Capacitive same-frequency mutual inductance system

Abstract

The invention discloses a capacitive same-frequency mutual inductance system, which outputs the same frequency of the measurement frequency of a capacitive detection module through a same-frequency waveform generator according to the principle of same-frequency interference. When a metal area of the rotary wing wheel covers a frequency output metal detection point of the same-frequency waveform generator and an input metal detection point of the charge sampling multiplexer, energy transfer (charge transfer) exists between the two metal detection points, so that a frequency output signal enters the capacitive detection module through a conductive metal film above; and the measured value of the capacitance value is multiplied. The same-frequency mutual inductance is larger than other interferences, so that the other interferences cannot influence the capacitive detection module like the same-frequency mutual inductance; the same-frequency interference phenomenon which is the most difficult to overcome is utilized, the signal-to-noise ratio and the anti-interference capacity of the capacitive inductor are improved, and the advantages that a detection system is high in stability, low in safety risk, high in system integration degree, low in cost, high in metering precision, low in power consumption and the like are met.

Description

Technical Field

[0001] The present invention relates to the field of inductive detection technology, and in particular to a capacitive same-frequency mutual induction system. Background Art

[0002] The current market mainly uses the LC oscillation principle as the flow metering design. When the rotating impeller rotates, when the sensing surface rotates to the metal area, the signal receiving circuit determines the position of the turntable in the metal area by detecting the signal attenuation change of the LC oscillation circuit, thereby counting the number of rotations to achieve the purpose of flow metering. By collecting the signal of the LC oscillation circuit, the number of rotations of the turntable is determined, and the flow rate of the fluid is further calculated. The principle of this technology is to use LC oscillation on the electromagnetic coil. When the detection inductor is in the non-metallic area, there is no inductor eddy current effect, and the signal attenuation rate is relatively small; when the detection inductor is in the metal area, an inductor eddy current effect will be formed, resulting in increased power consumption and faster attenuation of the sine wave signal. This method uses the inductor eddy current effect to consume its own power as a signal judgment.

[0003] The disadvantages of using the LC oscillation principle as a flow metering design are as follows: 1. Difficult PCB layout: Winding out the simulated coil shape requires special layout skills and design, and multiple tests and calibrations are required to match the inductance value, which increases the complexity and difficulty of PCB design. 2. Layout space limitation: Since winding out the simulated coil requires occupying the PCB layout space, the number of PCB layers needs to be increased to at least two layers in the routing design, which will increase the cost and manufacturing difficulty. 3. Coil shape and size limitation: In PCB design, the design parameters of the inductor coil need to be considered, such as the number of coil turns, coil diameter, corresponding height, etc., which will limit the PCB design. 4. High manufacturing cost: Since winding out the simulated coil requires attention to PCB layout design and manufacturing, in order to reduce the impedance value of the coil, the PCB routing design requires copper process or gold-plated PCB board, so the PCB manufacturing cost will be relatively high. 5. When winding out the simulated coil on the PCB, pay attention to the back of the detection surface, which will also be affected by the eddy current effect of the surrounding metal, and shielding methods need to be used to solve problems such as detection interference.

[0004] Capacitive mutual induction detection is a common non-contact detection technology. Its principle is to use the capacitive mutual induction coupling between the object to be detected and the capacitive sensor to detect the existence and location of the object by detecting the change in capacitance value.

[0005] Capacitive mutual induction detection uses the capacitive coupling between the object to be measured and the capacitive sensor to detect the presence of the object by detecting the change in capacitance value, and can transmit data to the intelligent system for processing. The design difficulty of using capacitive mutual induction detection for non-magnetic detection flow system is not less than that of using LC oscillation principle as flow metering design, and both will face interference during detection. However, compared with the advantages of using capacitive mutual induction detection as flow metering design, there are still great benefits: 1. It greatly reduces the difficulty of PCB layout design, and there is no need to wind out the shape of the coil. 2. There is no need for external capacitors and consider the matching inductance value of the coil. 3. There is no layout space restriction, only a little metal surface is needed, and there is no need to consider the coil shape, coil turns, coil diameter and other issues. 4. The PCB does not need to use a multilayer board, only a single panel is needed, which greatly reduces the cost. 5. The PCB can use a general metal process, and there is no need to use copper wiring or gold-plated wiring, which greatly reduces the PCB cost. 6. The LC oscillation power consumption problem is greatly solved.

[0006] However, factors such as the surrounding metal traces, components, and the chip's own magnetic field can interfere with the detection performance of the capacitive sensor and affect its accuracy and sensitivity. The general methods to reduce interference in capacitive mutual induction detection are:

[0007] 1. Choose the right capacitive sensing architecture: Different types of capacitive sensors have different sensitivities to magnetic fields and metals. Therefore, you can choose the right capacitive sensing architecture based on the actual application scenario to minimize surrounding interference.

[0008] 2. Use shielding technology around: When designing a circuit board, you can add shielding materials around the capacitive sensor to prevent interference from the surrounding metal traces, components, and chip magnetic fields.

[0009] 3. Improvement of PCB circuit layout: When designing the circuit board, the position of the capacitive sensor can be adjusted and the metal traces and components placed around it can be placed to reduce the interference it receives.

[0010] 4. Add filters: Filters can reduce the impact of power supply noise and environmental noise, and improve the signal-to-noise ratio and anti-interference ability of capacitive sensors.

[0011] The most severe and difficult to overcome interference in capacitive mutual inductance technology is co-frequency interference. When there is an interference signal with the same measurement frequency as the capacitive detection module in the external environment, the co-frequency interference will become larger.

[0012] This application aims to utilize the most difficult to overcome co-frequency interference phenomenon to improve the signal-to-noise ratio and anti-interference ability of capacitive sensors, so as to meet the advantages of high system stability and low safety risk, high system integration and low cost, high measurement accuracy and low power consumption, increase the service life of the capacitive mutual induction detection system, enhance the anti-interference ability to make the detection system run stably, and adapt to a wider range of measurement applications. Summary of the invention

[0013] In response to the problems in the related art, the present application discloses a capacitive same-frequency mutual induction system, which solves the problem that the capacitive mutual induction sensing detection technology in the related art is subject to same-frequency interference.

[0014] To achieve the above objectives, this application provides the following technical solutions:

[0015] A capacitive same-frequency mutual inductance system includes a capacitive detection module, the capacitive detection module can detect a change signal of a capacitance value, the capacitive detection module is signal-connected to a capacitive charge sampling unit, the capacitive charge sampling unit can sample the detection signal frequency of the capacitive detection module, the capacitive charge sampling unit is signal-connected to a same-frequency waveform generator, the capacitive charge sampling unit transmits the sampling frequency and phase information of the detection signal to the same-frequency waveform generator, the same-frequency waveform generator is signal-connected to the capacitive detection module, the same-frequency waveform generator outputs a same-frequency signal with the same frequency and the same phase as the detection signal, the frequency and phase of the output signal of the same-frequency waveform generator change with the frequency and phase changes of the detection signal of the capacitive detection module, and the same-frequency signal output by the same-frequency waveform generator doubles the signal value detected by the capacitive detection module.

[0016] As a further solution of the present application: the capacitive detection module includes multiple metal detection points, each of the metal detection points is respectively connected to the same frequency output multiplexer and the charge sampling multiplexer signal, the same frequency output multiplexer can control the metal detection point to perform same frequency output, the charge sampling multiplexer can control the metal detection point to perform charge sampling input, a rotatable rotating wing wheel is provided below the multiple metal detection points, a metal film is provided on the upper part of the rotating wing wheel, and the metal film can cover two of the metal detection points at the same time.

[0017] As a further solution of the present application: the same-frequency output multiplexer and the charge sampling multiplexer respectively control two adjacent metal detection points to perform same-frequency output and charge sampling input respectively.

[0018] As a further solution of the present application: the same-frequency waveform generator is connected to the same-frequency output multiplexer signal, and the same-frequency waveform generator outputs a same-frequency signal with the same frequency and phase as the detection signal to the metal detection point through the same-frequency output multiplexer.

[0019] As a further solution of the present application: the capacitive charge sampling unit includes a fixed capacitor for storing charge. The capacitive charge sampling unit can repeatedly store and release charge on the fixed capacitor to obtain a charging and discharging sampling frequency. The capacitance value of the induction capacitor is fixed. As the amount of charge gradually increases, the sampling frequency of the capacitive charge sampling unit will become faster.

[0020] As a further solution of the present application: the same-frequency waveform generator repeatedly stores and releases charges on the capacitor according to the capacitive charge sampling unit to obtain the sampling frequency of the capacitive charge sampling unit. The same-frequency waveform generator includes an amplifier and a driving circuit. The amplifier and the driving circuit can increase the amplitude of the same-frequency signal. The same-frequency waveform generator achieves the same-phase output as the signal waveform of the capacitive charge sampling unit.

[0021] As a further solution of the present application: the capacitive charge sampling unit signal is connected to the capacitance value control unit, and the capacitance value control unit can correct the total capacitance value difference so that the charge stored in the capacitive charge sampling unit reaches a fixed capacitance value.

[0022] As a further solution of the present application: the capacitance value control unit is connected to a sampling frequency counting unit, which can count the sampling frequency obtained by the capacitive charge sampling unit within a unit time. As the amount of charge increases, the number of sampling frequency counts will increase, and conversely, as the amount of charge decreases, the number of sampling frequency counts will decrease.

[0023] As a further solution of the present application: the sampling frequency counting unit is connected to the flow counting unit, and the flow counting unit calculates the cycle time of the gradual increase and decrease of the charge amount according to the number of times counted by the sampling frequency counting unit, and calculates the alternation of the rotation signals sensed by each other between the capacitive sensor blocks located on the rotating impeller, so that the speed of the alternation change and the number of revolutions of the rotating impeller are used as the instantaneous flow rate, thereby realizing flow measurement.

[0024] In summary, the beneficial effects of this application are:

[0025] A capacitive same-frequency mutual inductance system includes a capacitive detection module, which can detect a change signal of a capacitance value. The capacitive detection module is signal-connected to a capacitive charge sampling unit, which can sample the detection signal frequency of the capacitive detection module. The capacitive charge sampling unit is signal-connected to a same-frequency waveform generator. The capacitive charge sampling unit transmits the sampling frequency and phase information of the detection signal to the same-frequency waveform generator. The same-frequency waveform generator is signal-connected to the capacitive detection module. The same-frequency waveform generator outputs a same-frequency signal with the same frequency and phase as the detection signal. The frequency and phase of the output signal of the same-frequency waveform generator change with the frequency and phase changes of the detection signal of the capacitive detection module. The same-frequency signal output by the same-frequency waveform generator doubles the signal value detected by the capacitive detection module.

[0026] This application optimizes the capacitive mutual inductance charge transfer technology, and uses the principle of co-frequency interference to output the same frequency of the measurement frequency of the capacitive detection module through the co-frequency waveform generator. When the metal area of ​​the rotating impeller covers the frequency output metal detection point of the co-frequency waveform generator and the input metal detection point of the charge sampling multiplexer, there is energy transfer (charge transfer) between the two metal detection points, causing the frequency output signal to enter the capacitive detection module through the conductive metal film above, thereby doubling the measured value of the capacitance value. Because the co-frequency mutual inductance is greater than other interferences, other interferences cannot affect the capacitive detection module like the co-frequency mutual inductance.

[0027] This application utilizes the most difficult to overcome co-frequency interference phenomenon, improves the signal-to-noise ratio and anti-interference ability of the capacitive sensor, meets the advantages of high stability and low safety risk of the detection system, high system integration and low cost, high measurement accuracy and low power consumption, increases the service life of the capacitive mutual induction detection system, strengthens the anti-interference ability to make the detection system run stably, and adapt to a wider range of measurement applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings are used to provide further understanding of the present application and constitute a part of the specification. They are used to explain the present application together with the embodiments of the present application and do not constitute a limitation of the present application.

[0029] In the attached picture:

[0030] Figure 1 This is a schematic diagram of the process structure of the capacitive same-frequency mutual inductance system of this application.

[0031] Figure 2 This is a side view structural diagram of the rotating wing wheel and metal detection point of the capacitive same-frequency mutual induction system of this application.

[0032] Figure 3This is a schematic diagram of the top view of the rotating wing wheel and metal detection point of the capacitive same-frequency mutual induction system of this application.

[0033] Reference numerals:

[0034] 1. Rotating wing wheel; 2. Metal film; 31. First metal detection point; 32. Second metal detection point; 33. Third metal detection point; DETAILED DESCRIPTION

[0035] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The implementations described in the following exemplary embodiments do not represent all implementations consistent with the present application. Instead, they are merely examples of devices and methods consistent with some aspects disclosed in the present embodiments as detailed in the appended claims.

[0036] It should be noted that all directional indications in the embodiments (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0037] In addition, the descriptions of "first", "second", etc. in the embodiments are only for descriptive purposes, and do not specifically refer to the order or sequence, nor are they used to limit the present application. They are only used to distinguish components or operations described with the same technical terms, and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present application.

[0038] In order to further understand the content, features and effects of the present application, the following embodiments are given as examples and described in detail with reference to the accompanying drawings:

[0039] like Figure 1-3 As shown:

[0040] The capacitive same-frequency mutual induction system includes a capacitive detection module, which can detect a change signal of a capacitance value.

[0041] Among them, the capacitive detection module includes three metal detection points, each of which is respectively connected to the same-frequency output multiplexer and the charge sampling multiplexer signal. The same-frequency output multiplexer can control the metal detection point to perform same-frequency output, and the charge sampling multiplexer can control the metal detection point to perform charge sampling input. A rotatable rotating wing wheel 1 is provided below the three metal detection points, and a conductive metal film 2 is provided on the upper part of the rotating wing wheel 1. The metal film 2 can cover two metal detection points at the same time.

[0042] Three metal detection points are evenly arranged above the rotary wheel 1 , including a first metal detection point 31 , a second metal detection point 32 and a third metal detection point 33 .

[0043] The frequency output multiplexer and the charge sampling multiplexer respectively control two adjacent metal detection points to perform frequency output and charge sampling input respectively.

[0044] The charge sampling multiplexer is signal-connected with a capacitive charge sampling unit, which can sample the detection signal frequency of the capacitive detection module. The capacitive charge sampling unit is signal-connected with a co-frequency waveform generator, which transmits the sampling frequency and phase information of the detection signal to the co-frequency waveform generator. The co-frequency waveform generator is signal-connected with the capacitive detection module, and the co-frequency waveform generator outputs a co-frequency signal with the same frequency and phase as the detection signal. The frequency and phase of the output signal of the co-frequency waveform generator change with the frequency and phase of the detection signal of the capacitive detection module. The co-frequency signal output by the co-frequency waveform generator doubles the signal value detected by the capacitive detection module.

[0045] The same-frequency waveform generator is connected to the same-frequency output multiplexer signal, and the same-frequency waveform generator outputs a same-frequency signal with the same frequency and phase as the detection signal to the metal detection point through the same-frequency output multiplexer.

[0046] The capacitive charge sampling unit includes a fixed capacitor for storing charge. When the capacitor for storing charge reaches the upper limit of charge saturation, the charge is released from the capacitor until the capacitor for storing charge reaches the lower limit, and then the charge is stored again. The capacitive charge sampling unit repeatedly stores and releases charge from the fixed capacitor to obtain a sampling frequency of charge and discharge. The capacitance value of the inductive capacitor is fixed. As the amount of charge gradually increases, the sampling frequency of the capacitive charge sampling unit becomes faster.

[0047] The same-frequency waveform generator repeatedly stores and releases charges on the capacitor according to the capacitive charge sampling unit to obtain the sampling frequency of the capacitive charge sampling unit. The same-frequency waveform generator includes an amplifier and a drive circuit. The amplifier and the drive circuit can increase the amplitude of the same-frequency signal. The same-frequency waveform generator achieves the same-phase output as the signal waveform of the capacitive charge sampling unit.

[0048] The capacitive charge sampling unit signal is connected to the capacitance value control unit. The capacitive charge sampling unit uses a fixed capacitor to store charge, but the sampled capacitance value will be affected by the parasitic capacitance on the external PCB trace, the line capacitance value between the connected lines, and the parasitic capacitance differences on the chip.

[0049] The capacitance control unit can correct the total capacitance difference so that the charges stored in the capacitive charge sampling unit reach a fixed capacitance value.

[0050] The capacitance value control unit is connected to the sampling frequency counting unit. The capacitive charge sampling unit uses a fixed capacitor for storing charges. The frequency of storing and releasing charges is obtained by repeatedly storing and releasing charges on the capacitor.

[0051] The sampling frequency counting unit can count the sampling frequency obtained by the capacitive charge sampling unit in unit time. As the charge amount increases, the sampling frequency counting times will increase, and conversely, as the charge amount decreases, the sampling frequency counting times will decrease.

[0052] The sampling frequency counting unit is connected to the flow counting unit. The flow counting unit calculates the cycle time of the gradual increase and decrease of the charge amount according to the number of times the sampling frequency counting unit counts, and calculates the change of the rotation signal sensed by each other between the capacitive sensor blocks located on the rotating impeller 1, so that the speed of the alternation change and the number of revolutions of the rotating impeller 1 are used as the instantaneous flow rate, thereby realizing flow measurement.

[0053] In practical applications, the capacitive same-frequency mutual induction technology is described using three metal detection points as an example and is applied to a non-magnetic intelligent flow detection system. In addition, the more metal detection points there are, the higher the precision of the flow detection.

[0054] The rotating impeller of the non-magnetic intelligent flow detection system is located inside the detection flow meter. When liquid or gas flows through the flow meter, it will drive the impeller to rotate, and drive the rotating impeller 1 through the gear. At this time, the capacitive sensor located on the rotating impeller 1 senses the changes and alternations of the rotation signal between blocks, so that the alternation change speed and the number of revolutions of the rotating impeller 1 are converted into instantaneous flow, thereby realizing flow measurement.

[0055] When the flow rate through the flow meter is different, the alternating change speed and the speed of the rotating impeller 1 change accordingly. There is a corresponding relationship between the flow rate and the rotation speed and the number of turns. Only by accurately mastering the rotation speed and the number of turns can the non-magnetic intelligent flow meter measure accurately.

[0056] The capacitive mutual inductance charge transfer technology is used in the additional rotary impeller 1 metering device to solve the problem of flow detection accuracy.

[0057] During the rotation of the rotary wheel 1, when the charge sampling multiplexer is detected in real time, it points to the first metal detection point 31 as the capacitive detection point input, and the second metal detection point 32 is converted from the same frequency output multiplexer to the same frequency waveform generator module waveform to generate the same frequency signal output.

[0058] The so-called return of the charge sampling measurement value to normal means that it is in a state without being affected by the same frequency mutual inductance.

[0059] When the rotating wing wheel 1 rotates the conductive metal film 2 to cover the first metal detection point 31 and slowly moves toward the second metal detection point 32, the capacitive same-frequency mutual inductance detection gradually takes effect to generate the same-frequency mutual inductance.

[0060] When the metal film 2 gradually approaches the first metal detection point 31, the first metal detection point 31 and the conductive metal film 2 rotating on the rotating wing wheel 1 can be regarded as a capacitor, and a same-frequency mutual inductance signal with the same frequency but relatively small amplitude will be generated on the non-contact metal film 2. This is because the magnetic field of the induced current generates an induced electric field in the nearby metal film 2, causing the charge distribution on the metal film 2 to change.

[0061] As the conductive metal film 2 of the rotating wing wheel 1 gradually approaches the second metal point, the same frequency waveform signal can be regarded as a changed electric field to transfer charge to the metal film 2, and the first metal detection point 31 detects that between the sensing electrodes on the metal film 2, an alternating electric field is generated by the same frequency waveform signal flowing through the second metal detection point 32. As this alternating electric field gradually approaches, the amplitude of its same frequency mutual inductance signal becomes relatively larger and larger, and the amount of charge received by the first metal detection point 31 as a capacitive detection point will also increase accordingly. As the amount of charge on the induced capacitive detection point changes more and more, when the amount of charge reaches the maximum, it means that the conductive metal film 2 of the rotating wing wheel 1 has completely covered the first metal detection point 31 and the second metal detection point 32. The first metal detection point 31 detects that between the sensing electrodes on the metal film 2, an alternating electric field with the second metal point will be generated by the same frequency waveform signal. When the second metal detection point 32 flows a waveform signal with the same frequency and phase of the electric field, energy is transferred (charge transfer) between the second metal detection point 32 and the capacitive detection module, causing the signal with the same frequency and phase to enter the capacitive charge sampling unit, thereby doubling the measured value of the charge sampling.

[0062] When the conductive metal film 2 rotating on the rotating wing wheel 1 gradually separates from the first metal detection point 31, the first metal detection point 31, as the input end of the capacitive detection point, detects the alternating electric field generated by the waveform signal of the same frequency between the sensing electrodes on the metal film 2 and the second metal point flow. As this alternating electric field gradually separates, the amplitude of its same-frequency mutual inductance signal becomes relatively smaller and smaller, and the amount of charge received by the first metal detection point 31 as a capacitive detection point will also decrease accordingly. As the amount of charge on the induced capacitive detection point changes smaller and smaller, when the charge returns to normal, it means that the conductive metal film 2 rotating on the rotating wing wheel 1 has completely separated from the first metal detection point 31, resulting in the same-frequency and same-phase signals unable to enter the capacitive charge sampling unit, thereby causing the measured value of the charge sampling to return to normal.

[0063] This application optimizes the capacitive mutual inductance charge transfer technology, and uses the principle of same-frequency mutual inductance to output the same frequency of the measurement frequency of the capacitive detection module through the same-frequency waveform generator. When the metal area of ​​the rotating wing wheel 1 covers the frequency output metal detection point of the same-frequency waveform generator and the input metal detection point of the charge sampling multiplexer, there is energy transfer (charge transfer) between the two metal detection points, causing the frequency output signal to enter the capacitive detection module through the conductive metal film 2 above, thereby doubling the measured value of the capacitance value. Because the same-frequency mutual inductance is greater than other interference, other interference cannot affect the capacitive detection module like the same-frequency mutual inductance.

[0064] This application utilizes the most difficult to overcome co-frequency interference phenomenon, improves the signal-to-noise ratio and anti-interference ability of the capacitive sensor, meets the advantages of high stability and low safety risk of the detection system, high system integration and low cost, high measurement accuracy and low power consumption, increases the service life of the capacitive mutual induction detection system, strengthens the anti-interference ability to make the detection system run stably, and adapt to a wider range of measurement applications.

[0065] This application uses a single chip to complete capacitive same-frequency mutual inductance charge sampling technology, uses capacitive same-frequency mutual inductance charge transfer technology based on the principle of electromagnetic induction, and adds the alternating electric field caused by the same-frequency mutual inductance as the technology of the measurement signal processing module architecture, which has great improvements in power saving function, anti-interference, cost reduction, and reduced development difficulty, achieving the advantages of integrated innovation.

[0066] Finally, it should be noted that the above disclosure is only a preferred embodiment of the present application and is not intended to limit the present application. Although the present application is described in detail with reference to the aforementioned embodiments, it is still possible for a person skilled in the art to modify the technical solutions described in the aforementioned embodiments or to replace some of the technical features therein by equivalents. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application. The scope of the present application is limited only by the attached claims.

Claims

1. A capacitive same-frequency mutual induction system, comprising a capacitive detection module, wherein the capacitive detection module can detect a capacitance value change signal, and is characterized in that: The capacitive detection module is signal-connected to a capacitive charge sampling unit, which can sample the detection signal frequency of the capacitive detection module. The capacitive charge sampling unit is signal-connected to a same-frequency waveform generator, which transmits the sampling frequency and phase information of the detection signal to the same-frequency waveform generator. The same-frequency waveform generator is signal-connected to the capacitive detection module, and the same-frequency waveform generator outputs a same-frequency signal with the same frequency and phase as the detection signal. The frequency and phase of the output signal of the same-frequency waveform generator change with the frequency and phase of the detection signal of the capacitive detection module. The same-frequency signal output by the same-frequency waveform generator doubles the signal value detected by the capacitive detection module.

2. A capacitive same-frequency mutual induction system according to claim 1, characterized in that: The capacitive detection module includes multiple metal detection points, each of which is respectively connected to the same-frequency output multiplexer and the charge sampling multiplexer signal. The same-frequency output multiplexer can control the metal detection point to perform same-frequency output, and the charge sampling multiplexer can control the metal detection point to perform charge sampling input. A rotatable rotating wing wheel is provided below the multiple metal detection points, and a metal film is provided on the upper part of the rotating wing wheel. The metal film can cover two of the metal detection points at the same time.

3. A capacitive same-frequency mutual induction system according to claim 2, characterized in that: The same-frequency output multiplexer and the charge sampling multiplexer respectively control two adjacent metal detection points to perform same-frequency output and charge sampling input respectively.

4. A capacitive same-frequency mutual induction system according to claim 2, characterized in that: The same-frequency waveform generator is connected to the same-frequency output multiplexer signal, and the same-frequency waveform generator outputs a same-frequency signal having the same frequency and phase as the detection signal to the metal detection point through the same-frequency output multiplexer.

5. A capacitive same-frequency mutual induction system according to claim 2, characterized in that: The capacitive charge sampling unit includes a fixed capacitor for storing charge. The capacitive charge sampling unit can repeatedly store and release charge on the fixed capacitor to obtain a charging and discharging sampling frequency. The capacitance value of the inductive capacitor is fixed. As the amount of charge gradually increases, the sampling frequency of the capacitive charge sampling unit will become faster.

6. A capacitive same-frequency mutual induction system according to claim 5, characterized in that: The same-frequency waveform generator repeatedly stores and releases charges on the capacitor according to the capacitive charge sampling unit to obtain the sampling frequency of the capacitive charge sampling unit. The same-frequency waveform generator includes an amplifier and a driving circuit. The amplifier and the driving circuit can increase the amplitude of the same-frequency signal. The same-frequency waveform generator can output the same phase as the signal waveform of the capacitive charge sampling unit.

7. A capacitive same-frequency mutual induction system according to claim 6, characterized in that: The capacitive charge sampling unit signal is connected to the capacitance value control unit, and the capacitance value control unit can correct the total capacitance value difference so that the charge stored in the capacitive charge sampling unit reaches a fixed capacitance value.

8. A capacitive same-frequency mutual induction system according to claim 7, characterized in that: The capacitance value control unit is connected to a sampling frequency counting unit, which can count the sampling frequency obtained by the capacitive charge sampling unit within a unit time. As the amount of charge increases, the number of sampling frequency counts will increase, and conversely, as the amount of charge decreases, the number of sampling frequency counts will decrease.

9. A capacitive same-frequency mutual induction system according to claim 8, characterized in that: The sampling frequency counting unit is connected to the flow counting unit. The flow counting unit calculates the cycle time of the gradual increase and decrease of the charge amount according to the number of times counted by the sampling frequency counting unit, and calculates the change and alternation of the rotation signal sensed by each other between the capacitive sensor blocks located on the rotating impeller, so that the speed of the alternation change and the number of revolutions of the rotating impeller are used as the instantaneous flow, thereby realizing flow measurement.

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