A method for setting the first wave threshold voltage of an ultrasonic flow measurement device

Abstract

The present invention discloses a method for setting the first wave threshold voltage of an ultrasonic flow metering device, which relates to the field of ultrasonic flow metering devices. The method sets the threshold voltage range and initial value of a variable threshold comparator, emits ultrasonic signals of a specific frequency, and starts the receiving circuit to detect echo signals. When the amplitude of the echo signal exceeds the set threshold, the time of flight (TOF) is measured by a zero-crossing comparator and a time measurement circuit (TDC). By traversing all threshold settings, the relationship between different TOF values and thresholds is obtained, the threshold difference is calculated, the upper and lower limits of the threshold corresponding to the maximum threshold difference are found, and finally the optimal first wave threshold is calculated. The present invention can effectively avoid the miswave phenomenon caused by signal fluctuations, improve the accuracy and stability of ultrasonic flow metering, and is applicable to liquid or gas flow metering and billing devices.

Description

Technical Field

[0001] The present invention relates to the field of ultrasonic flow measurement devices, and particularly to a method for setting the first-wave threshold voltage for an ultrasonic flow measurement device. 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. Currently, the most commonly used ultrasonic flow measurement technologies are mainly the time-difference method and the cross-correlation method. The time-difference method mainly measures the time difference between the forward and reverse propagation of ultrasonic waves in a fluid. When the flow component of the fluid is in the same direction as the ultrasonic signal propagation direction, the ultrasonic propagation speed is increased, and the time for the transducer to receive the ultrasonic signal is shortened (referred to as forward flow); when the flow component of the fluid is in the opposite direction to the ultrasonic signal propagation direction, the ultrasonic propagation speed is decreased, and the time for the transducer to receive the ultrasonic signal is extended (referred to as reverse flow). By measuring the forward and reverse flight times and the flight time difference, the flow velocity of the fluid can be deduced, and then the flow rate can be calculated. The cross-correlation method is based on the correlation between two signals, and uses the correlation function to estimate the time delay of the received signal, thereby realizing flow measurement. Specifically, in some cases, correlation operations can be performed between the forward and reverse signals, or between the forward and reverse signals and the static reference wave to obtain time delay data.

[0003] However, the existing ultrasonic flow measurement technologies still have some deficiencies in practical applications. Traditional first-wave detection methods usually use a fixed threshold voltage, which is easily affected by factors such as temperature change, transducer aging / contamination, fluid pressure field change, and fluid flow velocity change, and the phenomenon of "wave skipping" often occurs, that is, the obtained stop timing identification signal shifts forward or backward by one or more periods. When the wave skipping phenomenon occurs, for the fixed first-wave threshold, compared with the first received wave, the second received wave detects the arrival time of the ultrasonic wave one cycle later, resulting in an incorrect calculation of the propagation time and affecting the accuracy and stability of flow measurement. In addition, the amplitude of the ultrasonic echo signal is easily affected by factors such as gas composition, temperature, and flow velocity and fluctuates. The traditional fixed threshold detection method is difficult to adapt to this amplitude change, and the phenomenon of misdetection is likely to occur, further reducing the accuracy and reliability of flow measurement. Summary of the Invention

[0004] Aiming at the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a method for setting the first-wave threshold voltage for an ultrasonic flow measurement device to solve one or more problems in the prior art.

[0005] To achieve the above purpose, the technical solution of the present invention is as follows:

[0006] A method for setting the first-wave threshold voltage of an ultrasonic flow metering device, comprising the following steps:

[0007] Step 1, set the threshold voltage range and initial value of the variable threshold comparator, and the initial value can be the minimum or maximum value within the threshold range.

[0008] Step 2, transmit an ultrasonic signal with a specific frequency.

[0009] Step 3, start the receiving circuit to detect the echo signal.

[0010] Step 4, when the amplitude of the echo signal exceeds the set threshold of the variable threshold comparator, detect the rising zero-crossing point of the echo signal through a zero-crossing comparator, and measure the time of flight TOF from the transmission start moment to the rising zero-crossing point moment by the time measurement circuit TDC.

[0011] 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.

[0012] Step 6, after completing the set values and corresponding TOF measurements within all threshold ranges, automatically process the data to obtain the relationship between different TOF values and thresholds, and calculate the threshold difference.

[0013] Step 7, obtain the threshold upper limit Fa and threshold lower limit Fb corresponding to the maximum threshold difference.

[0014] Step 8, calculate the optimal first-wave threshold as (Fa + Fb) / 2, and complete the setting of the first-wave detection threshold, so as to realize the automatic search for the first-wave threshold.

[0015] In the above technical solution, through the automated threshold voltage setting method, this 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, reduces measurement errors caused by improper threshold settings, especially in the case of fluid property changes or system aging, the advantages of this automated method are more obvious.

[0016] Specifically, the number of threshold gears of the variable threshold comparator is 64, 128, 256, 512 or 1024.

[0017] In the above technical solution, the selection of various numbers of threshold gears 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, and improves the accuracy of flow metering.

[0018] Specifically, the threshold of the zero-crossing comparator is fixed. When the amplified echo signal crosses zero, the zero-crossing comparator outputs a flip signal.

[0019] 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 design with a fixed threshold simplifies the design complexity of the system while improving the consistency and reliability of signal detection.

[0020] Specifically, the time measurement circuit TDC takes the start of ultrasonic transmission as the time start point, starts timing, 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.

[0021] 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 crucial for calculating the flow velocity and flow rate of the fluid. The accurate TOF value is the cornerstone for improving the flow measurement accuracy and directly affects the measurement result of the flowmeter.

[0022] Specifically, the step of automatically processing data includes:

[0023] Compare and analyze the TOF values under different threshold settings with the corresponding thresholds, and draw the relationship curve between the TOF value and the threshold to visually display the change of the time of flight under different thresholds, providing a basis for determining the optimal first wave threshold.

[0024] In the above technical solution, by comparing and analyzing the TOF values under different threshold settings and drawing the relationship curve, this 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 thus correctly carry out software design and implementation.

[0025] Specifically, the process of automatically finding the first wave threshold further includes:

[0026] After traversing all threshold ranges, filter the measurement data to eliminate abnormal data, so as to improve the accuracy and reliability of the data, thereby ensuring the accuracy of the finally calculated optimal first wave threshold.

[0027] The filtering process uses one or more of low-pass filtering and median filtering.

[0028] In the above technical solution, introducing filtering processing in the process of automatically finding the first wave threshold effectively eliminates abnormal data and noise interference. This data preprocessing step improves the quality of the measurement data, ensures the accuracy and reliability of the finally calculated optimal first wave threshold, and thus improves the overall performance of flow measurement.

[0029] Specifically, the ultrasonic flow measurement device includes a transmitting circuit, an ultrasonic transducer, an echo amplifier, a variable threshold comparator, a zero-crossing comparator, and a time-of-flight measurement circuit.

[0030] Among them, the transmitting circuit controls the transmission of ultrasonic signals at a specific frequency. The ultrasonic transducer realizes the transmission and reception of ultrasonic waves in the forward and reverse flows. The echo amplifier amplifies the received echo signal to a specific amplitude range. The variable threshold comparator compares the amplified echo signal with a set threshold. The zero-crossing comparator detects the zero-crossing point of the echo signal. The time-of-flight measurement circuit measures the time of flight from the start of transmission to the next echo zero-crossing point.

[0031] In the above technical solution, the components of the ultrasonic flow measurement 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 the time of flight. The precise cooperation of each component not only improves the accuracy of flow measurement but also enhances the stability and durability of the device.

[0032] Specifically, the method is applicable to liquid flow measurement devices and gas flow measurement devices, such as ultrasonic water meters or flow meters, ultrasonic gas meters or flow meters, ventilator oxygen flow measurement devices, carbon emission flow measurement devices, etc.

[0033] In the above technical solution, this technical solution is applicable to various types of flow measurement devices, demonstrating the wide applicability and flexibility of the method. This versatility enables the technical solution to be applied to different industrial and commercial environments, enhancing its market competitiveness and practical value.

[0034] Specifically, the verification steps for the optimal first-wave threshold of (Fa + Fb) / 2 are as follows:

[0035] During the process of adjusting from the minimum threshold Fmin to the maximum threshold Fmax, there is a relationship between the measured TOF value and the comparator threshold. Mark the ultrasonic wave transmission signal period as t, and mark the time of flight of the second echo zero-crossing point as T2. Then, when the threshold varies between F1 and F2, the measured TOF value is T2. When the threshold varies between F2 and F3, the measured TOF value is T2 + t. When the threshold varies between F3 and F4, the measured TOF value is T2 + 2t, and so on.

[0036] Calculate the threshold differences of F2 - F1, F3 - F2, F4 - F3, etc., find the upper threshold setting limit Fa and the lower limit Fb corresponding to the maximum threshold difference, and obtain the optimal first-wave threshold of (Fa + Fb) / 2.

[0037] 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 precision of flow measurement.

[0038] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0039] (1) By setting a variable threshold comparator, transmitting ultrasonic signals of a specific frequency, starting the receiving circuit, accurately measuring the time of flight (TOF) using a zero-crossing comparator and a time measurement circuit (TDC), and combining the methods of automatically processing data and traversing all threshold ranges, this solution can automatically determine the optimal first-wave threshold, thereby significantly improving the measurement accuracy and stability of the ultrasonic flow measurement device, effectively avoiding the false wave phenomenon caused by improper manual threshold setting, and ensuring reliable flow measurement results in a changing fluid environment.

[0040] (2) By combining the multi-gear design of the variable threshold comparator and the technical feature of automatically adjusting the threshold setting, this solution can adapt to echo signals with different amplitude ranges and precisely control the adjustment step of the threshold, enabling the ultrasonic flow measurement device to 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 precision of flow measurement. Especially in occasions where the fluid characteristics change greatly, it can maintain the consistency and reliability of the measurement results.

[0041] (3) Using the technical combination of a zero-crossing comparator with a fixed threshold 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 time of flight, which is crucial for improving the accuracy of flow measurement.

[0042] (4) During the process of automatically searching for the first-wave threshold, abnormal data and noise interference can be effectively eliminated, and the accuracy of the optimal first-wave threshold can be verified. Description of the Drawings

[0043] Figure 1 is the logic flowchart of a method for setting the first-wave threshold voltage of an ultrasonic flow measurement device according to the present invention.

[0044] Figure 2 is the waveform schematic diagram in the exemplary description of the present invention.

[0045] Figure 3 is the circuit logic diagram in the exemplary description of the present invention. Detailed Embodiments

[0046] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with the accompanying drawings and exemplary illustrations. It should be noted that the structures, ratios, sizes, etc. shown in the drawings of this specification are only used to cooperate with the content disclosed in the specification for those who are familiar with this technology to understand and read, and are not used to limit the limiting conditions for the implementation of the present invention. Therefore, they do not have substantial technical significance. Any modification of the structure, change of the proportional relationship or adjustment of the size, without affecting the effects that the present invention can produce and the objectives that can be achieved, should still fall within the scope covered by the technical content disclosed in the present invention.

[0047] Application Overview

[0048] Traditional processing methods usually rely on a fixed-threshold detection method, that is, a predefined threshold voltage is set to identify the first wave in the echo signal. This method is simple and easy to implement, but its obvious drawback is that it cannot adapt to changes in fluid characteristics, such as changes in fluid temperature, pressure, flow rate, as well as factors such as transducer aging or contamination, which will directly affect the amplitude and stability of the echo signal.

[0049] The main defect of the fixed-threshold method lies in its lack of flexibility and adaptability. When the fluid conditions change, the fixed threshold may not be able to accurately capture the first-wave signal, resulting in measurement errors or false-wave phenomena. In addition, the fixed threshold cannot distinguish between noise and the true first wave in the signal, which is particularly obvious in an environment with a high noise level or poor signal quality. Therefore, the performance and reliability of this method are limited in a dynamically changing industrial environment, especially in application scenarios that require high precision and high stability.

[0050] Exemplary Illustration

[0051] Please refer to Figure 1 、 Figure 2 For an ultrasonic flow measurement device described in the present invention, the device includes a transmitting circuit, an ultrasonic transducer, an echo amplifier, a variable-threshold comparator, a zero-crossing comparator, and a time-of-flight measurement circuit TDC. The transmitting circuit is used to transmit ultrasonic signals of a specific frequency, and these signals propagate in the fluid and generate echo signals. The echo signals are received by the ultrasonic transducer and amplified by the echo amplifier to a specific amplitude range to meet the requirements of subsequent signal processing.

[0052] Before starting the measurement, an initial threshold voltage needs to be set for the variable-threshold comparator, and this initial value 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 size of the echo signal amplitude and the required precision, and can be 64, 128, 256, 512, or 1024 to adapt to echo signals in different amplitude ranges.

[0053] 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).

[0054] 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.

[0055] 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, ...;

[0056] 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.

[0057] 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.

[0058] 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.

[0059] Specific working process

[0060] Please refer to Figure 3 , to understand the workflow.

[0061] 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.

[0062] Transmit ultrasonic signals of a specific frequency.

[0063] Activate the receiving circuit to detect echo signals.

[0064] 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 time of flight TOF from the transmission start moment to the rising zero-crossing point moment.

[0065] Determine whether all threshold settings are completed. If not, automatically adjust the threshold settings and repeat the transmission and reception processes until all threshold ranges are traversed.

[0066] After completing the setting values and corresponding TOF measurements within all threshold ranges, automatically process the data to obtain the relationship between different TOF values and thresholds, and calculate the threshold difference.

[0067] Find the upper threshold limit Fa and lower threshold limit 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.

[0068] During this process, the number of threshold gears is designed as 64, 128, 256, 512, or 1024 according to the amplitude of the echo signal and the required accuracy to adapt to echo signals in different amplitude ranges; the fixed threshold of the zero-crossing comparator ensures accurate detection of the zero-crossing point of the echo signal; the TDC starts timing with the start of ultrasonic transmission as the time start 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, filter the measurement data to eliminate abnormal data to improve the accuracy and reliability of the data and ensure the accuracy of the finally calculated optimal first-wave threshold.

[0069] The various technical features described above by way of example can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the various technical features in the above exemplary description are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as within the scope described in this specification.

Claims

1. A method for setting the first wave threshold voltage of an ultrasonic flow measurement device, characterized in that: Including the following steps: Step 1, set the threshold voltage range and initial value of the variable threshold comparator, where the initial value is the minimum or maximum value within the threshold range; Step 2, transmit ultrasonic signals of a specific frequency; Step 3, start the receiving circuit to detect echo signals; Step 4, when the amplitude of the echo signal exceeds the set threshold of the variable threshold comparator, detect the rising zero-crossing point of the echo signal through a zero-crossing comparator, and measure the time of flight TOF from the transmission start moment to the rising zero-crossing point moment 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 the setting values and corresponding TOF measurements within all threshold ranges, automatically process the data to obtain the relationship between different TOF values and thresholds, and calculate the threshold difference; Step 7, obtain the threshold upper limit Fa and threshold lower limit Fb corresponding to the maximum threshold difference; Step 8, calculate the optimal first-wave threshold as (Fa + Fb) / 2 and complete the setting of the first-wave detection threshold, thereby achieving automatic search for the first-wave threshold.

2. The first-wave threshold voltage setting method for an ultrasonic flow measurement device according to claim 1, characterized in that: The number of threshold gears of the variable threshold comparator is 64, 128, 256, 512 or 1024.

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

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

5. The first wave threshold voltage setting method for an ultrasonic flow metering device according to claim 1, characterized in that The step of automatically processing the data includes: comparing and analyzing the TOF values under different threshold settings with the corresponding thresholds, and drawing a relationship curve of the TOF values and thresholds to visually display the change of the time of flight under different thresholds, providing a basis for determining the optimal first-wave threshold.

6. The first wave threshold voltage setting method for an ultrasonic flow measurement device according to claim 1, characterized in that, The process of automatically searching for the first-wave threshold further includes: after traversing all threshold ranges, performing filtering processing on the measurement data to eliminate abnormal data, so as to improve the accuracy and reliability of the data, thereby ensuring the accuracy of the finally calculated optimal first-wave threshold; the filtering processing adopts one or more of low-pass filtering and median filtering.

7. A method for setting the first wave threshold voltage of an ultrasonic flow measurement device according to claim 1, characterized in that: The ultrasonic flow measurement device includes a transmitting circuit, an ultrasonic transducer, an echo amplifier, a variable threshold comparator, a zero-crossing comparator and a time of flight measurement circuit; wherein the transmitting circuit controls the transmission of ultrasonic signals 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 time of flight measurement circuit measures the time of flight from the start of transmission to the next echo zero-crossing point.

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

9. The first wave threshold voltage setting method for an ultrasonic flow measurement device according to claim 1, characterized in that, The verification steps for the optimal first wave threshold being (Fa + Fb) / 2 are as follows: During the process of adjusting from the minimum threshold Fmin to the maximum threshold Fmax, there is a relationship between the measured TOF value and the comparator threshold. Mark the ultrasonic wave transmission signal period as t, and mark the flight time of the second echo zero crossing as T2. Then, when the threshold changes between F1 and F2, the measured TOF value is T2; when the threshold changes between F2 and F3, the measured TOF value is T2 + t; when the threshold changes between F3 and F4, the measured TOF value is T2 + 2t, and so on. Calculate the threshold differences of F2 - F1, F3 - F2, F4 - F3, etc., find the upper threshold setting limit Fa and the lower limit Fb corresponding to the maximum threshold difference, and obtain the optimal first wave threshold as (Fa + Fb) / 2.

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