylinders with a radius of 0.09 mm and a height of 1 mm, with a spacing of 0.09 mm between adjacent cylinders. When the fluid passes through the fourth cylindrical array 27, solid impurities larger than 0.09 mm will be retained in the liquid storage tank 29. The fluid eventually flows to the liquid outlet of the liquid storage tank 29, which is connected to the flow channel pipe 2 to achieve the purpose of allowing pure fluid to flow into the liquid channel. Fluid flows into the liquid inlet of the cascade filtration structure 10 through the inlet 12 of the flow channel 2. After passing through the first cylindrical array 24, impurities larger than 0.15 mm will remain in the liquid storage tank 29. After passing through the second cylindrical array 25, solid impurities larger than 0.13 mm will remain in the liquid storage tank 29. When the fluid flows through the third cylindrical array 26, solid impurities larger than 0.11 mm will remain in the liquid storage tank 29. Finally, the fluid flows into the flow channel 2 through the fourth cylindrical array 27, and solid impurities larger than 0.09 mm will remain in the liquid storage tank 29.

[0037] In this embodiment, as Figure 3and Figure 5 As shown, the support structure 21 is a cross-shaped structure located on the side of the square groove near the back release cavity 11. The top of the back release cavity 11 corresponds to the bottom of the square groove and its length gradually increases along the bottom direction of the lower sensor base 4, and its cross section is an isosceles trapezoid.

[0038] In this embodiment, as Figure 1 and Figure 2 As shown, the upper sensor base 3 is provided with a first disassembly structure 19 and a second disassembly structure 20, and the lower sensor base 4 is provided with a first disassembly slot 7 and a second disassembly slot 9 corresponding to the first disassembly structure 19 and the second disassembly structure 20. The first disassembly structure 19 and the first disassembly slot 7, the second disassembly structure 20 and the second disassembly slot 9 are all connected to the upper sensor base 3 and the lower sensor base 4 by a snap-fit ​​structure.

[0039] In this embodiment, as Figure 1 and Figure 2 As shown, it also includes a positioning protrusion 18 and a positioning slot 8. The positioning protrusion 18 is disposed on the upper sensor base 3, and the positioning slot 8 is disposed on the lower sensor base 4. The positioning protrusion 18 is embedded in the positioning slot 8 to achieve positioning alignment between the upper sensor base 3 and the lower sensor base 4.

[0040] In this embodiment, as Figure 1 As shown, it also includes a wire groove and a wire hole 14 disposed on the lower sensor base 4, and the heating resistor 1, the first thermistor 5 and the second thermistor 6 are connected to the control system through the wires led out from the wire groove and the wire hole 14.

[0041] In this embodiment, the microcontroller is an STM32 microcontroller 16, and both the first signal conversion module and the second signal conversion module use MAX31865 modules. Both the first signal conversion module and the second signal conversion module are connected to the STM32 microcontroller 16 through an SPI interface. The first thermistor 5 and the second thermistor 6 are both connected to the first signal conversion module and the second signal conversion module using a three-wire connection.

[0042] Specifically, such as Figure 5As shown, the wires of the first thermistor 5 and the second thermistor 6 are connected to the receiving ends of the first MAX31865 module 15 and the second MAX31865 module 17 using a three-wire connection. The communication ports of the first MAX31865 module 15 and the second MAX31865 module 17 are connected to the SPI communication interface of the STM32 microcontroller 16. The thermistors are connected to the MAX31865 modules using a three-wire connection, combined with a Wheatstone bridge, signal amplification circuit, and A / D sampling circuit. The MAX31865 modules communicate with the STM32 microcontroller in real time using SPI. The method includes: constructing a thermal balance model of the heating resistor based on the second law of thermodynamics and the law of conservation of energy; the thermal balance model of the heating resistor is... Where I represents the current value across the heating resistor; R h h is the resistance value of the heating resistor. fc Indicates the forced convection heat transfer coefficient; A represents the surface area of ​​the straight pipe; T d This indicates the temperature of the fluid measured by the downstream temperature sensing resistor; T u This indicates the temperature of the fluid measured by the upstream temperature sensing resistor; h nc ΔT represents the natural convection heat transfer coefficient; λ represents the thermal conductivity of the sensor substrate; δ represents the thickness of the substrate under the heating resistor; ΔT c ε represents the temperature difference between the heating resistor and the substrate; ε represents the emissivity of the heating resistor surface; σ is the Stefen-Boltzmann constant, σ = 5.67 × 10⁻⁶. -8 (W / m 2 ).

[0043] The heat transfer of the sensor substrate is analyzed based on the thermal balance model of the heating resistor to obtain the thermal analytical model of the sensor substrate; a heat convection heat transfer model is constructed based on the second law of thermodynamics and the fluid driving method; a heat transfer model of the substrate is constructed based on heat conduction, heat radiation, and the heating resistor; the thermal analytical model of the sensor substrate is as follows: Where d represents the diameter of the fluid channel; l represents the length of the fluid channel; an equivalent circuit model corresponding to the two thermistors is constructed based on the preset resistance function and the thermal analysis information; the equivalent circuit model is as follows: T is the temperature corresponding to the change in the thermistor's resistance, R(T) is the resistance value at temperature T, R0 is the resistance value at 0℃, and a, b, and c are coefficients. When 0℃≤T≤+850℃, a is taken as 3.90830×10 -3 b = -5.775 × 10 -7 c=0; The thermal analysis information is used to perform force-thermal-electric coupling on the thermal balance model of the heating resistor and the equivalent circuit model to obtain the system-level equivalent circuit model corresponding to the sensor.

[0044] The detection principle of this invention is as follows: A first thermistor 5 and a second thermistor 6 are symmetrically arranged at both ends of a heating resistor 1, respectively detecting the temperature of the fluid upstream and downstream in the flow channel 2. The temperature field of the heating resistor 1 gradually shifts downstream as the fluid flow rate increases, creating a temperature difference between the two thermistors. The first MAX31865 module 15 and the second MAX31865 module 17 detect the change in the resistance value of the thermistors and convert it into a digital signal, which is then transmitted to the STM32 microcontroller 16. When there is no fluid to be measured in the flow channel 2, the heating resistor... The temperature field of resistor 1 is symmetrically distributed. There is no temperature difference between the two thermistors. The temperature value can be calculated by the functional relationship between the resistance value and the temperature of the thermistors. Therefore, when fluid flows through the flow channel 2 or the fluid flow rate changes, the fluid enters from the inlet 12 side and flows out from the outlet 13 side. At this time, the temperature field of heating resistor 1 will shift towards the second thermistor 6. The temperature difference can be obtained by detecting and identifying the resistance values ​​of the two thermistors. The flow rate of the fluid in the straight pipe 2 with the filter structure can be determined by the existing calculation algorithm.

[0045] The above description is merely a preferred embodiment of this utility model and does not constitute any limitation on this utility model. Any person skilled in the art can make many possible variations and modifications to the technical solution of this utility model, or modify it into equivalent embodiments, without departing from the scope of the technical solution of this utility model. Therefore, any modifications, equivalent changes, and alterations made to the above embodiments based on the technology of this utility model without departing from the scope of the technical solution of this utility model shall fall within the protection scope of this technical solution.

Claims

1. A microflow sensor, characterized by The system includes a sensor substrate and a control system. The sensor substrate has a flow channel extending from one side to the other. A heating resistor is located at the center of the flow channel. A first thermistor and a second thermistor are symmetrically arranged on both sides of the heating resistor, closely attached to the outer wall of the flow channel and adjacent to the inlet and outlet of the flow channel, respectively. A square groove is formed in the sensor substrate, and a back release cavity for heat exchange extends below the square groove. A support structure is provided on the side of the square groove near the back release cavity, from top to bottom, in which the heating resistor and the heat insulation layer are placed. A stepped filter structure is provided at the inlet of the flow channel. The control system includes a microcontroller. The first thermistor and the second thermistor are connected to the microcontroller through a first signal conversion module and a second signal conversion module, respectively.

2. The micro-flow sensor of claim 1, wherein, The sensor base includes a detachably connected upper sensor base and a lower sensor base. The upper end face of the lower sensor base has a lower mounting groove extending from one side to the other, and the lower end face of the upper sensor base has an upper mounting groove extending from one side to the other. The flow channel is embedded in the space enclosed by the upper mounting groove and the lower mounting groove. A square groove is provided below the middle part of the lower mounting groove, and the first thermistor and the second thermistor are symmetrically arranged on the left and right ends of the square groove.

3. The micro-flow sensor of claim 2, wherein, The tiered filtration structure includes an elliptical liquid storage tank perpendicular to the flow channel pipe. The liquid storage tank has a liquid inlet and a liquid outlet connected to the flow channel pipe on its sides near and away from the inlet, respectively. A top cover plate is bonded to the top of the liquid storage tank. Several layers of cylindrical arrays are arranged sequentially between the upper and lower ends of the liquid storage tank along the direction of liquid flow. The number of cylinders in the outermost cylindrical array gradually increases from the innermost cylindrical array to the outermost cylindrical array. The radius of the cylinders in the outermost cylindrical array to the innermost cylindrical array and the spacing between the cylinders in the outermost cylindrical array to the spacing between the cylinders in the innermost cylindrical array both decrease step by step.

4. The micro-flow sensor of claim 2, wherein, The support structure is a cross-shaped structure located on the side of the square groove near the rear release cavity. The top of the rear release cavity corresponds to the bottom of the square groove and its length gradually increases along the bottom direction of the lower sensor base, and its cross-section is an isosceles trapezoid.

5. The micro-flow sensor of claim 2, wherein, The upper sensor base is provided with a first disassembly structure and a second disassembly structure, and the lower sensor base is provided with a first disassembly slot and a second disassembly slot corresponding to the first disassembly structure and the second disassembly structure. The first disassembly structure and the first disassembly slot, the second disassembly structure and the second disassembly slot are all connected to the upper sensor base and the lower sensor base by a snap-fit ​​structure.

6. The micro-flow sensor of claim 5, wherein, It also includes a positioning protrusion and a positioning slot. The positioning protrusion is disposed on the upper sensor base, and the positioning slot is disposed on the lower sensor base. The positioning protrusion is embedded in the positioning slot to achieve positioning alignment between the upper sensor base and the lower sensor base.

7. The micro-flow sensor of claim 2, wherein, It also includes wire grooves and wire holes on the lower sensor substrate, and the heating resistor, the first thermistor and the second thermistor are connected to the control system through wires led out from the wire grooves and wire holes.

8. The micro-flow sensor of claim 1, wherein, The microcontroller is an STM32 microcontroller. Both the first signal conversion module and the second signal conversion module use MAX31865 modules. Both the first signal conversion module and the second signal conversion module are connected to the STM32 microcontroller through an SPI interface. Both the first thermistor and the second thermistor are connected to the first signal conversion module and the second signal conversion module using a three-wire connection.

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