An automatic adjustment method for trigger waves of ultrasonic flow meters and gas meters

Abstract

This invention discloses an automatic adjustment method for the trigger wave of an ultrasonic flow meter and a gas meter, the method comprising: obtaining the trigger voltage threshold Vth i Set the lower limit of signal-to-noise ratio (SNRmin) i Acquire the received wave signal and perform gain processing to determine the amplitude of the processed received wave signal. Calculate the signal-to-noise ratio (SNR) by combining the SNR with the noise amplitude. Compare the SNR with SNRmin. i A comparison is performed to determine the final trigger voltage threshold. When SNR < SNRmin3, detection is stopped and restarted based on a preset interval time threshold. When the amplitude of the processed received wave signal is higher than the final trigger voltage threshold, a square wave signal is output. During the output of the square wave signal, the received wave signal is continuously acquired and gain processing is performed, and the gain value used for gain processing is recalculated. This invention can improve the anti-interference performance of ultrasonic flow meters, enabling them to operate normally in more complex measurement situations and ensuring accurate measurement.

Description

Technical Field

[0001] This application relates to the field of ultrasonic flow meter technology, and more specifically, to an automatic adjustment method for the trigger wave of an ultrasonic flow meter and a gas meter. Background Technology

[0002] Ultrasonic flow meters (gas meters) have advantages such as extremely low starting flow rate, wide rangeability, and no mechanical rotating parts, making them widely used in gas and liquid metering. Due to power supply limitations in many situations, most ultrasonic flow meters are battery-powered. To reduce power consumption and extend battery life, most employ a time-difference method based on zero-crossing detection. Because the types of media measured by ultrasonic flow meters, media conditions, and environmental conditions are very diverse, especially when the medium is low-pressure natural gas, conventional battery-powered ultrasonic flow meters often exhibit large measurement deviations or fail to measure normally, frequently leading to metering-related trade disputes. Therefore, most gas ultrasonic flow meters on the market that use zero-crossing detection also overcome the measurement failure problem caused by wave skipping through various technologies. However, these technologies mainly focus on adjusting the trigger voltage threshold of the first wave detection by measuring the amplitude of the received signal, or determining whether the received wave signal meets the measurement requirements.

[0003] Most ultrasonic flow meters on the market are currently battery-powered. To reduce power consumption and achieve battery power, zero-crossing detection is generally used. However, current zero-crossing detection ultrasonic flow meters typically use a fixed initial wave detection. While this method offers good zero-point stability when the signal-to-noise ratio (SNR) meets requirements, it can lead to errors in initial wave identification, resulting in significant measurement errors or even malfunction, due to factors such as low medium pressure or significant environmental interference reducing the SNR of the amplified received signal. This can cause significant measurement errors or even prevent normal operation. To address this, different manufacturers have adopted various technologies, some automatically adjusting the initial wave trigger voltage threshold based on the amplitude of the received signal; others... Some methods identify and correct for forward or backward wave skipping by analyzing the peak position of the received wave; others use two trigger voltage thresholds, where a second wave triggers the second threshold when the initial wave fails to trigger due to a decrease in signal amplitude; still others use a first-wave trigger voltage threshold and a second trigger voltage threshold. Based on the ultrasonic transmission time obtained from the first wave trigger, the second trigger threshold is activated several waveform cycles after the first wave trigger. A comparator outputs several pulses for pulse width comparison, and the changes in pulse width are measured and calculated to determine the changes in the received wave, thus allowing for correction and adjustment. These methods are only effective when the signal-to-noise ratio (SNR) basically meets the measurement conditions. However, when the SNR of the received wave is so low that the noise amplitude in the received wave approaches or even exceeds the amplitude of the initial wave signal, these measures become ineffective.

[0004] Therefore, the existing technology has defects and urgently needs improvement. Summary of the Invention

[0005] In view of the above problems, the purpose of this invention is to provide an automatic adjustment method for the trigger wave of an ultrasonic flow meter and a gas meter. This method automatically adjusts the amplitude of the received wave signal by detecting the AGC circuit, while simultaneously detecting the signal amplitude and signal-to-noise ratio (SNR). When the signal amplitude reaches the design requirement range, the method automatically selects the corresponding trigger voltage threshold for the first, second, or third wave detection based on the SNR level. Furthermore, it sets a lower limit for the SNR corresponding to the trigger voltage threshold for the first, second, or third wave detection; that is, when the SNR is higher than the lower limit required for normal detection, the method adopts a trigger voltage adjustment method. The system uses an initial detection wave; when the signal-to-noise ratio (SNR) falls below the lower limit required for normal detection under the initial trigger detection, a second trigger detection wave is initiated; when the SNR falls below the lower limit required for the second trigger detection wave, it switches to a third detection wave; if the SNR falls further, detection stops to avoid erroneous measurements; after stopping detection, the detection process is initiated at set time intervals, the received wave signal is adjusted, and the SNR is detected. If the SNR then exceeds the minimum SNR lower limit required for the initial, first, or second trigger detection wave, it switches back to the appropriate initial, first, or second detection wave. This technology improves the anti-interference performance of the ultrasonic flow meter, enabling it to operate normally in complex measurement environments and ensuring accurate measurement.

[0006] The first aspect of this invention provides an automatic adjustment method for the trigger wave of an ultrasonic flow meter and a gas meter, comprising:

[0007] Obtain the system's pre-set trigger voltage threshold Vth i The trigger voltage thresholds include the first-wave trigger voltage threshold Vth1, the second-wave trigger voltage threshold Vth2, and the third-wave trigger voltage threshold Vth3.

[0008] Based on the trigger voltage threshold Vth i Set the lower limit of signal-to-noise ratio (SNRmin) i The lower limit of signal-to-noise ratio includes the lower limit of signal-to-noise ratio for the first-wave triggered detection (SNRmin1), the lower limit of signal-to-noise ratio for the second-wave triggered detection (SNRmin2), and the lower limit of signal-to-noise ratio for the third-wave detected (SNRmin3).

[0009] Acquire the received wave signal;

[0010] The received wave signal is subjected to gain processing to determine the amplitude of the processed received wave signal;

[0011] The signal-to-noise ratio (SNR) is calculated based on the amplitude of the processed received wave signal and the noise amplitude.

[0012] The signal-to-noise ratio (SNR) is compared with the lower limit of the signal-to-noise ratio (SNRmin). i By comparing the results, the final trigger voltage threshold can be determined.

[0013] When SNR < SNRmin3, stop detection and restart detection based on a preset interval time threshold;

[0014] The processed received wave signal is compared with the final trigger voltage threshold. When the amplitude of the processed received wave signal is higher than the final trigger voltage threshold, a square wave signal is output.

[0015] During the output of the square wave signal, the received wave signal is continuously acquired and the gain is processed. When the amplitude of the processed received wave signal is not within the preset target amplitude range, the gain value used for gain processing is recalculated.

[0016] In this scheme, the trigger voltage threshold Vth is used as the basis for... i Set the lower limit of signal-to-noise ratio (SNRmin) i The specific method is as follows:

[0017] ;

[0018] ;

[0019] Where i represents the i-th wave trigger, S represents the amplitude of the processed received wave signal, and N i Vth represents the noise amplitude triggered by the i-th wave. i ΔV is the trigger voltage threshold for the i-th wave, and ΔV is the preset voltage adjustment parameter.

[0020] In this scheme, the step of performing gain processing on the received wave signal and determining the processed received wave signal includes:

[0021] The received wave signal is subjected to gain processing based on the initial gain value or the gain value of the previous detection.

[0022] Determine whether the amplitude of the processed received wave signal is within the preset target amplitude range;

[0023] If so, output the amplitude of the processed received wave signal;

[0024] If not, the gain value is recalculated, and the received wave signal is processed again based on the recalculated gain value to obtain the amplitude of the processed received wave signal.

[0025] In this scheme, the signal-to-noise ratio (SNR) is compared with the lower limit of the signal-to-noise ratio (SNRmin). i The comparison was performed to determine the final trigger voltage threshold, including:

[0026] When SNR > SNRmin1, the initial trigger voltage threshold Vth1 is determined as the final trigger voltage threshold.

[0027] When SNRmin2≤SNR<SNRmin1, the second wave trigger voltage threshold Vth2 is determined as the final trigger voltage threshold.

[0028] When SNRmin3≤SNR<SNRmin2, the third wave trigger voltage threshold Vth3 is determined as the final trigger voltage threshold.

[0029] This plan also includes:

[0030] When SNR < SNRmin3, stop detection and record the cumulative stop time;

[0031] When the cumulative stop time exceeds the preset interval time threshold, the detection is restarted.

[0032] This plan also includes:

[0033] When the final trigger voltage threshold is the second wave trigger voltage threshold Vth2 or the third wave trigger voltage threshold Vth3, the forward and reverse acoustic wave transmission time corresponding to the square wave signal is corrected.

[0034] This plan also includes:

[0035] When SNR < SNRmin3, the maximum peak-to-peak change rate within the first preset time interval is calculated based on the historical received wave signals within the first preset time interval.

[0036] When the maximum peak-to-peak change rate within the first preset time interval is greater than the preset change rate threshold, the waveform freeze mode is entered.

[0037] Record the duration of the freeze mode based on the start time of the waveform freeze mode, and continue to acquire the received waveform signal;

[0038] The peak-to-peak change rate of the first wave is calculated based on the received wave signal within the second preset time interval.

[0039] When the rate of change of the first peak value is within the preset rate of change threshold range, the waveform freeze model termination condition is met, and the waveform freeze mode is exited.

[0040] If the waveform freeze model termination condition is still not met after the duration of the freeze mode exceeds a preset time threshold, then the detection will stop.

[0041] This plan also includes:

[0042] When entering waveform freeze mode, the historical received waveform signal within the first preset time interval is input into the preset waveform change prediction model, and the predicted waveform change curve is output; the predicted waveform change curve includes the first predicted waveform change curve corresponding to the duration of waveform freeze mode and the second predicted waveform change curve after exiting waveform freeze mode.

[0043] After exiting waveform freeze mode, the waveform correction scheme is determined based on the signal-to-noise ratio and waveform matching degree of the first valid received waveform signal.

[0044] Based on the waveform correction scheme, waveform correction is performed on the predicted received wave signal corresponding to the predicted waveform change curve and the effective received wave signal after exiting the waveform freeze mode.

[0045] In this scheme, the specific method for correcting the waveform of the valid received wave signal after exiting the waveform freeze mode based on the waveform correction scheme is as follows:

[0046] The first adjustment weight k of the first effective received wave signal is determined based on the signal-to-noise ratio of the first effective received wave signal. a(t) ;

[0047] The adjustment time interval is determined based on the waveform matching degree of the first valid received wave signal;

[0048] Based on the adjustment time interval and the first adjustment weight k of the first valid received wave signal a(t) The first adjustment weight of the subsequent effective received wave signal is set, and the first adjustment weight k of the effective received wave signal at the detection time t+m is determined. a(t+m) ;

[0049] Based on the detection time T, the first adjustment weight k of the effectively received wave signal is used. a(T) The second adjustment weight k is determined for the predicted received wave signal corresponding to the detection time. b(T) ;k b(T) =1-k a(T) ;

[0050] Based on the detection time T, the signal peak value of the effective received wave signal and the corresponding predicted received wave signal are weighted and calculated to determine the corrected signal peak value of the effective received wave signal.

[0051] The waveform of the effective received wave signal is updated based on the corrected signal peak value.

[0052] In this scheme, the specific method for correcting the waveform of the predicted received wave signal corresponding to the predicted waveform change curve based on the waveform correction scheme is as follows:

[0053] The third adjustment weight k of the first predicted received wave signal during the waveform freeze mode duration is applied. c(1) Set to 1;

[0054] The third adjustment weight k of the last predicted received wave signal during the waveform freeze mode duration is applied. c(n) Set to 1-k a(t) ;

[0055] Based on the third adjustment weight of the first predicted received wave signal and the third adjustment weight of the last predicted received wave signal within the duration of the waveform freeze mode, the third adjustment weight of other predicted received wave signals within the duration of the waveform freeze mode is determined by linear interpolation.

[0056] The peak value of each predicted received wave signal is weighted and calculated with the peak value of the first valid received wave signal to determine the corrected peak value of the predicted received wave signal during the duration of the waveform freeze mode.

[0057] The waveform of the predicted received wave signal is updated based on the corrected signal peak value.

[0058] This invention discloses an automatic adjustment method for the trigger wave of an ultrasonic flow meter and a gas meter, the method comprising: obtaining the trigger voltage threshold Vth i Set the lower limit of signal-to-noise ratio (SNRmin) i Acquire the received wave signal and perform gain processing to determine the amplitude of the processed received wave signal; calculate the signal-to-noise ratio (SNR) based on the amplitude of the processed received wave signal and the noise amplitude; compare the SNR with the lower limit of the SNR, SNRmin. i A comparison is performed to determine the final trigger voltage threshold. When SNR < SNRmin3, detection is stopped and restarted based on a preset interval time threshold. When the amplitude of the processed received wave signal is higher than the final trigger voltage threshold, a square wave signal is output. During the output of the square wave signal, the received wave signal is continuously acquired and gain processing is performed, and the gain value used for gain processing is recalculated. This invention can improve the anti-interference performance of ultrasonic flow meters, enabling them to operate normally in more complex measurement situations and ensuring accurate measurement. Attached Figure Description

[0059] Figure 1 The flowchart illustrates an automatic adjustment method for the trigger wave of an ultrasonic flow meter and gas meter provided by the present invention.

[0060] Figure 2 This invention provides a flowchart for gain processing of received wave signals.

[0061] Figure 3 A flowchart of the final trigger voltage threshold determination method provided by the present invention is shown;

[0062] Figure 4 A block diagram illustrating the working principle of the automatic adjustment of the trigger wave provided by the present invention is shown;

[0063] Figure 5 A schematic diagram of the first-wave detection method provided by the present invention is shown;

[0064] Figure 6A schematic diagram of the second-wave detection method provided by the present invention is shown;

[0065] Figure 7 A schematic diagram of the third-wave detection method provided by the present invention is shown. Detailed Implementation

[0066] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0067] 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 therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0068] Figure 1 The flowchart illustrates an automatic adjustment method for the trigger wave of an ultrasonic flow meter and gas meter provided by the present invention.

[0069] like Figure 1 As shown, this invention discloses an automatic adjustment method for the trigger wave of an ultrasonic flow meter and a gas meter, comprising:

[0070] S101, Obtain the system's pre-set trigger voltage threshold Vth i The trigger voltage thresholds include the first trigger voltage threshold Vth1, the second trigger voltage threshold Vth2, and the third trigger voltage threshold Vth3.

[0071] S102, based on trigger voltage threshold Vth i Set the lower limit of signal-to-noise ratio (SNRmin) i The lower limit of signal-to-noise ratio includes the lower limit of signal-to-noise ratio for the first-wave triggered detection (SNRmin1), the lower limit of signal-to-noise ratio for the second-wave triggered detection (SNRmin2), and the lower limit of signal-to-noise ratio for the third-wave detected (SNRmin3).

[0072] S103, acquire the received wave signal;

[0073] S104, perform gain processing on the received wave signal and determine the amplitude of the processed received wave signal;

[0074] S105, calculate the signal-to-noise ratio (SNR) based on the processed received wave signal amplitude and noise amplitude;

[0075] S106, compare the signal-to-noise ratio (SNR) with the lower limit of SNRmin. i By comparing the results, the final trigger voltage threshold can be determined.

[0076] S107, when SNR < SNRmin3, stop detection and restart detection based on a preset interval time threshold;

[0077] S108 compares the processed received wave signal with the final trigger voltage threshold. When the amplitude of the processed received wave signal is higher than the final trigger voltage threshold, a square wave signal is output.

[0078] S109: During the output of the square wave signal, the received wave signal is continuously acquired and the gain is processed. When the amplitude of the processed received wave signal is not within the preset target amplitude range, the gain value used for gain processing is recalculated.

[0079] According to an embodiment of the present invention, since the received signal has a certain range of variation, the trigger voltage threshold Vth is... i The system obtains the first wave trigger voltage threshold Vth1, the second wave trigger voltage threshold Vth2, and the third wave trigger voltage threshold Vth3 by analyzing historical received wave signals. These thresholds are determined by the peak values ​​of the first, second, and third waves when the target range of the received signal is at its minimum. The initial values ​​of these three thresholds are generally 10%, 30%, and 50% of the half-peak value of the received wave signal, respectively. The specific values ​​are determined by the system through analysis of historical received wave signals.

[0080] based on Figure 4 The diagram illustrates the working principle of the automatic trigger wave adjustment. Before each detection begins, system initialization is performed. Microprocessor 1 initializes the peak acquisition circuit 5, logic control circuit 2, trigger and zero-crossing control circuit 8, and voltage divider circuit 11 composed of digital potentiometers (or voltage divider resistors). This is achieved by reading the system's pre-set trigger voltage threshold Vth. i And determine the corresponding lower limit of signal-to-noise ratio (SNRmin) respectively. i .

[0081] Then, the microprocessor 1 initiates a round of detection by determining the detection time interval (e.g., one second or two seconds) according to a preset time threshold set by those skilled in the art through the system. Before each round of detection, the amplifier 6 (PGA) and related circuits are activated, and the amplifier 6 is adjusted according to the initial gain value or the gain value of the previous round of detection. At the same time, after an appropriate delay, the microprocessor 1 and the logic control circuit 3 control the enable comparator 4. Then, the microprocessor 1 starts to send the excitation wave signal, and after the shielding time set according to the aperture, the received wave signal 10 from the receiving transducer of the measurement channel and amplified by the amplifier 6 (PGA) is subjected to noise signal. The system acquires and detects the received wave signal. After the first trigger pulse is output by comparator 4, the system starts detecting the received wave signal. The acquired received wave signal is then processed by gain control. The amplitude of the processed received wave signal is then acquired, and the signal-to-noise ratio (SNR) is calculated in conjunction with the system's preset noise amplitude (the SNR corresponding to the received wave signal is also calculated using the SNR lower limit calculation formula). If the amplitude of the received wave signal reaches the system's preset target amplitude range, the next step is performed. Otherwise, the gain is recalculated based on the obtained received wave signal amplitude, and the above steps are repeated until the amplitude of the received wave signal reaches the preset target amplitude range.

[0082] Subsequently, based on the calculated signal-to-noise ratio (SNR), the microprocessor 1 controls the voltage divider circuit 11 (composed of a digital potentiometer or voltage divider resistors) to obtain the corresponding trigger level 3 (i.e., the trigger voltage threshold, Vth). i The voltage divider circuit consists of a reference voltage source Vref, a resistor R1, and an adjustable potentiometer R2. The microprocessor 1 adjusts the resistance value of the adjustable potentiometer R2 so that the voltage output by the voltage divider circuit 11 is equal to the calculated trigger voltage threshold Vth. i Specifically, the matching is as follows: When the signal-to-noise ratio (SNR) is higher than the set lower limit of the first-wave trigger detection SNRmin1, the microprocessor 1 controls the voltage divider circuit 11 of the digital potentiometer (or voltage divider resistors) to output the first-wave trigger voltage threshold Vth1; when the SNR is lower than the set lower limit of the first-wave trigger detection SNRmin1 but higher than the lower limit of the second-wave trigger detection SNRmin2, the microprocessor 1 controls the voltage divider circuit 11 of the digital potentiometer (or voltage divider resistors) to output the second-wave trigger voltage threshold Vth2; when the SNR is lower than the set lower limit of the second-wave trigger detection SNRmin2 but higher than the lower limit of the third-wave trigger detection SNRmin3, the microprocessor 1 controls the voltage divider circuit 11 of the digital potentiometer (or voltage divider resistors) to output the third-wave trigger voltage threshold Vth3.

[0083] Subsequently, the microprocessor 1 simultaneously activates the comparator 4 to compare the received signal 10 with the selected final trigger voltage threshold (first trigger voltage threshold Vth1, second trigger voltage threshold Vth2, or third trigger voltage threshold Vth3). When the amplitude of the received wave signal is higher than the final trigger voltage threshold, the output of the comparator 4 begins to flip and output a high level. This high level causes the trigger and zero-crossing control circuit 8 to control the comparator 7 to enter the zero-crossing comparison, thereby outputting a square wave signal 9 for timing processing.

[0084] like Figures 5-7 The diagrams shown illustrate how square wave signals are detected by the first, second, and third waves, respectively.

[0085] like Figure 5 As shown, within the preset noise detection time of the system, the current environment is determined to be a low noise environment by the signal-to-noise ratio of the received wave signal, i.e., SNR > SNRmin1. The first wave trigger level Vth1 (i.e. the first wave trigger voltage threshold) is determined as the final trigger voltage threshold. When the amplitude of the received wave signal (the processed received wave signal) output by amplifier 6 is higher than the first wave trigger level Vth1, comparator 4 outputs a trigger square wave, and comparator 7 outputs a square wave signal.

[0086] like Figure 6 As shown, within the preset noise detection time of the system, the current environment is determined to be a high-noise environment by the signal-to-noise ratio of the received wave signal, i.e., SNRmin2≤SNR<SNRmin1. The second wave trigger level Vth2 (i.e. the second wave trigger voltage threshold) is determined as the final trigger voltage threshold. When the amplitude of the received wave signal (the processed received wave signal) output by amplifier 6 is higher than the second wave trigger level Vth2, comparator 4 outputs a trigger square wave, and comparator 7 outputs a square wave signal.

[0087] like Figure 7 As shown, within the preset noise detection time of the system, the current environment is determined to be a high-noise environment by the signal-to-noise ratio of the received wave signal, i.e., SNRmin3≤SNR<SNRmin2. The third wave trigger level Vth3 (i.e. the third trigger voltage threshold) is determined as the final trigger voltage threshold. When the amplitude of the received wave signal (the processed received wave signal) output by amplifier 6 is higher than the third trigger level Vth3, comparator 4 outputs a trigger square wave, and comparator 7 outputs a square wave signal.

[0088] In addition, before the amplitude of the processed received wave signal exceeds the final trigger voltage threshold, the system will recalculate the signal-to-noise ratio (SNR) based on each acquired received wave signal, thereby dynamically adjusting the final trigger voltage threshold.

[0089] In addition, while controlling the relevant circuits (comparator 4 and comparator 7) to output square wave signals, microprocessor 1 continues to perform AD conversion on the peak value sampled by peak acquisition circuit 5 of received wave signal 10 to obtain the amplitude of received wave signal. If the amplitude of received wave signal meets the required preset target amplitude range, subsequent processing is performed; otherwise, the gain value is recalculated, the gain of amplifier 6 is adjusted, and the signal-to-noise ratio is detected. The above process is repeated until the amplitude of received wave signal 10 meets the required preset target amplitude range. At the same time, the signal-to-noise ratio SNR is calculated based on the recalculated processed received wave signal amplitude. This SNR is compared with the lower limit of SNRmin3 of the third wave trigger detection to determine whether to continue outputting square wave signal (i.e., SNR≥SNRmin3) or to stop detection (i.e., SNR<SNRmin3).

[0090] According to an embodiment of the present invention, based on the trigger voltage threshold Vth i Set the lower limit of signal-to-noise ratio (SNRmin) i The specific method is as follows:

[0091] ;

[0092] ;

[0093] Where i represents the i-th wave trigger, S represents the amplitude of the processed received wave signal, and N i Vthi represents the noise amplitude of the i-th trigger wave, Vthi is the trigger voltage threshold of the i-th wave, and ΔV is the preset voltage adjustment parameter.

[0094] It should be noted that, in order to ensure that noise does not cause false triggering and lead to wave skipping when using the first, second or third wave detection, the maximum noise amplitude corresponding to each lower limit of signal-to-noise ratio should be slightly lower than the corresponding trigger voltage threshold.

[0095] Where i ranges from 1 to 3, representing the first, second, and third wave triggers respectively. The received signal amplitude S typically ranges from 800 to 1000 mV, with the specific value determined by a preset target amplitude range. The preset voltage adjustment parameter ΔV typically ranges from 10 mV to 50 mV, with the specific value set by those skilled in the art based on actual needs. Using the above formulas, the lower limit of the signal-to-noise ratio (SNR) for the first wave trigger voltage threshold Vth1 (SNRmin1), the lower limit of the signal-to-noise ratio (SNR) for the second wave trigger voltage threshold Vth2 (SNRmin2), and the lower limit of the signal-to-noise ratio (SNR) for the third wave trigger voltage threshold Vth3 (SNRmin3) can be determined respectively.

[0096] Figure 2A flowchart of the gain processing of the received wave signal provided by the present invention is shown.

[0097] like Figure 2 As shown, according to an embodiment of the present invention, gain processing is performed on the received wave signal to determine the processed received wave signal, including:

[0098] S201, perform gain processing on the received wave signal based on the initial gain value or the gain value of the previous detection;

[0099] S202, determine whether the amplitude of the processed received wave signal is within the preset target amplitude range;

[0100] S203, if so, output the amplitude of the processed received wave signal;

[0101] S204. If not, recalculate the gain value and perform gain processing on the received wave signal again based on the recalculated gain value to obtain the amplitude of the processed received wave signal.

[0102] It should be noted that after acquiring the received wave signal in each round of detection, gain processing is performed on the currently received wave signal based on the gain value used in the previous round of detection. Peak adjustment is applied to the received wave signal to obtain the processed amplitude for subsequent calculations. In the first round of detection, gain processing is performed on the received wave signal based on the initial gain value. The processed amplitude of the received wave signal is compared with a preset target amplitude range. If the amplitude is within the preset target amplitude range, the next step of processing is performed; otherwise, the gain value is recalculated to bring the amplitude of the received wave signal within the preset target amplitude range, completing the gain processing step and obtaining the processed amplitude of the received wave signal.

[0103] The initial gain value and the preset target amplitude range are set by those skilled in the art according to actual needs.

[0104] Figure 3 A flowchart of the final trigger voltage threshold determination method provided by the present invention is shown.

[0105] like Figure 3 As shown in the embodiment of the present invention, the signal-to-noise ratio (SNR) and the lower limit of the signal-to-noise ratio (SNRmin) are compared. i The comparison was performed to determine the final trigger voltage threshold, including:

[0106] S301, when SNR>SNRmin1, the first trigger voltage threshold Vth1 is determined as the final trigger voltage threshold.

[0107] S302, when SNRmin2≤SNR<SNRmin1, the second wave trigger voltage threshold Vth2 is determined as the final trigger voltage threshold.

[0108] S303, when SNRmin3≤SNR<SNRmin2, the third wave trigger voltage threshold Vth3 is determined as the final trigger voltage threshold.

[0109] It should be noted that, based on Figure 4 The block diagram illustrating the automatic adjustment principle of the trigger wave shows that, based on the calculated signal-to-noise ratio (SNR), the microprocessor 1 controls the voltage divider circuit 11, composed of a digital potentiometer (or voltage divider resistors), to obtain the corresponding trigger level 3 (i.e., the trigger voltage threshold, Vth). i Specifically, when the signal-to-noise ratio (SNR) is higher than the set lower limit of the first-wave trigger detection SNRmin1, the microprocessor 1 controls the voltage divider circuit 11 of the digital potentiometer (or voltage divider resistors) to output the first-wave trigger voltage threshold Vth1; when the SNR is lower than the set lower limit of the first-wave trigger detection SNRmin1 and higher than the lower limit of the second-wave trigger detection SNRmin2, the microprocessor 1 controls the voltage divider circuit 11 of the digital potentiometer (or voltage divider resistors) to output the second-wave trigger voltage threshold Vth2; when the SNR is lower than the set lower limit of the second-wave trigger detection SNRmin2 and higher than the lower limit of the third-wave trigger detection SNRmin3, the microprocessor 1 controls the voltage divider circuit 11 of the digital potentiometer (or voltage divider resistors) to output the third-wave trigger voltage threshold Vth3.

[0110] According to an embodiment of the present invention, it further includes:

[0111] When SNR < SNRmin3, stop detection and record the cumulative stop time;

[0112] When the cumulative stop time exceeds the preset interval time threshold, the detection will be restarted.

[0113] It should be noted that when the obtained signal-to-noise ratio (SNR) is lower than the set lower limit SNRmin3 for the third wave trigger detection, it indicates that the noise is already extremely high, making correct detection difficult, and the microprocessor stops the detection process. Based on the time the detection stopped, a cumulative stop time is recorded. This cumulative stop time is compared with a preset interval threshold. When the cumulative stop time exceeds the preset interval threshold, the signal gain processing and SNR detection process are restarted to determine if the test conditions have been restored. For example, the test conditions can be determined by checking whether the reacquired SNR meets the final trigger voltage threshold adjustment, thereby resuming the trigger detection process for the corresponding received wave or continuing to stop detection.

[0114] The preset interval time threshold is set by those skilled in the art according to actual needs.

[0115] According to an embodiment of the present invention, it further includes:

[0116] When the final trigger voltage threshold is the second wave trigger voltage threshold Vth2 or the third wave trigger voltage threshold Vth3, the forward and reverse acoustic wave transmission time corresponding to the square wave signal is corrected.

[0117] It should be noted that when using the second wave trigger, the propagation time of the sound waves in both directions will be one period T longer than that of the first wave trigger. Therefore, one period T needs to be subtracted for correction when calculating the duration of both directions. Similarly, when using the third wave trigger, the propagation time of the sound waves in both directions will be two periods T longer than that of the first wave trigger. Therefore, two periods T need to be subtracted for correction when calculating the duration of both directions. The period T is determined by the system based on the sampling frequency of the excitation signal. For example, if the excitation signal is 200kHz, the period T = 5µs. Alternatively, the average period of the detection can be used for correction calculation.

[0118] According to an embodiment of the present invention, it further includes:

[0119] When SNR < SNRmin3, the maximum peak-to-peak change rate within the first preset time interval is calculated based on the historical received wave signals within the first preset time interval.

[0120] When the maximum peak-to-peak change rate within the first preset time interval exceeds the preset change rate threshold, the waveform freeze mode is entered.

[0121] Record the duration of the freeze mode based on the start time of the waveform freeze mode, and continue to acquire the received waveform signal;

[0122] The peak-to-peak change rate of the first wave is calculated based on the received wave signal within the second preset time interval.

[0123] When the rate of change of the first peak value is within the preset rate of change threshold range, the waveform freeze model termination condition is met, and the waveform freeze mode is exited.

[0124] If the waveform freeze mode duration exceeds the preset time threshold and the termination condition is still not met, then the detection will stop.

[0125] It should be noted that the system determines the signal-to-noise ratio (SNR) and the lower limit of the SNR (SNRmin) by comparing these parameters. iThe system determines whether to stop or resume detection based on the magnitude of the interference. However, when short-duration (e.g., less than 50ms) and densely distributed transient interference occurs, the system needs to repeatedly trigger the stop and resume detection commands, which requires significant system computational pressure. When the processor cannot meet the computational demands, it cannot stop or resume detection in time, resulting in the presence of some trigger wave signals with high signal-to-noise ratios or the loss of the trigger wave signals for the stopped detection portion. This leads to a large error between the detected traffic data and the actual traffic data. A waveform freeze mode can be added to the stop detection determination to handle short-duration transient interference.

[0126] When SNR < SNRmin3, the detection time corresponding to the current detection is determined as the end time of the first preset time interval. The first preset time interval is determined by combining this with its pre-set length. Based on the historical detection times within the first preset time interval, the corresponding historical received wave signals are retrieved from the database. Each received wave signal acquired during a detection is bound to its corresponding detection time and stored in the database. The peak difference between the minimum and maximum peak values ​​in the selected historical received wave signals is calculated to determine the maximum peak-to-peak change rate. When the maximum peak-to-peak change rate is greater than a preset change rate threshold, a short-duration but significant transient interference is identified, and the waveform freeze mode is entered first; otherwise, detection is stopped directly.

[0127] The start time of the waveform freeze mode is determined as the start time of the first second preset time interval. Each second preset time interval is determined based on the pre-set interval length. Each second preset time interval is verified sequentially according to time. First, the absolute value of the peak difference between adjacent received wave signals within the second preset time interval is calculated. The absolute value of the peak difference between each adjacent received wave signal is multiplied by its corresponding rate of change weight, and the results are accumulated to determine the first peak-to-peak rate of change. The rate of change weight corresponding to the absolute value of the peak difference between adjacent received wave signals is determined by the system based on the time difference between the detection time of the previous received wave signal and the current detection time. The closer to the current detection time, the higher the rate of change weight corresponding to the absolute value of the peak difference between the corresponding adjacent received wave signals.

[0128] The lengths of the first preset time interval and the second preset time interval are set by those skilled in the art according to actual needs, and the preset rate of change threshold, the preset rate of change threshold interval and the preset time threshold are all set by those skilled in the art according to actual needs.

[0129] According to an embodiment of the present invention, it further includes:

[0130] When entering waveform freeze mode, the historical received waveform signal within the first preset time interval is input into the preset waveform change prediction model, and the predicted waveform change curve is output; the predicted waveform change curve includes the first predicted waveform change curve corresponding to the duration of waveform freeze mode and the second predicted waveform change curve after exiting waveform freeze mode.

[0131] After exiting waveform freeze mode, the waveform correction scheme is determined based on the signal-to-noise ratio and waveform matching degree of the first valid received waveform signal.

[0132] Based on the waveform correction scheme, waveform correction is performed on the predicted received wave signal corresponding to the predicted waveform change curve and the effective received wave signal after exiting the waveform freeze mode.

[0133] It should be noted that the preset waveform change prediction model is trained from historical received waveform signals obtained during the historical detection process. The preset waveform change prediction model can predict the waveform change of the received waveform signal in the future based on the waveform change of the received waveform signal in a certain period of time.

[0134] The first valid received wave signal is the first received wave signal obtained after exiting waveform freeze mode.

[0135] The predicted received wave signal in waveform freeze mode is predicted by a preset waveform change prediction model, and there may be some fluctuation deviation between it and the actual received wave signal under noise-free conditions. Similarly, the received wave signal may also be subject to some noise interference for a period of time after exiting waveform freeze mode. Different waveform correction schemes are used to correct the waveform of the predicted received wave signal corresponding to the predicted waveform change curve and the effective received wave signal after exiting waveform freeze mode, thereby eliminating waveform deviation.

[0136] According to an embodiment of the present invention, the method for correcting the waveform of the valid received waveform signal after exiting the waveform freeze mode based on the waveform correction scheme is as follows:

[0137] The first adjustment weight k of the first valid received wave signal is determined based on the signal-to-noise ratio of the first valid received wave signal. a(t) ;

[0138] The adjustment time interval is determined based on the waveform matching degree of the first valid received wave signal;

[0139] Based on the adjustment time interval and the first adjustment weight k of the first valid received wave signal a(t) The first adjustment weight of the subsequent effective received wave signal is set, and the first adjustment weight k of the effective received wave signal at the detection time t+m is determined. a(t+m) ;

[0140] Based on the detection time T, the first adjustment weight k of the effectively received wave signal is used. a(T) The second adjustment weight k is determined for the predicted received wave signal corresponding to the detection time. b(T) ;k b(T) =1-k a(T) ;

[0141] Based on the detection time T, the signal peak value of the effective received wave signal and the corresponding predicted received wave signal are weighted and calculated to determine the corrected signal peak value of the effective received wave signal.

[0142] The waveform of the effective received wave signal is updated based on the corrected signal peak value.

[0143] It should be noted that the first adjustment weight k of the first valid received waveform signal after exiting waveform freeze mode is... a(t) The system determines the first adjustment weight k based on the signal-to-noise ratio (SNR) of the first valid received signal. The higher the SNR, the higher the corresponding adjustment weight k. a(t) The higher the value, the better. For example, when SNR = 15dB, k... a(t) =0.5; when SNR=10dB, k a(t) =0.3. The waveform matching degree is obtained by comparing the waveform of the first valid received wave signal with the system's preset reference waveform. The system determines the adjustment time interval based on the waveform matching degree of the first valid received wave signal; the higher the waveform matching degree, the smaller the corresponding adjustment time interval. For example, when the waveform matching degree is greater than 80%, the preset time interval is 2ms; when the waveform matching degree is between 60% and 80%, the preset time interval is 3ms. The adjustment weight k is based on the adjustment time interval and the first valid received wave signal. a(t) The system adjusts the weight per unit time interval based on the signal-to-noise ratio and waveform matching degree of the first valid received wave signal (e.g., increasing the first adjustment weight by 0.1 for each preset time interval) to set the first adjustment weight for subsequent valid received wave signals after exiting the waveform freeze mode. The detection time t+m is the m-th detection time after the detection time t corresponding to the first valid received wave signal after exiting the waveform freeze mode. For example, if there are x preset time intervals between detection time t+1 and detection time t, then the first adjustment weight k for the valid received wave signal at detection time t+1 is... a( t+1 ) =k a(t) +x×e, where e is the weight adjustment magnitude per unit time interval.

[0144] The detection time T includes the detection time t corresponding to the first valid received wave signal and the detection time t+m corresponding to subsequent valid received wave signals. The peak value of the valid received wave signal after correction is calculated, and the waveform of the valid received wave signal is updated using this corrected peak value, thus completing the waveform correction of the valid received wave signal.

[0145] The specific method for calculating the peak value of the effectively received wave signal after correction is as follows:

[0146] ;

[0147] Among them, VT A(T) VT is the peak value of the effective received wave signal corresponding to the detection time T. a(T) To detect the peak value of the effective received wave signal corresponding to the detection time T, VT b(T) For the detection time T, corresponding to the predicted peak value of the received wave signal, k a(T) k is the first adjustment weight for the effective received wave signal corresponding to the detection time T. b(T) The second adjustment weight is the predicted received wave signal corresponding to the detection time T.

[0148] In addition, when the first adjustment weight of the effective received wave signal corresponding to a certain detection time is calculated to be greater than or equal to 1, the first adjustment weight of the effective received wave signal corresponding to that detection time is set to 1, and the calculation of the first adjustment weight of the effective received wave signal corresponding to subsequent detection times is cancelled. Subsequent detection times are all calculated based on the received wave signal actually detected.

[0149] According to an embodiment of the present invention, the method for waveform correction of the predicted received wave signal corresponding to the predicted waveform change curve based on the waveform correction scheme is as follows:

[0150] The third adjustment weight k of the first predicted received wave signal during the waveform freeze mode duration is applied. c(1) Set to 1;

[0151] The third adjustment weight k of the last predicted received wave signal during the waveform freeze mode duration is applied. c(n) Set to 1-k a(t) ;

[0152] Based on the third adjustment weight of the first predicted received wave signal and the third adjustment weight of the last predicted received wave signal within the duration of the waveform freeze mode, the third adjustment weight of other predicted received wave signals within the duration of the waveform freeze mode is determined by linear interpolation.

[0153] The peak value of each predicted received wave signal is weighted and calculated with the peak value of the first valid received wave signal to determine the corrected peak value of the predicted received wave signal during the duration of the waveform freeze mode.

[0154] The waveform of the predicted received wave signal is updated based on the corrected signal peak value.

[0155] It should be noted that the specific method for calculating the peak value of the predicted received wave signal after correction is as follows:

[0156] ;

[0157] Among them, VT A(j) VT represents the peak value of the j-th predicted received waveform signal after correction within the duration of the waveform freeze mode. a(j) VT represents the peak value of the j-th predicted received waveform signal within the duration of the waveform freeze mode. a(t) k is the peak value of the first valid received waveform signal after exiting waveform freeze mode. c(j) The third adjustment weight is the one corresponding to the j-th predicted received wave signal.

[0158] All information (including but not limited to user equipment information, user personal information, etc.), data (including but not limited to data used for analysis, stored data, displayed data, etc.), and signals (including but not limited to signals transmitted between user terminals and other devices) involved in this application have been authorized by the user or fully authorized by all parties, and the collection, use, and processing of related data must comply with the relevant laws, regulations, and standards of the relevant countries and regions. For example, the "received wave signals" and "historical received wave signals" mentioned in this disclosure were obtained under full authorization.

[0159] This invention discloses an automatic adjustment method for the trigger wave of an ultrasonic flow meter and a gas meter, the method comprising: obtaining the trigger voltage threshold Vth i Set the lower limit of signal-to-noise ratio (SNRmin) i Acquire the received wave signal and perform gain processing to determine the amplitude of the processed received wave signal; calculate the signal-to-noise ratio (SNR) based on the amplitude of the processed received wave signal and the noise amplitude; compare the SNR with the lower limit of the SNR, SNRmin. iA comparison is performed to determine the final trigger voltage threshold. When SNR < SNRmin3, detection is stopped and restarted based on a preset interval time threshold. When the amplitude of the processed received wave signal is higher than the final trigger voltage threshold, a square wave signal is output. During the output of the square wave signal, the received wave signal is continuously acquired and gain processing is performed, and the gain value used for gain processing is recalculated. This invention can improve the anti-interference performance of ultrasonic flow meters, enabling them to operate normally in more complex measurement situations and ensuring accurate measurement.

[0160] In the several embodiments provided in this application, it should be understood that the disclosed devices and methods can be implemented in other ways. The device embodiments described above are merely illustrative. For example, the division of units is only a logical functional division, and in actual implementation, there may be other division methods, such as: multiple units or components can be combined, or integrated into another system, or some features can be ignored or not executed. In addition, the coupling, direct coupling, or communication connection between the various components shown or discussed can be through some interfaces, and the indirect coupling or communication connection between devices or units can be electrical, mechanical, or other forms.

[0161] The units described above as separate components may or may not be physically separate. The components shown as units may or may not be physical units. They may be located in one place or distributed across multiple network units. Some or all of the units may be selected to achieve the purpose of this embodiment according to actual needs.

[0162] In addition, in the various embodiments of the present invention, each functional unit can be integrated into one processing unit, or each unit can be a separate unit, or two or more units can be integrated into one unit; the integrated unit can be implemented in hardware or in the form of hardware plus software functional units.

[0163] Those skilled in the art will understand that all or part of the steps of the above method embodiments can be implemented by hardware related to program instructions. The aforementioned program can be stored in a computer-readable storage medium. When the program is executed, it performs the steps of the above method embodiments. The aforementioned storage medium includes various media capable of storing program code, such as mobile storage devices, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0164] Alternatively, if the integrated units of this invention are implemented as software functional modules and sold or used as independent products, they can also be stored in a computer-readable storage medium. Based on this understanding, the technical solutions of the embodiments of this invention, or the parts that contribute to the prior art, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the methods of the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as mobile storage devices, ROM, RAM, magnetic disks, or optical disks.

Claims

1. An automatic adjustment method for the trigger wave of an ultrasonic flow meter and a gas meter, characterized in that, include: Obtain the system's pre-set trigger voltage threshold Vth i The trigger voltage thresholds include the first-wave trigger voltage threshold Vth1, the second-wave trigger voltage threshold Vth2, and the third-wave trigger voltage threshold Vth3. Based on the trigger voltage threshold Vth i Set the lower limit of signal-to-noise ratio (SNRmin) i The lower limit of signal-to-noise ratio includes the lower limit of signal-to-noise ratio for the first-wave triggered detection (SNRmin1), the lower limit of signal-to-noise ratio for the second-wave triggered detection (SNRmin2), and the lower limit of signal-to-noise ratio for the third-wave detected (SNRmin3). Acquire the received wave signal; The received wave signal is subjected to gain processing to determine the amplitude of the processed received wave signal; The signal-to-noise ratio (SNR) is calculated based on the amplitude of the processed received wave signal and the noise amplitude. The signal-to-noise ratio (SNR) is compared with the lower limit of the signal-to-noise ratio (SNRmin). i By comparing the results, the final trigger voltage threshold can be determined. When SNR < SNRmin3, stop detection and restart detection based on a preset interval time threshold; The processed received wave signal is compared with the final trigger voltage threshold. When the amplitude of the processed received wave signal is higher than the final trigger voltage threshold, a square wave signal is output. During the output of the square wave signal, the received wave signal is continuously acquired and the gain is processed. When the amplitude of the processed received wave signal is not within the preset target amplitude range, the gain value used for gain processing is recalculated.

2. The automatic adjustment method for the trigger wave of an ultrasonic flow meter and gas meter according to claim 1, characterized in that, The trigger voltage threshold Vth i Set the lower limit of signal-to-noise ratio (SNRmin) i The specific method is as follows: ； ； Where i represents the i-th wave trigger, S represents the amplitude of the processed received wave signal, and N i Vth represents the noise amplitude triggered by the i-th wave. i ΔV is the trigger voltage threshold for the i-th wave, and ΔV is the preset voltage adjustment parameter.

3. The automatic adjustment method for the trigger wave of an ultrasonic flow meter and gas meter according to claim 1, characterized in that, The step of performing gain processing on the received wave signal and determining the processed received wave signal includes: The received wave signal is subjected to gain processing based on the initial gain value or the gain value of the previous detection. Determine whether the amplitude of the processed received wave signal is within the preset target amplitude range; If so, output the amplitude of the processed received wave signal; If not, the gain value is recalculated, and the received wave signal is processed again based on the recalculated gain value to obtain the amplitude of the processed received wave signal.

4. The automatic adjustment method for the trigger wave of an ultrasonic flow meter and gas meter according to claim 1, characterized in that, The signal-to-noise ratio (SNR) is compared with the lower limit of the signal-to-noise ratio (SNRmin). i The comparison was performed to determine the final trigger voltage threshold, including: When SNR > SNRmin1, the initial trigger voltage threshold Vth1 is determined as the final trigger voltage threshold. When SNRmin2≤SNR<SNRmin1, the second wave trigger voltage threshold Vth2 is determined as the final trigger voltage threshold. When SNRmin3≤SNR<SNRmin2, the third wave trigger voltage threshold Vth3 is determined as the final trigger voltage threshold.

5. The automatic adjustment method for the trigger wave of an ultrasonic flow meter and gas meter according to claim 1, characterized in that, Also includes: When SNR < SNRmin3, stop detection and record the cumulative stop time; When the cumulative stop time exceeds the preset interval time threshold, the detection is restarted.

6. The automatic adjustment method for the trigger wave of an ultrasonic flow meter and gas meter according to claim 1, characterized in that, Also includes: When the final trigger voltage threshold is the second wave trigger voltage threshold Vth2 or the third wave trigger voltage threshold Vth3, the forward and reverse acoustic wave transmission time corresponding to the square wave signal is corrected.

7. The automatic adjustment method for the trigger wave of an ultrasonic flow meter and gas meter according to claim 1, characterized in that, Also includes: When SNR < SNRmin3, the maximum peak-to-peak change rate within the first preset time interval is calculated based on the historical received wave signals within the first preset time interval. When the maximum peak-to-peak change rate within the first preset time interval is greater than the preset change rate threshold, the waveform freeze mode is entered. Record the duration of the freeze mode based on the start time of the waveform freeze mode, and continue to acquire the received waveform signal; The peak-to-peak change rate of the first wave is calculated based on the received wave signal within the second preset time interval. When the rate of change of the first peak value is within the preset rate of change threshold range, the waveform freeze model termination condition is met, and the waveform freeze mode is exited. If the waveform freeze model termination condition is still not met after the duration of the freeze mode exceeds a preset time threshold, then the detection will stop.

8. The automatic adjustment method for the trigger wave of an ultrasonic flow meter and gas meter according to claim 7, characterized in that, Also includes: When entering waveform freeze mode, the historical received waveform signal within the first preset time interval is input into the preset waveform change prediction model, and the predicted waveform change curve is output; the predicted waveform change curve includes the first predicted waveform change curve corresponding to the duration of waveform freeze mode and the second predicted waveform change curve after exiting waveform freeze mode. After exiting waveform freeze mode, the waveform correction scheme is determined based on the signal-to-noise ratio and waveform matching degree of the first valid received waveform signal. Based on the waveform correction scheme, waveform correction is performed on the predicted received wave signal corresponding to the predicted waveform change curve and the effective received wave signal after exiting the waveform freeze mode.

9. The automatic adjustment method for the trigger wave of an ultrasonic flow meter and gas meter according to claim 8, characterized in that, The specific method for correcting the waveform of the valid received wave signal after exiting the waveform freeze mode based on the waveform correction scheme is as follows: The first adjustment weight k of the first effective received wave signal is determined based on the signal-to-noise ratio of the first effective received wave signal. a(t) ; The adjustment time interval is determined based on the waveform matching degree of the first valid received wave signal; Based on the adjustment time interval and the first adjustment weight k of the first valid received wave signal a(t) The first adjustment weight of the subsequent effective received wave signal is set, and the first adjustment weight k of the effective received wave signal at the detection time t+m is determined. a(t+m) ; Based on the detection time T, the first adjustment weight k of the effectively received wave signal is used. a(T) The second adjustment weight k is determined for the predicted received wave signal corresponding to the detection time. b(T) ;k b(T) =1-k a(T) ; Based on the detection time T, the signal peak value of the effective received wave signal and the corresponding predicted received wave signal are weighted and calculated to determine the corrected signal peak value of the effective received wave signal. The waveform of the effective received wave signal is updated based on the corrected signal peak value.

10. The automatic adjustment method for the trigger wave of an ultrasonic flow meter and gas meter according to claim 8, characterized in that, The specific method for correcting the waveform of the predicted received wave signal corresponding to the predicted waveform change curve based on the waveform correction scheme is as follows: The third adjustment weight k of the first predicted received wave signal during the waveform freeze mode duration is applied. c(1) Set to 1; The third adjustment weight k of the last predicted received wave signal during the waveform freeze mode duration is applied. c(n) Set to 1-k a(t) ; Based on the third adjustment weight of the first predicted received wave signal and the third adjustment weight of the last predicted received wave signal within the duration of the waveform freeze mode, the third adjustment weight of other predicted received wave signals within the duration of the waveform freeze mode is determined by linear interpolation. The peak value of each predicted received wave signal is weighted and calculated with the peak value of the first valid received wave signal to determine the corrected peak value of the predicted received wave signal during the duration of the waveform freeze mode. The waveform of the predicted received wave signal is updated based on the corrected signal peak value.

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