Double-frequency anti-interference ultrasonic water meter and metering method thereof

Abstract

The invention discloses a double-frequency anti-interference ultrasonic water meter and a metering method thereof, and relates to the technical field of fluid metering. A 500kHz sound velocity reference channel is constructed in a self-transmitting and self-receiving mode of a single transducer, the sound path length under solidified pure water is calibrated through a factory, the current water quality sound velocity is calculated in real time in a zero flow state, the zero offset of a 1MHz main channel is dynamically corrected, and a high-precision temperature sensor is omitted. Meanwhile, online water quality diagnosis is realized by utilizing a double-frequency cooperation mechanism: turbidity is quantized according to the amplitude ratio of 500kHz and 1MHz signals (based on the characteristics of high-frequency scattering sensitivity and high low-frequency penetrability), and bubbles are detected according to the time domain volatility of the 1MHz signals; and dynamically optimizing the flow metering precision of the main channel according to a diagnosis result by combining a sound velocity compensation model (the sound velocity is inversely proportional to the turbidity) and a graded bubble compensation model (the sound velocity or the flow is corrected according to the volatility). According to the method, medium interference is effectively overcome, measurement reliability is improved, and real-time monitoring and reporting of basic water quality (turbidity and bubbles) are achieved at low cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of fluid metering technology, in particular to a dual-frequency anti-interference ultrasonic water meter and a metering method thereof. BACKGROUND

[0002] As the core metering equipment of modern water supply network, the metering accuracy of ultrasonic water meter is directly related to the fairness of water resource management and trade settlement. The current mainstream reflective ultrasonic water meter generally adopts single-frequency measurement technology (usually 1MHz) to calculate the flow rate by measuring the time difference of forward and reverse flow sound wave propagation. However, there are three key defects in practical application: firstly, the inherent sound path asymmetry of reflective structure leads to zero drift, and the traditional single-time calibration at factory cannot adapt to the dynamic fluctuation of sound velocity caused by water quality change; secondly, bubbles and turbidity in the medium can significantly change the sound wave propagation characteristics, and the single-frequency system is difficult to distinguish the interference of bubbles and turbidity, resulting in the failure of compensation strategy; thirdly, in order to realize dynamic calibration, a high-precision temperature sensor is often added, which not only increases the cost, but also the temperature model cannot accurately reflect the direct influence of water quality change on sound velocity. According to the industry test data, under the working condition of 5% gas content and 50NTU turbidity, the measurement error of traditional single-frequency water meter can reach ±2.5%, which is far beyond the requirement of ±1% of ISO 4064 standard.

[0003] The typical scheme of the "ultrasonic water meter temperature correction method without temperature sensor" disclosed in Chinese patent CN106885609A measures the corresponding ultrasonic time of flight at several temperatures; judges whether the different time of flights are within the reasonable time of flight; establishes the scatter plot of the reciprocal of the time of flight and the sound velocity corresponding to each temperature, the segmented correction curve and the curve equation according to the sound velocity and the time of flight corresponding to several different temperatures; calculates the average time of flight; calculates the measured sound velocity according to the curve equation; establishes the fitting curve of the sound velocity of ultrasonic wave in water and temperature; and obtains the corresponding fluid temperature. The present application can obtain accurate fluid temperature without temperature sensor, improve the accuracy of temperature compensation of ultrasonic water meter, accurately obtain the sound velocity corresponding to different temperatures in water, thereby improve the measurement accuracy of time difference method ultrasonic water meter, expand the use compatibility of ultrasonic water meter for different ultrasonic flow sensors, and reduce the hardware cost of ultrasonic water meter.

[0004] Defects of prior art:

[0005] 1. Zero drift problem: the sound path of reflective ultrasonic water meter is asymmetric (d1≠d2), and the traditional single-time zero flow calibration (factory calibration) cannot dynamically compensate; the previous dynamic compensation usually detects in real time by means of temperature sensor and dynamically calibrates zero flow by temperature model compensation algorithm, but the indirect temperature model has insufficient accuracy, and the influence of water quality factor is not introduced.

[0006] 2. Medium interference: bubbles / turbidity change the sound velocity propagation characteristics, introduce measurement errors, single frequency cannot effectively analyze bubbles / turbidity, and further cannot give a clear algorithm compensation strategy;

[0007] 3. The shortcomings of the double transducer pair measurement of sound velocity: one transducer transmits and the other transducer receives, there is a channel time difference, there is a sound velocity measurement error; and due to the short sound path, it cannot be applied to small caliber ultrasonic water meters; one more transducer increases the cost.

[0008] 4. Lack of basic water quality diagnosis function: professional turbidity sensors cannot be applied to household end due to cost problems.

[0009] Based on the defects of the prior art and the analysis of the comparison file, the following technical bottlenecks need to be broken through in this field:

[0010] Firstly, a real-time sound velocity measurement mechanism independent of temperature sensors needs to be established to fundamentally solve the zero drift problem of reflective water meters;

[0011] Secondly, a dual-frequency collaborative diagnosis method must be developed to simultaneously distinguish bubble and turbidity interference and quantify their influence degree;

[0012] Finally, a sound velocity-water quality coupling compensation model needs to be built to convert the diagnosis results into dynamic correction parameters.

[0013] The core of these problems is how to realize medium-adaptive accurate measurement through acoustic hardware architecture innovation and signal processing algorithm collaboration under the premise of controllable cost, which is the key technical problem to be solved by the present application. SUMMARY

[0014] In view of the above existing problems, the present application is proposed.

[0015] Therefore, the present application provides a dual-frequency anti-interference ultrasonic water meter and its measurement method to solve the problems of zero drift and measurement error caused by water quality interference (bubble, turbidity) of reflective ultrasonic water meters.

[0016] To solve the above technical problems, the present application provides the following technical solutions:

[0017] In a first aspect, the present application provides a dual-frequency anti-interference ultrasonic water meter measurement method, which includes the following steps,

[0018] Step 1: transmit ultrasonic waves through a 500 kHz self-transmitting and self-receiving channel, reflect them by a reflector, and receive them by the same transducer, calculate the real-time sound velocity c based on the factory-calibrated fixed sound path length d3 and the time difference t under zero flow state ture ;

[0019] Step 2: In the 1MHz main flow channel, simultaneously collect the transit times T21 and T12 in the forward and reverse flow directions;

[0020] Step 3: Calculate the turbidity value using the amplitude ratio of the dual-frequency received signals, and simultaneously extract the time-domain fluctuation rate of the 1MHz signal to characterize the bubble concentration;

[0021] Step 4: Convert the real-time speed of sound c ture Turbidity value and bubble concentration are input into the dynamic compensation engine to generate the main channel sound velocity correction factor and flow compensation coefficient.

[0022] Step 5: Calculate the actual flow rate based on the corrected sound velocity. When the bubble concentration exceeds the threshold, start the defoaming program and freeze the output.

[0023] As a preferred embodiment of the dual-frequency anti-interference ultrasonic water meter metering method of the present invention, wherein: the real-time sound velocity c ture The specific calculation process is as follows:

[0024] When the flow rate is detected to be below 0.001m for 5 consecutive seconds 3 When the current is / h, it is determined to be in a zero-current state and the 500kHz self-transmitting and self-receiving channel is activated. The embedded controller generates a 3-cycle sinusoidal pulse with a pulse width of 6μs to excite transducer B to emit ultrasonic waves, which are focused by the parabolic reflector and return to the same transducer.

[0025] The receiver uses a cross-correlation algorithm to accurately capture the reflected wave peak and measures the time difference t from transmission to reception with a resolution of 10 ns.

[0026] The factory calibration parameter d3, pre-stored in the EEPROM, is called. d3 = c0 × t0, where d3 is the 500kHz self-transmitting and self-receiving path length, c0 is the standard velocity of sound in pure water at 20℃, and t0 is the time difference between transmitting and receiving the reflected signal. The calibration environment is 20℃ pure water, with an accuracy of ±0.01mm. The arithmetic unit executes the calibration... ture =d3 / t to calculate the real-time speed of sound;

[0027] Simultaneously collect temperature sensor data mounted on the back of transducer B. If the current water temperature deviates from the calibrated temperature by more than ±2℃, activate the sound velocity-temperature compensation model c. temp =1402.5+4.5T-0.04T2, where T is the temperature in Celsius, and c is initially corrected;

[0028] The corrected sound velocity value is compared with the current 1MHz main channel bidirectional time difference ΔT. zero The data are stored together in a circular buffer. When the buffer is full of 30 sets of data, the sound speed-time difference curve is generated based on the least squares method to predict the parameters of the next cycle.

[0029] As a preferred embodiment of the dual-frequency anti-interference ultrasonic water meter metering method of the present invention, the specific implementation process of the turbidity calculation is as follows:

[0030] The dual-channel synchronous ADC simultaneously acquires 500kHz and 1MHz received signals at a sampling rate of 5MSPS. A fourth-order Butterworth digital bandpass filter with a bandwidth of 490-510kHz is used for the 500kHz channel, and an equivalent filter with a bandwidth of 990-1010kHz is used for the 1MHz channel.

[0031] The envelope curve is extracted by applying a 16th-order FIR Hilbert transformer to the filtered signal, and the envelope peak values ​​of the last 100 sampling points of the two channels are detected inside the FPGA.

[0032] Calculate the dual-frequency amplitude ratio R = (1MHz peak envelope) / (500kHz peak envelope + 10) -6 Avoid division by zero errors;

[0033] Call the pre-calibrated turbidity conversion parameters a, b, and d (obtained through laboratory calibration of 0–100 NTU standard turbidity solutions), and execute NTU = a × e in the floating-point arithmetic unit. b×R +d exponent calculation;

[0034] The results of every 10 measurements are smoothed using median filtering to eliminate sudden noise interference.

[0035] As a preferred embodiment of the dual-frequency anti-interference ultrasonic water meter metering method of the present invention, the specific implementation process of the bubble detection is as follows:

[0036] For the time-domain signal after filtering the 1MHz channel, sliding segmentation is performed with a window length of 500 sampling points and a step size of 250 points;

[0037] Within each window, the arithmetic mean μ and standard deviation σ of the signal amplitude are calculated in real time, and the volatility F = σ / (μ + 10) is calculated using a hardware divider. -6 );

[0038] Three levels of bubble concentration determination thresholds are set: when F < 0.1, it is marked as Level 1 (low bubble influence); when 0.1 ≤ F < 0.3, it is marked as Level 2 (medium bubble influence); and when F ≥ 0.3, it is marked as Level 3 (high bubble influence).

[0039] The mechanical defoaming device is immediately activated upon encountering a level 3 bubble state, while the flow output is frozen and a 10-second countdown is activated.

[0040] Volatility is continuously monitored during the freeze period. If the F value does not drop below 0.3 within 10 seconds, the freeze period is extended until the target is met.

[0041] As a preferred embodiment of the dual-frequency anti-interference ultrasonic water meter metering method of the present invention, the specific implementation process of the dynamic compensation engine is as follows:

[0042] Receive the NTU value output from the turbidity calculation module, and calculate the turbidity compensation coefficient K through polynomial interpolation. turb =1 - 2.5 × 10 -5 ×NTU corrects the main channel sound velocity to c turb =c×K turb ;

[0043] Combining the volatility F output by the bubble detection module with the grading label, if it is a level 1 bubble, then the secondary correction coefficient K is calculated. bubble =1 - 0.03 × F, outputting the final speed of sound c corr =c turb ×K bubble ;

[0044] If it is a level 2 bubble, the speed of sound remains constant, and the original flow rate Q is compensated for. corr =Q / (1+0.5×F);

[0045] The compensated flow data is input into a second-order Kalman filter with process noise variance set to 0.001 and observation noise variance set to 0.1, and the output is the smoothed final flow value.

[0046] When a level 3 bubble is detected, the Kalman filter input is frozen and the last valid output value is retained.

[0047] Secondly, the present invention provides a dual-frequency anti-interference ultrasonic water meter system, comprising,

[0048] The measurement tube section integrates a parabolic reflector and a plane reflector group, in which the parabolic reflector and the 500kHz transducer form a self-emitting and self-receiving reference channel with a fixed sound path length of d3.

[0049] The plane mirror assembly and two 1MHz transducers form the main flow measurement channel of the V-shaped acoustic path;

[0050] The signal processing unit includes a dual-channel time-to-digital converter (TDC) and a programmable gain amplifier (PGA).

[0051] The dynamic compensation processor has a built-in three-dimensional compensation lookup table;

[0052] The mechanical defoaming module is integrated at the front end of the water inlet, including a 30° spiral guide vane and a piezoelectric ceramic cavitation generator;

[0053] The included angle of the mirrors of the planar reflector group is 110°, which makes the sound path length of the main channel reach 2.8 times the pipe diameter.

[0054] As a preferred embodiment of the dual-frequency anti-interference ultrasonic water meter system described in this invention, the specific structure of the self-transmitting and self-receiving reference channel is as follows:

[0055] The focal length of the parabolic mirror is designed to be 8.0±0.1mm, and the surface roughness Ra≤0.4μm.

[0056] The 500kHz transducer is installed precisely at the focal point of the parabolic surface, with its central axis forming an angle ≤0.5° with the optical axis of the reflecting mirror.

[0057] An acoustic insulating sponge with a thickness of 3 mm and an opening ratio of ≥90% is placed between the transducer and the reflector to absorb side-scattered waves.

[0058] The calibration of d3 was performed using the laser interferometric positioning method. The measurement was repeated 100 times in a pure water environment at 20±0.1℃, and the average value was taken. The calibration results were written into the read-only memory.

[0059] In a preferred embodiment of the dual-frequency anti-interference ultrasonic water meter system described in this invention, the hardware configuration of the signal processing unit is as follows:

[0060] Time measurement uses a TDC-GP22 chip with a time resolution of 55 ps;

[0061] The programmable gain amplifier has 32 gain settings from 0 to 60 dB, and the automatic gain control (AGC) circuit dynamically adjusts the gain according to the signal amplitude.

[0062] The bandpass filter uses a switched capacitor filter MAX297, and its center frequency can be digitally adjusted via the SPI interface.

[0063] The Hilbert converter is implemented on an Altera Cyclone IV FPGA and uses a 16-stage pipeline architecture to process 5MSPS data streams.

[0064] As a preferred embodiment of the dual-frequency anti-interference ultrasonic water meter system of the present invention, the working method of the dynamic compensation processor is as follows:

[0065] It has 512 built-in three-dimensional compensation parameters, including temperature (20-30℃, step 0.2℃), turbidity (0-100 NTU, step 5 NTU), and bubble fluctuation rate (0-0.4, step 0.02).

[0066] Parameter interpolation is achieved using a radial basis function (RBF) neural network. The hidden layer of the network contains 48 neurons, and the activation function is a Gaussian function.

[0067] The system automatically performs a parameter self-check every 24 hours. When it detects 10 consecutive compensation deviations exceeding ±0.5%, a calibration alarm is triggered.

[0068] As a preferred embodiment of the dual-frequency anti-interference ultrasonic water meter system of the present invention, the control logic of the mechanical defoaming module is as follows:

[0069] When the bubble classification is marked as level 2, the spiral guide vane is activated to form a swirling flow field. At the same time, the piezoelectric ceramic cavitation generator is driven at a frequency of 40kHz to generate cavitation bubble groups with a diameter of 50 to 100μm, which are continuously operated for 30±5 seconds.

[0070] When marked as Level 3, it continues to run until volatility F < 0.25. If the target is not met within 300 seconds, it switches to pulse mode, working for 10 seconds and pausing for 5 seconds.

[0071] The inlet is equipped with a conical flow stabilizer, with its opening ratio decreasing from 80% to 40% along the water flow direction, which is used to break up large air bubbles.

[0072] Thirdly, the present invention provides a computer device, including a memory and a processor, wherein the memory stores a computer program, wherein when the computer program is executed by the processor, it implements any step of the dual-frequency anti-interference ultrasonic water meter metering method as described in the first aspect of the present invention.

[0073] Fourthly, the present invention provides a computer-readable storage medium having a computer program stored thereon, wherein: when the computer program is executed by a processor, it implements any step of the dual-frequency anti-interference ultrasonic water meter metering method as described in the first aspect of the present invention.

[0074] The beneficial effects of this invention are:

[0075] First, a real-time sound velocity benchmark for current water quality is provided. The construction mechanism of this benchmark is groundbreaking at the physical level: by embedding a factory-calibrated fixed sound path length d3 (accuracy ±0.01mm) into a 500kHz self-transmitting and self-receiving channel, and combining it with the real-time ultrasonic round-trip time t measured under zero-flow conditions, the sound velocity value c is directly calculated. ture =d³ / t, this sound velocity value accurately reflects the comprehensive physical characteristics of the current water quality (including the effects of temperature, turbidity, and dissolved substances), with an accuracy of 0.03% and completely independent of external sensors. This benchmark serves as the core basis for dynamic zero-point calibration, successfully eliminating the inherent zero-point drift caused by the asymmetry of the sound path in reflective water meters. Laboratory verification has shown that within a water temperature range of 10–30℃ and a turbidity range of 0–50 NTU, the zero-point offset is stably suppressed to 0.001m. 3 Within / h, the accuracy is improved by 85% compared to the traditional temperature compensation model.

[0076] Secondly, online water quality diagnosis is achieved through dual-frequency collaboration. This mechanism creatively utilizes the differences in the physical characteristics of sound waves: 500kHz low-frequency waves have strong penetration of suspended particles, while 1MHz high-frequency waves are highly sensitive to scattering. Through dual-channel signal processing, the amplitude ratio is calculated in real time to accurately quantify turbidity (error ≤ ±3NTU). Simultaneously, the time-domain fluctuation rate F=σ / μ of the 1MHz signal is extracted to characterize the bubble concentration (grading accuracy 98.7%). The diagnostic results directly drive the compensation engine to perform main channel metering optimization. Turbidity compensation adopts an inverse sound velocity model, while bubble compensation dynamically switches between sound velocity correction and flow rate correction according to the grading strategy. Even under harsh conditions with 30% gas content and 100NTU turbidity, it still maintains a metering accuracy of ±1.5%, which is 40% more adaptable than the international standard ISO 4064.

[0077] More importantly, it enables real-time reporting of water quality at low cost. This advantage stems from the deep reuse of hardware architecture: the sound velocity reference channel and the dual-frequency diagnostic module share the same set of transducers and processor resources, and can output three types of parameters, namely flow rate, turbidity, and bubble concentration, through only algorithm upgrades. The data is transmitted back to the water platform via the NB-IoT module at an ultra-low load of 0.1KB every 15 minutes. The daily transmission volume of household water meters only increases by 0.5KB, but a water quality monitoring network covering the end of the pipe network is built. This allows water companies to grasp turbidity anomalies of more than 20 NTU and air blockage risks with fluctuation rates of more than 0.25 for the first time on a large scale. Compared with the deployment of professional sensor solutions, it reduces operation and maintenance costs by 92% and provides direct data support for pipeline corrosion early warning and secondary pollution prevention and control.

[0078] The above three points form a closed loop of "measurement-diagnosis-reporting". With a hardware cost increase of only 7%, the measurement error under all operating conditions is reduced to within ±1%. At the same time, a single water meter is upgraded to a water quality monitoring node in the pipeline network, promoting the strategic transformation of smart water management from flow measurement to multi-parameter perception. Attached Figure Description

[0079] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0080] Figure 1 This is a flowchart of a dual-frequency anti-interference ultrasonic water meter metering method in Example 1.

[0081] Figure 2 This is an overall structural diagram of a dual-frequency anti-interference ultrasonic water meter system in Example 2.

[0082] Figure 3This is a schematic diagram of the overall principle topology of a dual-frequency anti-interference ultrasonic water meter system in Example 4.

[0083] Figure 4 This is a dual-frequency collaborative architecture of a dual-frequency anti-interference ultrasonic water meter system in Example 4.

[0084] Figure 2 The components are: 1. Measurement chamber; 2. Casing pipe; 3. Ultrasonic transducer C; 4. Ultrasonic transducer D; 5. Reflector A; 6. Ultrasonic transducer B; 7. Reflector B. Detailed Implementation

[0085] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0086] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0087] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0088] Example 1, referring to Figure 1 This is the first embodiment of the present invention, which provides a dual-frequency anti-interference ultrasonic water meter metering method, including the following steps:

[0089] Step 1: Transmit ultrasonic waves through a 500kHz self-transmitting and self-receiving channel. After reflection by a mirror, the waves are received by the same transducer. Calculate the real-time sound velocity c based on the factory-calibrated fixed path length d3 and the time difference t under zero-current conditions. ture ;

[0090] Step 2: In the 1MHz main flow channel, simultaneously collect the transit times T21 and T12 in the forward and reverse flow directions;

[0091] Step 3: Calculate the turbidity value using the amplitude ratio of the dual-frequency received signals, and simultaneously extract the time-domain fluctuation rate of the 1MHz signal to characterize the bubble concentration;

[0092] Step 4: Convert the real-time speed of sound c ture Turbidity value and bubble concentration are input into the dynamic compensation engine to generate the main channel sound velocity correction factor and flow compensation coefficient.

[0093] Step 5: Calculate the actual flow rate based on the corrected sound velocity. When the bubble concentration exceeds the threshold, start the defoaming program and freeze the output.

[0094] Real-time speed of sound c ture The specific calculation process is as follows:

[0095] When the flow rate is detected to be below 0.001m for 5 consecutive seconds 3 When the current is / h, it is determined to be in a zero-current state and the 500kHz self-transmitting and self-receiving channel is activated. The embedded controller generates a 3-cycle sinusoidal pulse with a pulse width of 6μs to excite transducer B to emit ultrasonic waves, which are focused by the parabolic reflector and return to the same transducer.

[0096] The receiver uses a cross-correlation algorithm to accurately capture the reflected wave peak and measures the time difference t from transmission to reception with a resolution of 10 ns.

[0097] The factory calibration parameter d3, pre-stored in the EEPROM, is called. d3 = c0 × t0, where d3 is the 500kHz self-transmitting and self-receiving path length, c0 is the standard velocity of sound in pure water at 20℃, and t0 is the time difference between transmitting and receiving the reflected signal. The calibration environment is 20℃ pure water, with an accuracy of ±0.01mm. The arithmetic unit executes the calibration... ture =d3 / t to calculate the real-time speed of sound;

[0098] Simultaneously collect temperature sensor data mounted on the back of transducer B. If the current water temperature deviates from the calibrated temperature by more than ±2℃, activate the sound velocity-temperature compensation model c. temp =1402.5+4.5T-0.04T2, where T is the temperature in Celsius, and c is initially corrected;

[0099] The corrected sound velocity value is compared with the current 1MHz main channel bidirectional time difference ΔT. zero The data are stored together in a circular buffer. When the buffer is full of 30 sets of data, the sound speed-time difference curve is generated based on the least squares method to predict the parameters of the next cycle.

[0100] The specific implementation process for turbidity calculation is as follows:

[0101] The dual-channel synchronous ADC simultaneously acquires 500kHz and 1MHz received signals at a sampling rate of 5MSPS. A fourth-order Butterworth digital bandpass filter with a bandwidth of 490-510kHz is used for the 500kHz channel, and an equivalent filter with a bandwidth of 990-1010kHz is used for the 1MHz channel.

[0102] The envelope curve is extracted by applying a 16th-order FIR Hilbert transformer to the filtered signal, and the envelope peak values ​​of the last 100 sampling points of the two channels are detected inside the FPGA.

[0103] Calculate the dual-frequency amplitude ratio R = (1MHz peak envelope) / (500kHz peak envelope + 10) -6 Avoid division by zero errors;

[0104] Call the pre-calibrated turbidity conversion parameters a, b, and d (obtained through laboratory calibration of 0–100 NTU standard turbidity solutions), and execute NTU = a × e in the floating-point arithmetic unit. b×R +d exponent calculation;

[0105] The results of every 10 measurements are smoothed using median filtering to eliminate sudden noise interference.

[0106] The specific implementation process of bubble detection is as follows:

[0107] For the time-domain signal after filtering the 1MHz channel, sliding segmentation is performed with a window length of 500 sampling points and a step size of 250 points;

[0108] Within each window, the arithmetic mean μ and standard deviation σ of the signal amplitude are calculated in real time, and the volatility F = σ / (μ + 10) is calculated using a hardware divider. -6 );

[0109] Three levels of bubble concentration determination thresholds are set: when F < 0.1, it is marked as Level 1 (low bubble influence); when 0.1 ≤ F < 0.3, it is marked as Level 2 (medium bubble influence); and when F ≥ 0.3, it is marked as Level 3 (high bubble influence).

[0110] The mechanical defoaming device is immediately activated upon encountering a level 3 bubble state, while the flow output is frozen and a 10-second countdown is activated.

[0111] Volatility is continuously monitored during the freeze period. If the F value does not drop below 0.3 within 10 seconds, the freeze period is extended until the target is met.

[0112] The specific implementation process of the dynamic compensation engine is as follows:

[0113] Receive the NTU value output from the turbidity calculation module, and calculate the turbidity compensation coefficient K through polynomial interpolation. turb =1 - 2.5 × 10 -5 ×NTU corrects the main channel sound velocity to c turb =c×K turb ;

[0114] Combining the volatility F output by the bubble detection module with the grading label, if it is a level 1 bubble, then the secondary correction coefficient K is calculated. bubble =1 - 0.03 × F, outputting the final speed of sound c corr =c turb ×K bubble ;

[0115] If it is a level 2 bubble, the speed of sound remains constant, and the original flow rate Q is compensated for. corr =Q / (1+0.5×F);

[0116] The compensated flow data is input into a second-order Kalman filter with process noise variance set to 0.001 and observation noise variance set to 0.1, and the output is the smoothed final flow value.

[0117] When a level 3 bubble is detected, the Kalman filter input is frozen and the last valid output value is retained.

[0118] Example 2, refer to Figure 2 This is the second embodiment of the present invention, which provides a dual-frequency anti-interference ultrasonic water meter system, comprising:

[0119] The measurement tube section integrates a parabolic reflector and a plane reflector group, in which the parabolic reflector and the 500kHz transducer form a self-emitting and self-receiving reference channel with a fixed sound path length of d3.

[0120] The plane mirror assembly and two 1MHz transducers form the main flow measurement channel of the V-shaped acoustic path;

[0121] The signal processing unit includes a dual-channel time-to-digital converter (TDC) and a programmable gain amplifier (PGA).

[0122] The dynamic compensation processor has a built-in three-dimensional compensation lookup table;

[0123] The mechanical defoaming module is integrated at the front end of the water inlet, including a 30° spiral guide vane and a piezoelectric ceramic cavitation generator;

[0124] The included angle of the mirrors in the plane mirror assembly is 110°, which makes the sound path length of the main channel reach 2.8 times the pipe diameter.

[0125] The specific structure of the self-transmitting and self-receiving reference channel is as follows:

[0126] The focal length of the parabolic mirror is designed to be 8.0±0.1mm, and the surface roughness Ra≤0.4μm.

[0127] The 500kHz transducer is installed precisely at the focal point of the parabolic surface, with its central axis forming an angle ≤0.5° with the optical axis of the reflecting mirror.

[0128] An acoustic insulating sponge with a thickness of 3 mm and an opening ratio of ≥90% is placed between the transducer and the reflector to absorb side-scattered waves.

[0129] The calibration of d3 was performed using the laser interferometric positioning method. The measurement was repeated 100 times in a pure water environment at 20±0.1℃, and the average value was taken. The calibration results were written into the read-only memory.

[0130] The hardware configuration of the signal processing unit is as follows:

[0131] Time measurement uses a TDC-GP22 chip with a time resolution of 55 ps;

[0132] The programmable gain amplifier has 32 gain settings from 0 to 60 dB, and the automatic gain control (AGC) circuit dynamically adjusts the gain according to the signal amplitude.

[0133] The bandpass filter uses a switched capacitor filter MAX297, and its center frequency can be digitally adjusted via the SPI interface.

[0134] The Hilbert converter is implemented on an Altera Cyclone IV FPGA and uses a 16-stage pipeline architecture to process 5MSPS data streams.

[0135] The working method of the dynamic compensation processor is as follows:

[0136] It has 512 built-in three-dimensional compensation parameters, including temperature (20-30℃, step 0.2℃), turbidity (0-100 NTU, step 5 NTU), and bubble fluctuation rate (0-0.4, step 0.02).

[0137] Parameter interpolation is achieved using a radial basis function (RBF) neural network. The hidden layer of the network contains 48 neurons, and the activation function is a Gaussian function.

[0138] The system automatically performs a parameter self-check every 24 hours. When it detects 10 consecutive compensation deviations exceeding ±0.5%, a calibration alarm is triggered.

[0139] The control logic of the mechanical defoaming module is as follows:

[0140] When the bubble classification is marked as level 2, the spiral guide vane is activated to form a swirling flow field. At the same time, the piezoelectric ceramic cavitation generator is driven at a frequency of 40kHz to generate cavitation bubble groups with a diameter of 50 to 100μm, which are continuously operated for 30±5 seconds.

[0141] When marked as Level 3, it continues to run until volatility F < 0.25. If the target is not met within 300 seconds, it switches to pulse mode, working for 10 seconds and pausing for 5 seconds.

[0142] The inlet is equipped with a conical flow stabilizer, with its opening ratio decreasing from 80% to 40% along the water flow direction, which is used to break up large air bubbles.

[0143] Example 3, referring to Figure 1 The third embodiment of the present invention describes the specific workflow and implementation method of a dual-frequency anti-interference ultrasonic water meter measurement method as follows:

[0144] When water flows through the measuring pipe section, the system first detects the instantaneous flow rate through a flow sensor. If the flow rate is below 0.001 m³ / h for 5 consecutive seconds... 3 / h indicates a zero-current state and activates the sound velocity reference measurement: a 500kHz transducer emits a 3-cycle sinusoidal pulse with a pulse width of 6μs. The ultrasonic wave is focused by a parabolic reflector and propagates along a fixed sound path d3, returning to the same transducer. The TDC chip accurately captures the time difference t between transmission and reception with a resolution of 55ps, calls the factory calibration value d3 (calibrated by laser interferometry in pure water at 20℃) pre-stored in the read-only memory, and executes c through the floating-point arithmetic unit. ture =d3 / t to calculate real-time sound velocity; synchronously collect temperature sensor data mounted on the back of the transducer; when the water temperature deviates from the calibration temperature by more than ±2℃, a compensation model c is used. temp =1402.5+4.5T-0.04T2 is used to make an initial correction to the speed of sound, and the correction result is stored in a circular buffer.

[0145] Simultaneously with the start of the sound velocity measurement, the 1MHz main flow channel operates synchronously: two 1MHz transducers emit ultrasonic waves through a V-shaped reflector array with a 110° angle. High-speed timers record the transit times T21 in the downstream direction and T12 in the upstream direction, respectively, achieving a measurement accuracy of 0.1ns. The dual-frequency received signals undergo synchronous processing: the 500kHz channel uses a 490–510kHz bandpass filter to eliminate environmental noise, and the 1MHz channel uses a 990–1010kHz filter to optimize the signal-to-noise ratio. The filtered signals are then input to a 16th-order Hilbert transformer based on an FPGA to extract the envelope. The envelope data from the last 100 sampling points of each channel are extracted to calculate the 500kHz peak value. 500 and 1MHz peak 1m ; using the amplitude ratio formula R = Peak 1m / (Peak 500 +10 －6 Calculate the dual-frequency amplitude ratio and input it into the exponential model NTU = a·e b·R +d outputs turbidity value (coefficients a, b, d calibrated with standard turbidity solution); simultaneously performs bubble detection on the 1MHz time-domain signal: the signal is segmented with a window length of 500 sampling points and a step size of 250 points, and the standard deviation σ and mean μ of the signal amplitude within each window are calculated in real time. The volatility F = σ / (μ + 10) is obtained through a hardware divider. －6 Bubble concentration is graded according to threshold (F < 0.1 is grade 1, 0.1 ≤ F < 0.3 is grade 2, and F ≥ 0.3 is grade 3).

[0146] The dynamic compensation engine receives real-time sound speed c ture After marking the turbidity NTU and bubble classification, a three-stage processing is initiated: first, sound velocity correction is performed based on the turbidity value. turb= c × (1 - 2.5 × 10) -5 ×NTU); secondly, select the compensation mode based on bubble grading—if it is a level 1 bubble, then correct the sound velocity c a second time. corr =c turb ×(1-0.03×F), if it is a level 2 bubble, then keep the speed of sound constant and perform Q on the original flow rate Q. corr =Q / (1+0.5×F); Finally, the compensated parameters are input into a second-order Kalman filter with a preset process noise variance of 0.001 and an observation noise variance of 0.1, and the output is a smooth flow value. When a level 3 bubble is detected, the flow output is immediately frozen and the defoaming program is activated: the 30° spiral guide vane at the inlet is started to form a swirling flow field, and at the same time, the piezoelectric ceramic cavitation generator is driven at a frequency of 40kHz to generate cavitation bubble groups of 50~100μm, which continues to run until the fluctuation rate F<0.25 (maximum 300 seconds, after which a pulse mode of 10 seconds of operation and 5 seconds of rest is switched). All diagnostic data (velocity of sound c, turbidity NTU, bubble level) are packaged into a 0.1KB data packet every 15 minutes and uploaded to the water platform through the NB-IoT module. During this period, the system continuously monitors the changes in water quality parameters and dynamically updates the compensation parameters, forming a closed loop of "measurement-diagnosis-compensation-control".

[0147] This process maintains a metering accuracy of ±1.5% even under extreme operating conditions (30% gas content + 100 NTU turbidity), with a daily power consumption increase of no more than 0.5 Wh. Furthermore, it absorbs scattered interference through acoustic isolation sponge (open area ≥90%) to ensure signal purity, fundamentally solving the problems of zero drift and media interference in reflective water meters.

[0148] Example 4, refer to Figures 2 to 4 The fourth embodiment of the present invention describes the working process and specific implementation of a dual-frequency anti-interference ultrasonic water meter system as follows:

[0149] When the water flows into the measuring chamber 1 inside the casing pipe 2 from the inlet, it first flows through the conical flow stabilizer (not shown in the figure, the opening ratio decreases from 80% to 40% along the water flow direction) to break up air bubbles with a diameter greater than 1mm; the water then flows through the V-shaped main measuring channel composed of ultrasonic transducer C3, ultrasonic transducer D4 and reflector A5, and the sound velocity reference channel composed of ultrasonic transducer B6 and parabolic reflector B7. After system startup, parallel dual-channel measurements are performed: In the 500kHz sound velocity reference channel, transducer B6 emits a 3-cycle sinusoidal pulse (pulse width 6μs). The ultrasonic wave is focused by a parabolic reflector B7 with a focal length of 8.0mm to form a sound beam with a diameter ≤3mm. The reflected wave returns to the same transducer along a fixed sound path d3. The d3 value calibrated by laser interferometry (average of 100 measurements in a 20℃ pure water environment, accuracy ±0.01mm) is pre-stored in read-only memory. The TDC chip measures the transit time t with a resolution of 0.1ns, and the result is obtained through cture =d3 / t calculates the real-time sound velocity. When the temperature sensor mounted on the back of transducer B detects a water temperature deviation of ±2℃ from the calibration value, the sound velocity-temperature compensation model c is automatically activated. temp =1402.5+4.5T-0.04T2 is corrected.

[0150] During the simultaneous 1MHz main flow measurement, transducers C3 and D4 emit ultrasonic waves through a V-shaped reflector group 5 with a 110° angle (see reflector arrangement). Figure 2 An extended acoustic path 2.8 times the pipe diameter was constructed. A high-speed timer recorded the transit time T21 in the downstream direction and T12 in the upstream direction (accuracy 0.1 ns). The dual-frequency received signals underwent synchronous processing: the 500kHz signal was filtered through a 490–510kHz bandpass filter to eliminate ambient noise, and the 1MHz signal was filtered through a 990–1010kHz filter to optimize the signal-to-noise ratio. The filtered data was then input to a 16th-order Hilbert transformer based on FPGA to extract the envelope, and the peak envelope was calculated from the last 100 sampling points of both channels. 500 and Peak 1m The water quality diagnostic module calculates the dual-frequency amplitude ratio R = Peak in real time. 1m / (Peak 500 +10 －6 Substituting this into the laboratory-calibrated exponential model NTU=a·e b·R +d (a, b, d are calibrated from 0-100 NTU standard turbidity solution) outputs turbidity value; simultaneously, bubble detection is performed on the 1MHz signal: using 500 sampling points as the window and 250 points as the step size, the signal is segmented in real time, and the standard deviation σ and mean μ of the amplitude of each window are calculated in real time. The volatility F = σ / (μ+10) is obtained through a hardware divider. -6 Bubble concentration is graded according to threshold (F < 0.1 is grade 1, 0.1 ≤ F < 0.3 is grade 2, and F ≥ 0.3 is grade 3).

[0151] The dynamic compensation engine receives the velocity of sound (c), turbidity NTU, and bubble classification markers, and then performs three levels of optimization: First, based on turbidity (c)... turb = c × (1 - 2.5 × 10) -5 ×NTU) corrects the velocity of sound; secondly, selects the compensation mode according to the bubble level—for level 1 bubbles, c is used. corr =c turb ×(1-0.03×F) Second-order correction of sound velocity, Q is applied to the original flow rate Q for stage 2 bubbles. corr=Q / (1+0.5×F) correction; finally, the parameters are input into a second-order Kalman filter with a preset process noise variance of 0.001 and an observation noise variance of 0.1 to output a smoothed flow value. When a level 3 bubble is detected, the flow output is immediately frozen and the mechanical defoaming module is activated: the 30° spiral guide vane at the inlet is activated to form a swirling flow field, and at the same time, the piezoelectric ceramic cavitation generator is driven at a frequency of 40kHz to generate cavitation bubble groups of 50~100μm, which continues to run until the fluctuation rate F<0.25 (if it does not meet the standard after more than 300 seconds, it switches to a pulse mode of working for 10 seconds and pausing for 5 seconds). All diagnostic data (sound velocity, turbidity, bubble level) are packaged into a 0.1KB data packet every 15 minutes and uploaded to the water management platform via NB-IoT or RS485.

[0152] The power system employs dual backup of batteries and supercapacitors (see...). Figure 3 Topology: Under normal operation, the system is powered by a supercapacitor. In the event of a power outage, it automatically switches to battery power and enters a low-power mode, ensuring no data loss for 72 hours. Throughout the process, the acoustic isolation sponge (3mm thick, porosity ≥90%) placed between the transducer and the reflector effectively absorbs side-scattered waves, while the parabolic reflector's surface roughness Ra≤0.4μm design ensures accurate sound wave focusing. Under extreme conditions (30% gas content + 100NTU turbidity), the system's measurement error is ≤±1.5%, and the daily power consumption increment is controlled within 0.5Wh, achieving a closed-loop process of "measurement-diagnosis-compensation-reporting".

[0153] This embodiment also provides a computer device applicable to dual-frequency anti-interference ultrasonic water meters and their metering methods, including: a memory and a processor; the memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions to realize the dual-frequency anti-interference ultrasonic water meter and its metering method as proposed in the above embodiment.

[0154] The computer device can be a terminal, comprising a processor, memory, communication interface, display screen, and input devices connected via a system bus. The processor provides computing and control capabilities. The memory includes non-volatile storage media and internal memory. The non-volatile storage media stores the operating system and computer programs. The internal memory provides an environment for the operation of the operating system and computer programs stored in the non-volatile storage media. The communication interface is used for wired or wireless communication with external terminals; wireless communication can be achieved through Wi-Fi, carrier networks, NFC (Near Field Communication), or other technologies. The display screen can be an LCD screen or an e-ink screen. The input devices can be a touch layer covering the display screen, buttons, a trackball, or a touchpad on the computer device's casing, or an external keyboard, touchpad, or mouse.

[0155] This embodiment also provides a storage medium storing a computer program, which, when executed by a processor, implements the dual-frequency anti-interference ultrasonic water meter and its metering method as proposed in the above embodiments. The storage medium can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as Static Random Access Memory (SRAM), Electrically Erasable Programmable Read-Only Memory (EEPROM), Erasable Programmable Read Only Memory (EPROM), Programmable Red-Only Memory (PROM), Read-Only Memory (ROM), magnetic storage, flash memory, magnetic disk, or optical disk.

[0156] In summary, a real-time sound velocity benchmark for current water quality is provided. The construction mechanism of this benchmark is groundbreaking at the physical level: by embedding a factory-calibrated fixed sound path length d3 (accuracy ±0.01mm) into a 500kHz self-transmitting and self-receiving channel, and combining it with the real-time ultrasonic round-trip time t measured under zero-flow conditions, the sound velocity value c is directly calculated. ture =d³ / t, this sound velocity value accurately reflects the comprehensive physical characteristics of the current water quality (including the effects of temperature, turbidity, and dissolved substances), with an accuracy of 0.03% and completely independent of external sensors. This benchmark serves as the core basis for dynamic zero-point calibration, successfully eliminating the inherent zero-point drift caused by the asymmetry of the sound path in reflective water meters. Laboratory verification has shown that within a water temperature range of 10–30℃ and a turbidity range of 0–50 NTU, the zero-point offset is stably suppressed to 0.001m. 3 Within / h, the accuracy is improved by 85% compared to the traditional temperature compensation model.

[0157] Secondly, online water quality diagnosis is achieved through dual-frequency collaboration. This mechanism creatively utilizes the differences in the physical characteristics of sound waves: 500kHz low-frequency waves have strong penetration of suspended particles, while 1MHz high-frequency waves are highly sensitive to scattering. Through dual-channel signal processing, the amplitude ratio is calculated in real time to accurately quantify turbidity (error ≤ ±3NTU). Simultaneously, the time-domain fluctuation rate F=σ / μ of the 1MHz signal is extracted to characterize the bubble concentration (grading accuracy 98.7%). The diagnostic results directly drive the compensation engine to perform main channel metering optimization. Turbidity compensation adopts an inverse sound velocity model, while bubble compensation dynamically switches between sound velocity correction and flow rate correction according to the grading strategy. Even under harsh conditions with 30% gas content and 100NTU turbidity, it still maintains a metering accuracy of ±1.5%, which is 40% more adaptable than the international standard ISO 4064.

[0158] More importantly, it enables real-time reporting of water quality at low cost. This advantage stems from the deep reuse of hardware architecture: the sound velocity reference channel and the dual-frequency diagnostic module share the same set of transducers and processor resources, and can output three types of parameters, namely flow rate, turbidity, and bubble concentration, through only algorithm upgrades. The data is transmitted back to the water platform via the NB-IoT module at an ultra-low load of 0.1KB every 15 minutes. The daily transmission volume of household water meters only increases by 0.5KB, but a water quality monitoring network covering the end of the pipe network is built. This allows water companies to grasp turbidity anomalies of more than 20 NTU and air blockage risks with fluctuation rates of more than 0.25 for the first time on a large scale. Compared with the deployment of professional sensor solutions, it reduces operation and maintenance costs by 92% and provides direct data support for pipeline corrosion early warning and secondary pollution prevention and control.

[0159] The above three points form a closed loop of "measurement-diagnosis-reporting". With a hardware cost increase of only 7%, the measurement error under all operating conditions is reduced to within ±1%. At the same time, a single water meter is upgraded to a water quality monitoring node in the pipeline network, promoting the strategic transformation of smart water management from flow measurement to multi-parameter perception.

[0160] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A dual-frequency anti-interference ultrasonic water meter metering method, characterized in that, Includes the following steps: Step 1: Transmit ultrasonic waves through a 500kHz self-transmitting and self-receiving channel. After reflection by a mirror, the waves are received by the same transducer. Calculate the real-time sound velocity c based on the factory-calibrated fixed path length d3 and the time difference t under zero-current conditions. ture ; Step 2: In the 1MHz main flow channel, simultaneously collect the transit times T21 and T12 in the forward and reverse flow directions; Step 3: Calculate the turbidity value using the amplitude ratio of the dual-frequency received signals, and simultaneously extract the time-domain fluctuation rate of the 1MHz signal to characterize the bubble concentration; Step 4: Convert the real-time speed of sound c ture Turbidity value and bubble concentration are input into the dynamic compensation engine to generate the main channel sound velocity correction factor and flow compensation coefficient. Step 5: Calculate the actual flow rate based on the corrected sound velocity. When the bubble concentration exceeds the threshold, start the defoaming program and freeze the output.

2. The dual-frequency anti-interference ultrasonic water meter metering method as described in claim 1, characterized in that: The real-time speed of sound c ture The specific calculation process is as follows: When the flow rate is detected to be below 0.001m for 5 consecutive seconds 3 When the current is / h, it is determined to be in a zero-current state and the 500kHz self-transmitting and self-receiving channel is activated. The embedded controller generates a 3-cycle sinusoidal pulse with a pulse width of 6μs to excite transducer B to emit ultrasonic waves, which are focused by the parabolic reflector and return to the same transducer. The receiver uses a cross-correlation algorithm to accurately capture the reflected wave peak and measures the time difference t from transmission to reception with a resolution of 10 ns. The factory calibration parameter d3, pre-stored in the EEPROM, is called. d3 = c0 × t0, where d3 is the 500kHz self-transmitting and self-receiving path length, c0 is the standard velocity of sound in pure water at 20℃, and t0 is the time difference between transmitting and receiving the reflected signal. The calibration environment is 20℃ pure water, with an accuracy of ±0.01mm. The arithmetic unit executes the calibration... ture =d3 / t to calculate the real-time speed of sound; Simultaneously collect temperature sensor data mounted on the back of transducer B. If the current water temperature deviates from the calibrated temperature by more than ±2℃, activate the sound velocity-temperature compensation model c. temp =1402.5+4.5T-0.04T2, where T is the temperature in Celsius, and c is initially corrected; The corrected sound velocity value is compared with the current 1MHz main channel bidirectional time difference ΔT. zero The data are stored together in a circular buffer. When the buffer is full of 30 sets of data, the sound speed-time difference curve is generated based on the least squares method to predict the parameters of the next cycle.

3. The dual-frequency anti-interference ultrasonic water meter metering method as described in claim 2, characterized in that: The specific implementation process for the turbidity calculation is as follows: The dual-channel synchronous ADC simultaneously acquires 500kHz and 1MHz received signals at a sampling rate of 5MSPS. A fourth-order Butterworth digital bandpass filter with a bandwidth of 490-510kHz is used for the 500kHz channel, and an equivalent filter with a bandwidth of 990-1010kHz is used for the 1MHz channel. The envelope curve is extracted by applying a 16th-order FIR Hilbert transformer to the filtered signal, and the envelope peak values ​​of the last 100 sampling points of the two channels are detected inside the FPGA. Calculate the dual-frequency amplitude ratio R = (1MHz peak envelope) / (500kHz peak envelope + 10) -6 Avoid division by zero errors; Call the pre-calibrated turbidity conversion parameters a, b, and d (obtained through laboratory calibration of 0–100 NTU standard turbidity solutions), and execute NTU = a × e in the floating-point arithmetic unit. b×R +d exponent calculation; The results of every 10 measurements are smoothed using median filtering to eliminate sudden noise interference.

4. The dual-frequency anti-interference ultrasonic water meter metering method as described in claim 3, characterized in that: The specific implementation process of the bubble detection is as follows: For the time-domain signal after filtering the 1MHz channel, sliding segmentation is performed with a window length of 500 sampling points and a step size of 250 points; Within each window, the arithmetic mean μ and standard deviation σ of the signal amplitude are calculated in real time, and the volatility F = σ / (μ + 10) is calculated using a hardware divider. -6 ); Three levels of bubble concentration determination thresholds are set: when F < 0.1, it is marked as Level 1 (low bubble influence); when 0.1 ≤ F < 0.3, it is marked as Level 2 (medium bubble influence); and when F ≥ 0.3, it is marked as Level 3 (high bubble influence). The mechanical defoaming device is immediately activated upon encountering a level 3 bubble state, while the flow output is frozen and a 10-second countdown is activated. Volatility is continuously monitored during the freeze period. If the F value does not drop below 0.3 within 10 seconds, the freeze period is extended until the target is met.

5. The dual-frequency anti-interference ultrasonic water meter metering method as described in claim 4, characterized in that: The specific implementation process of the dynamic compensation engine is as follows: Receive the NTU value output from the turbidity calculation module, and calculate the turbidity compensation coefficient K through polynomial interpolation. turb =1 - 2.5 × 10 -5 ×NTU corrects the main channel sound velocity to c turb =c×K turb ; Combining the volatility F output by the bubble detection module with the grading label, if it is a level 1 bubble, then the secondary correction coefficient K is calculated. bubble =1 - 0.03 × F, outputting the final speed of sound c corr =c turb ×K bubble ; If it is a level 2 bubble, the speed of sound remains constant, and the original flow rate Q is compensated for. corr =Q / (1+0.5×F); The compensated flow data is input into a second-order Kalman filter with process noise variance set to 0.001 and observation noise variance set to 0.1, and the output is the smoothed final flow value. When a level 3 bubble is detected, the Kalman filter input is frozen and the last valid output value is retained.

6. A dual-frequency anti-interference ultrasonic water meter system, based on the dual-frequency anti-interference ultrasonic water meter metering method according to any one of claims 1 to 5, characterized in that, include: The measurement tube section integrates a parabolic reflector and a plane reflector group, in which the parabolic reflector and the 500kHz transducer form a self-emitting and self-receiving reference channel with a fixed sound path length of d3. The plane mirror assembly and two 1MHz transducers form the main flow measurement channel of the V-shaped acoustic path; The signal processing unit includes a dual-channel time-to-digital converter (TDC) and a programmable gain amplifier (PGA). The dynamic compensation processor has a built-in three-dimensional compensation lookup table; The mechanical defoaming module is integrated at the front end of the water inlet, including a 30° spiral guide vane and a piezoelectric ceramic cavitation generator; The included angle of the mirrors of the planar reflector group is 110°, which makes the sound path length of the main channel reach 2.8 times the pipe diameter.

7. The dual-frequency anti-interference ultrasonic water meter system as described in claim 6, characterized in that: The specific structure of the self-transmitting and self-receiving reference channel is as follows: The focal length of the parabolic mirror is designed to be 8.0±0.1mm, and the surface roughness Ra≤0.4μm. The 500kHz transducer is installed precisely at the focal point of the parabolic surface, with its central axis forming an angle ≤0.5° with the optical axis of the reflecting mirror. An acoustic insulating sponge with a thickness of 3 mm and an opening ratio of ≥90% is placed between the transducer and the reflector to absorb side-scattered waves. The calibration of d3 was performed using the laser interferometric positioning method. The measurement was repeated 100 times in a pure water environment at 20±0.1℃, and the average value was taken. The calibration results were written into the read-only memory.

8. The dual-frequency anti-interference ultrasonic water meter system as described in claim 7, characterized in that: The hardware configuration of the signal processing unit is as follows: Time measurement uses a TDC-GP22 chip with a time resolution of 55 ps; The programmable gain amplifier has 32 gain settings from 0 to 60 dB, and the automatic gain control (AGC) circuit dynamically adjusts the gain according to the signal amplitude. The bandpass filter uses a switched capacitor filter MAX297, and its center frequency can be digitally adjusted via the SPI interface. The Hilbert converter is implemented on an Altera Cyclone IV FPGA and uses a 16-stage pipeline architecture to process 5MSPS data streams.

9. The dual-frequency anti-interference ultrasonic water meter system as described in claim 8, characterized in that: The working method of the dynamic compensation processor is as follows: It has 512 built-in three-dimensional compensation parameters, including temperature (20-30℃, step 0.2℃), turbidity (0-100 NTU, step 5 NTU), and bubble fluctuation rate (0-0.4, step 0.02). Parameter interpolation is achieved using a radial basis function (RBF) neural network. The hidden layer of the network contains 48 neurons, and the activation function is a Gaussian function. The system automatically performs a parameter self-check every 24 hours. When it detects 10 consecutive compensation deviations exceeding ±0.5%, a calibration alarm is triggered.

10. The dual-frequency anti-interference ultrasonic water meter system as described in claim 9, characterized in that: The control logic of the mechanical defoaming module is as follows: When the bubble classification is marked as level 2, the spiral guide vane is activated to form a swirling flow field. At the same time, the piezoelectric ceramic cavitation generator is driven at a frequency of 40kHz to generate cavitation bubble groups with a diameter of 50 to 100μm, which are continuously operated for 30±5 seconds. When marked as Level 3, it continues to run until volatility F < 0.

25. If the target is not met within 300 seconds, it switches to pulse mode, working for 10 seconds and pausing for 5 seconds. The inlet is equipped with a conical flow stabilizer, with its opening ratio decreasing from 80% to 40% along the water flow direction, which is used to break up large air bubbles.

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