A method for determining the position of a received waveform for an ultrasonic flow metering device

Abstract

The present invention provides a method for determining the position of a received waveform of an ultrasonic flow metering device, aiming to improve the reliability of time-of-flight measurements and reduce flow metering errors. The method uses a variable threshold comparator to detect the head wave and tail wave, dynamically adjusting the threshold to adapt to different detection stages to ensure accurate identification of the echo signal. Combining zero-crossing time-of-flight measurement and pulse width difference comparison, the present invention can determine the tail wave position, infer the echo waveform position forward, and determine the accuracy of the zero-crossing point. In addition, by adjusting the phase of the transmitted ultrasonic signal to enhance the tail wave characteristics, the measurement accuracy is further improved. This method is applicable to flow measurement fields such as water meters, heat meters, and gas meters, and effectively reduces metering errors caused by signal fluctuations or interference.

Description

Technical Field

[0001] The present invention relates to the field of ultrasonic metering equipment, and in particular to a method for determining the position of a received waveform used in an ultrasonic flow metering device. Background Art

[0002] In the field of ultrasonic flow measurement, flow measurement typically relies on the principle of ultrasonic time of flight (ToF). This technology is widely used in flow meters such as water, heat, and gas meters, with the time difference method being a primary measurement method. Specifically, by calculating the difference in the time of flight (dToF) of ultrasonic waves traveling downstream and upstream, the flow velocity can be determined, and the flow rate can be derived.

[0003] To accurately measure the time of flight for both upstream and downstream flow, the key is to reliably identify the echo signals and determine their corresponding echo sequence. Only by accurately identifying the arrival times of echoes at the same location in both upstream and downstream conditions can the time of flight difference be accurately calculated, thereby obtaining precise flow data.

[0004] Traditional first-wave threshold detection compares an amplified ultrasonic echo signal with a preset threshold to determine whether an echo signal has arrived. When the echo signal's amplitude exceeds the threshold, the system assumes the first wave of the echo signal has been received and begins measuring the time-of-flight of the subsequent echo's zero crossing. However, the first-wave amplitude fluctuates due to factors such as temperature, flow rate, and gas composition. Relying solely on first-wave threshold detection to determine the echo signal's location can lead to misidentification, thus affecting the accuracy of measurement results. Summary of the Invention

[0005] In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a method for determining the position of a received waveform for an ultrasonic flow metering device, so as to solve one or more problems in the prior art.

[0006] To achieve the above object, the technical solution of the present invention is as follows:

[0007] A method for determining the position of a received waveform for an ultrasonic flow metering device comprises the following steps:

[0008] A variable threshold comparator is used for first wave detection, and the first wave detection threshold is set to Vf.

[0009] Measure the ultrasonic flight time of n zero crossing points after the first wave.

[0010] Starting from the mth zero-crossing point, the same variable threshold comparator is used to detect the coda wave pulse width, and the coda wave pulse width detection threshold is set to Vp.

[0011] Measure the width of k pulse waveforms and calculate the difference between the widths of the previous and next pulses.

[0012] The difference is compared with the expected threshold Pe. When the difference exceeds Pe, it indicates that the beginning of the wake is detected, thereby determining the wake position.

[0013] According to the tail wave position and the known ultrasonic emission period, the echo waveform position corresponding to each zero crossing point is calculated forward.

[0014] By comparing the flight times of two consecutive measurements of the same zero-crossing point, if the difference exceeds a preset time threshold, the zero-crossing point is determined to be inaccurate. If the zero-crossing point accuracy is determined to be accurate and the wake position has not changed significantly compared to the previous measurement, the flight time measurement is considered valid.

[0015] In this technical solution, a variable-threshold comparator is used to detect the head and tail waves, combined with measurements of the zero-crossing time-of-flight and pulse width difference, to provide a precise method for determining the position of the received waveform. This method can improve the measurement reliability of ultrasonic flowmeters in the presence of fluctuations or interference, reduce flow measurement errors, and thus enhance measurement accuracy and overall device performance.

[0016] Furthermore, if the absolute value of the pulse width difference is greater than Pe, it is determined to be the echo tail wave drop point.

[0017] The zero-crossing point corresponding to the falling point of the echo tail wave is marked as B1, and the flight time of each zero-crossing point is calculated forward based on B1.

[0018] By comparing the zero-crossing flight time of two consecutive measurements, if the change exceeds a preset threshold, it is determined that a wrong cycle has occurred.

[0019] In this technical solution, the ability to accurately identify zero-crossings during time-of-flight measurements is enhanced by determining the echo tail drop point and cycle mismatch. This improved identification helps ensure the stability and consistency of measurement results, avoids measurement errors caused by signal fluctuations or interference, and further improves flow measurement accuracy.

[0020] Furthermore, the method further comprises the following steps:

[0021] Determine the initial phase of the transmitted ultrasonic signal.

[0022] According to the fluid properties and the expected echo signal characteristics, the phase of the transmitted ultrasonic signal is adjusted to optimize the tail wave part of the echo signal.

[0023] The ultrasonic signal is transmitted using the adjusted phase, the echo signal is received, and the changes in the tail wave characteristics are observed.

[0024] The effect of phase adjustment is evaluated based on the changes in coda wave characteristics, and further phase adjustment is performed when the changes in coda wave characteristics do not meet expectations or cannot meet measurement accuracy requirements.

[0025] In the above technical solution, the tail wave part of the echo signal is optimized by adjusting the phase of the transmitted ultrasonic signal, so that the tail wave feature is more obvious and easy to identify.

[0026] Specifically, the conditions for determining whether the change in coda characteristics meets expectations include:

[0027] Compare the amplitude changes of the coda wave signal before and after the phase adjustment. If the amplitude change exceeds the preset amplitude threshold, it is considered that the coda wave characteristic change is in line with expectations.

[0028] The stability index of the coda wave signal before and after phase adjustment is calculated. If the coda wave signal meets the expected requirements under different application environments, it is considered to meet the stability requirements.

[0029] In the above technical solution, the effect of phase adjustment is evaluated through specific judgment conditions, ensuring that the change in the coda wave characteristics is in line with expectations and that the measurement accuracy meets the requirements.

[0030] Preferably, the ultrasonic flow metering device further includes a transmitting circuit for controlling the transmission of an electrical signal of a specific frequency to the transducer.

[0031] The ultrasonic transducer includes a pair of transducers to realize the transmission of ultrasonic signals and the reception of echo signals.

[0032] The variable gain amplifier amplifies the echo signal by configuring the amplification gain.

[0033] The zero-crossing comparator compares the amplified subsequent echo signal with the zero point after the variable threshold comparator detects the first wave, and outputs a comparison level when the echo signal crosses the zero point.

[0034] The flight time measurement unit starts the time measurement by taking the start of ultrasonic transmission as the time measurement starting point, and starts timing until the effective echo zero crossing point output by the zero-crossing comparator is taken as the end point, and measures the ultrasonic flight time.

[0035] The pulse width measurement unit measures the width of one or more pulse signals output by the variable threshold comparator to obtain a pulse width value.

[0036] In this technical solution, the transmitting circuit enables precise control of the specific frequency electrical signal to the transducer. This control capability is fundamental to accurate ultrasonic flow measurement, helping to ensure the stability and consistency of the transmitted signal, thereby improving the accuracy of the entire flow measurement process.

[0037] Through the ultrasonic transducer, the effective transmission of ultrasonic signals and the accurate reception of echo signals are achieved.

[0038] The variable gain amplifier provides flexible configuration of the echo signal amplification gain, so that the flow metering device can adapt to different signal strengths and measurement conditions.

[0039] It achieves accurate comparison between the amplified echo signal and the zero point, providing an accurate reference point for the measurement of flight time.

[0040] This achieves precise timing from the start of ultrasonic transmission to the effective echo zero-crossing point, improving the accuracy of flow calculation and the response speed of the device.

[0041] The accurate measurement of the output pulse signal width of the variable threshold comparator is achieved.

[0042] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0043] (1) Using a variable threshold comparator to detect the head wave and tail wave, measure the ultrasonic flight time of the zero point, and determine the tail wave position based on the pulse width difference, the present invention can maintain high measurement accuracy in complex fluid environments, effectively identify and correct errors caused by signal fluctuations or interference, and significantly improve the accuracy and reliability of flow measurement, which is different from the limitations of the single threshold and the detection method using only the head wave in the prior art.

[0044] (2) After detecting the falling point of the echo tail wave, the wrong period phenomenon is determined, and possible measurement errors are effectively identified and corrected, ensuring that the continuity and consistency of the measurement process can be maintained even under the influence of changes in fluid flow rate or other external conditions, thereby improving the stability of the flow metering device and the reliability of long-term operation.

[0045] (3) The phase adjustment technology of the transmitted ultrasonic signal can optimize the recognition of the tail wave signal according to the fluid characteristics and the expected echo signal characteristics, and enhance the stability and measurability of the signal. This ability to dynamically adjust the phase enables the flow metering device to adapt to different measurement environments and conditions, improving the accuracy of the measurement results and the applicability of the device.

[0046] (4) transmitting circuit, ultrasonic transducer, variable gain amplifier, zero-crossing comparator, time-of-flight measurement unit and pulse width measurement unit. The present invention constructs a comprehensive ultrasonic flow metering device, which can not only accurately control and measure ultrasonic signals, but also flexibly respond to different signal conditions and environmental changes, thereby improving the overall performance and measurement accuracy of the flow metering device and making the device more efficient and stable in practical applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 The present invention is a logic diagram of a method for determining the position of a received waveform of an ultrasonic flow metering device.

[0048] Figure 2 This is a schematic diagram of the ultrasonic echo waveform position recognition principle in the present invention.

[0049] Figure 3 It is a schematic diagram of the ultrasonic flow metering device in the present invention. DETAILED DESCRIPTION

[0050] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and exemplary explanations. 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 intended to limit the conditions for the implementation of the present invention. Therefore, they have no technical significance. Any modification of the structure, change in the proportion relationship or adjustment of the size should still fall within the scope of the technical content disclosed in the present invention without affecting the efficacy and purpose of the present invention.

[0051] Application Overview

[0052] In the industry, when faced with the problem of determining the position of the received waveform in ultrasonic flow metering devices, conventional solutions mainly rely on the time difference method and the Doppler effect method.

[0053] The time-of-flight method calculates flow velocity and, in turn, flow rate by measuring the difference in ultrasonic flight time between downstream and upstream directions. This method is suitable for fluids filling closed pipes, but it has some practical limitations. For example, ultrasonic flowmeters have a limited temperature range and are generally only suitable for fluids below 200°C. Furthermore, the complex measurement circuitry of ultrasonic flowmeters requires extremely high accuracy in sound velocity measurement to ensure accurate results.

[0054] The Doppler effect method calculates flow velocity by measuring frequency changes caused by scatterers in a flowing fluid. While suitable for measuring non-uniform fluids, it presents challenges when measuring highly corrosive, radioactive, flammable, and explosive fluids. Its main drawbacks lie in its strict requirements for pipeline conditions, such as the need for full pipes, the cleanliness of the pipe interior, and the ultrasonic conductivity of the pipe material. Furthermore, ultrasonic flowmeters are susceptible to interference from bubbles, scaling, and ultrasonic noise from pumps and other sound sources, affecting measurement accuracy.

[0055] Example

[0056] Please refer to Figure 1In order to implement the received waveform position discrimination method of the ultrasonic flow metering device, the pre-measurement configuration is first performed. At this stage, it is necessary to set the frequency and quantity of ultrasonic waves emitted by the transmission control circuit, as well as the detection threshold of the variable threshold comparator. Specifically, the first wave detection threshold is set to Vf, and the detection threshold of the variable threshold comparator is switched from Vf to the tail wave detection threshold Vp starting from the third zero crossing point. At the same time, the number of zero crossing points n is set to 4, that is, the ultrasonic flight time of the four zero crossing points F1, F2, F3, and F4 is measured, and the pulse waveform widths P1, P2, P3, P4, and P5 output by the variable threshold comparator are measured starting from the zero crossing point F4, and the expected value Pe of the pulse waveform width difference detection is set.

[0057] The transmission control circuit controls the ultrasonic transducer to emit ultrasonic waves of a configured frequency and quantity. At time Tm after the ultrasonic wave is emitted, the variable threshold comparator begins detecting the echo signal. The Tm time is adjusted to ensure that no echo signal detection is performed during this period, thereby shielding against interference. When the detected echo signal amplitude exceeds the first-wave detection threshold, the echo signal is considered received, the next zero-crossing output is marked as F1, and time-of-flight measurement begins.

[0058] Upon receiving the zero-crossing point F3, the detection threshold of the variable threshold comparator switches from the first wave detection threshold Vf to the tail wave detection threshold Vp. The flight time measurement unit measures the flight time from the transmission to the zero-crossing indicator points F1, F2, F3, and F4 output by the zero-crossing comparator. Simultaneously, the echo pulse width measurement unit begins measuring the pulse widths P1, P2, P3, P4, and P5 of the pulse signal output by the variable threshold comparator.

[0059] Next, calculate the adjacent pulse width differences (P2-P1, P3-P2, P4-P3, and P5-P4) and compare them with the expected detection value, Pe. If the absolute value of the P4-P3 difference is greater than Pe, it indicates a significant drop in the echo waveform. Find the point where the coda wave drops, and label the corresponding zero crossing point as B1. Using B1, extrapolate the coda wave positions corresponding to the zero crossings of F1, F2, F3, and F4 and label them B7, B6, B5, and B4.

[0060] During actual operation, changes in the waveform of the echo signal may be observed, that is, from waveform A to waveform B. This change may be caused by changes in the fluid flow rate, changes in the fluid density, changes in the reflection characteristics of the pipe wall, or other interference factors on the signal propagation path. In order to adapt to such changes and ensure the accuracy of the measurement, the ultrasonic flow metering device of the present invention is designed with a flexible threshold adjustment mechanism. When the amplitude of the echo signal becomes smaller, so that the echo signal cannot be detected under the first wave detection threshold Vf, the system will wait until the amplitude of the echo signal exceeds the first wave detection threshold Vf. In this example, if the amplitude at the echo peak position 1 is less than the first wave detection threshold Vf, the system will detect that the peak of the echo signal exceeds the first wave detection threshold Vf at the echo peak position 2, and start the subsequent measurement process.

[0061] As the waveform changes, the zero-crossing point measurement will also change accordingly. The original zero-crossing points F1, F2, F3, and F4 may become F*1, F*2, F*3, and F*4, and the pulse width measurement value will also change accordingly to P*1, P*2, P*3, P*4, and P*5.

[0062] Please refer to Figure 2 The system calculates new pulse width differences, such as P*2-P*1, P*3-P*2, P*4-P*3, and P*5-P*4, and compares them with the expected detection value Pe. If the absolute value of P*3-P*2 is greater than Pe, the system identifies the coda drop point corresponding to P*3. Even when the waveform changes, the coda drop point can be correctly identified, thus ensuring the accuracy of the measurement results.

[0063] Please refer to Figure 3 In the present invention, the ultrasonic flow metering device includes a transmitting circuit, an ultrasonic transducer, a variable gain amplifier, a variable threshold comparator, a zero-crossing comparator, a time-of-flight measurement unit, an echo pulse width measurement unit, a time-to-digital converter (TDC), and a calculation and control unit. The transmitting circuit controls the transmission of an electrical signal of a specific frequency to the transducer; the ultrasonic transducer includes a pair of transducers to achieve the transmission of ultrasonic signals and the reception of echo signals; the variable gain amplifier amplifies the echo signal; the variable threshold comparator compares the echo signal output by the amplifier with a set threshold and outputs a comparison level; after detecting the first wave, the zero-crossing comparator compares the amplified subsequent echo signal with the zero point and outputs a comparison level; the time-of-flight measurement unit measures the ultrasonic flight time; the pulse width measurement unit measures the width of the pulse signal; the time-to-digital converter converts the starting time pulse signal into a digital signal; and the calculation and control unit implements data processing, gain control strategy calculation, and overall hardware parameter control.

[0064] To ensure accurate measurements, the frequency of the transmitted ultrasonic signal should be adjusted based on the fluid characteristics and operating conditions of the flow metering device. For example, if the fluid velocity is low or the pipe diameter is small, the ultrasonic signal frequency may need to be increased to obtain more accurate measurements. Similarly, the gain setting of the variable-gain amplifier should be optimized based on the received echo signal strength to ensure that the signal is above the noise level but not saturated.

[0065] When implementing the present invention, the effects of environmental factors on measurement results should also be considered, such as temperature changes, variations in pipe material, or changes in fluid composition. These factors may affect the propagation speed and attenuation of ultrasonic signals. Therefore, the calculation and control unit should include appropriate compensation algorithms to ensure accurate measurement results.

[0066] Specific working process

[0067] Before performing measurement configuration, set the frequency and number of ultrasonic waves emitted by the transmission control circuit, as well as the detection threshold of the variable threshold comparator. Set the first wave detection threshold to Vf. Starting at the third zero crossing, switch the detection threshold of the variable threshold comparator to the tail wave detection threshold, Vp. Set the number of zero crossings, n, to 4. This means measuring the ultrasonic flight time at four zero crossings, F1, F2, F3, and F4. Starting at zero crossing F4, measure the pulse waveform widths, P1, P2, P3, P4, and P5. Also, set the expected value, Pe, for detecting the difference in pulse waveform widths.

[0068] The transmission control circuit controls the ultrasonic transducer to emit ultrasonic waves of a specific frequency and quantity. At time Tm after the ultrasonic wave is emitted, the variable threshold comparator begins detecting the echo signal. Tm is adjusted to prevent echo detection during this time, thereby shielding against interference. When the detected echo signal amplitude exceeds the first-wave detection threshold, an echo signal is considered received. The next zero-crossing output is labeled F1, and time-of-flight measurement begins.

[0069] Upon receiving the zero-crossing point F3, the detection threshold of the variable threshold comparator switches from the first wave detection threshold Vf to the tail wave detection threshold Vp. The flight time measurement unit measures the flight time from the transmission to the zero-crossing indicator points F1, F2, F3, and F4 output by the zero-crossing comparator. Simultaneously, the echo pulse width measurement unit begins measuring the pulse widths P1, P2, P3, P4, and P5 of the pulse signal output by the variable threshold comparator.

[0070] Calculate the adjacent pulse width differences (P2-P1, P3-P2, P4-P3, and P5-P4) and compare them with the expected detection value, Pe. If the absolute value of the P4-P3 difference is greater than Pe, it indicates a significant drop in the echo waveform. Find the point where the coda wave drops, and mark the corresponding zero crossing as B1. Based on B1, extrapolate the coda wave positions corresponding to the zero crossings of F1, F2, F3, and F4 and label them B7, B6, B5, and B4.

[0071] When the waveform changes, the system will recalculate the pulse width difference based on the new waveform characteristics and compare it with Pe to identify the new tail wave drop point.

[0072] 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 determining the position of a received waveform of an ultrasonic flow meter, characterized in that: The following steps are involved: Use a variable threshold comparator to perform first wave detection, and set the first wave detection threshold to Vf; Measure the ultrasonic flight time of n zero-crossing points after the first wave; Starting from the mth zero-crossing point, the same variable threshold comparator is used to detect the coda wave pulse width, and the coda wave pulse width detection threshold is set to Vp; Measure the width of k pulse waveforms and calculate the difference between the previous and next pulse widths; The difference is compared with the expected threshold Pe. When the difference exceeds Pe, it indicates that the beginning of the wake is detected, thereby determining the wake position; According to the tail wave position and the known ultrasonic emission period, the echo waveform position corresponding to each zero-crossing point is calculated forward; By comparing the flight times of the same zero-crossing point measured twice in succession, including measuring the ultrasonic flight times of n zero-crossing points after the first wave, and the echo waveform position time corresponding to each zero-crossing point extrapolated forward; if the difference exceeds the preset time threshold, it is judged that the zero-crossing point is inaccurate; if the zero-crossing point accuracy is judged to be accurate and the tail wave position has not changed significantly compared with the previous measurement, the flight time measurement is considered valid.

2. A method for determining the position of a received waveform for an ultrasonic flow meter according to claim 1, characterized in that: If the absolute value of the pulse width difference is greater than Pe, it is determined to be the echo tail wave drop point; Mark the zero-crossing point corresponding to the falling point of the echo tail wave as B1, and calculate the flight time of each zero-crossing point based on B1; By comparing the zero-crossing flight time of two consecutive measurements, if the change exceeds a preset threshold, it is determined that a wrong cycle has occurred.

3. A method for determining the position of a received waveform for an ultrasonic flow metering device according to claim 1, characterized in that: The following steps are also included: Determine the initial phase of the transmitted ultrasonic signal; Adjust the phase of the transmitted ultrasonic signal according to the fluid properties and the expected echo signal characteristics to optimize the tail wave part of the echo signal; The ultrasonic signal is transmitted using the adjusted phase, the echo signal is received, and the changes in the tail wave characteristics are observed; The effect of phase adjustment is evaluated based on the changes in coda wave characteristics, and further phase adjustment is performed when the changes in coda wave characteristics do not meet expectations or cannot meet measurement accuracy requirements.

4. A method for determining the position of a received waveform for an ultrasonic flow metering device according to claim 3, characterized in that: The specific conditions for determining whether the change in coda wave characteristics is in line with expectations or meets the measurement accuracy requirements include: Compare the amplitude changes of the coda wave signal before and after the phase adjustment. If the amplitude change exceeds the preset amplitude threshold, it is considered that the coda wave characteristic change is in line with expectations. The stability index of the coda wave signal before and after phase adjustment is calculated. If the coda wave signal meets the expected requirements under different application environments, it is considered to meet the stability requirements.

5. The method for determining the position of a received waveform for an ultrasonic flow metering device according to claim 1, wherein: The ultrasonic flow metering device also includes: A transmitting circuit, used for controlling the transmission of an electrical signal of a specific frequency to the transducer; Ultrasonic transducer, including a pair of transducers, to transmit ultrasonic signals and receive echo signals; A variable gain amplifier amplifies the echo signal by configuring the amplification gain; The zero-crossing comparator compares the amplified subsequent echo signal with the zero point after the variable threshold comparator detects the first wave, and outputs the comparison level when the echo signal crosses the zero point; The time-of-flight measurement unit starts the measurement by taking the start of ultrasonic transmission as the time measurement starting point, and starts timing until the effective echo zero-crossing point output by the zero-crossing comparator is used as the end point, and measures the ultrasonic flight time; The pulse width measurement unit measures the width of one or more pulse signals output by the variable threshold comparator to obtain a pulse width value.

Images