Microwave resonance type liquid flowmeter based on three-capacitor structure

Abstract

The invention relates to a microwave resonance type liquid flowmeter based on a three-capacitor structure, and belongs to the technical field of microwave sensors. The microwave resonance type liquid flowmeter is formed by establishing the heating unit at the front end, the sensing unit at the middle end and the waste liquid collecting device at the rear end, the dielectric constant of liquid can be changed through the heating effect of the front heating unit, and then the capacitance value in the sensing unit is changed; according to the three-capacitance microwave resonator, the flow or the flow velocity of fluid can be detected by measuring the change of the resonant frequency, the problems of low sensitivity, low resolution and the like of a traditional sensor can be solved, and the flowing state information of the liquid can be accurately obtained by monitoring the resonant frequency of the three-capacitance microwave resonator and analyzing data.

Description

Technical Field

[0001] The invention relates to a microwave resonance type liquid flow meter based on a three-capacitor structure, belonging to the technical field of microwave sensors. Background Art

[0002] From the optimization and control of industrial production processes to resource monitoring in environmental protection, as well as fine operations in the fields of medical treatment and scientific research, accurate and reliable measurement of liquid flow rate is indispensable. Among them, liquid flow rate sensors are the core technical equipment to achieve this key task.

[0003] In modern manufacturing, such as automobile manufacturing and electronic product production, many production processes involve precise measurement and control of liquids. In addition, industrial automation production lines have extremely high requirements for real-time monitoring and precise control of liquid flow rates. For example, the cooling system of an automobile engine requires precise control of the flow rate of the coolant to ensure that the engine runs at the optimal temperature and improves the performance and life of the engine. In the manufacturing process of electronic products, the precise flow rate control of certain chemical reagents is crucial for processes such as circuit board cleaning and etching, which directly affects the quality and yield of the product. For example, in chemical production, the conduct of various chemical reactions often depends on the precise flow rate ratio of raw materials. Whether it is the refining process in petrochemicals or the synthesis reaction in fine chemicals, a slight deviation in the liquid flow rate may lead to incomplete chemical reactions or the occurrence of side reactions, thereby affecting the quality and output of the product and may even cause safety accidents.

[0004] There are many types of liquid flow rate sensors, including ultrasonic sensors, vortex flow sensors, magnetic sensors and mechanical sensors, etc. Each sensor has its specific application scenarios and technical characteristics. However, these types of liquid flow rate sensors still have the following problems:

[0005] (1) Ultrasonic sensors are easily affected by the properties of fluids. Different types of fluids (such as gas, liquid, muddy water, etc.) will have different effects on ultrasonic propagation, and calibration may be required for different fluids. In addition, the requirements for the measurement environment are high, and its accuracy may be affected by factors such as temperature, pressure, and pipe material. Therefore, compensation measures need to be considered in specific environments.

[0006] (2) The vortex flow sensor also has high requirements for fluid properties. It is more sensitive to the density, viscosity and other properties of the fluid. Moreover, when the fluid flow state is complex or there is pulsating flow, the frequency of the vortex may be disturbed, affecting the measurement accuracy. In addition, for very low or very high flow rates, the measurement accuracy may be reduced.

[0007] (3) Magnetic sensors are only suitable for conductive fluids and cannot be used for insulating fluids such as gas and oil. It is also necessary to ensure that the fluid flow in the pipeline is completely filled, that is, the fluid must completely occupy the cross-section of the pipeline, otherwise, the measurement results may be affected. Compared with other types of flow meters, the initial investment of magnetic flow meters is higher and different fluids may require electrodes of different materials (such as stainless steel, alloy, etc.) to prevent corrosion or scaling.

[0008] (4) Mechanical flow sensors may wear out over time due to the constant movement of mechanical parts during operation, especially when there are particles or corrosive substances in the fluid. Regular maintenance may be required. Compared with other high-precision flow meters, mechanical flow sensors may have lower accuracy, especially in complex fluid environments. Factors such as bubbles, impurities, and viscosity changes in the fluid may also affect the accuracy of the sensor.

[0009] Therefore, there is currently a lack of a liquid flow meter or liquid flow sensor that can solve the above problems. Summary of the invention

[0010] In order to solve the above problems, the present invention proposes a microwave resonant liquid flow meter based on a three-capacitor structure, which converts liquids with different flow rates into liquids with different temperatures. Liquids with different temperatures exhibit different dielectric constants, and can therefore be sensed by a microwave resonant sensor that is sensitive to the dielectric constant, and outputs the sensor response relationship between the resonant frequency and the flow rate. Microwave sensors have the characteristics of high sensitivity, short response time, high resolution, and low cost, and can occupy a place in the current field of high-performance flow sensors.

[0011] The present invention provides a microwave resonance type liquid flow meter based on a three-capacitor structure, comprising:

[0012] A heating unit, the heating unit comprising a sampling tube and a multi-resistance heating system arranged on the sampling tube, wherein two ends of the sampling tube are respectively a sampling tube liquid inlet and a sampling tube liquid outlet;

[0013] A sensing unit, the sensing unit comprising a three-capacitance sensor module and a PDMS fluid channel unit covered on the three-capacitance sensor module, wherein the PDMS fluid cavity liquid inlet of the PDMS fluid channel unit is connected to the liquid outlet of the sampling tube, and the PDMS fluid cavity liquid outlet of the fluid channel unit is connected to a waste liquid collection device; the three-capacitance sensor module comprises a substrate and a three-capacitance array arranged on the substrate and covered by the PDMS fluid channel unit;

[0014] A waste liquid collection device connected to the fluid channel unit;

[0015] When the microwave resonance type liquid flow meter is used for detection, the liquid to be measured passes through the sampling tube and the PDMS fluid cavity unit in sequence and is recovered by the waste liquid collection device. When passing through the sampling tube, the multi-resistance heating system heats the liquid to be measured, thereby changing the dielectric constant of the liquid; after entering the PDMS fluid cavity unit, the liquid to be measured is detected by a three-capacitor microwave resonator formed by a three-capacitor array; liquids with different flow rates can achieve different temperatures after being output from the heating unit, and liquids with different temperatures present different dielectric constants, which can be effectively detected by the three-capacitor microwave resonator in the subsequent sensing unit; after entering the fluid cavity unit, since the three-capacitor microwave resonator can radiate electromagnetic flux in the horizontal plane and the vertical plane, the electromagnetic flux can contact the liquid in the PDMS fluid cavity unit in the horizontal and vertical directions, thereby increasing the interaction between the electromagnetic flux and the liquid to be measured.

[0016] More specifically, for a three-capacitor resonator, the general resonant frequency formula is expressed as,

[0017]

[0018] Among them C 等效 The equivalent capacitance value of the three capacitors in the three-capacitor resonator proposed by the present invention, when liquids of different temperatures flow through the area where the three capacitors are located, can cause the capacitance value of the three capacitors to change, thereby causing the change of the resonant frequency f, realizing the sensing response, and accurately obtaining the flow rate of the measured liquid before entering the heating unit through the relationship curve established by the change of the resonant frequency and the change of the liquid flow rate. At the same time, the present invention can generate a microwave signal with a specific frequency through a microwave resonator, and the signal can be detected by a vector network analyzer (VNA).

[0019] Furthermore, the multi-resistance heating system includes three resistance wires distributed in a straight line and wound around the sampling tube. The three resistance wires are each individually connected to a constant-voltage DC power supply. When powered on, they can provide stable and uniform heat to the sampling tube, and can provide different stable temperature gradient ranges by controlling the voltage of the DC power supply.

[0020] Furthermore, the outer wall of the sampling tube is coated with fluorine and ceramic coating, which is used to insulate the current of the three resistance wires and play a role in heat preservation.

[0021] Furthermore, the substrate is provided with an input port, a three-capacitor array, and an output port connected in sequence. The three-capacitor array includes a first enhanced capacitor, a finger capacitor, and a second enhanced capacitor. By combining the parasitic inductance parameters of the metal transmission line constituting its structure, a resonance effect of capacitance and inductance is formed, thereby forming a three-capacitor microwave resonator.

[0022] Furthermore, the fluid channel unit includes an arched tube cavity, which is a sealed cavity. The arched tube cavity is set on both sides of the three-capacitor microwave resonator and covers the three-capacitor array.

[0023] Preferably, the material of the PDMS fluid channel unit is polydimethylsiloxane; and the material of the substrate is glass.

[0024] Furthermore, the double-layer spiral complementary structure of the first enhanced capacitor is composed of two metal sheets that are wound into a spiral shape and then interspersed in the gap, and the winding direction is counterclockwise; the two metal sheets are respectively arranged in a plane of low height to form a hierarchical structure of upper and lower layers, including an upper metal sheet and a lower metal sheet that are connected between layers through a connecting bridge, and the connecting bridge is a bridge-type structure composed of metal wires suspended on the substrate, and is separated from the substrate by air; the two metal sheets that are wound into a spiral shape and then interspersed in the gap are respectively a spiral excitation electrode and a spiral sensing electrode, and the plates of the spiral excitation electrode are equally spaced from the input port to the inside and spiral counterclockwise, and the plates of the spiral sensing electrode are equally spaced to the outside and spiral clockwise; the upper metal sheet and the lower metal sheet of the first enhanced capacitor are respectively connected to the input port and the interdigital capacitor, and the upper metal sheet and the lower metal sheet of the second enhanced capacitor are respectively connected to the interdigital capacitor and the output port. The interdigital sensing electrodes and the interdigital excitation electrodes are interpolated with each other to form a forked complementary structure, and adjacent sensing strip electrodes and excitation strip electrodes are a group and are periodically arranged in the same plane.

[0025] The invention also provides the application of the microwave resonance type liquid flow meter in chemical industry, sewage treatment and drinking water treatment facilities.

[0026] Beneficial effects of the present invention:

[0027] The present invention forms a microwave resonance type liquid flowmeter by establishing a heating unit at the front end, a sensing unit at the middle end and a waste liquid collection device at the rear end. The dielectric constant of the liquid can be changed by the heating effect of the front heating unit, thereby changing the capacitance value in the sensing unit. The flow rate or flow velocity of the fluid can be detected by measuring the change in the resonant frequency. The problems of low sensitivity and resolution of traditional sensors can be overcome. By monitoring the resonant frequency of the three-capacitor microwave resonator and analyzing the data, the flow state information of the liquid can be accurately obtained.

[0028] The invention can make the liquid flow meter measure the flow velocity of the liquid in real time through the high-speed response characteristic of the microwave resonator, and is suitable for detecting the dynamic flow velocity of the liquid. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the overall structure of the microwave resonance type liquid flow meter of the present invention.

[0030] Figure 2 It is a schematic diagram of the heating unit of the present invention.

[0031] Figure 3 Schematic diagram of the sensor unit of the present invention.

[0032] Figure 4 These are the microwave simulation results of the liquid flow rate under different dielectric constants of the present invention.

[0033] In the figure, 1, heating unit; 2, sensor unit; 3, waste liquid collection device; 4, sensor unit liquid inlet; 5, sensor unit liquid outlet; 6, sampling tube; 7, sampling tube liquid inlet; 8, sampling tube liquid outlet; 9, 11, 13, positive electrode; 10, 12, 14, negative electrode; 15, resistance wire; 16, first resistance wire unit; 17, second resistance wire unit; 18, third resistance wire unit; 19, PDMS fluid cavity liquid inlet; 20, PDMS fluid cavity liquid outlet; 21, PDMS fluid cavity unit; 22, input end; 23, output end; 24, first enhanced capacitor; 25, interdigital capacitor; 26, second enhanced capacitor; 27, three-capacitor sensor module. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] In the present invention, unless otherwise clearly specified and limited, the terms "connected", "connected", and "fixed" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0036] In the present invention, the "first" and "second" are only used to distinguish similar components / parts with different positions or different characteristics, and have no other limiting meanings; the "upper" refers to the direction of each component away from the ground, and the "lower" refers to the direction of each component away from the ground.

[0037] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0038] Example 1

[0039] The present invention provides a microwave resonance type liquid flow meter based on a three-capacitor structure, comprising:

[0040] A heating unit 1, the heating unit 1 comprises a sampling tube 6, and a multi-resistance heating system arranged on the sampling tube 6, wherein two ends of the sampling tube 6 are respectively a sampling tube liquid inlet 7 and a sampling tube liquid outlet 8; the multi-resistance heating system comprises three resistance wires 15 distributed in a straight line and wound around the sampling tube, the three resistance wires 15 are a first resistance wire unit 16, a second resistance wire unit 17, and a third resistance wire unit 18, the three resistance wires are individually connected to a constant voltage DC power supply, respectively at the positive pole (9, 11, 13) and the negative pole (10, 12, 14), and can provide stable and uniform heat to the sampling tube after being powered on, and can provide different stable temperature gradient ranges by controlling the voltage of the DC power supply;

[0041] The sensing unit 2 comprises a three-capacitance sensor module 27 and a PDMS fluid channel unit 21 covering the three-capacitance sensor module 27, wherein the PDMS fluid cavity liquid inlet 19 of the PDMS fluid channel unit 21 is connected to the sampling tube liquid outlet 8, and the PDMS fluid cavity liquid outlet of the fluid channel unit 21 is connected to the waste liquid collection device 3; the three-capacitance sensor module 27 comprises a substrate and a three-capacitance array arranged on the substrate and covered by the PDMS fluid channel unit;

[0042] Preferably, the material of the substrate is glass; preferably, the outer wall of the sampling tube 6 is coated with fluorine and ceramic coating, which is used to insulate the current of the three resistance wires 15 and achieve heat preservation effect;

[0043] The three-capacitor array includes a first enhanced capacitor 24, a finger capacitor 25, and a second enhanced capacitor 26. By combining the parasitic inductance parameters of the metal transmission line constituting the structure, a resonance effect of capacitance and inductance is formed, thereby forming a three-capacitor microwave resonator. The three-capacitor microwave resonator is processed on a glass substrate by an evaporation process to form 600nm copper as the metal material of the resonator; the fluid cavity unit 21 includes an arched tube cavity, which is a sealed cavity. The arched tube cavity is set on both sides of the three-capacitor microwave resonator and covers the three-capacitor array; the material of the PDMS fluid cavity unit is preferably polydimethylsiloxane;

[0044] A waste liquid collection device 3, connected to the PDMS fluid chamber liquid outlet 20;

[0045] When the microwave resonance type liquid flow meter is used for detection, the liquid to be measured passes through the sampling tube 6 and the PDMS fluid cavity unit 21 in sequence and is recovered by the waste liquid collection device 3. When passing through the sampling tube, the multi-resistance heating system heats the liquid to be measured, thereby changing the dielectric constant of the liquid; after entering the PDMS fluid cavity unit 21, the liquid to be measured is detected by the three-capacitor microwave resonator; the faster the liquid flow rate, the lower the temperature of heating rise, and the slower the liquid flow rate, the higher the temperature of heating rise. Therefore, liquids with different flow rates can achieve different temperatures after being output from the heating unit, and liquids with different temperatures present different dielectric constants, which can be effectively detected by the three-capacitor microwave resonator in the subsequent sensing unit; after entering the PDMS fluid cavity unit, since the three-capacitor microwave resonator can radiate electromagnetic flux in the horizontal and vertical planes, the electromagnetic flux can effectively contact the liquid in the PDMS fluid cavity unit 21 in the horizontal and vertical directions, increasing the interaction between the electromagnetic flux and the liquid to be measured, which helps to improve the sensitivity of the sensor and lays a foundation for the subsequent improvement of the sensing sensitivity;

[0046] The working principle of the present invention is:

[0047] Based on the relationship between the first enhanced capacitor 24, the interdigital capacitor 25, the second enhanced capacitor 26 and the dielectric constant in the three-capacitor microwave resonator, when the dielectric constant of the measured liquid changes, the capacitance value will also change accordingly, causing the resonant frequency of the microwave resonator to change. The flow rate of the measured liquid at the inlet of the sampling tube can be accurately obtained through the relationship curve established by the pre-calibrated resonant frequency and the liquid flow rate. Specifically:

[0048] Liquids with different flow rates have different temperatures after flowing out of the heating unit 1. Different temperatures lead to different dielectric constants, different dielectric constants lead to different capacitance values, and different capacitance values ​​lead to different resonant frequencies. The present invention uses the relationship between the resonant frequency and the liquid flow rate to characterize the sensor response. More specifically, for a three-capacitor resonator, its general resonant frequency formula is expressed as:

[0049]

[0050] Among them C 等效 The equivalent capacitance values ​​of the three capacitors in the three-capacitor microwave resonator proposed by the present invention are as follows. When liquids of different temperatures flow through the area where the three capacitors are located, the capacitance values ​​of the three capacitors can all be changed, thereby causing the change of the resonant frequency f, realizing the sensing response, and accurately obtaining the flow rate of the measured liquid before entering the heating unit through the relationship curve established by the change of the resonant frequency and the change of the liquid flow rate. At the same time, the present invention can generate a microwave signal with a specific frequency through the three-capacitor microwave resonator, and the signal can be detected by a vector network analyzer (VNA).

[0051] Furthermore, the double-layer spiral complementary structure of the first enhanced capacitor 24 is composed of two metal sheets that are wound into a spiral and then interspersed in the gap, and the winding direction is counterclockwise; the two metal sheets are respectively arranged in a plane of no height to form a hierarchical structure of upper and lower layers, including an upper metal sheet and a lower metal sheet that are connected between layers through a connecting bridge, and the connecting bridge is a bridge structure composed of metal wires suspended on the substrate, and is separated from the substrate by air; the two metal sheets that are wound into a spiral and interspersed in the gap are respectively a spiral excitation electrode and a spiral sensing electrode, and the plates of the spiral excitation electrode are equally spaced from the input port to spiral counterclockwise inward, and the plates of the spiral sensing electrode are equally spaced to spiral clockwise outward. Arranging the capacitor array in this way can expand the effective plane in three-dimensional space, increase the surface area of ​​the capacitor plates, thereby increasing the capacitance, and is more conducive to the adsorption and desorption process of electrons on the electrode surface; among them, the double-layer spiral complementary structure of the enhanced capacitor and the fork-shaped complementary structure of the fork-finger capacitor can achieve a larger capacitance value on the same area, which is more suitable for integrated circuits and small electronic devices, so that the two capacitors show good capacitance characteristics, and under the action of their own parasitic series inductance and resistance, they can both produce resonance effects independently and can be used as detection sensitive areas.

[0052] The upper metal sheet and the lower metal sheet of the first enhanced capacitor 24 are connected to the input port 22 and the interdigital capacitor 25 respectively, and the upper metal sheet and the lower metal sheet of the second enhanced capacitor 26 are connected to the interdigital capacitor 25 and the output port 23 respectively.

[0053] Preferably, the interdigital sensing electrodes and the interdigital excitation electrodes are interpolated with each other to form a forked complementary structure, and adjacent sensing strip electrodes and excitation strip electrodes are arranged periodically in the same plane as a group. The advantage of setting up the interdigital capacitor in this way is that the structure is stable, and its performance changes relatively little under the influence of environmental factors such as temperature and humidity changes, and it can maintain good stability.

[0054] Example 2

[0055] This embodiment demonstrates a liquid flow meter used for accurate preparation of chemical experimental solutions.

[0056] In chemical experiments, it is crucial to accurately prepare solutions, and the liquid flow meter is one of the key tools to achieve this goal. The process of using a liquid flow meter to accurately prepare solutions in chemical experiments mainly includes the following steps:

[0057] (1) Connect the liquid flow meter proposed in the present invention to the liquid supply system (such as a medicine bottle or a liquid storage tank) and the receiving container (such as a beaker, a measuring cylinder, etc.) to ensure that they are airtight and leak-proof;

[0058] (2) Calculate the required flow rate based on the concentration and volume of the solution to be prepared. Ensure that the flow meter is set to the required flow rate;

[0059] (3) Before using the flow meter, calibrate it to ensure that the flow meter readings are accurate. This can be done using a flow standard or by comparing it to a known volume of liquid flowing out;

[0060] (4) Testing the heating unit proposed by the present invention, controlling the voltage value outputted from the outside, accurately controlling the heating temperature of the heating unit, and adjusting the liquid temperature and the detection scheme of the subsequent sensing unit, that is, at what temperature the reaction time, sensitivity, linearity and other performances of the subsequent sensing unit are relatively good;

[0061] (5) Turn on the liquid flow meter to ensure stable liquid flow and observe the frequency parameters displayed by the vector network analyzer (VNA);

[0062] (6) Record flow rate, time and other data to calculate the concentration of the solution in the final chemical experiment;

[0063] (7) Continuously monitor the flow meter reading and make adjustments when necessary to ensure the required preparation accuracy;

[0064] (8) When the liquid flows into the receiving container, it can be stirred in time to promote uniform mixing. After reaching the predetermined volume, the flow meter is turned off to ensure that no residual liquid flows out.

[0065] like Figure 4As shown, the present invention simulated the liquid based on different temperatures in the early stage, that is, the microwave resonant liquid flow meter with three capacitor structures proposed in the present invention was simulated by different dielectric constants (smaller range of variation, specifically about 5). It can be seen that at the resonant frequency of 10.4GHz, different liquid temperatures can present different resonant frequencies. With the increase of the dielectric constant, the resonant frequencies are 10.45GHz, 10.42GHz, 1.39GHz, 10.35GHz, and 10.28GHz, respectively. Therefore, the liquid flow meter proposed in the present invention can characterize the sensing response relationship through the relationship between the resonant frequency and the liquid flow rate.

[0066] Example 3

[0067] This embodiment demonstrates a multi-region tuned bandpass filter with high design flexibility.

[0068] The tuning function enables the filter to select and enhance signals of specific frequencies while suppressing other unwanted frequencies. This is crucial for fields such as communication systems, audio processing, and signal processing. The three-capacitor microwave resonator proposed in the present invention can be effectively applied to filter applications and can tune the frequency response of the filter so that the filter can adapt to different requirements in different application scenarios or signal environments, and can optimize the transmission characteristics of the filter.

[0069] The three-capacitor microwave resonator proposed in the present invention can realize the tuning function in the three capacitance areas. By changing the number of turns, line width, line spacing and inner diameter of the first enhanced capacitor 24 and the second enhanced capacitor 26, its capacitance value can be effectively changed and the resonance performance can be tuned; by changing the fork index, finger width and finger spacing of the fork finger capacitor 25, its capacitance value can be effectively changed and the resonator performance can be further tuned.

[0070] Therefore, the three-capacitor microwave resonator proposed in the present invention can tune the resonator performance by adjusting a single or multiple capacitors, has high design flexibility and multi-region tuning function, and lays a solid foundation for the subsequent application of microwave filters.

[0071] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Anyone familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the definition of the claims.

Claims

1. A microwave resonant liquid flow meter based on a three-capacitor structure, characterized in that: include: A heating unit, the heating unit comprising a sampling tube and a multi-resistance heating system arranged on the sampling tube, wherein two ends of the sampling tube are respectively a sampling tube liquid inlet and a sampling tube liquid outlet; A sensing unit, the sensing unit comprising a three-capacitance sensor module and a PDMS fluid cavity unit covering the three-capacitance sensor module, wherein the PDMS fluid cavity liquid inlet of the PDMS fluid cavity unit is connected to the liquid outlet of the sampling tube, and the PDMS fluid cavity liquid outlet of the fluid cavity unit is connected to a waste liquid collection device; The three-capacitor sensor module includes a substrate and a three-capacitor array disposed on the substrate and covered by a PDMS fluid channel unit; A waste liquid collection device connected to the fluid channel unit; When the microwave resonance type liquid flow meter is used for detection, the liquid to be measured passes through the sampling tube and the PDMS fluid cavity unit in sequence and is recovered by the waste liquid collection device. When passing through the sampling tube, the multi-resistance heating system heats the liquid to be measured, thereby changing the dielectric constant of the liquid; after entering the PDMS fluid cavity unit, the liquid to be measured is detected by a three-capacitor microwave resonator formed by a three-capacitor array; liquids with different flow rates can achieve different temperatures after being output from the heating unit, and liquids with different temperatures present different dielectric constants, which can be effectively detected by the three-capacitor microwave resonator in the subsequent sensing unit; after entering the fluid cavity unit, since the three-capacitor microwave resonator can radiate electromagnetic flux in the horizontal plane and the vertical plane, the electromagnetic flux can contact the liquid in the PDMS fluid cavity unit in the horizontal and vertical directions, thereby increasing the interaction between the electromagnetic flux and the liquid to be measured.

2. The microwave resonance type liquid flow meter according to claim 1, characterized in that: The multi-resistance heating system includes three resistance wires distributed in a straight line and wound around a sampling tube. The three resistance wires are individually connected to a constant-voltage DC power supply. After being powered on, they can provide stable and uniform heat to the sampling tube, and can provide different stable temperature gradient ranges by controlling the voltage of the DC power supply.

3. The microwave resonance type liquid flow meter according to claim 2, characterized in that: The outer wall of the sampling tube is coated with fluorine and ceramic coating, which is used to insulate the current of the three resistance wires and has a heat preservation effect.

4. The microwave resonance type liquid flow meter according to claim 3, characterized in that: The substrate is provided with an input port, a three-capacitor array, and an output port which are connected in sequence. The three-capacitor array includes a first enhanced capacitor, a forked capacitor, and a second enhanced capacitor. By combining the parasitic inductance parameters of the metal transmission line constituting its structure, a resonance effect of capacitance and inductance is formed, thereby forming a three-capacitor microwave resonator.

5. The microwave resonance type liquid flow meter according to claim 4, characterized in that: The fluid channel unit comprises an arched tube cavity, which is a sealed cavity. The arched tube cavity is arranged on both sides of the three-capacitor microwave resonator and covers the three-capacitor array.

6. The microwave resonance type liquid flow meter according to claim 5, characterized in that: The material of the PDMS fluid channel unit is polydimethylsiloxane; the material of the substrate is glass.

7. The microwave resonance type liquid flow meter according to claim 1, characterized in that: The first enhanced capacitor and the second enhanced capacitor both have a double-layer spiral complementary structure, and the interdigital capacitor has interdigital sensing electrodes and interdigital excitation electrodes that are complementary and interspersed. The interdigital sensing electrodes and the interdigital excitation electrodes both have parasitic series inductance and resistance and can produce a resonance effect without externally connecting other inductors.

8. The microwave resonance type liquid flow meter according to claim 7, characterized in that: The double-layer spiral complementary structure of the first enhanced capacitor is composed of two metal sheets that are wound into a spiral shape and then interlaced in the gap, and the winding direction is counterclockwise; the two metal sheets are respectively arranged in a plane with no height to form a hierarchical structure of upper and lower layers, including an upper metal sheet and a lower metal sheet that are connected between layers through a connecting bridge, and the connecting bridge is a bridge structure composed of metal wires suspended on the substrate, and is separated from the substrate by air; the two metal sheets that are wound into a spiral shape and then interlaced in the gap are respectively a spiral excitation electrode and a spiral sensing electrode, the pole plates of the spiral excitation electrode are equally spaced from the input port to the inside and spiral counterclockwise, and the pole plates of the spiral sensing electrode are equally spaced to the outside and spiral clockwise; the upper metal sheet and the lower metal sheet of the first enhanced capacitor are respectively connected to the input port and the interdigital capacitor, and the upper metal sheet and the lower metal sheet of the second enhanced capacitor are respectively connected to the interdigital capacitor and the output port.

9. The microwave resonance type liquid flow meter according to claim 8, characterized in that: The interdigital sensing electrodes and the interdigital excitation electrodes are interpolated with each other to form a forked complementary structure, and adjacent sensing strip electrodes and excitation strip electrodes are a group and are periodically arranged in the same plane.

10. Application of the microwave resonance liquid flow meter according to any one of claims 1 to 9 in chemical industry, sewage treatment and drinking water treatment facilities.

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