Non-magnetic flow sensor based on electromagnetic wave resonance absorption principle

Abstract

The utility model relates to a kind of non-magnetic flow sensor based on electromagnetic wave resonance absorption principle.The sensor includes: located in glass cover and rotates with the signal taking pointer shaft signal taking wheel and its fixed resonance absorption sheet, and located outside the sensor head of glass cover;Sensor head contains annular excitation coil and its inboard receiving coil, excitation frequency is equal or close to the resonance frequency of resonance absorption sheet.When resonance absorption sheet turns to receiving coil action area, due to resonance absorption, receiving coil output produces significant amplitude change, and accordingly output and the pulse corresponding to the number of angle turns.Resonance absorption sheet uses FPC or PCB integrated LC parallel resonance structure, signal taking wheel is provided with glue filling shallow groove to realize waterproof packaging;Sensor head is multilayer PCB coil, and receiving coil can be three-phase 120 ° distribution.The scheme significantly improves effective signal and anti-interference ability, supports intermittent excitation low-power sampling, and is suitable for non-magnetic signal taking of mechanical water meter and other meters.

Description

Technical Field

[0001] This utility model relates to the field of water meter measurement technology, and in particular to a non-magnetic flow sensor based on the principle of electromagnetic wave resonance absorption and its signal acquisition method. Background Technology

[0002] Traditional "magnetic" signal acquisition schemes use permanent magnets on a signal wheel and a magnetic sensor outside a glass cover for reading. While simple in structure and low in cost, they are susceptible to interference from external magnetic fields or ferromagnetic objects, and can even be misaligned due to artificial magnetic obstruction. "Non-magnetic" signal acquisition schemes use a stainless steel semi-circular plate (signal plate) in conjunction with a high-frequency induction coil outside the glass, relying on eddy current absorption to achieve angular position detection. This avoids external magnetic interference and is welcomed by water companies. However, due to installation space limitations, the diameter of the signal wheel is limited, and there is a gap of approximately 7–10 mm between the glass cover and the coil. The impact of eddy current absorption on the high-frequency electromagnetic field is only on the order of 1%, easily overwhelmed by excitation background and environmental noise. This results in weak effective signals, high amplification, poor anti-interference capabilities, and narrow error tolerance. Over the long term, this can lead to a risk of deviation between electromechanical conversion values ​​and mechanical readings. To simultaneously meet the comprehensive requirements of non-magnetic interference, strong signal, low power consumption and engineering feasibility, it is necessary to propose a novel non-magnetic signal acquisition device that significantly enhances coupling in structure, naturally filters out irrelevant interference in the frequency domain, and supports intermittent sampling in terms of power consumption. Utility Model Content

[0003] To overcome the shortcomings of the prior art, this utility model provides a non-magnetic flow sensor based on the principle of electromagnetic wave resonance absorption and its signal acquisition method.

[0004] A non-magnetic flow sensor based on the principle of electromagnetic wave resonance absorption, applied to a mechanical meter with a glass cover, is characterized by: Below the glass cover is a signal-collecting wheel that rotates with the signal-collecting pointer axis. A sensor head, coaxially arranged with the signal-collecting wheel, is located on the outside of the glass cover. A resonant absorption plate for generating resonant absorption of electromagnetic fields of a specific frequency is fixed on the signal-collecting wheel. The sensor head includes an excitation coil for generating a high-frequency magnetic field and at least one receiving coil located inside it. The excitation coil operates at the same frequency as the resonant absorption plate, such that when the resonant absorption plate rotates to the operating area of ​​the receiving coil, the receiving coil outputs a signal that periodically changes with the rotation angle, forming a pulse corresponding to the number of rotations of the signal-collecting wheel.

[0005] Furthermore, in order to better realize this utility model, the resonant absorption sheet is a parallel resonant circuit disposed on the same dielectric substrate, and the parallel resonant circuit is composed of an inductor and a capacitor; wherein, the inductor is a sector-shaped coil occupying a range of 180°, and the capacitor is a capacitor composed of double-sided copper foil occupying the remaining range of 180°.

[0006] Furthermore, to better realize this utility model, the dielectric substrate is a flexible FPC or a rigid PCB; the electrodes of the capacitor element are interdigitated or partitioned and provided with anti-eddy current dividing grooves; the inductor elements are respectively arranged on opposite sides of the dielectric substrate and connected through through holes to improve the inductance and resonant Q value.

[0007] Furthermore, in order to better realize this utility model, the upper surface of the receiver wheel is provided with a circular shallow groove, the resonance absorption sheet is placed in the shallow groove and sealed and fixed by potting glue, and the lower part of the receiver wheel has a connecting part that cooperates with the receiver pointer shaft.

[0008] Furthermore, in order to better realize this utility model, the sensor head is made of multi-layer PCB, the excitation coil is arranged in a ring, and at least one receiving coil is arranged in the inner circumferential area of ​​the ring excitation coil.

[0009] Furthermore, in order to better realize this utility model, the receiving coil is in three groups and distributed at 120° intervals on the circumference for angular position determination and anti-interference enhancement.

[0010] Furthermore, in order to better realize this utility model, the operating frequency of the excitation coil is an adjustable narrow band, covering the actual resonant point of the resonant absorption plate, with a range of 13MHz to 17MHz.

[0011] A signal acquisition method based on the above-mentioned electromagnetic wave resonant absorption principle of a non-magnetic flow sensor is characterized by: periodically applying a short-time excitation with the same resonant frequency as the resonant absorption plate to the excitation coil, sampling the amplitude change of the receiving coil located in the excitation coil, and determining that the signal acquisition wheel has rotated through the corresponding angle when the amplitude appears at a minimum value in a predetermined order among different receiving coils, and outputting a counting pulse corresponding to the number of rotations of the signal acquisition wheel.

[0012] The beneficial effects of this utility model are: This utility model relates to an electromagnetic wave resonant absorption type non-magnetic signal receiver (resonant absorber) manufactured using FPC technology. A 180° fan-shaped inductor coil and a parallel-plate capacitor with metal on both sides and a substrate material as dielectric are fabricated on the resonant absorber using copper foil. The inductor and capacitor form a parallel resonant circuit, and the Q value of the resonant circuit can reach 40-50 (the Q value of the prototype sample reached 53 at 15.8MHz). Due to the resonance effect, the resonant absorber achieves very strong resonant absorption of the excitation electromagnetic wave during resonance, with an effect far greater than that of traditional stainless steel sheets. Actual testing showed an effective signal of 60mV, while the effective signal of traditional stainless steel sheets is less than 1mV.

[0013] This invention utilizes the principle of electromagnetic wave resonance absorption. Through resonance, it achieves strong absorption of electromagnetic waves at specific frequencies, thereby enhancing the effective signal. The resulting advantages are twofold: First, the effective signal is stronger, with anti-interference capability improved by more than 50 times, and signal acquisition is more accurate. Second, it is effective only for specific frequencies, thus indirectly creating a filtering effect that shields interference from other frequencies, resulting in better anti-interference capability. In traditional non-magnetic flow sensors, due to the weak signal, a higher amplification factor is necessary, and the amplifier's spectrum is very wide, making it susceptible to interference. This invention, however, can operate in a relatively narrow bandwidth environment and is insensitive to electromagnetic waves of other frequencies.

[0014] This invention utilizes resonant absorption to increase the effective signal amplitude by more than 50 times, greatly reducing the difficulty of designing the reading circuit and significantly lowering the cost. Attached Figure Description

[0015] Figure 1 This is a wiring diagram of the first type of resonant absorbing sheet of this utility model; Figure 2 This is a wiring diagram of the second type of resonant absorbing sheet of this utility model; Figure 3 A schematic diagram of the signal-collecting wheel structure of a traditional stainless steel eddy current absorber non-magnetic flow sensor; Figure 4 This is a schematic diagram of the structure of the signal-collecting wheel of this utility model; Figure 5 This is a wiring diagram of the receiving and identification coil of this utility model; Figure 6 This is a schematic diagram of a traditional non-magnetic flow sensor. Figure 7 This is an equivalent schematic diagram of the resonant absorption sheet of this utility model. Detailed Implementation

[0016] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0017] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0018] Figures 1-7 This is a specific embodiment of the present invention, which is an electromagnetic wave resonant absorption type non-magnetic flow sensor.

[0019] 1. Electromagnetic wave resonant absorbing sheet This embodiment relates to an electromagnetic wave resonant absorption type non-magnetic flow sensor, the main feature of which is that the semi-circular stainless steel absorbing plate installed on the traditional non-magnetic signal wheel is replaced with an "electromagnetic wave resonant absorption plate", hereinafter referred to as the resonant absorption plate.

[0020] (1) The resonant absorption sheet is preferably made of FPC. In this embodiment, the resonant absorption sheet is made of double-sided FPC with a polyimide substrate of 0.13mm thickness. According to the information provided by the FPC manufacturer: the FPC substrate thickness of this specification is 25uM, the surface copper foil thickness is 17.5uM, and the surface protective layer is 35uM.

[0021] (2) Two devices are fabricated on the resonant absorption sheet using copper foil: one is a sector coil (inductor L) occupying 180°, and the other is a capacitor (capacitor C) composed of double-sided copper foil occupying the remaining 180°. The coil L and capacitor C are connected in parallel to form a resonant circuit, and the resonant frequency can be calculated using the following formula: f = 1 / (2*Pi*(L*C)) 0.5 ) Formula 1 whether Figure 1 Figure 2 For the given pattern, the characteristics of the resonant absorber include: Firstly, the resonant absorber is preferably manufactured using a polyimide FPC, but a rigid PCB can also be used. The advantages of using an FPC are: firstly, the finished material is very thin, occupying little space, and the resonant absorber can be placed as close as possible to the receiving coil; secondly, the FPC substrate (base) is very thin, only 25µm, allowing capacitors to be fabricated on the resonant absorber using the parallel-plate capacitor principle. This means that all the LC circuit components constituting the resonance can be directly manufactured on the PCB without the need for additional soldering components (soldering capacitors), resulting in lower cost and simpler process. Of course, a rigid PCB can also be used, but the thicker substrate makes it difficult to increase the capacitance of the parallel-plate capacitor, leading to an excessively high resonant frequency for the resonant absorber. Alternatively, a capacitor can be soldered onto the PCB to resonate with the coil on the PCB, but this increases cost and process complexity. Therefore, using a rigid PCB to manufacture the resonant absorber is the secondary option of this invention.

[0022] Furthermore, even if FPC is used for manufacturing, there can be positions on the FPC for soldering capacitors. An external capacitor can be added to resonate with the coil on the FPC, but the result is increased cost and increased process difficulty, so it is better to choose the preferred solution.

[0023] On the resonant absorption sheet, the coil and capacitor each occupy half of the area, each occupying a 180° sector range. This is the preferred solution. Of course, the area of ​​the coil or the area of ​​the capacitor can be deliberately reduced, but the effect will not be better than the preferred solution. This cannot be used as an excuse to circumvent this utility model.

[0024] Secondly, the resonant absorption sheet is preferably manufactured using a double-sided FPC / PCB process. The double-sided process has a lower cost and can well meet the design requirements. Of course, it is also possible to use a four-layer board or more layers of process, but this will increase the cost without much improvement in performance, so it is a secondary option.

[0025] Third, on the resonant absorber sheet, the coil is made of two layers of copper foil, top and bottom, connected by a via. The coil is composed of curved and straight lines, which is the preferred solution. Of course, a coil can also be composed of curved + curved + straight lines, which will achieve the same effect but will not be better than the preferred solution and cannot be used as an excuse to circumvent this utility model. In this embodiment, an FPC resonant absorber sheet with a diameter of 13mm and a thickness of 0.13mm was trial-produced. The coil inductance in the semi-circular fan-shaped area is approximately 1.5uH.

[0026] Fourth, a parallel-plate capacitor is manufactured using double-sided copper foil from an FPC in the lower semicircle of the resonant absorber. The copper foil of the parallel-plate capacitor is interdigitated. In the first layout scheme, each interdigit is a large arc, separated from each other by arc-shaped "anti-eddy current slots." This is the preferred design. The function of the anti-eddy current slots is to prevent the generation of large eddy currents within the large-area interconnected copper foil, thereby preventing excessive absorption of the excitation magnetic field. The anti-eddy current slots of the resonant absorber can have many shapes, as long as they achieve the purpose of separating the large-area copper foil constituting the parallel-plate capacitor. Therefore, using other shapes of anti-eddy current slots cannot be used as an excuse to circumvent this utility model. The second layout scheme fully reflects this point. To prevent the generation of eddy currents in the continuous large-area capacitor plates, the second layout scheme also uses an interdigitated layout, with anti-eddy current slots between the interdigitates.

[0027] According to information provided by the FPC manufacturer, the dielectric constant of the polyimide substrate is approximately 3.4, while the plate area of ​​the parallel plate capacitor designed by the inventor is approximately 52 mm². 2 Based on a substrate thickness of 25µm, substituting this into the formula for calculating the capacitance of a parallel plate capacitor: C=ε ｒ Formula 2: *ε0*S / L After substituting the data, the calculated capacitance value is approximately 62.6 pF.

[0028] The resonant frequency calculated by substituting the measured inductance into Formula 1 is approximately 16.42MHz. However, the actual measured resonant frequency is approximately 15.8MHz. Therefore, it can be inferred that the influence of distributed capacitance should also be considered. In fact, there is also a large capacitance between the coil lines. Therefore, the measured resonant frequency of the absorption sheet is 15.8MHz, which is within expectations.

[0029] At 15.8MHz, the inductive reactance of a 1.5uH inductor is ZL = 2*Pi * f *L = 148.9 ohms. Simulation data from PCB design tools indicates the coil resistance is approximately 2.6 ohms. Therefore, the estimated Q value of the resonant circuit is 148.9 / 2.6 = 57.3, while the actual measured value is around 53, which is close to the estimated value. The reason for the lower actual value may be the presence of other conductive materials in the test environment that absorb the electromagnetic field.

[0030] Fifth, regardless of whether it's the first or second layout, the common characteristic of the resonant absorbing sheet is: Firstly, manufacturing using FPC / PCB technology is the preferred solution. Of course, it is also possible to manufacture using enameled wire coils and capacitors in series, but the cost is high. Although it can achieve the same effect as the preferred solution of this utility model, it will bring high cost, installation and protection difficulties, and cannot be used as an excuse to bypass this utility model.

[0031] Secondly, an inductor L and a parallel plate capacitor C are fabricated on the resonant absorption sheet using FPC / PCB copper foil (metal foil), and the two are connected in parallel to form an LC parallel resonant circuit. This design gives the resonant absorption sheet the characteristic of resonant absorption of electromagnetic waves of a specific frequency, which is the most important innovation of this utility model.

[0032] Of course, parallel plate capacitors can be manufactured without FPC substrates, and finished capacitor components can be used to achieve the same effect, but this increases the difficulty of the process and the cost, and does not yield better returns.

[0033] Furthermore, in the second layout, the wiring of the inductor coil in both the TOP and BOTTOM layers extends by half a turn on the outer ring of the parallel plate capacitor electrode. The advantage of doing this is that it increases the mutual inductance between the inductor coil and the excitation coil of the identification coil, thereby increasing the strength of the effective signal.

[0034] 2. Design of a non-magnetic flow meter indicator wheel Traditional semi-circular stainless steel receiver plates can be directly immersed in water; therefore, traditional non-magnetic flow receiver wheels do not require consideration of waterproofing. However, the resonant absorption receiver plate involved in this embodiment is manufactured using FPC, thus requiring waterproofing measures. This embodiment relates to a receiver wheel with a glue-filled sealing groove, see... Figure 4.

[0035] The resonant absorption non-magnetic signal-collecting wheel of this embodiment differs from the traditional non-magnetic signal-collecting wheel (see...). Figure 3 Compared to other types, its main feature is that it has a resonant absorption sheet mounting and potting groove on its top surface. This resonant absorption sheet mounting and potting groove is a shallow circular groove with a diameter slightly larger than the resonant absorption sheet and a depth of about 0.3 mm. During production, the resonant absorption sheet is placed into the "resonant absorption sheet mounting and potting groove", and then epoxy resin potting glue is dripped into the shallow groove to protect the resonant absorption sheet.

[0036] The bottom surface of the resonant absorption non-magnetic receiver wheel has a pointer-to-insert handle, and the bottom of the pointer-to-insert handle is oiled with a pointer-to-insert hole, so that the potted resonant absorption non-magnetic receiver wheel can be inserted into the non-magnetic receiver wheel shaft of the water meter.

[0037] 3. Identification of coil structure and identification methods (1) Identification coil structure like Figure 5 As shown, the identification coil of the non-magnetic flow sensor is preferably manufactured using a 4-layer PCB. A 2-layer PCB design can also be used, but due to insufficient trace space on a 2-layer PCB, the inductance of the coil is insufficient, making it difficult to obtain a high Q value. Therefore, manufacturing with a 4-layer PCB is the preferred solution.

[0038] The non-magnetic flow sensor identification coil preferably consists of four coils: an excitation coil, an A-phase receiving coil, a B-phase receiving coil, and a C-phase receiving coil.

[0039] The excitation coil is circular. In this embodiment, the excitation coil is manufactured using the TOP layer and Mid1 layer of a 4-layer PCB, which is a preferred solution. Of course, other layers can also be used to manufacture the excitation coil. The three-phase receiving coils ABC each occupy a 120° range of the circumference, forming three directional receiving coils in space. When the excitation coil is supplied with an excitation signal with the same resonant frequency as the resonant absorption plate, the resonant absorption plate will have a strong resonant absorption on the excitation coil. The amount of absorption will form a vector in space. By synthesizing the three-phase vectors of ABC, the angular position of the resonant absorption plate can be obtained, thereby realizing the rotation recognition of the non-magnetic signal receiving wheel.

[0040] (2) Identify the installation location of the coil The identification coil is installed on the surface of the water meter's glass cover and inside the water meter's electrical housing. To improve sensitivity, the identification coil should be placed as close as possible to the resonant absorption plate on the non-magnetic signal wheel under the water meter's glass cover.

[0041] Currently, based on actual production needs, the distance between the resonant absorption sheet and the identification coil consists of the following parts: First, the potting depth of the resonant absorption sheet, calculated at 0.2mm; second, the distance between the surface of the resonant non-magnetic flow metering wheel and the bottom surface of the glass, calculated at 0.5mm; third, the glass thickness, calculated at 5.5mm; and fourth, the wall thickness of the water meter's electrical components, calculated at 1.5mm. The total distance is 7.7mm.

[0042] At this distance, the effective signal amplitude of the receiving coil of the resonant absorption type non-magnetic flow sensor involved in this embodiment reaches 60mV, while the effective signal amplitude of the traditional stainless steel sheet receiving plate is less than 1mV.

[0043] (3) Coil resonant excitation and received signal sampling The identification coil tested in this embodiment has an inductance of approximately 1.95uH and a coil resistance of approximately 3.1 ohms. At 15.8MHz, the Q value is approximately 62.4. When the excitation signal amplitude reaches 3V, the coil resonant current is approximately 11mA. After being reduced by a factor of Q, the current of the drive signal is only 0.2mA. Therefore, the electromagnetic wave resonant absorption non-magnetic flow sensor involved in this embodiment has very low power consumption.

[0044] After rectification and filtering, the receiving coil can be directly sampled by the microcontroller. If a voltage doubler rectifier circuit is used, the signal amplitude will double, reaching 100-120mV. Therefore, this embodiment can greatly simplify the design of the signal processing circuit and significantly reduce costs.

[0045] (4) Calculation of actual power consumption Through actual testing, the electromagnetic resonant absorption non-magnetic flow sensor of this embodiment only needs to emit a 10µs excitation signal to achieve signal sampling during reading. Using an ADC with a conversion rate of 1MHz, assuming a full-speed microcontroller operating current of 4mA, a working time of 15µs, and a sampling period of 32ms, the average power consumption of non-magnetic sampling is 4mA * 15µs / 32000µs = 1.875µA. Considering the microcontroller's own average power consumption of approximately 1µA, the total average power consumption is approximately 2.875µA, making it the lowest power consumption non-magnetic flow sensor currently available. This performance is attributed to the use of resonant excitation and resonant absorption principles.

[0046] 3. Working Principle To clearly explain the working principle of this embodiment, it is necessary to explain the working principle of a traditional non-magnetic flow sensor, see [link to documentation]. Figure 6 .

[0047] A non-magnetic flow sensor is essentially a rotary sensor. Its purpose is to detect the rotation of a pointer wheel on the water meter outside the glass cover, so that the sensor outputs a pulse for each rotation, thereby converting the mechanical reading of the water meter into pulses.

[0048] exist Figure 6 In this system, a non-magnetic sensor wheel is installed on a pointer shaft inside the water meter (sensor pointer shaft). Driven by the rotation of the sensor pointer shaft, the non-magnetic sensor wheel rotates accordingly. Each rotation represents a certain amount of water flowing through the water meter.

[0049] Outside the water meter, on the glass cover, coaxially with the non-magnetic signal wheel, is installed a "non-magnetic flow recognition coil," or simply the recognition coil. The recognition coil is typically manufactured using PCB technology. The advantages of PCB manufacturing are: good process repeatability, good parameter consistency, and low cost. The recognition coil consists of four sub-coils: an excitation sub-coil, and three-phase (A, B, C) receiving sub-coils.

[0050] Its working principle is as follows: First, a high-frequency excitation signal is passed through the excitation coil, generating a high-frequency magnetic field perpendicular to the coil plane. At the same time, under the action of the high-frequency magnetic field, the three-phase receiving coils A, B, and C will induce voltages. When the semi-circular stainless steel eddy current absorber on the non-magnetic signal-collecting wheel is directly below a certain receiving coil, the induced voltage of that receiving coil will decrease because the stainless steel eddy current absorber has a strong absorption effect on the electromagnetic field. Based on the changes in the induced voltages of the three coils A, B, and C, it can be deduced whether the non-magnetic signal-collecting wheel has rotated one revolution.

[0051] The above describes the working principle of a traditional non-magnetic flow sensor, and is only used to illustrate the principle of a non-magnetic flow sensor.

[0052] The main feature of the electromagnetic wave resonant absorption non-magnetic flow sensor in this embodiment is that a resonant absorption plate is installed on the non-magnetic flow signal wheel.

[0053] The resonant absorber is circular, preferably manufactured using an FPC (fiberglass reinforced plastic) substrate made of polyimide. A 180° fan-shaped coil is fabricated on the resonant absorber using copper foil from the FPC. The coil is wired on both sides, and the two sides are connected by through-holes. The ends of the coils are connected to the plates of a parallel-plate capacitor fabricated in another semi-circular space on the resonant absorber. Thus, the inductor and the parallel-plate capacitor form an LC resonant circuit, and the resonant frequency can be calculated using Formula 1. In this embodiment, a resonant absorber with a thickness of 0.13 mm and a diameter of 13 mm was fabricated, and its resonant frequency was measured to be 15.8 MHz (approximately 16 MHz). At this frequency, its Q value was measured to be approximately 53.

[0054] The equivalent principle diagram of the resonant absorption sheet involved in this embodiment is shown in [reference needed]. Figure 7 : The inductor L is made using a metal coil on an FPC, while the capacitor C is made using double-sided metal from an FPC as parallel plate capacitor plates, with the dielectric between the capacitor plates being an FPC substrate.

[0055] With the support of this embodiment, a non-magnetic signal-collecting wheel with electromagnetic wave resonant absorption characteristics replaces the traditional semi-circular stainless steel eddy current absorption signal-collecting wheel. The resonant absorption sheet has a strong resonant absorption effect on electromagnetic waves of specific frequencies, thereby enhancing the output signal strength of the identification coil. Actual manufacturing verification has proven that this embodiment has a significant effect on improving the effective output signal; the actual tested effective signal reaches 40-60mV, while the effective signal using the traditional semi-circular stainless steel eddy current absorption sheet is less than 1mV.

[0056] In this embodiment, a shallow circular groove needs to be opened on the non-magnetic sensor wheel of the water meter, called the resonance absorption sheet mounting and potting groove. The resonance absorption sheet is installed in this shallow groove and potted with glue. The non-magnetic sensor wheel of the water meter is installed on the sensor pointer shaft of the water meter and sealed under the glass cover of the water meter.

[0057] Inside the electrical housing of the water meter, on the glass cover of the water meter, a non-magnetic flow recognition coil needs to be installed close to the glass cover and directly above the non-magnetic signal wheel of the water meter.

[0058] The identification coil consists of four coils. In this embodiment, the identification coil is manufactured using a 4-layer PCB. The excitation coil is circular, occupying the TOP layer and MID1 layer, with a total of 10 turns; The three receiving coils occupy the MID2 and BOTTOM layers of the 4-layer board respectively. The three receiving coils are ABC and are spatially 120° apart.

[0059] When a specific frequency excitation signal is applied to the excitation coil, a high-frequency electromagnetic field is generated in the direction perpendicular to the coil plane. This high-frequency electromagnetic field is sensed by the ABC three-phase receiving coils, generating a high-frequency induced voltage.

[0060] When the sector-shaped resonant coil on the non-magnetic signal-collecting wheel rotates past the three receiving coils A, B, and C, the high-frequency excitation signal will be absorbed by the resonant absorption plate. When the excitation frequency is close to or equal to the characteristic frequency of the resonant absorption plate, the absorption amplitude will increase significantly, theoretically increasing the Q value by a factor of 1. In actual testing, the effective signal amplitude of the receiving coil tested by the utility model reached 60mV, far exceeding that of the traditional stainless steel semi-circular absorption plate.

[0061] The most important innovation of this embodiment is that the signal strength of the effective signal of the identification coil is enhanced by installing a resonant absorption plate on the non-magnetic signal wheel. This embodiment has achieved very outstanding results.

[0062] Furthermore, the excitation frequency must resonate with the resonant absorber to amplify the effective signal. Therefore, the frequency of the excitation signal needs to be matched to that of the resonant absorber. In this embodiment, a resonant absorber with a resonant frequency of approximately 15.8 MHz was fabricated. During testing, it was found that the effective signal exceeded 30 mV within the excitation frequency range of 13 MHz to 17 MHz. Therefore, this embodiment has good adaptability and can compensate for process deviations, thus demonstrating good engineering feasibility.

[0063] In this embodiment, the identification coil is located above the glass cover of the water meter, approximately 7.4-8 mm away from the resonant absorption plate. The identification coil consists of an excitation coil and three-phase (ABC) receiving coils, which are spatially aligned at 120°. The amount of excitation signal absorbed by the resonant absorption plate and the signal values ​​refracted onto the three coils constitute three spatial vectors. Based on the synthesis of these three vectors, the rotation angle of the non-magnetic signal-collecting wheel can be obtained, thereby acquiring its rotation data.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of this utility model and are not intended to limit it. Any other modifications or equivalent substitutions made by those skilled in the art to the technical solution of this utility model, as long as they do not depart from the spirit and scope of the technical solution of this utility model, should be covered within the scope of the claims of this utility model.

Claims

1. A non-magnetic flow sensor based on the principle of electromagnetic wave resonance absorption, applied to a mechanical meter with a glass cover, characterized in that: Below the glass cover is a signal-collecting wheel that rotates with the signal-collecting pointer axis. A sensor head, coaxially arranged with the signal-collecting wheel, is located on the outside of the glass cover. A resonant absorption plate for generating resonant absorption of electromagnetic fields of a specific frequency is fixed on the signal-collecting wheel. The sensor head includes an excitation coil for generating a high-frequency magnetic field and at least one receiving coil located inside it. The excitation coil operates at the same frequency as the resonant absorption plate, such that when the resonant absorption plate rotates to the operating area of ​​the receiving coil, the receiving coil outputs a signal that periodically changes with the rotation angle, forming a pulse corresponding to the number of rotations of the signal-collecting wheel.

2. The non-magnetic flow sensor based on the electromagnetic wave resonance absorption principle according to claim 1, characterized in that: The resonant absorption sheet is a parallel resonant circuit disposed on the same dielectric substrate. The parallel resonant circuit is composed of an inductor and a capacitor. The inductor is a sector coil occupying 180° of the range, and the capacitor is a capacitor composed of double-sided copper foil occupying the remaining 180° of the range.

3. The non-magnetic flow sensor based on the electromagnetic wave resonance absorption principle according to claim 2, characterized in that: The dielectric substrate is a flexible FPC or a rigid PCB; the electrodes of the capacitor element are interdigitated or partitioned and provided with anti-eddy current dividing grooves; the inductor elements are respectively arranged on opposite sides of the dielectric substrate and connected by through holes. Wiring on both sides can increase the number of turns to improve the inductance and resonant Q value.

4. The non-magnetic flow sensor based on the electromagnetic wave resonance absorption principle according to claim 1, characterized in that: The upper surface of the signal-collecting wheel is provided with a circular shallow groove, the resonance absorption sheet is placed in the shallow groove and sealed and fixed by potting glue, and the lower part of the signal-collecting wheel has a connecting part that cooperates with the signal-collecting pointer shaft.

5. The non-magnetic flow sensor based on the electromagnetic wave resonance absorption principle according to claim 1, characterized in that: The sensor head is made of a multi-layer PCB, the excitation coil is arranged in a ring, and at least one receiving coil is located in the inner circumferential region of the ring excitation coil.

6. The non-magnetic flow sensor based on the electromagnetic wave resonance absorption principle according to claim 5, characterized in that: The receiving coils are in three groups and are distributed 120° apart on the circumference for angular position determination and anti-interference enhancement.

7. The non-magnetic flow sensor based on the electromagnetic wave resonance absorption principle according to claim 1, characterized in that: The operating frequency of the excitation coil is an adjustable narrow band, covering the actual resonant point of the resonant absorption plate, ranging from 13MHz to 17MHz.

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