Head wave threshold voltage setting method for ultrasonic flow metering device

Abstract

The invention discloses a head wave threshold voltage setting method for an ultrasonic flow metering device, which relates to the field of ultrasonic flow metering devices, and comprises the following steps: setting a threshold voltage range and an initial value of a variable threshold comparator, transmitting an ultrasonic signal with a specific frequency, and starting a receiving circuit to detect an echo signal. When the amplitude of the echo signal exceeds a set threshold value, the time of flight TOF is measured through a zero-crossing comparator and a time measurement circuit TDC. And traversing all threshold settings to obtain a relationship between different TOF values and thresholds, calculating threshold differences, finding out an upper threshold limit and a lower threshold limit corresponding to the maximum threshold difference, and finally calculating an optimal head wave threshold. The method can effectively avoid the wrong wave phenomenon caused by signal fluctuation, improves the accuracy and stability of ultrasonic flow metering, and is suitable for liquid or gas flow metering and billing devices.

Description

Technical Field

[0001] The invention relates to the field of ultrasonic flow metering devices, and in particular to a method for setting a first-wave threshold voltage for ultrasonic flow metering devices. Background Art

[0002] Ultrasonic flow measurement technology has been widely used in the flow measurement market due to its advantages such as high measurement accuracy, large range ratio, wide measurement range, no pressure field loss and non-contact measurement. At present, the most commonly used ultrasonic flow measurement technologies are mainly time difference method and cross-correlation method. The time difference method mainly measures the time difference of ultrasonic wave propagation in the fluid in the forward and reverse flow. When the flow component of the fluid and the propagation direction of the ultrasonic signal are the same, the ultrasonic wave propagation speed is increased, and the time for the transducer to receive the ultrasonic signal is shortened (called forward flow); when the flow component of the fluid and the propagation direction of the ultrasonic signal are opposite, the ultrasonic wave propagation speed is reduced, and the time for the transducer to receive the ultrasonic signal is extended (called reverse flow). By measuring the forward and reverse flow flight time and the flight time difference, the flow velocity of the fluid can be inferred, and then the flow rate can be calculated. The cross-correlation rule is based on the correlation between the two signals, and the correlation function is used to estimate the delay of the received signal, thereby realizing flow measurement. In specific cases, the delay data can be obtained by performing correlation operations between the forward and reverse flow signals, or between the forward and reverse flow signals and the static reference wave.

[0003] However, the existing ultrasonic flow metering technology still has some shortcomings in practical applications. The traditional first wave detection method usually uses a fixed threshold voltage, which is easily affected by factors such as temperature changes, transducer aging / contamination, fluid pressure field changes, and fluid flow rate changes. The "wave jump" phenomenon often occurs, that is, the obtained stop timing mark signal is offset forward or backward by one or more cycles. When the wave jump phenomenon occurs, for the fixed first wave threshold, the second receiving wave detects the arrival of the ultrasonic wave one cycle later than the first receiving wave, resulting in errors in the calculation of the propagation time, affecting the accuracy and stability of the flow measurement. In addition, the amplitude of the ultrasonic echo signal is easily affected by factors such as gas composition, temperature, and flow rate and fluctuates. The traditional fixed threshold detection method is difficult to adapt to this amplitude change and is prone to wrong wave phenomena, further reducing the accuracy and reliability of flow measurement. Summary of the invention

[0004] In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a method for setting a first-wave threshold voltage for an ultrasonic flow metering device, so as to solve one or more problems in the prior art.

[0005] To achieve the above object, the technical solution of the present invention is as follows: A method for setting a first wave threshold voltage for an ultrasonic flow metering device comprises the following steps: Step 1: setting a threshold voltage range and an initial value of a variable threshold comparator, wherein the initial value may be a minimum value or a maximum value within the threshold range.

[0006] Step 2: Transmit an ultrasonic signal of a specific frequency.

[0007] Step 3: Start the receiving circuit to detect the echo signal.

[0008] Step 4: When the amplitude of the echo signal exceeds the set threshold of the variable threshold comparator, the zero-crossing point of the echo signal is detected by the zero-crossing comparator, and the time measurement circuit TDC measures the flight time TOF from the transmission start time to the rising zero-crossing point time.

[0009] Step 5, determine whether all threshold settings are completed. If not, automatically adjust the threshold settings and repeat steps 2 to 4 until all threshold ranges are traversed.

[0010] Step 6: After completing all the setting values ​​within the threshold range and the corresponding TOF measurements, automatically process the data to obtain the relationship between different TOF values ​​and thresholds, and calculate the threshold difference.

[0011] Step 7: Obtain the upper threshold Fa and the lower threshold Fb corresponding to the maximum threshold difference.

[0012] Step 8, calculate the optimal first wave threshold as (Fa+Fb) / 2, and complete the first wave detection threshold setting, so as to realize automatic search for the first wave threshold.

[0013] In the above technical solution, through the automated threshold voltage setting method, the technical solution can ensure that the ultrasonic flow metering device can accurately detect the first wave signal under different operating conditions. The method of automatically traversing all threshold ranges and calculating the optimal first wave threshold improves the accuracy and stability of flow metering and reduces the measurement error caused by improper threshold setting. Especially in the case of changes in fluid properties or system aging, the advantages of this automated method are more obvious.

[0014] Specifically, the number of threshold levels of the variable threshold comparator is 64, 128, 256, 512 or 1024.

[0015] In the above technical solution, the selection of multiple threshold levels enables the ultrasonic flow metering device to adapt to echo signals with different amplitude ranges, thereby improving the flexibility and adaptability of the system. This design enables the device to adjust the threshold more finely to adapt to different measurement environments and requirements, thereby improving the accuracy of flow metering.

[0016] Specifically, the threshold of the zero-crossing comparator is fixed, and when the amplified echo signal crosses the zero point, the zero-crossing comparator outputs a flip signal.

[0017] In the above technical solution, the zero-crossing comparator with a fixed threshold can stably detect the zero-crossing point of the echo signal, reducing misjudgment caused by threshold fluctuations. This fixed threshold design simplifies the design complexity of the system and improves the consistency and reliability of signal detection.

[0018] Specifically, the time measurement circuit TDC starts timing with the start of ultrasonic transmission as the starting point, ends timing at the next echo zero crossing point after the variable threshold comparator outputs an echo detection indication signal, and outputs the measured flight time TOF.

[0019] In the above technical solution, the high-precision timing function of the time measurement circuit TDC ensures the accurate measurement of the time of flight TOF, which is essential for calculating the flow velocity and flow rate of the fluid. Accurate TOF value is the cornerstone of improving the flow measurement accuracy and directly affects the measurement results of the flow meter.

[0020] Specifically, the step of automatically processing data includes: The TOF values ​​under different threshold settings are compared and analyzed with the corresponding thresholds, and the relationship curve between the TOF value and the threshold is drawn to intuitively display the change of flight time under different thresholds, providing a basis for determining the optimal first wave threshold.

[0021] In the above technical solution, by comparing and analyzing the TOF values ​​under different threshold settings and drawing a relationship curve, the technical solution provides an intuitive method to observe and analyze the relationship between the threshold and the TOF value. This intuitive display helps to understand the method and then correctly design and implement the software.

[0022] Specifically, the process of automatically finding the first wave threshold also includes: After traversing all threshold ranges, the measured data is filtered to remove abnormal data to improve the accuracy and reliability of the data, thereby ensuring the accuracy of the optimal first-wave threshold finally calculated.

[0023] The filtering process adopts one or more of low-pass filtering and median filtering.

[0024] In the above technical solution, filtering is introduced in the process of automatically finding the first wave threshold, which effectively eliminates abnormal data and noise interference. This data preprocessing step improves the quality of the measured data, ensures the accuracy and reliability of the optimal first wave threshold finally calculated, and thus improves the overall performance of flow measurement.

[0025] Specifically, the ultrasonic flow metering device includes a transmitting circuit, an ultrasonic transducer, an echo amplifier, a variable threshold comparator, a zero-crossing comparator and a flight time measurement circuit.

[0026] The transmitting circuit controls the transmission of an ultrasonic signal of a specific frequency, the ultrasonic transducer realizes the transmission and reception of ultrasonic waves in the downstream and upstream directions, the echo amplifier amplifies the received echo signal to a specific amplitude range, the variable threshold comparator compares the amplified echo signal with the set threshold, the zero-crossing comparator detects the zero-crossing point of the echo signal, and the flight time measurement circuit measures the flight time from the start of the transmission to the next echo zero-crossing point.

[0027] In the above technical solution, the components of the ultrasonic flow metering device and their collaborative working methods are described in detail. This design enables the device to accurately transmit and receive ultrasonic signals and accurately measure flight time. The precise coordination of each component not only improves the accuracy of flow measurement, but also enhances the stability and durability of the device.

[0028] Specifically, the method is applicable to liquid flow metering devices and gas flow metering devices, such as ultrasonic water meters or flow meters, ultrasonic gas meters or flow meters, ventilator oxygen flow metering devices, carbon emission flow metering devices, etc.

[0029] In the above technical solution, the technical solution is applicable to various types of flow metering devices, showing the wide applicability and flexibility of the method. This versatility enables the technical solution to be applied to different industrial and commercial environments, improving its market competitiveness and practical value.

[0030] Specifically, the verification steps for the optimal first wave threshold of (Fa+Fb) / 2 are as follows: In the process of adjusting from the minimum threshold Fmin to the maximum threshold Fmax, the relationship between the measured TOF value and the comparator threshold is as follows: the ultrasonic wave signal period is marked as t, and the flight time of the second echo zero crossing point is marked as T2. The threshold varies between F1 and F2, and the measured TOF value is T2. The threshold varies between F2 and F3, and the measured TOF value is T2+t. The threshold varies between F3 and F4, and the measured TOF value is T2+2t, and so on.

[0031] Calculate the threshold differences of F2-F1, F3-F2, F4-F3, ..., find the upper and lower limits Fa and Fb of the threshold setting corresponding to the maximum threshold difference, and get the optimal first wave threshold as (Fa+Fb) / 2.

[0032] In the above technical solution, through detailed verification steps, the technical solution provides a scientific method to verify the accuracy of the optimal first wave threshold. This method based on signal propagation theory and measurement error analysis ensures the scientificity and accuracy of the optimal first wave threshold, thereby improving the reliability and accuracy of flow measurement.

[0033] Compared with the prior art, the beneficial technical effects of the present invention are as follows: (I) By setting a variable threshold comparator, emitting an ultrasonic signal of a specific frequency, starting the receiving circuit, and using a zero-crossing comparator and a time measurement circuit (TDC) to accurately measure the time of flight (TOF), combined with a method of automatically processing data and traversing all threshold ranges, this scheme can automatically determine the optimal first-wave threshold, thereby significantly improving the measurement accuracy and stability of the ultrasonic flow metering device, effectively avoiding the wrong wave phenomenon caused by improper manual setting of the threshold, and ensuring that reliable flow measurement results can be obtained in a changing fluid environment.

[0034] (II) By combining the multi-position design of the variable threshold comparator and the technical features of automatically adjusting the threshold setting, this solution can adapt to echo signals with different amplitude ranges and accurately control the threshold adjustment step, so that the ultrasonic flow metering device can achieve refined flow control and management under various fluid conditions. This design not only enhances the adaptability and flexibility of the system, but also improves the accuracy of flow metering, especially in situations where the fluid characteristics vary greatly, and can maintain the consistency and reliability of the measurement results.

[0035] (iii) By utilizing the technical combination of a fixed-threshold zero-crossing comparator and a high-precision time measurement circuit TDC, this solution ensures the accurate detection of the zero-crossing point of the echo signal and the precise measurement of the flight time, which is crucial to improving the accuracy of flow measurement.

[0036] (IV) In the process of automatically finding the first-wave threshold, it is possible to effectively eliminate abnormal data and noise interference, and verify the accuracy of the optimal first-wave threshold. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 The present invention is a logic flow chart of a method for setting a first wave threshold voltage of an ultrasonic flow metering device.

[0038] Figure 2 It is a waveform diagram in an exemplary description of the present invention.

[0039] Figure 3 is a circuit logic diagram in an exemplary description of the present invention. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical scheme and advantages of the present invention more clear, the present invention is further described in detail below in conjunction with the accompanying drawings and exemplary descriptions. It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the limiting conditions for the implementation of the present invention, so they have no technical substantive significance. Any structural modification, change in proportional relationship or adjustment of size, without affecting the effects and purposes that can be achieved by the present invention, should still fall within the scope of the technical content disclosed by the present invention.

[0041] Application Overview Traditional processing methods usually rely on fixed threshold detection, that is, setting a predefined threshold voltage to identify the first wave in the echo signal. This method is simple and easy to implement, but its obvious disadvantage is that it cannot adapt to changes in fluid characteristics, such as changes in fluid temperature, pressure, flow rate, and aging or contamination of the transducer, which will directly affect the amplitude and stability of the echo signal.

[0042] The main drawback of the fixed threshold method is its lack of flexibility and adaptability. When the fluid conditions change, the fixed threshold may not accurately capture the first wave signal, resulting in measurement errors or false waves. In addition, the fixed threshold cannot distinguish between the noise in the signal and the real first wave, which is particularly evident in environments with high noise levels or poor signal quality. Therefore, the performance and reliability of this method are limited in dynamically changing industrial environments, especially in applications that require high accuracy and high stability.

[0043] Example Please refer to Figure 1 , Figure 2 The ultrasonic flow metering device described in the present invention includes a transmitting circuit, an ultrasonic transducer, an echo amplifier, a variable threshold comparator, a zero-crossing comparator and a flight time measurement circuit TDC. The transmitting circuit is used to transmit ultrasonic signals of a specific frequency, which propagate in the fluid and generate echo signals. The echo signal is received by the ultrasonic transducer and amplified by the echo amplifier to a specific amplitude range to meet the requirements of subsequent signal processing.

[0044] Before starting the measurement, it is necessary to set an initial threshold voltage for the variable threshold comparator, which can be the minimum or maximum value of the threshold voltage range. This step provides a starting point for the subsequent threshold scanning process. The number of threshold levels of the variable threshold comparator is designed according to the amplitude of the echo signal and the required accuracy, and can be 64, 128, 256, 512 or 1024 to accommodate echo signals with different amplitude ranges.

[0045] When the amplitude of the echo signal exceeds the set threshold of the variable threshold comparator, the zero-crossing comparator detects the rising zero-crossing point of the echo signal. The time measurement circuit (TDC) starts timing from the start of the transmission, and ends timing at the next echo zero-crossing point after the variable threshold comparator outputs the echo detection indication signal, and outputs the measured time of flight (TOF).

[0046] In order to find the optimal first wave threshold, the system automatically adjusts the threshold setting and repeats the transmission and reception process until all threshold ranges are traversed. After completing the set values ​​and corresponding TOF measurements within all threshold ranges, the system automatically processes the data, obtains the relationship between different TOF values ​​and thresholds, and calculates the threshold difference. By finding the upper threshold Fa and lower threshold Fb corresponding to the maximum threshold difference, the system calculates the optimal first wave threshold as (Fa+Fb) / 2 and completes the first wave detection threshold setting.

[0047] The specific steps include: in the process of adjusting from the minimum threshold Fmin to the maximum threshold Fmax, the relationship between the measured TOF value and the comparator threshold is measured, the ultrasonic wave signal period is marked as t, and the flight time of the second echo zero crossing point is marked as T2, then the threshold changes between F1 and F2, and the measured TOF value is T2; the threshold changes between F2 and F3, and the measured TOF value is T2+t; the threshold changes between F3 and F4, and the measured TOF value is T2+2t, ...; Calculate the threshold differences of F2-F1, F3-F2, F4-F3, ..., find the upper and lower limits Fa and Fb of the threshold setting corresponding to the maximum threshold difference, and get the optimal first wave threshold as (Fa+Fb) / 2.

[0048] After traversing all threshold ranges, the measured data is filtered to remove abnormal data to improve the accuracy and reliability of the data. The filtering process can be done by low-pass filtering, median filtering and other methods, and the specific parameters are set according to the signal characteristics and noise level.

[0049] Finally, this method is applicable to various types of liquid flow metering devices and gas flow metering devices, such as ultrasonic water meter or flow meter, ultrasonic gas meter or flow meter, ventilator oxygen flow metering device, carbon emission flow metering device, etc.

[0050] Specific working process Please refer to Figure 3 , to understand the workflow.

[0051] Sets the threshold voltage range and initial value of the variable threshold comparator. The initial value is the minimum or maximum value in the range.

[0052] Transmits ultrasonic signals of a specific frequency.

[0053] Start the receiving circuit to detect the echo signal.

[0054] When the amplitude of the echo signal exceeds the threshold set by the variable threshold comparator, the zero-crossing comparator detects the rising zero-crossing point of the echo signal, and the time measurement circuit TDC measures the flight time TOF from the transmission start time to the rising zero-crossing point time.

[0055] It is determined whether all threshold settings are completed. If not, the threshold settings are automatically adjusted and the transmission and reception processes are repeated until all threshold ranges are traversed.

[0056] After completing the setting values ​​and corresponding TOF measurements within all threshold ranges, the data is automatically processed to obtain the relationship between different TOF values ​​and thresholds, and the threshold difference is calculated.

[0057] Find the upper threshold Fa and lower threshold Fb corresponding to the maximum threshold difference, calculate the optimal first wave threshold as (Fa+Fb) / 2, and complete the first wave detection threshold setting.

[0058] In this process, the number of threshold levels is designed to be 64, 128, 256, 512 or 1024 according to the amplitude of the echo signal and the required accuracy to adapt to echo signals with different amplitude ranges; the fixed threshold of the zero-crossing comparator ensures the accurate detection of the zero-crossing point of the echo signal; the TDC starts timing with the start of ultrasonic transmission as the time starting point, and ends timing at the next echo zero-crossing point after the variable threshold comparator outputs the echo detection indication signal, and outputs the measured TOF; after traversing all threshold ranges, the measured data is filtered to eliminate abnormal data to improve the accuracy and reliability of the data and ensure the accuracy of the optimal first-wave threshold finally calculated.

[0059] The various technical features described in the above exemplary embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the various technical features in the above exemplary embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

Claims

1. A method for setting the first wave threshold voltage of an ultrasonic flow metering device, characterized in that: The following steps are involved: Step 1, setting a threshold voltage range and an initial value of a variable threshold comparator, wherein the initial value may be a minimum value or a maximum value within the threshold range; Step 2, emitting an ultrasonic signal of a specific frequency; Step 3, start the receiving circuit to detect the echo signal; Step 4, when the amplitude of the echo signal exceeds the set threshold of the variable threshold comparator, the rising zero crossing point of the echo signal is detected by the zero crossing comparator, and the flight time TOF from the transmission start time to the rising zero crossing point is measured by the time measurement circuit TDC; Step 5, determine whether all threshold settings are completed. If not, automatically adjust the threshold settings and repeat steps 2 to 4 until all threshold ranges are traversed; Step 6, after completing all the set values ​​within the threshold range and the corresponding TOF measurements, automatically process the data to obtain the relationship between different TOF values ​​and thresholds, and calculate the threshold difference; Step 7, obtaining the upper threshold Fa and the lower threshold Fb corresponding to the maximum threshold difference; Step 8, calculate the optimal first wave threshold as (Fa+Fb) / 2, and complete the first wave detection threshold setting, so as to realize automatic search for the first wave threshold.

2. A method for setting the first wave threshold voltage for an ultrasonic flow metering device as claimed in claim 1, characterized in that: The variable threshold comparator has a threshold level number of 64, 128, 256, 512 or 1024.

3. A method for setting the first wave threshold voltage for an ultrasonic flow metering device as claimed in claim 1, characterized in that: The threshold of the zero-crossing comparator is fixed, and when the amplified echo signal crosses the zero point, the zero-crossing comparator outputs a flip signal.

4. A method for setting the first wave threshold voltage for an ultrasonic flow metering device as claimed in claim 1, characterized in that: The time measurement circuit TDC starts timing with the start of ultrasonic transmission as the time starting point, ends timing at the next echo zero crossing point after the variable threshold comparator outputs the echo detection indication signal, and outputs the measured flight time TOF.

5. A method for setting the first wave threshold voltage for an ultrasonic flow metering device as claimed in claim 1, characterized in that: The steps of automatically processing data include: The TOF values ​​under different threshold settings are compared and analyzed with the corresponding thresholds, and the relationship curve between the TOF value and the threshold is drawn to intuitively display the change of flight time under different thresholds, providing a basis for determining the optimal first wave threshold.

6. A method for setting the first wave threshold voltage for an ultrasonic flow metering device as claimed in claim 1, characterized in that: The process of automatically finding the first wave threshold value also includes: After traversing all threshold ranges, the measured data is filtered to remove abnormal data to improve the accuracy and reliability of the data, thereby ensuring the accuracy of the optimal first wave threshold finally calculated; The filtering process adopts one or more of low-pass filtering and median filtering.

7. A method for setting the first wave threshold voltage for an ultrasonic flow metering device as claimed in claim 1, characterized in that: The ultrasonic flow metering device includes a transmitting circuit, an ultrasonic transducer, an echo amplifier, a variable threshold comparator, a zero-crossing comparator and a flight time measurement circuit; The transmitting circuit controls the transmission of an ultrasonic signal of a specific frequency, the ultrasonic transducer realizes the transmission and reception of ultrasonic waves in the downstream and upstream directions, the echo amplifier amplifies the received echo signal to a specific amplitude range, the variable threshold comparator compares the amplified echo signal with the set threshold, the zero-crossing comparator detects the zero-crossing point of the echo signal, and the flight time measurement circuit measures the flight time from the start of the transmission to the next echo zero-crossing point.

8. A method for setting the first wave threshold voltage for an ultrasonic flow metering device as claimed in claim 1, characterized in that: The method is applicable to liquid flow metering devices and gas flow metering devices, such as ultrasonic water meters or flow meters, ultrasonic gas meters or flow meters, ventilator oxygen flow metering devices, carbon emission flow metering devices, etc.

9. A method for setting the first wave threshold voltage for an ultrasonic flow metering device as claimed in claim 1, characterized in that: The verification steps for the optimal first wave threshold of (Fa+Fb) / 2 are: In the process of adjusting from the minimum threshold Fmin to the maximum threshold Fmax, the relationship between the measured TOF value and the comparator threshold is as follows: the ultrasonic wave signal period is marked as t, and the flight time of the second echo zero crossing point is marked as T2. The threshold changes between F1 and F2, and the measured TOF value is T2; the threshold changes between F2 and F3, and the measured TOF value is T2+t; the threshold changes between F3 and F4, and the measured TOF value is T2+2t, ...; Calculate the threshold differences of F2-F1, F3-F2, F4-F3, ..., find the upper and lower limits Fa and Fb of the threshold setting corresponding to the maximum threshold difference, and get the optimal first wave threshold as (Fa+Fb) / 2.

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