Receiving waveform position discrimination method for ultrasonic flow metering device

Abstract

The invention provides a receiving waveform position judging method of an ultrasonic flow metering device, and aims to improve the reliability of flight time measurement and reduce flow metering errors. According to the method, head wave and tail wave detection is achieved through the variable threshold comparator, the threshold is dynamically adjusted to adapt to different detection stages, and it is ensured that echo signals are accurately recognized. Through combination of zero crossing point flight time measurement and pulse width difference comparison, the method can determine the position of a tail wave, forwards presumes the position of an echo waveform, and judges the accuracy of a zero crossing point. In addition, the measurement accuracy is further improved by adjusting the phase of the transmitted ultrasonic signal to enhance the tail wave characteristic. The method is suitable for the field of flow measurement of water meters, heat meters, gas meters and the like, and metering errors caused by signal fluctuation or interference are effectively reduced.

Description

Technical Field

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

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

[0003] In order to accurately measure the flight time of downstream and upstream flow, the key is to reliably identify the echo signal and determine its corresponding echo sequence. Only by accurately identifying the echo arrival time at the same position in the downstream and upstream conditions can the flight time difference be accurately calculated, thereby obtaining accurate flow data.

[0004] The traditional first wave threshold detection method compares the amplified ultrasonic echo signal with the preset threshold to determine whether the echo signal has arrived. When the amplitude of the echo signal exceeds the set threshold, the system considers that the first wave of the echo signal has been received and starts to measure the flight time of the subsequent echo zero crossing. However, the amplitude of the first wave is easily affected by factors such as temperature, flow rate and gas composition and fluctuates. Relying solely on the first wave threshold detection to determine the position of the echo signal may lead to incorrect identification, thereby affecting the accuracy of the 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 tail wave pulse width, and the tail wave pulse width detection threshold is set to Vp.

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

[0012] The difference is compared with the expected threshold value 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 time of the same zero-crossing point measured twice in succession, if the difference exceeds the preset time threshold, the zero-crossing point is determined to be inaccurate. If the zero-crossing 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 the above technical solution, a variable threshold comparator is used to detect the head wave and tail wave, and combined with the measurement of zero-crossing flight time and pulse width difference, an accurate method for determining the position of the received waveform is provided. This method can improve the measurement reliability of the ultrasonic flow metering device under fluctuations or interference, reduce flow metering errors, and thus improve the measurement accuracy and the overall performance of the device.

[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 the above technical solution, by determining the drop point of the echo tail wave and the phenomenon of mis-cycle, the ability to identify the accuracy of the zero-crossing point in the flight time measurement process is enhanced. This improvement in identification ability helps to ensure the stability and consistency of the measurement results, avoids measurement errors caused by signal fluctuations or interference, and further improves the accuracy of flow measurement.

[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] According to the changes in the tail wave characteristics, the effect of adjusting the phase is evaluated, and when the tail wave characteristic changes do not meet expectations or cannot meet the measurement accuracy requirements, further phase adjustments are made.

[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 specific conditions for determining whether the change in the coda wave characteristics meets expectations include:

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

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

[0029] In the above technical solution, the effect of phase adjustment is evaluated through specific judgment conditions, ensuring that the change of 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 comprises 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 sending of ultrasonic signals and the receiving 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 starting point, starting the timing, and ends at the effective echo zero crossing point output by the zero-crossing comparator, 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 the above technical solution, the transmission circuit realizes the precise control of the specific frequency electrical signal to the transducer. This control capability is the basis for accurate ultrasonic flow measurement, which helps to ensure the stability and consistency of the transmission signal, thereby improving the accuracy of the entire flow measurement process.

[0037] Through the ultrasonic transducer, the effective sending 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 realizes the accurate comparison between the amplified echo signal and the zero point, and provides an accurate reference point for the measurement of flight time.

[0040] It realizes the precise timing from the start of ultrasonic transmission to the zero crossing of the effective echo, thus 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 realized.

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

[0043] (1) By 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 a complex fluid environment, can 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 of only using the head wave in the prior art.

[0044] (ii) After the echo tail wave descending point is detected, the out-of-cycle 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 when the fluid flow rate changes or other external conditions affect it, thereby improving the stability of the flow metering device and the reliability of long-term operation.

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

[0046] (iv) transmitting circuit, ultrasonic transducer, variable gain amplifier, zero-crossing comparator, flight time 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 schematic diagram of a receiving waveform position determination method for an ultrasonic flow metering device.

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

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

[0050] 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.

[0051] Application Overview

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

[0053] The time difference method calculates the flow velocity by measuring the difference in ultrasonic flight time in the downstream and upstream directions, and then obtains the flow rate. This method is suitable for fluids that fill closed pipes, but there are some limitations in practical applications. For example, ultrasonic flow meters have limited temperature ranges for fluids and are usually only suitable for fluid measurements below 200°C. In addition, the measurement circuit of ultrasonic flow meters is complex, and the measurement accuracy of sound velocity is extremely high to ensure the accuracy of the measurement results.

[0054] The Doppler effect method calculates the flow rate by measuring the frequency change caused by scatterers in the flowing fluid. It is suitable for the measurement of non-uniform fluids, but there are challenges in the measurement of highly corrosive, radioactive, flammable, and explosive fluids. The shortcomings are mainly reflected in the high requirements for pipeline conditions, such as the need for full pipe conditions, the cleanliness of the inner wall of the pipeline, and the conductivity of the pipeline material to ultrasonic waves. In addition, ultrasonic flow meters are easily interfered by ultrasonic noise mixed with bubbles, scaling, pumps and other sound sources, which affects the measurement accuracy.

[0055] Example

[0056] Please refer to Figure 1In order to realize the receiving waveform position discrimination method of the ultrasonic flow metering device, the configuration before measurement is first performed. At this stage, it is necessary to set the frequency and quantity of ultrasonic waves emitted by the transmitting 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 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 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 transmit ultrasonic waves of the configured frequency and quantity. At Tm time after the ultrasonic wave is transmitted, the variable threshold comparator starts to detect the echo signal. The Tm time is adjusted to ensure that the echo signal detection is not performed during this period, thereby shielding interference. When the echo signal amplitude is detected to exceed the first wave detection threshold, it is considered that the echo signal is received, the output of the next zero crossing point is marked as F1, and the flight time measurement begins.

[0058] When receiving the zero crossing point F3, the detection threshold of the variable threshold comparator is switched 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 emission to the zero crossing indication points F1, F2, F3, and F4 output by the zero crossing comparator. At the same time, the echo pulse width measurement unit starts to measure the pulse widths P1, P2, P3, P4, and P5 of the pulse signals output by the variable threshold comparator.

[0059] Then, calculate the adjacent pulse width differences P2-P1, P3-P2, P4-P3, P5-P4, and compare them with the detection expectation Pe. If the absolute value of the difference between P4 and P3 is greater than Pe, it indicates that the echo waveform has dropped significantly. Find the tail wave drop point, mark the zero crossing point corresponding to this point as B1, and calculate the tail wave positions corresponding to the zero crossing points of F1, F2, F3, and F4 measured forward based on B1 as 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, a flexible threshold adjustment mechanism is designed for the ultrasonic flow metering device of the present invention. 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 measurement of the zero-crossing point will also change accordingly. The original zero-crossing points F1, F2, F3, F4 may become F*1, F*2, F*3, F*4, and the pulse width measurement value will also change to P*1, P*2, P*3, P*4, P*5 accordingly.

[0062] Please refer to Figure 2 , the system will calculate the new pulse width difference, such as P*2-P*1, P*3-P*2, P*4-P*3, P*5-P*4, and compare it with the expected detection value Pe. If it is found that the absolute value of P*3-P*2 is greater than Pe, the system will identify the tail wave drop point corresponding to P*3, and even if the waveform changes, it can correctly identify the tail wave drop point, thereby ensuring the accuracy of the measurement result.

[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 flight time 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 realize 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 the 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 flight time 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 start time pulse signal into a digital signal; the calculation and control unit realizes data processing, gain control strategy calculation, and overall hardware parameter control.

[0064] To ensure the accuracy of the measurement, the frequency of the transmitted ultrasonic signal should be adjusted according to the characteristics of the fluid and the operating conditions of the flow metering device. For example, if the flow rate of the fluid is low or the pipe diameter is small, it may be necessary to increase the frequency of the ultrasonic signal to obtain more accurate measurement results. Similarly, the gain setting of the variable gain amplifier should be optimized according to 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 influence of environmental factors on the measurement results should also be considered, such as temperature changes, changes in pipe materials or fluid composition. These factors may affect the propagation speed and attenuation of ultrasonic signals, so the calculation and control unit should include corresponding compensation algorithms to ensure the accuracy of the measurement results.

[0066] Specific working process

[0067] Before the measurement, set the frequency and quantity of ultrasonic waves emitted by the emission control circuit, as well as the detection threshold of the variable threshold comparator. The first wave detection threshold is set to Vf, and starting from the third zero crossing point, the detection threshold of the variable threshold comparator is switched to the tail wave detection threshold Vp. 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 are measured starting from the zero crossing point F4, and the pulse waveform width difference detection expected value Pe is set at the same time.

[0068] The emission control circuit controls the ultrasonic transducer to emit ultrasonic waves of a specific frequency and quantity. At Tm time after the ultrasonic wave is emitted, the variable threshold comparator starts to detect the echo signal. The Tm time is adjusted to ensure that no echo signal detection is performed during this period, thereby shielding interference. When the echo signal amplitude is detected to exceed the first wave detection threshold, it is considered that the echo signal is received, the output of the next zero crossing is marked as F1, and the flight time measurement begins.

[0069] When receiving the zero crossing point F3, the detection threshold of the variable threshold comparator is switched 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 emission to the zero crossing indication points F1, F2, F3, and F4 output by the zero crossing comparator. At the same time, the echo pulse width measurement unit starts to measure the pulse widths P1, P2, P3, P4, and P5 of the pulse signals output by the variable threshold comparator.

[0070] Calculate the adjacent pulse width differences P2-P1, P3-P2, P4-P3, P5-P4, and compare them with the detection expectation value Pe. If the absolute value of the difference between P4 and P3 is greater than Pe, it indicates that the echo waveform has dropped significantly. Find the tail wave drop point, mark the zero crossing point corresponding to this point as B1, and calculate the tail wave positions corresponding to the zero crossing points of F1, F2, F3, and F4 measured forward based on B1 as B7, B6, B5, and B4.

[0071] When the waveform changes, the system recalculates the pulse width difference based on the new waveform characteristics and compares 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 metering device, 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 tail wave pulse width, and the tail 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 value 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 time of the same zero-crossing point measured twice in succession, if the difference exceeds the preset time threshold, the zero-crossing point is judged to be inaccurate; if the zero-crossing point accuracy is judged to be accurate and the wake 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 metering device as claimed in 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; 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; 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 as claimed in claim 1, characterized in that: The following steps are also included: Determine the initial phase of the transmitted ultrasonic signal; According to the fluid characteristics 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; The ultrasonic signal is transmitted using the adjusted phase, the echo signal is received, and the changes in the tail wave characteristics are observed; According to the changes in the tail wave characteristics, the effect of adjusting the phase is evaluated, and when the tail wave characteristic changes do not meet expectations or cannot meet the measurement accuracy requirements, further phase adjustments are made.

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

5. A method for determining the position of a received waveform for an ultrasonic flow metering device as claimed in claim 1, characterized in that: 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; An ultrasonic transducer, comprising a pair of transducers, for transmitting ultrasonic signals and receiving 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 a comparison level when the echo signal crosses the zero point; The flight time measurement unit starts the time measurement by starting the ultrasonic transmission and starts the timing until the effective echo zero crossing point output by the zero-crossing comparator is taken as the end point, and the ultrasonic flight time is measured; 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.

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