Circuit and method for resisting white noise interference of ultrasonic water meter

Abstract

The invention discloses a circuit and method for resisting white noise interference of an ultrasonic water meter. The circuit comprises a transmitting end ultrasonic transducer, a transmitting coding circuit, a digital clock chip, a microprocessor unit, a receiving coding circuit and a receiving end ultrasonic transducer. The digital clock chip is connected with the transmitting end ultrasonic transducer through the microprocessor unit and the transmitting coding circuit in sequence; the microprocessor unit is connected with a receiving end ultrasonic transducer through a receiving coding circuit in sequence; the digital clock chip is respectively connected with the transmitting end ultrasonic transducer, the transmitting coding circuit, the receiving coding circuit and the receiving end ultrasonic transducer. The white noise interference resistance of the ultrasonic water meter is improved.

Description

Technical Field

[0001] This application relates to the field of electronic technology, and in particular to a circuit and method for resisting white noise interference in an ultrasonic water meter. Background Technology

[0002] When white noise is present in the installation environment of an ultrasonic water meter, if the white noise contains frequencies that are the same as or close to the 1MHz frequency generated by the ultrasonic transducer, and the amplitude of the white noise at this frequency is high, it will interfere with the transmission of the effective signal generated by the ultrasonic transducer in the water. This can also cause the digital clock chip to misinterpret the ultrasonic signal received, mistaking the white noise for a valid signal, thus affecting the ultrasonic water meter's measurement. This is especially true in composite material water meter pipe sections, such as those made of nylon or PPS, where external white noise is more likely to enter the pipe and interfere with the effective signal. Summary of the Invention

[0003] In view of this, this application provides a circuit and method for resisting white noise interference in ultrasonic water meters.

[0004] This application discloses a circuit for resisting white noise interference in an ultrasonic water meter, which includes a transmitting ultrasonic transducer, a transmitting encoding circuit, a digital clock chip, a microprocessor unit, a receiving encoding circuit, and a receiving ultrasonic transducer; the digital clock chip is connected to the transmitting ultrasonic transducer in sequence through the microprocessor unit and the transmitting encoding circuit; the microprocessor unit is connected to the receiving ultrasonic transducer in sequence through the receiving encoding circuit; the digital clock chip is connected to the transmitting ultrasonic transducer, the transmitting encoding circuit, the receiving encoding circuit, and the receiving ultrasonic transducer respectively.

[0005] Furthermore, the transmit encoding circuit includes a first resistor, a first MOSFET, and a second resistor; one end of the first resistor is connected to the microprocessor unit, and the other end is connected to the gate of the first MOSFET; the source of the first MOSFET is grounded, and the drain is connected to the digital clock chip through the second resistor.

[0006] Furthermore, the receiving encoding circuit includes a comparator, a third resistor, a fourth resistor, a first diode, a second diode, and a verification circuit; the verification circuit includes a third diode, a fifth resistor, a sixth resistor, and a first capacitor; The signal received by the ultrasonic transducer at the receiving end is input to the comparator. At the same time, the microprocessor unit outputs a voltage threshold to the comparator through its built-in analog-to-digital converter. The comparator outputs multiple bits representing the ultrasonic signal, which are transmitted to the microprocessor unit through the first diode for decoding to determine whether the ultrasonic signal is a valid signal and whether it is affected by external environmental white noise interference. Simultaneously, the multiple bits representing the ultrasonic signal output by the comparator are transmitted to the verification circuit through the second diode. A 1 in the multiple bits indicates that the first capacitor is charged through the sixth resistor, and a 0 in the multiple bits indicates that the first capacitor is discharged through the fifth resistor.

[0007] Furthermore, the voltage across the first capacitor is acquired using the analog-to-digital converter built into the microprocessor unit to assess whether the ultrasonic signal is affected by external white noise, causing waveform distortion or phase error; if an abnormality is found, the transmission time measured in the corresponding period is discarded.

[0008] Furthermore, the ultrasonic transducer and digital clock chip at the receiving end are both connected to the non-inverting input of the comparator through the first resistor, and the microprocessor unit is connected to the inverting input of the comparator through the fourth resistor. The output of the comparator is connected to the anode of the first diode and the anode of the second diode. The cathode of the first diode is connected to the microprocessor unit. The cathode of the second diode is connected to the microprocessor unit through the sixth resistor. The cathode of the second diode is connected to the microprocessor unit in sequence through the third diode and the fifth resistor. The common terminal of the sixth resistor and the fifth resistor is grounded through the first capacitor.

[0009] This application also discloses a method for resisting white noise interference in ultrasonic water meters, applicable to the aforementioned circuit for resisting white noise interference in ultrasonic water meters, comprising: A digital clock chip transmits an electrical signal to the transmitting ultrasonic transducer. The transmitting ultrasonic transducer converts the electrical signal into an ultrasonic signal and transmits it within the water meter pipe section to the receiving ultrasonic transducer. The receiving ultrasonic transducer receives the ultrasonic signal and converts it back into an electrical signal, which is then sent to the digital clock chip. When the electrical signal received by the digital clock chip is higher than the signal detection interrupt voltage threshold, the transmission time of the signal from the transmitting ultrasonic transducer to the receiving ultrasonic transducer is calculated. This allows the calculation of the ultrasonic signal's transmission time in the water, and consequently, the current water flow rate.

[0010] Furthermore, the digital clock chip transmits M-cycle electrical signals. During several cycles of the M-cycle electrical signals, the microprocessor unit outputs a high level, causing the first MOSFET to conduct. The second resistor is grounded through the first MOSFET. Part of the current driving the transmitting ultrasonic transducer by the digital clock chip flows to the transmitting ultrasonic transducer, and part flows to the transmitting encoding circuit, reducing the driving current of the transmitting ultrasonic transducer and thus reducing the amplitude of the ultrasonic signal transmitted by the transmitting ultrasonic transducer.

[0011] Furthermore, the receiving encoding circuit has a rising edge voltage trigger, which compares the voltage of the ultrasonic signal received by the ultrasonic transducer at the receiving end with the threshold voltage. If the voltage of the ultrasonic signal received by the ultrasonic transducer at the receiving end exceeds the threshold voltage and is a rising edge, a high level is output, resulting in a total of K cycle electrical signals. The K cycle electrical signals are encoded into multiple bits, which are composed of a preamble and a data code; K is less than M. The preamble is encoded with 00 to reduce the current flowing through the ultrasonic transducer at the receiver, thereby changing the amplitude of the ultrasonic signal, but without affecting the signal detection interrupt voltage threshold Vth_TDC of the digital clock chip; the data code is encoded with 00 to prevent interference from external environmental white noise.

[0012] Furthermore, the threshold voltage of the receiving encoding path is dynamically adjusted, which adjusts the received signal strength according to the amplitude of the preamble. The threshold voltage is dynamically adjusted based on the average amplitude of the preamble, using the following formula:

[0013] Where Vth_comparer is the threshold voltage, Vth_comparer_pek is the average value of the preamble peak, k and q are both scaling factors, and N is the total number of preambles. It is the peak voltage of the preamble pulse, which is acquired by the peak detection circuit.

[0014] Furthermore, by utilizing the equal interval between 10s in multiple bits, the time window of each subsequent data pulse is accurately predicted by calculating the average interval ΔT at the pulse start point. , ];

[0015] in, Let be the start time of the i-th time window. This is the end time of the (i-1)th time window.

[0016] Due to the adoption of the above technical solution, this application has the following advantages: by adopting the principle of voltage regulation encoding and decoding, the received signal is determined to be a valid signal through encoding and decoding, thereby improving the ultrasonic water meter's ability to resist white noise interference. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments recorded in the embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings.

[0018] Figure 1 This is a circuit diagram illustrating the anti-white noise interference of an ultrasonic water meter according to an embodiment of this application. Figure 2 This is a schematic diagram of the transmission encoding circuit in an embodiment of this application; Figure 3 This is a schematic diagram of the transmission waveform in an embodiment of this application; Figure 4 This is a schematic diagram of the receiving encoding circuit according to an embodiment of this application. Detailed Implementation

[0019] The present application will be further described in conjunction with the accompanying drawings and embodiments. The described embodiments are only some, not all, of the embodiments of the present application. All other embodiments obtained by those skilled in the art should fall within the protection scope of the embodiments of the present application.

[0020] See Figure 1 This application provides an embodiment of a circuit for resisting white noise interference in an ultrasonic water meter, which includes a transmitting ultrasonic transducer A1, a transmitting encoding circuit A2, a digital clock chip A3, a microprocessor unit (MCU) A4, a receiving encoding circuit A5, and a receiving ultrasonic transducer A6; the digital clock chip A3 is connected to the transmitting ultrasonic transducer A1 in sequence through the microprocessor unit (MCU) A4 and the transmitting encoding circuit A2; the microprocessor unit (MCU) A4 is connected to the receiving ultrasonic transducer A6 in sequence through the receiving encoding circuit A5; the digital clock chip A3 is connected to the transmitting ultrasonic transducer A1, the transmitting encoding circuit A2, the receiving encoding circuit A5, and the receiving ultrasonic transducer A6 respectively.

[0021] Optionally, see Figure 2 The transmitting encoding circuit A2 includes a first resistor R1, a first MOSFET Q1, and a second resistor R2. One end of the first resistor R1 is connected to the microprocessor unit (MCU) A4, and the other end is connected to the gate of the first MOSFET Q1. The source of the first MOSFET Q1 is grounded, and the drain is connected to the digital clock chip A3 through the second resistor R2.

[0022] Optionally, see Figure 4 The receiving encoding circuit A5 includes a comparator U1, a third resistor R3, a fourth resistor R4, a first diode D1, a second diode D2, and a verification circuit; the verification circuit includes a third diode D3, a fifth resistor R5, a sixth resistor R6, and a first capacitor C1. The signal received by the ultrasonic transducer A6 at the receiving end is input to comparator U1. At the same time, the microprocessor unit (MCU) A4 outputs a voltage threshold to comparator U1 through its built-in analog-to-digital converter (DAC). Comparator U1 outputs multiple bits representing the ultrasonic signal, which are transmitted to the microprocessor unit (MCU) A4 through the first diode D1 for decoding to determine whether the ultrasonic signal is a valid signal and whether it is affected by external environmental white noise interference. Simultaneously, the multiple bits representing the ultrasonic signal output by comparator U1 are transmitted to the verification circuit through the second diode D2. A 1 in the multiple bits indicates that the first capacitor C1 is charged through the sixth resistor R6, and a 0 in the multiple bits indicates that the first capacitor C1 is discharged through the fifth resistor R5.

[0023] Optionally, the analog-to-digital converter (DAC) built into the microprocessor unit (MCU) A4 is used to acquire the voltage across the first capacitor C1 to assess whether the ultrasonic signal is affected by external white noise, causing waveform distortion or phase error; if an abnormality is found, the transmission time measured in the corresponding period is discarded.

[0024] For example, the signal received by the ultrasonic transducer A6 at the receiving end is input to comparator U1. Simultaneously, the MCU outputs Vth_comparer through the DAC. At this time, U1 outputs 10 10 00 10 10 10 10 10 10 10 00 00 10 10 10 10, which is transmitted to the MCU via D1 for decoding. The MCU determines whether this ultrasonic signal is valid and whether it is affected by external white noise interference. Simultaneously, the output 10 10 00 10 10 10 10 10 10 10 10 10 from U1 is transmitted via D2 to the time-based preamble and data code verification circuit (check circuit) composed of R6, R5, C1, and D3. A 1 in the bit charges C1 through R6, and a 0 discharges C1 through R5. R6 is 100Ω, R5 is 1KΩ, and C1 is 1uF.

[0025] Charging time constant: τ_charge = R_charge × C = 100Ω × 1μF = 100μs; where R_charge is R6 and C is C1; Discharging time constant: τ_discharge = R_discharge × C = 1kΩ × 1μF = 1ms; where R_discharge is R5; The duration of each bit is T = 1 μs, which is much smaller than the time constant, so a linear approximation is used: For bit 1 (charging): ΔV_charge=(3.3-V_current)×(T / τ_charge)=(3.3-V_current)×0.01 Where ΔV_charge is the voltage change value, and V_current is the current voltage of C1; For bit 0 (discharge): ΔV_discharge=-V_current×(T / τ_discharge)=-V_current×0.001.

[0026] Example calculations are shown in Table 1: Table 1. Voltage variation values ​​for different bit values

[0027] Ultimately, the voltage across the 1uF capacitor C1 was 0.371V. The MCU's ADC function was used to acquire the voltage across C1 to assess whether the ultrasonic signal was affected by external white noise, causing waveform distortion or phase error. If an anomaly was detected, the transmission time of the corresponding cycle was discarded, increasing the robustness of the transmission time measurement and improving the measurement accuracy.

[0028] Optionally, the ultrasonic transducer A6 and the digital clock chip A3 at the receiving end are both connected to the non-inverting input of the comparator U1 through the first resistor R1. The microprocessor unit (MCU) A4 is connected to the inverting input of the comparator U1 through the fourth resistor R4. The output of the comparator U1 is connected to the anode of the first diode D1 and the anode of the second diode D2. The cathode of the first diode D1 is connected to the microprocessor unit (MCU) A4. The cathode of the second diode D2 is connected to the microprocessor unit (MCU) A4 through the sixth resistor R6. The cathode of the second diode D2 is connected to the microprocessor unit (MCU) A4 in sequence through the third diode D3 and the fifth resistor R5. The common terminal of the sixth resistor R6 and the fifth resistor R5 is grounded through the first capacitor C1.

[0029] This application also discloses a method for resisting white noise interference in ultrasonic water meters, applicable to the aforementioned circuit for resisting white noise interference in ultrasonic water meters, comprising: A digital clock chip A3 transmits an electrical signal to the transmitting ultrasonic transducer A1. The transmitting ultrasonic transducer A1 converts the electrical signal into an ultrasonic signal and transmits it within the water meter pipe section to the receiving ultrasonic transducer A6. The receiving ultrasonic transducer A6 receives the ultrasonic signal and converts it back into an electrical signal, which is then sent to the digital clock chip A3. When the electrical signal received by the digital clock chip A3 is higher than the signal detection interrupt voltage threshold Vth_TDC, the transmission time of the signal from the transmitting ultrasonic transducer A1 to the receiving ultrasonic transducer A6 is calculated. This allows the calculation of the ultrasonic signal's transmission time in the water, and consequently, the current water flow rate.

[0030] If there is external white noise interference, especially if it is 1MHz, there is a risk that the digital clock metering chip may erroneously trigger the ultrasonic signal, resulting in inaccurate calculations of the ultrasonic signal's transmission time in the water, and consequently, inaccurate calculations of the current water flow rate. This could lead to the ultrasonic water meter misinterpreting water usage even when no water is being used, causing serious metering errors.

[0031] Based on this, a voltage regulation encoding and decoding principle was invented, and an ultrasonic transmission signal voltage regulation encoding circuit and an ultrasonic receiving signal decoding circuit were designed to embed digital codes into a simple 1MHz ultrasonic signal, thereby improving the ultrasonic signal recognition and preventing the ultrasonic measurement from being affected by external environmental signal interference.

[0032] Optionally, the digital clock chip A3 transmits M (e.g., 20) cycles of electrical signals. During several cycles of the M cycles (e.g., when the 8th, 15th, and 16th electrical signals are first transmitted), the microprocessor unit (MCU) A4 controls the I / O port pin to output a high level, causing the first MOSFET Q1 to conduct. The second resistor R2 is grounded through the first MOSFET Q1. A portion (Itotal_transmit) of the current (Iultrasound_transmit) driving the transmitting ultrasonic transducer A1 by the digital clock chip A3 flows to the transmitting ultrasonic transducer A1, and a portion (Iencode_transmit) flows to the transmitting encoding circuit A2, reducing the driving current of the transmitting ultrasonic transducer A1 and thus reducing the amplitude of the ultrasonic signal transmitted by the transmitting ultrasonic transducer A1.

[0033] See Figure 3 A7 represents the voltage and time waveform of the ultrasonic signal generated by the receiving ultrasonic transducer A6. A7-1 and A7-2 represent the 6th and 7th ultrasonic signal waveforms, respectively, and A7-3 represents the 8th ultrasonic signal waveform. Because of the transmitting encoding circuit A2, the amplitude of waveform A7-3 is smaller than that of A7-1 and A7-2. Similarly, the ultrasonic signal emitted by the transmitting ultrasonic transducer A1 is an encoded ultrasonic signal.

[0034] Optionally, the receiving encoding circuit A5 has a rising edge voltage trigger. If the voltage of the ultrasonic signal received by the ultrasonic transducer A6 at the receiving end exceeds the threshold voltage Vth_comparer and is a rising edge, a high level is output, resulting in a total of K cycle electrical signals. The K cycle electrical signals are encoded into multiple bits, which are composed of a preamble and a data code; K is less than M. The preamble is encoded with 00 to reduce the current flowing through the ultrasonic transducer A6 at the receiver, thereby changing the amplitude of the ultrasonic signal, but without affecting the signal detection interrupt voltage threshold Vth_TDC of the digital clock chip; the data code is encoded with 00 to prevent interference from external white noise.

[0035] For example, the transmitting ultrasonic transducer A1 emits 20 cycles of 1MHz ultrasonic signals, and the receiving ultrasonic transducer A6 receives 20 cycles of 1MHz ultrasonic signals. The receiving encoding circuit A5 has a rising edge voltage trigger; after reaching the threshold voltage Vth_comparer and a rising edge is reached, it outputs a high level. Thus, in this case, 20 cycles of 1MHz ultrasonic signals are received. Starting from the 6th received ultrasonic signal, the received voltage amplitude exceeds the threshold voltage Vth, meaning a total of 15 voltages exceed the threshold voltage Vth_comparer. This can be encoded as 10 ... Then, secondary encoding is performed. First, the preamble is modified. The first five preambles are changed to 10 10 00 10 10. This means that when the ultrasonic signal transmits eight signals, a parallel circuit is used across the transducer to shunt the current, reducing the current flowing through the transducer and thus altering the ultrasonic signal amplitude. The ultrasonic signal amplitude is reduced by 15%, but this does not affect the signal detection interrupt Vth_TDC of the digital clock chip. Similarly, the data code is encoded as 10 10 10 10 0000 10 10 10 10.

[0036] The reason for this encoding is that external environmental white noise will be superimposed on the original 20 ultrasonic signals, causing an increase in the amplitude of the 20 ultrasonic signals. Therefore, by encoding with 0s in the preamble and data codes, interference from external environmental white noise can be effectively prevented.

[0037] Meanwhile, the threshold voltage Vth_comparer of the receiving circuit is dynamically adjusted, changing the received signal strength based on the amplitude of the preamble. Different water temperatures affect the transmission efficiency of ultrasonic signals in water, thus impacting the amplitude of the received ultrasonic signal. Furthermore, with increased usage time, ultrasonic transducers experience aging, reducing their ability to convert electrical signals into ultrasonic signals, which also affects the received ultrasonic signal amplitude. Therefore, adding dynamic adjustment to Vth_comparer significantly improves its robustness.

[0038] Optionally, the threshold voltage Vth_comparer of the receiving encoding path is dynamically adjusted, which adjusts the received signal strength according to the amplitude of the preamble. The threshold voltage Vth_comparer is dynamically adjusted based on the average amplitude of the preamble, using the following formula:

[0039]

[0040] Where Vth_comparer_pek is the average value of the preamble peaks, k (usually 0.5-0.7) and q (e.g., 0.85) are scaling factors, and N is the total number of preambles. It is the peak voltage of the preamble pulse, which is acquired by the peak detection circuit.

[0041] Optionally, by utilizing the equal interval between 10s in multiple bits, the average interval of the pulse start point can be calculated. To accurately predict the time window of each subsequent data pulse [ , ] ;

[0042] in, Let be the start time of the i-th time window. This is the end time of the (i-1)th time window.

[0043] For example, a time-based preamble and data code verification (corresponding to a verification circuit) are also added. The preamble is: 1010 00 10 10, where 00 is in the middle and symmetrical. The data code is 10 10 10 10 00 00 10 10 10 10, where 00 00 is in the middle and the remaining data is symmetrical. In the hardware circuit, when a 10 appears, the capacitor is charging; when a 00 appears, the capacitor is discharging. The charge from two 10s will be released by one 00. Because capacitor charging introduces a time variable, a normal 1MHz periodic ultrasonic signal will have a fixed periodicity after the received voltage reaches the trigger level Vth_comparer and then falls below it. If the time changes, it may be due to white noise interference in the environment, causing waveform distortion or phase change of the ultrasonic signal, which may falsely trigger Vth_comparer. Simultaneously, the MCU records the acquisition time for each data acquisition. Utilizing the equal interval characteristic between 10 bits in the bitstream (00 bits are not processed), the average interval between pulse start points is calculated. To accurately predict the time window of each subsequent data pulse [ , Instead of relying on threshold triggering, it uses [this method / mechanism].

[0044] The reason for adding time as a verification variable is that the digital clock chip used in ultrasonic water meters works by measuring the time difference between the transmitted and received ultrasonic signals. If the waveform is distorted or the phase changes, the digital clock chip will measure the time difference in error, leading to measurement errors. By introducing time-based preamble and data code verification, if a data point fails verification, it is fed back to the digital clock chip, causing it to discard the ultrasonic transmission time measured that time.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and not to limit them. Although this application has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of this application. Any modifications or equivalent substitutions that do not depart from the spirit and scope of this application should be covered within the protection scope of the claims of this application.

Claims

1. A circuit for resisting white noise interference in an ultrasonic water meter, characterized in that, It includes a transmitting ultrasonic transducer, a transmitting encoding circuit, a digital clock chip, a microprocessor unit, a receiving encoding circuit, and a receiving ultrasonic transducer; the digital clock chip is connected to the transmitting ultrasonic transducer in sequence through the microprocessor unit and the transmitting encoding circuit; the microprocessor unit is connected to the receiving ultrasonic transducer in sequence through the receiving encoding circuit; the digital clock chip is connected to the transmitting ultrasonic transducer, the transmitting encoding circuit, the receiving encoding circuit, and the receiving ultrasonic transducer respectively.

2. The circuit for resisting white noise interference in an ultrasonic water meter according to claim 1, characterized in that, The transmit encoding circuit includes a first resistor, a first MOS transistor, and a second resistor; one end of the first resistor is connected to the microprocessor unit, and the other end is connected to the gate of the first MOS transistor; the source of the first MOS transistor is grounded, and the drain is connected to the digital clock chip through the second resistor.

3. The circuit for resisting white noise interference in an ultrasonic water meter according to claim 1, characterized in that, The receiving encoding circuit includes a comparator, a third resistor, a fourth resistor, a first diode, a second diode, and a verification circuit; the verification circuit includes a third diode, a fifth resistor, a sixth resistor, and a first capacitor. The signal received by the ultrasonic transducer at the receiving end is input to the comparator. At the same time, the microprocessor unit outputs a voltage threshold to the comparator through its built-in analog-to-digital converter. The comparator outputs multiple bits representing the ultrasonic signal, which are transmitted to the microprocessor unit through the first diode for decoding to determine whether the ultrasonic signal is a valid signal and whether it is affected by external environmental white noise interference. Simultaneously, the multiple bits representing the ultrasonic signal output by the comparator are transmitted to the verification circuit through the second diode. A 1 in the multiple bits indicates that the first capacitor is charged through the sixth resistor, and a 0 in the multiple bits indicates that the first capacitor is discharged through the fifth resistor.

4. The circuit for resisting white noise interference in an ultrasonic water meter according to claim 3, characterized in that, The voltage across the first capacitor is acquired using the analog-to-digital converter built into the microprocessor unit to assess whether the ultrasonic signal is affected by external white noise, causing waveform distortion or phase error; if an abnormality is found, the transmission time measured in the corresponding period is discarded.

5. The circuit for resisting white noise interference in an ultrasonic water meter according to claim 3, characterized in that, The ultrasonic transducer and digital clock chip at the receiving end are both connected to the non-inverting input of the comparator through the first resistor. The microprocessor unit is connected to the inverting input of the comparator through the fourth resistor. The output of the comparator is connected to the anode of the first diode and the anode of the second diode. The cathode of the first diode is connected to the microprocessor unit. The cathode of the second diode is connected to the microprocessor unit through the sixth resistor. The cathode of the second diode is connected to the microprocessor unit in sequence through the third diode and the fifth resistor. The common terminal of the sixth resistor and the fifth resistor is grounded through the first capacitor.

6. A method for resisting white noise interference in an ultrasonic water meter, applicable to the circuit for resisting white noise interference in an ultrasonic water meter as described in any one of claims 1-6, characterized in that, include: A digital clock chip transmits an electrical signal to the transmitting ultrasonic transducer. The transmitting ultrasonic transducer converts the electrical signal into an ultrasonic signal and transmits it within the water meter pipe section to the receiving ultrasonic transducer. The receiving ultrasonic transducer receives the ultrasonic signal and converts it back into an electrical signal, which is then sent to the digital clock chip. When the electrical signal received by the digital clock chip is higher than the signal detection interrupt voltage threshold Vth_TDC, the transmission time of the signal from the transmitting ultrasonic transducer to the receiving ultrasonic transducer is calculated. This allows the calculation of the ultrasonic signal's transmission time in the water, and consequently, the current water flow rate.

7. The method for resisting white noise interference in an ultrasonic water meter according to claim 6, characterized in that, The digital clock chip transmits M-cycle electrical signals. During several cycles of the M-cycle electrical signals, the microprocessor unit outputs a high level, causing the first MOSFET to conduct. The second resistor is grounded through the first MOSFET. Part of the current driving the ultrasonic transducer at the transmitting end of the digital clock chip flows to the ultrasonic transducer at the transmitting end, and part flows to the transmitting encoding circuit, reducing the driving current of the ultrasonic transducer at the transmitting end, thereby reducing the amplitude of the ultrasonic signal transmitted by the ultrasonic transducer at the transmitting end.

8. The method for resisting white noise interference in an ultrasonic water meter according to claim 7, characterized in that, The receiving encoding circuit has a rising edge voltage trigger. If the voltage of the ultrasonic signal received by the ultrasonic transducer at the receiving end exceeds the threshold voltage and is a rising edge, a high level is output, resulting in a total of K cycle electrical signals. The K cycle electrical signals are encoded into multiple bits, which are composed of a preamble and a data code; K is less than M. The preamble is encoded with 00 to reduce the current flowing through the ultrasonic transducer at the receiver, thereby changing the amplitude of the ultrasonic signal, but without affecting the signal detection interrupt voltage threshold Vth_TDC of the digital clock chip; the data code is encoded with 00 to prevent interference from external environmental white noise.

9. The method for resisting white noise interference in an ultrasonic water meter according to claim 8, characterized in that, The threshold voltage of the receiving encoding path is dynamically adjusted, which adjusts the received signal strength according to the amplitude of the preamble. The threshold voltage is dynamically adjusted based on the average amplitude of the preamble, using the following formula: Where Vth_comparer is the threshold voltage, Vth_comparer_pek is the average value of the preamble peak, k and q are both scaling factors, and N is the total number of preambles. It is the peak voltage of the preamble pulse, which is acquired by the peak detection circuit.

10. The method for resisting white noise interference in an ultrasonic water meter according to claim 9, characterized in that, By utilizing the equal interval between 10s in multiple bits, the time window of each subsequent data pulse can be accurately predicted by calculating the average interval ΔT at the pulse start point. , ]; in, Let be the start time of the i-th time window. This is the end time of the (i-1)th time window.

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