Ultrahigh-frequency resonance excitation low-power-consumption electromagnetic flowmeter and special chip thereof

Abstract

The invention relates to an ultrahigh frequency resonance excitation low power consumption electromagnetic flowmeter and a special chip thereof, a sensor core is installed in a sensor core waterproof box, the sensor core waterproof box is installed in the middle of a sensor core support, and the sensor core waterproof box divides a measuring pipeline in the sensor core support into two parts; signal processing PCBs are installed on the front face and the back face of the sensor core support respectively, special chips are arranged in the two signal processing PCBs respectively, and the sensor core support is installed in a metal pipeline. The purpose of reducing power consumption is achieved by shortening the excitation time and forming resonance through inductance and capacitance of the excitation coil; and the excitation coil and the measurement electrode are manufactured by adopting the multi-layer PCB, so that the manufacturing cost is greatly reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of electromagnetic flowmeters, and in particular to an ultra-high frequency resonant excitation low power consumption electromagnetic flowmeter and a dedicated chip thereof. Background Art

[0002] Electromagnetic flowmeter is a high-precision, long-life flowmeter designed based on the principle of electromagnetic induction. Its basic principle is: the flowing conductive liquid cuts the magnetic lines of force in the direction of movement, which will generate induced electromotive force at both ends of the liquid. If the magnetic induction intensity is constant at B, then according to the law of electromagnetic induction, the induced electromotive force U = BLV, where B is the magnetic induction intensity, L is the width of the water flow that effectively cuts the magnetic lines of force, V is the water flow velocity, and U is the magnitude of the induced electromotive force. Therefore, as long as the magnetic induction intensity B is constant and the pipeline parameter L is fixed, it can be obtained that: U is proportional to V, U = K * V, and the water flow velocity V can be calculated by measuring the value of U. The volume flow rate of the flowmeter can be obtained by multiplying the water flow velocity by the cross-sectional area of ​​the pipeline: Flux = V * S, where S is the effective cross-sectional area of ​​the pipeline.

[0003] The above is the working principle of the electromagnetic flowmeter, from which we can infer the shortcomings of the electromagnetic flowmeter as follows: First, the power consumption is large. When the electromagnetic flowmeter realizes water flow measurement, due to the polarization effect of water, there is an uncertain polarization voltage between the two measuring electrodes. In order to overcome the polarization voltage, alternating excitation is required instead of permanent magnet excitation. This causes the electromagnetic flowmeter to require a larger excitation current.

[0004] Second, the cost is high. The electromagnetic flowmeter requires a larger excitation coil and an insulating layer is required inside the pipeline, which leads to a high manufacturing cost.

[0005] At present, household water meters are developing in the direction of intelligence, but due to the limitations of cost and technological maturity, the intelligence of household water meters is generally achieved by adding electromechanical conversion devices to mechanical instruments. The advantages of this intelligent direction are: good technical continuity and retention of the durability of mechanical water meters; but the disadvantages are also very obvious: mechanical to electrical conversion is required, accuracy is difficult to improve, and the base meter has a short life.

[0006] Therefore, the industry has long hoped to find a way to fully electronicize household smart water meters. To this end, many companies in the global measurement industry have made continuous efforts. At present, the more promising methods include: ultrasonic flowmeters and electromagnetic flowmeters. The advantages of ultrasonic flowmeters are: high accuracy and low power consumption, but the disadvantages are also very obvious: the transducer has poor noise resistance and has a high probability of damage under strong vibration and thermal fatigue. There is currently no good way to overcome this; while electromagnetic flowmeters have the advantages of high accuracy, long life, and good noise resistance, but their power consumption and cost have become the difficulties in the industry.

[0007] To this end, this application designs an ultra-high frequency resonant excitation low-power electromagnetic flowmeter and its dedicated chip, which targets the power consumption and cost shortcomings of the electromagnetic flowmeter, and overcomes these two shortcomings of the electromagnetic flowmeter in a very novel and effective way, opening up a new path for the full electronicization of water meters. Summary of the invention

[0008] In order to make up for the deficiencies in the prior art, the present invention provides an ultra-high frequency resonant excitation low power consumption electromagnetic flowmeter and its dedicated chip. The basic design concept is: first, by shortening the excitation time and using the inductance and capacitance of the excitation coil to form resonance, the purpose of reducing power consumption is achieved; second, a multi-layer PCB is used to manufacture the excitation coil and the lead-out of the measuring electrode, thereby greatly reducing the manufacturing cost.

[0009] The present invention is achieved through the following technical solutions: 1. Mechanical structure The main advantage of the ultra-high frequency resonant excitation low power consumption electromagnetic flowmeter of the present invention is the excitation winding and electrode formed in one piece on the PCB board. This component is the core component of the flow sensor and is named "sensor core" for the convenience of description. The "integrated excitation winding and electrode" derived from the excitation winding and measuring electrode of the electromagnetic flowmeter manufactured using multi-layer PCB is also called the sensor core. The advantages of using PCB technology for manufacturing are: high process repeatability, low manufacturing cost, and compact structure.

[0010] The preferred manufacturing process is to use a multi-layer PCB, in which the excitation winding occupies the inner metal layer and the measuring electrode occupies the surface metal. The PCB has two surfaces, Top and Bottom, and measuring electrodes are manufactured on both the Top and Bottom layers. The signals of the electrodes on both sides are connected in series and then led out. The advantage of this is that the amplitude of the measurement signal is doubled.

[0011] An electrode welding Pad is manufactured on the sensor core PCB, and a measuring electrode is welded on the electrode welding Pad. Since the measuring electrode is in contact with water, it is preferably made of stainless steel. It can also be made of Hastelloy, or other corrosion-resistant metals or alloys as electrodes, and stainless steel is preferably used.

[0012] The excitation coil and the measuring electrode lead pad are manufactured using a multi-layer PCB process. This has the advantages of low manufacturing cost and good process repeatability. However, the disadvantage is that the excitation coil is made of PCB copper foil. Since the thickness of the PCB copper foil is small, the resistance of the coil is large. The test data of the current trial samples is: the coil resistance is about 1.5 ohms, which will result in a small excitation current of only about 2A when directly powered by a 3.6V battery, and the Q value of the resonant circuit is also small, only 50-100.

[0013] To solve this problem, you can also use the following method: only use PCB to manufacture the measuring electrode lead pad and lead line (PCB board as support), and the excitation coil is wound with enameled wire.

[0014] It is preferred to use a double-sided PCB board with a thickness of 0.6 mm as the electrode support, and paste a single layer of enameled wire winding on the upper and lower surfaces of the PCB. Fig. 9 Green line schematic part. If the thickness of the enameled wire wound on the upper and lower surfaces of the PCB is 0.5mm, the total thickness = 1.6mm. This is the preferred design. The effective thickness of the sensor core is as thin as possible, which can provide the flow meter with as large a pipe area as possible and reduce pressure loss. The advantages of using enameled wire to realize the excitation winding are: the coil resistance is very small, the resonant circuit Q value of the resonant excitation can be greatly improved, and a large excitation current can be obtained, which increases the measurement signal amplitude. During the trial production, the inventor used enameled wire with an outer diameter of 0.5mm, 16 turns in a single layer, and 32 turns in two layers. The actual measured inductance is 22uH, and the winding resistance is only 0.16 ohms. At 1Mhz ultra-high frequency excitation, the inductor impedance ZL = 138.2 ohms, and the resonant circuit Q value can theoretically reach: Q = 138.2 / 0.16 = 864, and the maximum excitation current can theoretically reach: 3.6V / 0.16 ohms = 22.5A. The high Q value means that only a small energy excitation is required to achieve a long time of measurement, which is more conducive to reducing power consumption.

[0015] In order to achieve electrical isolation from water, the "sensor core" made of multi-layer PCB needs to be installed inside a plastic shell. For the convenience of description, it is named "sensor core box", preferably made of plastic with good water resistance, such as PPO or PPS, etc. Two electrode lead holes are made on the bottom of the sensor core box. To achieve better waterproof effect, when the sensor core is installed in the "sensor core box", the inside of the "sensor core box" should be filled with epoxy resin potting glue. In order to achieve electrical isolation from water, the sensor core can also be directly injected into the plastic.

[0016] In order to achieve flow measurement, the present invention designs an electromagnetic flowmeter core bracket, referred to as: sensor core bracket, which is made of plastic with good water resistance, such as nylon, polyphenylene sulfide (PPO), polysulfone (PPS), etc. The sensor core bracket is a section of cylindrical pipe, the middle of which is a measuring pipe, and a magnetic shielding tape winding limit groove is opened in the middle position of the outer side of the cylindrical pipe. After the waterproof sensor core and the signal processing PCB board and the excitation drive PCB board are installed in place, the magnetic shielding tape can be wound in this "magnetic shielding tape winding limit groove". The magnetic shielding tape is made of Permalloy strip with a thickness of about 0.05-0.1mm. The multi-layer winding forms an external magnetic shielding, and the winding thickness is about 0.5mm. "Signal processing PCB board installation cavity" is opened on the two sides of the sensor core bracket, and the electromagnetic flowmeter signal processing PCB and the excitation signal driving PCB are installed in these two cavities, one of which is installed with the excitation signal driving PCB board, and the other is installed with the measurement signal processing PCB board. In the middle of the signal processing PCB installation cavity, there is a sensor core waterproof box installation slot with arcs on both sides. This slot runs through the upper and lower signal processing PCB installation cavities and is used to install the waterproof sensor core. From this structure, it can be seen that the waterproof sensor core is installed in the middle of the measuring pipe. A "waterproof glue potting cavity" is opened around the waterproof sensor core installation slot. After the waterproof sensor core is installed in the waterproof sensor core installation slot, it is necessary to pot epoxy resin sealant in this cavity to achieve water and electricity isolation between the measuring pipe and the electrical part.

[0017] After the sensor core bracket and the waterproof sensor core are combined, it is called: electromagnetic flowmeter measuring core. After the waterproof sensor core is inserted into the sensor core bracket, the measuring pipe is divided into two parts, and the waterproof sensor core is in the middle of the measuring pipe. The advantages of this are: First, the excitation signal is in the middle of the pipe, away from the metal of the magnetic field shielding layer of the electromagnetic flowmeter and the metal of the outer pipe. When high-frequency resonant excitation is achieved, the absorption of these metal layers is minimal, and the excitation coil can maintain a very high Q value. Second, the pipe is divided into two parts, so the measurement signal can be divided into two sides, and the measurement signals on both sides can be connected in series to obtain twice the measurement voltage, so the measurement accuracy is higher.

[0018] The electromagnetic flowmeter measures the core, and a magnetic shielding tape is wound on the outside. The magnetic shielding tape has a signal lead-out hole. The magnetic shielding tape can provide a good shielding environment to prevent the measurement accuracy from being affected by changes in the external magnetic circuit. The present invention preferably uses a 0.1mm thick Permalloy tape as the magnetic shielding layer material, winding 4-5 layers to form a magnetic shielding layer with a total thickness of 0.4-0.5mm. The shielding tape can also be made of pure iron or silicon steel materials, which will be more cost-effective. A signal lead-out hole is opened on the shielding tape, and the electromagnetic flowmeter can be powered and the signal can be output to the outside.

[0019] The electromagnetic flowmeter measuring core is the core measuring component of the present invention. In order to prevent the electrical signal from being short-circuited by the metal pipe, the electromagnetic flowmeter measuring core also needs to extend a section of "lining pipe" upstream and downstream. The lining pipe is made of plastic materials with good water resistance, such as nylon, polyphenylene sulfide (PPO), polysulfone (PPS), etc. The lining pipe is inserted into the "lining pipe pair slot" on the electromagnetic flowmeter measuring core by gluing. "Sealing ring grooves" are opened on the two top surfaces of the cylinder of the electromagnetic flowmeter measuring core for installing sealing rings. The sealing ring can prevent water from bypassing the gap between the metal pipe and the lining pipe and entering the electrical signal cavity. There is one sealing ring upstream and downstream of the electromagnetic flowmeter measuring core, and sealing needs to be achieved on both sides.

[0020] A metal pipe needs to be put on the outside of the electromagnetic flowmeter measuring core with an inner liner. The metal pipe is divided into two parts: the upstream pipe and the downstream pipe, which are fixed with screws. The upstream pipe is made with a signal lead-out hole and an electrical box mounting chassis. The waterproof sensor core is installed vertically in the pipeline, dividing the pipeline into two. The plane of the waterproof sensor core is perpendicular to the plane of the electrical housing fixing plate, that is, in the vertical direction, the waterproof sensor core divides the water flow into two left and right diversions. This installation direction can reduce the deposition of impurities in the water flow on the electrode surface of the waterproof sensor core, improve the anti-fouling ability, and extend the service life of the flowmeter.

[0021] The sealing ring installed on the top surface of the cylindrical body of the electromagnetic flowmeter measuring core is used between the upstream and downstream metal pipes and the electromagnetic flowmeter measuring core with the inner lining pipe to achieve sealing, which can prevent water from entering the electrical processing chamber of the electromagnetic flowmeter from the gap between the metal pipe and the inner lining pipe. At the same time, in order to enhance the sealing effect, sealant can also be applied between the metal pipe and the inner lining pipe.

[0022] 2. Circuit design The ultra-high frequency resonant excitation of the present invention is the key to achieving low power consumption, so a separate chapter is taken out to describe the circuit design part of the present invention.

[0023] The present invention relates to a low-power electromagnetic flowmeter with ultra-high frequency resonant excitation. In order to obtain good power consumption characteristics and signal measurement characteristics, it is necessary to realize signal processing such as precise driving of the excitation circuit, high-gain amplification of the signal, high-speed data acquisition, and temperature compensation. Therefore, it is necessary to design two special chips, one of which is used to realize excitation and synchronous signal output, and the other chip is used to realize measurement signal processing to finally obtain a flow signal.

[0024] (1) Ultra-high frequency resonant excitation Excitation consumption is the biggest factor that causes excessive power consumption of electromagnetic flowmeters. Therefore, how to reduce excitation consumption and successfully complete flow measurement is the key to realizing low-power electromagnetic flowmeters.

[0025] The present invention has two key innovative designs for realizing ultra-high frequency resonant excitation: first, the excitation coil is installed in the middle of the pipeline, away from metal parts to ensure that the high-frequency electromagnetic field will not be absorbed by the metal, the excitation coil maintains a high Q value, and the resonant current is used to oscillate repeatedly to realize the measurement of the electromagnetic flowmeter; second, an efficient excitation and high-Q value low-loss driving circuit is required.

[0026] like Fig.12 As shown, L1 is the excitation winding. The inventor has produced an excitation winding with an inductance of about 22uH, and uses this value as an example and as a calculation basis to support the present invention; C1 is a resonant capacitor, N1 and N2 are two N-channel MOS tubes, which are connected in reverse series to form a bidirectional analog switch structure. When DRV1 = high, DRV2 = low, and the voltage difference is sufficient to drive the MOS tube to turn on, the excitation coil L1 is charged and stored through VCC. The final energy storage current of L1 can be controlled by the driving time. Assuming that the maximum energy storage current is 2A, the driving of DRV1 and DRV2 is stopped after the current reaches the value, and the bidirectional analog switch composed of N1N2 is turned off. At this time, L1 and C1 form a free LC resonance, and the resonant frequency is approximately equal to: F = 1 / (2*π*SQRT(LC) = 1.0231Mhz. At the resonant frequency, the inductor impedance ZL = 141 ohms. Assuming that the DC resistance of the winding is about 1.5 ohms, the Q value of the LC loop is approximately: Q = ZL / R = 92.3. This Q value shows that the energy loss of the LC loop in one oscillation cycle is very small, only about 1 / 100, so only a very short excitation pulse is needed to obtain a long measurement opportunity. This is an important innovation of the present invention. After a short-term large current excitation, the high Q value oscillation of the LC loop is used to obtain a longer measurement time.

[0027] According to the 3.6V power supply calculation, L*di / dt = 3.6V, substituting the inductance value of 22uH and the final excitation current of 2A, the excitation drive time dt = 12.22uS can be calculated. According to the measurement once per second, the average power consumption of excitation is: I = 0.5 * 2A * 12.22uS / 1S = 12.22uA.

[0028] The Q value of the LC circuit can provide at least 100 cycles of measurement. According to the measurement time of 100 cycles, the time left for measurement reaches 97.8uS. During this time, the excitation magnetic field is provided by the LC resonant circuit and no longer consumes power supply current. This is the fundamental reason why the present invention obtains ultra-low power consumption characteristics.

[0029] In order to realize the excitation drive of the excitation coil and maintain a high Q value of LC resonance after the excitation drive is completed, N1N2 is connected in series in reverse to form a bidirectional analog switch. When the analog switch is turned off, it can block both the forward signal and the reverse signal. The excitation inductor L1 and the resonant capacitor C1 form an LC free resonance circuit. If L1 is made of PCB coil, the Q value can reach more than 90, and if it is wound with enameled wire, it can reach more than 800.

[0030] N1N2 should use high-voltage MOS tubes, calculated according to the initial resonance current of 2A, the resonance frequency is calculated according to 1.0231MHZ, the resonance impedance = 141 ohms, the resonance voltage is as high as: 282Vac, and the peak voltage reaches: 397V. Therefore, N1N2 should use high-voltage MOS tubes, preferably SiC MOS tubes. The advantages of SiC MOS tubes are: the output capacitance Coss of the device is small, the DS leakage current is very small, the driving efficiency is high, and the LC loop Q value is high. Of course, GaN MOS or SiMOS can also be used, but the disadvantages are that the DS leakage current is large and the LC loop Q value is low, which is a secondary option of the present invention.

[0031] To further improve the Q value, a higher resonant frequency can be selected. For example, if the resonant frequency is increased to 2Mhz, the excitation winding can be manufactured using PCB, and Q = 282 / 1.5 = 188 can be achieved, while the enameled wire excitation winding Q = 282 / 0.16 = 1762.5. At such a high Q value, more excitation cycle measurement time can be obtained, which can effectively improve the measurement accuracy, and the average excitation current is only 12-15uA, which is the most innovative design of the present invention.

[0032] However, if the resonant frequency is doubled, the withstand voltage of the analog switch will also be doubled. Still calculated based on the excitation current of 2A, the resonant voltage is as high as 562Vac and the peak voltage reaches 795V. Therefore, SiC MOS with good voltage resistance is preferably used for analog switches.

[0033] (2) Separation of excitation signal drive and measurement signal The present invention separates the excitation drive signal and the measurement signal from a structural point of view, wherein the excitation signal occupies one lead-out terminal of the sensor core, while the measurement signal occupies the other lead-out terminal. In the circuit, the excitation drive PCB and the measurement signal processing PCB are separated from each other, and the large excitation resonant current locally forms a loop, thereby greatly reducing the interference of the excitation current on the measurement signal.

[0034] In order to limit the large current of the excitation resonant circuit to the excitation drive board, the present invention is designed Fig.13In the excitation drive circuit, C2C3 is the power filter capacitor, L1C1 and Cx form a resonant circuit, and Cx is the distributed capacitance of the analog switch. Due to the existence of Cx, part of the resonant current will flow through the power supply, but since Cx is small, for example, using SiC MOS, Cx can be reduced to less than 100P. The resonant voltage is calculated according to 100P, calculated according to 280Vac, and the power filter capacitor is calculated according to 4.8uF. The residual voltage of Cx connected in series to the power supply = 5.8mV, so it can be ignored. In this way, the excitation resonant current can be limited to the L1C1CX circuit, and will not interfere with other circuits through the power supply. In order to further reduce the coupling of the excitation resonant current to other circuits through the power supply, the power filter capacitor can be increased, for example, it can be increased to 10uF, or even larger. If it is increased to 10uF, the resonant current converted to the power supply residual voltage can be lower than 2.8mV.

[0035] (3) Measurement signal processing circuit The disadvantage of electromagnetic flowmeter is that the amplitude of the measurement signal is very small, so a high-multiple amplifier is needed to amplify the measurement signal, and the high-multiple amplifier is easily interfered or self-excited, which eventually leads to measurement failure. The method for estimating the measurement signal of the ultra-high frequency resonant excitation low-power electromagnetic flowmeter involved in the present invention is as follows: The actual manufacturing area is: 2.75cm 2 The excitation PCB coil has 32 turns in total and an inductance of 21.6uH. When the excitation current = 2A, the magnetic induction intensity B on the coil surface is calculated as follows: L * di / dt = N * dΦ / dt, and further deduction is: L *di = N * dΦ Substituting the values ​​of L, di and N, we can calculate dΦ = 21.6uH * 2A / 32 = 1.35uWb Then according to B*S = dΦ, and substitute the effective area of ​​the coil 2.75cm 2 Calculated B = 1.35uWb / 2.75cm 2 = 4.9mT.

[0036] Then according to the law of electromagnetic induction, U = BLV, L is the distance between the measuring electrodes = 15mm, V is the flow velocity, and the minimum calculation is 8mm / S. Substituting into the above formula, it is calculated that U = 4.9mT * 15mm * 8mm / S = 588nV. The present invention adopts a double-sided measuring electrode series connection method, and the measuring voltage can be doubled, so the minimum output voltage = 1.176uV.

[0037] Calculated according to the measurement range ratio of 400, the maximum signal output voltage = 1.176uV * 400 = 470.4uV.

[0038] If you want to amplify the maximum signal to 3V, the required amplification factor is Av = 3000mV / 0.47mV = 6383 times.

[0039] Therefore, it can be estimated that the amplifier should have an amplification factor of 5000-10000 times. This is a serious challenge, and the most serious problem is: the amplifier self-excitation.

[0040] In order to solve the self-excitation problem that may be caused by high-multiple amplifier circuits, the present invention adopts "high-frequency passband amplification" and "low-pass amplification", a two-stage series amplifier circuit, and the passbands of the two are separated by a large distance to eliminate the coupling of front and rear amplification and avoid self-excitation: First, under high-frequency resonant excitation modulation, the measuring electrode outputs an AC signal with the same excitation current waveform. Assuming that the resonant frequency is about 1Mhz, the signal output by the electrode is also 1Mhz AC. Therefore, the pre-amplifier circuit of the amplifier can be designed as: a passband AC amplifier with a bandwidth of 0.5 - 1.5Mhz, and the amplification factor is controlled at 100-250 times. Amplifiers of this factor are relatively easy to implement, will not self-excite, and have high anti-interference capabilities.

[0041] Secondly, synchronous rectification realizes AC-DC conversion. As mentioned above, the original signal output by the measuring electrode of the electromagnetic flowmeter involved in the present invention is a high-frequency AC signal. Assuming that the excitation resonance frequency is approximately 1Mhz, the original signal is also a 1Mhz signal. However, such a high-frequency AC signal is not conducive to direct ADC sampling by the single-chip microcomputer. The best solution is to convert the AC signal into DC, and the most commonly used circuit for converting AC to DC is: diode rectification. However, it is well known that diodes do not have ideal rectification characteristics. The turn-on voltage of the diode will cause nonlinear rectification, especially when the signal amplitude is small, the rectification nonlinearity of the diode will lead to serious deviations.

[0042] To solve this problem, the present invention adopts "synchronous rectification", and the synchronization source is: the resonant voltage signal of the excitation resonant circuit. According to the law of electromagnetic induction U = BLV, it can be concluded that the induced potential U is synchronized with the magnetic induction intensity B, and according to Biot-Savart's law (or Ampere's law), B is synchronized with the current, so it can be concluded that the output signal of the electromagnetic flowmeter is synchronized with the excitation resonant circuit, so it is necessary to shape the excitation resonant signal to obtain a square wave signal of a logic level, which is the signal detection (rectification) "synchronization signal", and this synchronization signal generation circuit needs to be designed inside the "excitation drive" dedicated chip.

[0043] The signal pre-amplifier uses an AC passband amplifier, and the amplification factor is 100-250 times as the preferred value. According to 200 times, after the original signal is amplified, the output voltage is about: 235uV - 94mV, and the frequency is about 1Mhz. Then it enters the synchronous rectification circuit. The synchronous rectification is designed as a full-wave rectification mode. The rectification switch uses a MOS tube, and the MOS tube gate is driven by a synchronous signal. Fig.14 : N1N2N3N4 are four N-channel MOS tubes, forming a bridge synchronous rectification circuit. The front-stage AC amplifier adopts differential output, which becomes a pure AC signal after the DC component is isolated by C1C2. N3N2 is driven by DRV1 and DRV2 forward devices, which has the same phase as the synchronization signal. When the synchronization signal is high, N3N2 is turned on and the bridge output is through N3N2. N1N4 is driven by NOT1 and NOT2 two inverters, which has the opposite phase to the synchronization signal. When the synchronization signal is low, N1N4 is turned on and the bridge output is through N1N4. C3C4R1 forms a π-type filter circuit, which filters out the pulsating components in the rectified signal, and the detection output becomes a DC pulse. Finally, after detection, the signal is converted from a high-frequency AC of about 1Mhz to a DC pulse. The DC pulse width is calculated as 100uS, and the frequency is about 10Khz. After detection, the signal frequency has shifted greatly from the original 1Mhz to 10Khz. The output of the post-amplifier will not be coupled to the pre-amplifier, so the self-excitation of high-gain amplification can be effectively avoided. The post-amplifier uses a low-pass amplifier with a turning frequency of about 50Khz. The passband of the pre-amplifier completely avoids the low-passband of the post-stage, so the post-amplifier will not produce self-excitation coupling to the pre-stage. The amplification factor of the post-stage low-pass amplifier can be set to: 50-100 times. The total amplification factor: 5000-25000 times, and it is designed to be adjustable in multiples, so that it can meet the use of electromagnetic flowmeters of different calibers. Since the amplitude of the electromagnetic flowmeter measurement signal is very small, a high-multiple amplifier is required, and the signal bandwidth of the traditional electromagnetic flowmeter is in the low frequency band, and the passbands of the front and rear amplifiers are consistent, which will cause the post-stage amplified output signal to couple to the front stage, which is very easy to cause the amplifier to self-excite. The present invention can make full use of the advantages of "ultra-high frequency resonant excitation", and the excitation resonance frequency is as high as 1Mhz or even above, so the pre-amplifier and the post-amplifier can be used. The way of not being in the same passband to achieve signal isolation can effectively avoid self-excitation.

[0044] The preferred front stage uses a passband amplifier, the center frequency can be determined according to the selected excitation resonance frequency, and the front and rear select 0.25 - 0.5Mhz bandwidth (preferred value), the preferred range of the front stage amplification factor is: 100 - 250 times, such a design is very easy to integrate into an integrated circuit, and can obtain stable amplification.

[0045] The preferred post-stage uses a low-pass filter with a corner frequency of about 50Khz, which is far away from the high-frequency passband of the previous stage. Therefore, no coupling between the previous and next stages will be formed. Even if the total amplification factor exceeds 100,000, no self-excitation will be formed. Its principle is similar to that of a superheterodyne wireless receiver.

[0046] The unique amplifier structure of the present invention determines that the present invention can obtain accurate flow measurement. In the signal amplification circuit involved in the present invention, the front and rear amplifiers use different passbands. The advantage of this is that the front and rear signals will not be coupled, avoiding self-excitation. To achieve this goal, it is necessary to insert a signal synchronous detection conversion circuit between the front and rear amplifiers. The present invention utilizes the synchronous relationship between the excitation resonance signal and the measurement signal, and shapes the excitation resonance signal into a square wave as the "synchronization signal" of synchronous detection, which is used to control the opening action of the detection MOS bridge. The advantage of this is: accurate detection is achieved by utilizing the synchronous conduction of MOS.

[0047] 3. Dedicated chip design The present invention relates to an ultra-high frequency resonant excitation low-power electromagnetic flowmeter, which has the following advantages: first, ultra-high frequency resonant excitation can greatly reduce the excitation power consumption, the driving circuit only needs to provide an initial excitation current, and the subsequent signal measurement can be completed by using the resonance of the excitation coil and the capacitor, which is the key to achieving low power consumption; second, by utilizing the characteristics of ultra-high frequency excitation, the amplification circuit of the measurement signal can be divided into: a high-frequency passband amplification at the front stage and a low-pass amplification at the back stage, with a synchronous detection conversion inserted in between, so that a stable high-multiple gain can be obtained and the measurement accuracy is improved.

[0048] However, the above circuit is relatively complex and costly, so a more appropriate method is to design a dedicated chip.

[0049] According to the unique structure of the present invention: the excitation processing and signal processing are on both sides of the measuring pipe, occupying one side respectively. The advantage of this design is that the strong excitation resonance current will be limited to the excitation processing PCB, while the signal processing PCB is placed separately, which effectively avoids the resonance current interfering with the measurement signal.

[0050] Therefore, the dedicated chip can be divided into two parts according to its function: excitation drive and synchronization signal generation chip, and signal processing and flow generation chip.

[0051] (1) Excitation drive and synchronization signal generation chip like Fig.10As shown, L1 is the excitation winding inductance, C1 is the resonant capacitor, and Cx is the distributed capacitance of N1N2. N1N2 is an N-channel MOS tube, and the two tubes are connected in series inversely to form a bidirectional analog switch structure. SiC MOS is preferably used, which has the advantages of high voltage resistance and low loss. T1 is an analog switch driving coupling transformer, and the coupling pulse width is 5-20uS. C2C3L2C4C5 constitutes a power supply filter circuit, which can effectively isolate the interference of the excitation resonance current on the power supply. The excitation drive and synchronization signal generation chip integrates a pulse transformer driver and an excitation resonance signal shaping circuit. The pulse transformer driver is used to amplify the input excitation signal to a power that can drive the pulse transformer; the excitation resonance signal shaping circuit is used to shape the excitation resonance signal into a square wave as a "synchronization signal" for the electromagnetic flowmeter signal detection transformation.

[0052] (2) Electromagnetic flowmeter signal processing and flow generation chip The output signal of the measuring electrode of the electromagnetic flowmeter is a high-frequency signal synchronized with the resonant excitation signal, and the signal amplitude is very small. The estimated signal voltage is only: 1.176uV - 0.47mV, so it needs 5000-10000 times amplification to perform ADC sampling, so as to complete the subsequent flow calculation. However, the high-multiple amplification circuit is very easy to self-excite, resulting in signal amplification failure. To solve this problem, the present invention adopts the method of connecting the front-stage high-frequency bandpass amplifier and the rear-stage low-pass amplifier in series, inserting the detection transformation in the middle, which effectively avoids self-excitation.

[0053] After the original signal is amplified by the front stage and then synchronously detected, it becomes a DC pulse signal with a width of about 100 excitation resonance cycles. The width is preferably 50-100 excitation signal cycles, so that the passbands of the front and rear amplifiers can be effectively distinguished and self-excitation is not easy. If the DC pulse width is too narrow, the passbands of the front and rear amplifiers will overlap and self-excitation will be easy. If it is too wide, the signal processing time will be too long and the circuit power consumption will be too large. Therefore, 100 excitation resonance cycles are preferred.

[0054] During the excitation and signal measurement process of the electromagnetic flowmeter involved in the present invention, there will be problems caused by temperature. For example, when the excitation drive pulse width is the same, the temperature will cause the internal resistance of the analog switch and the internal resistance of the coil to change. Under the same pulse width, the excitation current obtained is inconsistent, which will cause measurement errors. In order to overcome the influence of temperature on the measurement accuracy, the electromagnetic flowmeter signal processing and flow generation chip needs to have a temperature compensation function.

[0055] The built-in PN junction temperature measurement signal conditioning circuit can provide accurate temperature measurement to the microcontroller, and the temperature compensation of flow measurement is realized by the microcontroller core integrated in the chip.

[0056] The chip has a built-in measurement signal processing circuit, which consists of a front-stage passband amplifier, a detection transformer, and a rear-stage low-pass amplifier. The input original signal is the electrode signal of the electromagnetic flowmeter. The synchronization signal comes from the waveform shaping of the excitation resonance circuit. The synchronization signal is used to control the detection action of the synchronization bridge.

[0057] The chip has a built-in single-chip microcomputer core, a high-speed ADC, a program data memory, and a communication interface. The high-speed ADC is used to measure temperature and flow signals, and the communication interface is used to implement functional configuration and output flow data.

[0058] The beneficial effects of the present invention are: 1. Comparison with traditional electromagnetic flowmeters and good effects of the present invention The basic principle of the ultra-high frequency resonant excitation low power consumption electromagnetic flowmeter involved in the present invention is: through the free oscillation of the LC resonant circuit, only one charging pulse is needed, and then the resonance can be used to obtain repeated excitation for a longer time, thereby obtaining a longer measurement time and achieving the purpose of ultra-low power consumption.

[0059] To achieve this goal, the inventors structurally installed the excitation coil in the middle of the measuring pipe, away from metal parts, so as to avoid the high-frequency electromagnetic field being absorbed by the metal parts, thereby obtaining a higher Q value. The traditional electromagnetic flowmeter places the excitation coil outside the pipe. Although the excitation coil is easier to waterproof, the electromagnetic field generated by the excitation of the external metal pipe coil obtained by the excitation of the excitation coil close to the magnetic shielding layer will be absorbed by the metal parts. Therefore, the electromagnetic flowmeter with a traditional structure cannot adopt the "ultra-high frequency resonant excitation" of the present invention.

[0060] At the same time, the inventor preferably uses SiC MOS to realize the bidirectional analog switch to drive the excitation coil. The loss of SiC MOS is very small, and the bidirectional blocking effect of the bidirectional analog switch is utilized, so the resonant circuit can obtain a high Q value. The traditional electromagnetic flowmeter uses bidirectional DC pulse excitation, so the excitation drive of the bidirectional analog switch structure is not required. The advantage of bidirectional DC pulse excitation is that a stable excitation current can be obtained, but the disadvantage is that the magnetic force cycle is long and the power consumption is large. The present invention uses a high-voltage and high-current bidirectional analog switch to drive the excitation, which can utilize the resonance effect of the coil and the resonant capacitor to provide a longer signal measurement time, and utilizes the resonance effect of the LC circuit, so that the power supply is no longer required to provide electrical energy during the measurement period, thereby achieving the purpose of reducing power consumption. The actual sample trial production test of the present invention can reduce the excitation power consumption to less than 15uA. The present invention preferably uses a bidirectional analog switch composed of SiC MOS as the excitation drive, and its purpose is to reduce the consumption of the switch device during the resonant excitation period and improve the Q value of the resonant excitation LC circuit, which is an important advantage of the present invention. Of course, ordinary Si MOS with low switching efficiency can also be used, but the effect is poor and cannot be used as an excuse to bypass the present invention.

[0061] At the same time, because the measured signal is very weak, the inventor makes full use of the characteristics of synchronization between the output signal and the excitation resonance, as well as the ultra-high frequency resonant excitation characteristics, inserts a detection transformation in the middle of the amplifier, separates the passband of the front-stage amplifier and the rear-stage amplifier, thereby avoiding front-to-back coupling and self-excitation, and obtaining a high-power stable amplifier. The traditional electromagnetic flowmeter adopts a direct amplification circuit structure, and the signal bandwidth between the front and rear stages is consistent, so it is very easy to self-excite, and the measurement error is large. The present invention can obtain stable amplification of up to 10,000 to 100,000 times, and the measurement accuracy is higher.

[0062] At the same time, considering that the excitation and the absorption of electromagnetic waves by the surrounding materials will change with temperature, the inventors use temperature adjustment to achieve flow-temperature compensation, so that high accuracy can be obtained within the entire temperature range.

[0063] Through the above technical measures, the good results obtained are: First, when the electromagnetic flow meter measures once per second, the average power consumption is 13-15uA; Second, the minimum measured flow rate is 5-8mm / S. Converted to DN15 pipe, the minimum flow rate reaches 4.5 - 7.2L / H, the maximum flow rate is calculated as 3000L / H, and the range ratio reaches: 416 - 666. 2. Comparison with ultrasonic flowmeter With the development of intelligent metering instruments, water meter manufacturers around the world are seeking the full electronic road of intelligent water meters. To achieve this goal, domestic and foreign counterparts have made a lot of efforts. At present, the most popular solution is ultrasonic flow meter water meter, but ultrasonic flow meter uses piezoelectric ceramic transducer, piezoelectric ceramic is relatively fragile. When encountering strong vibration and long-term high and low temperature aging, piezoelectric ceramic will have internal stratification and fracture failure, and lose its metering function. At the same time, the dirt in the water will continue to deposit on the surface of the transducer, causing transducer mismatch, thereby causing large measurement errors. For a long time, the industry has always believed that electromagnetic flowmeter is a more noise-resistant, more accurate and more stable flow measurement method, but for a long time, electromagnetic flowmeters have required a large current for excitation, so the power consumption is large, so they cannot be used for the full electronicization of small-diameter water meters.

[0064] The present invention uses ultra-high frequency resonant excitation to achieve low power consumption of electromagnetic flowmeters, and uses a special signal processing method to achieve a stable high-power amplifier, thereby achieving low power consumption without losing accuracy, and even obtaining higher measurement accuracy. Therefore, the present invention opens a new era of fully electronic water meters, which has a huge driving effect on the development of water meters and flow meters worldwide. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1 It is a schematic diagram of the overall installation structure of the ultra-high frequency resonant excitation low power consumption electromagnetic flowmeter of the present invention; Figure 2 For the present invention Figure 1 Schematic diagram of the three-dimensional structure after removing the electrical processing housing and metal pipes; Figure 3 For the present invention Figure 2 Schematic diagram of the three-dimensional structure after removing the magnetic shielding tape; Figure 4 It is a schematic diagram of the three-dimensional structure of the sensor core bracket of the present invention; Figure 5 It is a schematic diagram of the three-dimensional structure of the waterproof sensor core of the present invention; Figure 6 An exploded view of the waterproof sensor core of the present invention; Figure 7 It is a schematic diagram of the three-dimensional structure of the sensor core of the present invention; Figure 8 A schematic diagram of the winding layout of the excitation winding of a multi-layer PCB board and the measurement electrode pad and signal lead-out structure of the sensor core of the present invention; Fig. 9 Another schematic diagram of the multi-layer PCB board excitation winding layout and measurement electrode pads and signal lead-out structure of the sensor core of the present invention; Fig.10 This is a working principle diagram of the excitation drive and synchronization signal generation chip of the present invention; Fig.11 The electromagnetic flowmeter signal processing and flow generation chip block diagram of the present invention; Fig.12 The ultra-high frequency resonant excitation circuit diagram of the present invention; Fig.13 A circuit design diagram for reducing the interference of the excitation resonance current on the measurement signal of the present invention; Fig.14 This is a synchronous rectification (synchronous detection) circuit diagram of the present invention.

[0066] In the figure, 1. Sensor core, 2. Sensor core waterproof box, 3. Sensor core bracket, 4. Lined pipe, 5. Magnetic shielding tape, 6. Downstream metal pipe, 7. Upstream metal pipe, 8. Screws, 101. Multilayer PCB board, 102. Signal lead ear, 103. Measuring electrode, 201. Sensor core box, 202. Sensor core box cover, 203. Electrode lead hole, 301. Measuring pipe, 302. Sensor core waterproof box installation slot, 303. Waterproof glue potting cavity, 304. Signal processing PCB installation cavity, 305. Magnetic shielding tape winding limit slot, 306. Sealing ring slot, 307. Lined pipe docking slot, 308. Sealing ring, 501. First signal line lead hole, 701. Electrical box installation chassis, 702. Second signal line lead hole. DETAILED DESCRIPTION

[0067] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Generally, the components of the embodiments of the present invention described and shown in the accompanying drawings here can be arranged and designed in various different configurations.

[0068] 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 invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present invention.

[0069] Figure 1-Figure 14 This is a specific embodiment of the present invention, which is an ultra-high frequency resonant excitation low-power electromagnetic flowmeter. The inventor realizes ultra-high frequency resonant excitation and low-power design from a structural point of view, and designs a sensor core supported by a PCB board, and obtains a waterproof sensor core after waterproof treatment. The inventor further designs a sensor core bracket, which is essentially a section of measuring pipe, and the waterproof sensor core is inserted in the middle of the sensor core bracket, and the waterproof sensor core divides the measuring pipe into two.

[0070] The purpose of the inventor adopting such an electromagnetic flow measurement structure is: First, place the excitation coil in the middle of the measuring pipe, away from metal parts (magnetic shielding tape and metal pipe parts) to prevent the high-frequency electromagnetic field from being absorbed by the metal, which causes the Q value of the resonant excitation to be too low. Therefore, placing the waterproof sensor core in the middle of the measuring pipe is the key to realizing the "ultra-high frequency resonant excitation" of the present invention. Its physical principle is: the eddy current effect of the high-frequency electromagnetic field. The structure adopted in the present invention can effectively avoid the eddy current effect and improve the Q value of the excitation resonant circuit. In actual measurements, the inventor can obtain a Q value of about 65 when using a PCB excitation coil, and a Q value of about 620 when using an enameled wire excitation coil.

[0071] Second, the measuring electrode is divided into two sides, the positive and negative sides, and the electrode signals on the two sides can be connected in series, so that the amplitude of the measuring signal is doubled, the sensitivity is improved, and the measurement accuracy is improved.

[0072] Furthermore, the sensor core bracket is designed with a magnetic shielding tape winding groove, which can be used to wind a magnetic shielding tape with a thickness of 0.4-0.5mm on the sensor core. This magnetic shielding tape protects the signal processing circuit of the electromagnetic flowmeter inside, which can effectively avoid external signal interference. At the same time, it also forms a stable magnetic space to prevent external magnetic materials from affecting the excitation magnetic field.

[0073] Furthermore, the inventors designed a liner pipe pair slot and a sealing ring slot on the sensor core bracket, wherein the liner pipe pair slot can be inserted into the liner pipe to form an insulating layer to prevent the metal pipe from short-circuiting the measurement signal; and the sealing ring slot can be placed with a sealing ring to isolate the gap between the metal pipe and the liner pipe from leaking. The final effect is to provide a dry working environment for the signal processing circuit of the electromagnetic flowmeter and achieve water-electricity separation.

[0074] Furthermore, the inventors use a unique bidirectional analog switch-driven excitation drive and resonant circuit. The bidirectional analog switch is preferably made of N-channel SiC MOS in reverse series. The advantages of SiC MOS are small parasitic capacitance, low leakage, and high Q value of the excitation resonant circuit. High-frequency resonant excitation is the most critical technical link of the present invention. Its effect is that only a short-term turn-on current is required to use the resonant circuit to achieve long-term measurement, and power consumption is greatly reduced. The principle is: in the excitation charging stage: L * di / dt = Vbat, this is the inductance transient equation, where: L is the inductance of the excitation coil, di is the current increment, dt is the time increment, Vbat is the power supply voltage, the inventor uses enameled wire to wind 32 turns of coil, and obtains an area of ​​2.75cm 2, the inductance is about 21.6uH, the DC resistance of the excitation coil is 0.16 ohm, substitute the above data into the inductance transient equation, and set the current increment = 2A, the power supply voltage is selected as 3.6V, it can be calculated that the time required for excitation charging is dt = 12uS. If it is measured once per second, the average current Ip = 0.5 * 2A * 12uS / 1S = 12uA.

[0075] This is the reason why the present invention achieves low power consumption. Since the resonant circuit composed of the excitation coil and the resonant capacitor has a high Q value, only one excitation charge is required to achieve subsequent signal measurement under the free oscillation of the resonant circuit. The inventor uses enameled wire to wind the coil, and the actual measured resonant Q value in the pipeline reaches 620, obtaining a very stable test effect, and the excitation power consumption is only 12uA.

[0076] Furthermore, since the original output signal of the electromagnetic flowmeter is very small, it is estimated to be about 1.176uV-0.47mV, and it needs to be amplified 5000-10000 times for ADC sampling. In the design of traditional electromagnetic flowmeters, a direct amplification circuit is used. Under such a high gain, the amplifier is very easy to self-excite. In the present invention, the inventor cleverly uses the frequency band difference between the ultra-high frequency excitation and the effective signal to divide the amplifier into two stages: high-frequency passband amplification and low-pass amplification. Since the passbands of the front and rear amplifiers are far apart, there will be no front and rear coupling, avoiding self-excitation, and the detection conversion is inserted between the front and rear amplifiers. Such an amplifier structure can allow the amplification factor to reach 20,000-100,000 or more, which is of great significance to improving the measurement accuracy. In addition, the inventor makes full use of the characteristic U = BLV of the electromagnetic induction law, and there is a strict synchronization relationship between the measurement signals U and B. The excitation resonance signal is shaped to obtain a square wave, which is used as a synchronous detection control signal to control the switching action of the detection bridge. This is a key technical measure to achieve detection conversion, which has good innovation and practicality.

[0077] Furthermore, the present invention preferably uses 50-100 times the excitation resonance cycle time to collect the flow signal. The purpose of this is to produce a 50-100 times change in the bandwidth of the original signal and the signal after detection, and to fully isolate the passbands of the front and rear amplifiers. This is the best solution to obtain a high-power stable amplifier and is also one of the most outstanding innovations of the present invention.

[0078] According to the calculation of 100 times the excitation resonance period, according to the resonant frequency of 1Mhz, the signal processing time is 100uS, according to the measurement circuit function fully turned on, the average power consumption is 10mA, and the measurement is performed once per second. The average power consumption of signal processing is: 0.1mS *10mA / 1S = 1uA. Considering the average excitation power consumption of 12uA, it is predicted that the average power consumption of the ultra-high frequency resonant excitation low-power electromagnetic flowmeter involved in the present invention is: 13 - 15uA.

[0079] Furthermore, the ultra-high frequency resonant excitation low power consumption electromagnetic flowmeter involved in the present invention has a high design difficulty in the circuits such as excitation drive, excitation resonance shaping, front-stage signal amplification, synchronous detection, rear-stage signal amplification, flow temperature compensation, etc. Therefore, in order to better realize the present invention, the preferred solution is to design two dedicated chips, one of which is: excitation drive and synchronous signal generation chip, and the other is: electromagnetic flowmeter signal processing and flow generation chip. The role and working principle of the two chips have been described in the previous text and will not be repeated here.

[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Other modifications or equivalent substitutions made to the technical solution of the present invention by ordinary technicians in the field should be included in the scope of the claims of the present invention as long as they do not depart from the spirit and scope of the technical solution of the present invention.

Claims

1. An ultra-high frequency resonant excitation low power consumption electromagnetic flowmeter, comprising a sensor core (1), characterized in that: The sensor core (1) is installed in a sensor core waterproof box (2), the sensor core waterproof box (2) is installed in the middle of a sensor core bracket (3), the sensor core waterproof box (2) divides a measuring pipe (301) in the sensor core bracket (3) into two parts, a signal processing PCB board and an excitation signal driving PCB board are installed on the front and back sides of the sensor core bracket (3), and dedicated chips are respectively arranged in the two PCB boards. The sensor core bracket (3) is installed in the metal pipe.

2. The ultra-high frequency resonant excitation low power consumption electromagnetic flowmeter according to claim 1, characterized in that: The sensor core (1) is an "integrated excitation winding and electrode" for leading out the excitation winding and measuring electrode of an electromagnetic flowmeter manufactured using a multi-layer PCB (101). Signal lead-out ears (102) protrude from both ends of the multi-layer PCB (101). The excitation winding is arranged on the inner metal layer of the multi-layer PCB (101), and the measuring electrode (103) is arranged on the surface metal of the multi-layer PCB (101). The PCB has two surfaces, Top and Bottom. The measuring electrodes (103) are manufactured on both the Top and Bottom layers. The signals of the electrodes on both surfaces are connected in series and then led out. An electrode welding pad is manufactured on the multi-layer PCB (101), and the measuring electrode (103) is welded on the electrode welding pad. The material of the measuring electrode (103) is a corrosion-resistant metal or alloy, including stainless steel and Hastelloy. The sensor core (1) can also be manufactured using only the PCB to manufacture the measuring electrode lead-out pad and the lead-out circuit. The PCB serves as a support, and the excitation coil is wound using enameled wire. In this case, the excitation coil is placed on the upper and lower surfaces of the PCB.

3. The ultra-high frequency resonant excitation low power consumption electromagnetic flowmeter according to claim 1, characterized in that: The sensor core waterproof box (2) is made of plastic, including PPO or PPS. Two electrode lead-out holes (203) are opened on the sensor core box (201) and the sensor core box cover (202). The sensor core (1) is placed in the Changan device core box (201) and then filled with epoxy resin potting glue. The sensor core (1) can also be directly injection molded, with the sensor core (1) as the injection molding skeleton, and the outside is injection molded into the appearance of the sensor core waterproof box (2).

4. The ultra-high frequency resonant excitation low power consumption electromagnetic flowmeter according to claim 1, characterized in that: The sensor core bracket (3) is made of plastic, including PA, PPO, and PPS. The sensor core bracket (3) is a cylindrical hollow pipe, and the middle hollow pipe is a measuring pipe (301). Signal processing PCB board mounting cavities (304) are provided on two sides of the sensor core bracket (3). Electromagnetic flowmeter signal processing PCBs are installed in the two cavities, one of which is provided with an excitation signal driving PCB board, and the other is provided with a measuring signal processing PCB board. A sensor core waterproof box mounting slot (302) with arcs on both sides is provided in the middle of the signal processing PCB board mounting cavity (304). The slot passes through the upper and lower signal processing PCB board mounting cavities (304), and the sensor core waterproof box (2) is installed. Around the sensor core waterproof box mounting slot (302), a sensor core waterproof box is mounted. A waterproof glue potting cavity (303) is provided. After the sensor core waterproof box (2) is installed in place, epoxy resin sealant is potted in the cavity to achieve water and electricity isolation between the measuring pipe (301) and the electrical part. A magnetic shielding tape winding limit groove (305) is provided at the middle position of the outer side of the sensor core bracket (3). After the sensor core waterproof box (2) and the signal processing PCB and the excitation signal driving PCB are installed in place, a magnetic shielding tape (5) is wound in the magnetic shielding tape winding limit groove (305). The magnetic shielding tape (5) is made of Permalloy or pure iron or silicon steel strip material. The strip material thickness is 0.05-0.1 mm. The multi-layer winding forms an external magnetic shield. The winding thickness is 0.5 mm. A first signal line lead-out hole (501) is provided on the magnetic shielding tape (5) to supply power to the electromagnetic flow meter and output the signal to the outside.

5. The ultra-high frequency resonant excitation low power consumption electromagnetic flowmeter according to claim 4, characterized in that: The sensor core bracket (3) is provided with an inner lining pipe (4) inserted in each pair at the top and bottom, which plays an insulating role in electrical signals and prevents water from contacting the metal pipe wall and causing a signal short circuit. The inner lining pipe (4) is made of plastic and is inserted into the inner lining pipe docking groove (307) of the sensor core bracket (3) by coating with an adhesive. The two top surfaces of the sensor core bracket (3) are provided with sealing ring grooves (306) for installing sealing rings (308) to prevent water from bypassing the gap between the metal pipe and the inner lining pipe (4) and entering the electrical signal cavity. A metal pipe is sheathed on the outside of the inner lining pipe (4), which is divided into a downstream metal pipe (6) and an upstream metal pipe (7 ), the upstream refers to the direction from which the water flow is coming, the upstream metal pipe (7) is provided with a second signal line lead-out hole (702) and an electrical box mounting chassis (701) with screw holes, the upstream and downstream metal pipes are fixed by screws (8), or the two are threadedly connected; the plane of the sensor core waterproof box (2) is perpendicular to the plane of the electrical box mounting chassis (701), that is, in the vertical direction, the sensor core waterproof box (2) divides the water flow into two left and right branches, which can reduce the deposition of impurities in the water flow on the surface of the measuring electrode (103), improve the anti-fouling ability, and extend the service life; the metal pipe and the lining pipe (4) can be coated with sealant.

6. A special chip for an ultra-high frequency resonant excitation low power consumption electromagnetic flowmeter, with two chips, which are respectively installed in the excitation signal driving PCB board and the measurement signal processing PCB board, characterized in that: The dedicated chip installed on the excitation signal driving PCB board is an excitation driving and synchronization signal generating chip, which integrates a pulse transformer driver and an excitation resonance signal shaping circuit; The pulse transformer driver is used to amplify the input excitation signal to a power that can drive the pulse transformer; the excitation resonance signal shaping circuit is used to shape the excitation resonance signal into a square wave as a "synchronization signal" for the electromagnetic flowmeter signal detection transformation; The dedicated chip installed in the measurement signal processing PCB board is an electromagnetic flowmeter signal processing and flow information generation chip, which integrates a PN junction temperature measurement conditioning circuit, a measurement signal conditioning circuit, and a single-chip microcomputer core; the PN junction temperature measurement conditioning circuit is used to realize the current temperature measurement of the flowmeter, and realizes the temperature correction of the flow in cooperation with the single-chip microcomputer program; the measurement signal conditioning circuit includes: a front-stage passband amplifier, a detection transformation, and a rear-stage low-pass amplifier. The detection transformation is realized by a synchronous rectification circuit. The synchronization signal is input from the outside and is obtained by shaping the excitation resonance signal; the single-chip microcomputer core provides work management of the dedicated chip, including: working parameter configuration, flow temperature adjustment, and excitation signal generation action.

7. The dedicated chip for the ultra-high frequency resonant excitation low power consumption electromagnetic flowmeter according to claim 6, characterized in that: The excitation drive and synchronization signal generation chip includes a circuit that uses a high-voltage analog switch to implement excitation drive. N1N2 is connected in reverse series to form a bidirectional analog switch. When the analog switch is turned off, it can block both the forward signal and the reverse signal. The excitation inductor L1 and the resonant capacitor C1 form an LC free resonance circuit. If L1 is made of a PCB coil, the Q value can reach more than 90, and if it is wound with enameled wire, it can reach more than 800; N1N2 uses a SiC MOS tube or a GaN MOS tube or a Si MOS tube.

8. The dedicated chip for the ultra-high frequency resonant excitation low power consumption electromagnetic flowmeter according to claim 6, characterized in that: The excitation drive and synchronization signal generation chip includes a circuit for reducing the interference of the excitation resonance current on the measurement signal. In order to limit the large current of the excitation resonance loop to the excitation drive board, C2C3 is a power filter capacitor, L1C1 and Cx constitute a resonant loop, and Cx is a distributed capacitor of the analog switch. Due to the existence of Cx, a part of the resonant current will flow through the power supply, but since Cx is small, for example, by using SiC MOS, Cx can be reduced to below 100P. According to 100P calculation, the resonant voltage is calculated according to 280Vac, and the power filter capacitor is calculated according to 4.8uF. The residual voltage of Cx connected in series to the power supply = 5.8mV, so it can be ignored, so that the excitation resonance current can be limited to the inside of the L1C1CX loop, and will not interfere with other circuits through the power supply; in order to further reduce the coupling of the excitation resonance current to other circuits through the power supply, the power filter capacitor can be increased, for example, it can be increased to 10uF, or even larger. If it is increased to 10uF, the resonant current converted to the power supply residual voltage can be lower than 2.8mV.

9. The dedicated chip for the ultra-high frequency resonant excitation low power consumption electromagnetic flowmeter according to claim 6, characterized in that: In the measurement signal conditioning circuit, the center frequency of the front-stage passband amplifier can be determined according to the selected excitation resonance frequency, and the front and rear select a bandwidth of 0.25-0.5Mhz, and the preferred range of the front-stage amplification factor is: 100-250 times. Such a design is very easy to be integrated into an integrated circuit, and stable amplification can be obtained; the turning frequency of the rear-stage low-pass amplifier is selected to be 50Khz, which is very different from the high-frequency passband of the front stage, so that coupling between the front and rear stages will not be formed, and even if the total amplification factor exceeds 100,000, self-excitation will not be formed; a signal detection conversion circuit is inserted between the front and rear amplifiers, and the synchronization relationship between the excitation resonance signal and the measurement signal is used to shape the excitation resonance signal into a square wave as the "synchronization signal" of the synchronous detection, which is used to control the opening action of the detection MOS bridge.

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