A method and system for measuring the time of flight of an annular ultrasonic flowmeter.

Abstract

This invention discloses a method and system for measuring the time of flight of an ultrasonic flowmeter using the ring-ring method. The invention first determines the amplification factor of the echo circuit and the magnitude of the first threshold voltage. Second, by comparing the number of pulses after echo processing, it determines whether the pulse signal can be used as the excitation signal for the ring-ring method measurement. Then, after reaching the required number of ring-ring method measurements, it determines three time points by comparing the final amplified and filtered echo signal with the first and second threshold voltages. Finally, it judges the relationship between these three time points; if the rules are met, the flight time is obtained through the time measurement circuit; otherwise, the measurement is repeated. This invention achieves consistent adjustment of the echo signal peak value by changing the amplification factor of the echo circuit in real time, dynamically adjusts the first threshold voltage to eliminate the influence of reflected wave signals, and reduces interference from echo signal distortion by judging the number of pulses after echo processing. The time point determination greatly improves the accuracy of the measurement.

Description

Technical Field

[0001] This invention belongs to the field of flow detection technology, and relates to a method and system for measuring the flight time of an ultrasonic flow meter using the ringing method. Background Technology

[0002] The time-difference method (TDD) for ultrasonic water meters works by using a pair of ultrasonic transducers to alternately transmit and receive ultrasonic waves. The water flow velocity is indirectly measured by observing the time difference between the upstream and downstream propagation of the ultrasonic waves, ultimately achieving water flow rate measurement. While this method offers advantages such as a large range ratio, high sensitivity, low starting flow rate, and low pressure loss, its measurement accuracy is low under conditions of small diameter and low flow velocity. This is mainly because the short sound path and short upstream and downstream flight times necessitate high precision in time measurement, which existing clock frequencies often fail to meet.

[0003] Traditional surround sound methods virtually increase the sound path by multiplying the propagation time of ultrasound waves within the pipe. However, during the surround sound measurement process, ultrasound waves are reflected during propagation, and the reflected wave signal is superimposed on the echo signal, resulting in a superposition of the reflected wave and echo waveform. Figure 1 As shown, the reflected wave will initially superimpose on the beginning of the echo signal after two reflections, affecting the time-of-flight measurement. Simultaneously, the ringing method is susceptible to external interference, leading to waveform distortion and thus affecting the time-of-flight measurement. Summary of the Invention

[0004] This invention provides a method and system for measuring the flight time of an ultrasonic flow meter using the ringing method, in order to solve the problems of existing ringing methods being susceptible to interference and having inaccurate flight time measurements.

[0005] In a first aspect, the present invention provides a method for measuring the time of flight of an annular ultrasonic flowmeter, the method comprising the following steps:

[0006] Determine the amplification factor of the echo circuit and the magnitude of the first threshold voltage;

[0007] By comparing the number of pulses after echo processing, it can be determined whether the pulse signal can be used as the excitation signal for ringing method measurement;

[0008] After the number of cycles of the ringing method measurement is reached, the three time points are determined by comparing the echo signal obtained by the final amplification and filtering with the first threshold voltage and the second threshold voltage.

[0009] Determine the relationship between the three time points mentioned above. If the rules are met, the flight time is obtained through the time measurement circuit; otherwise, the measurement is repeated.

[0010] Secondly, the present invention provides a time-of-flight measurement system for an annular ultrasonic flowmeter, comprising:

[0011] The prediction module is used to determine the amplification factor of the echo circuit and the magnitude of the first threshold voltage.

[0012] The excitation signal determination module is used to determine whether a pulse signal can be used as the excitation signal for ringing method measurement by comparing the number of pulses after echo processing.

[0013] The time point determination module is used to determine three time points after the ringing method has been cycled a certain number of times, based on the comparison between the echo signal obtained by the final amplification and filtering and the first threshold voltage and the second threshold voltage.

[0014] The decision-making module is used to determine the relationship between the three time points mentioned above. If the rules are met, the flight time is obtained through the time measurement circuit; otherwise, the measurement is repeated.

[0015] The beneficial effects of this invention are as follows: By changing the amplification factor of the echo circuit, this invention achieves consistent adjustment of the peak value of the echo signal; dynamically adjusting the first threshold voltage eliminates the influence of the reflected wave signal; at the same time, the determination of the number of pulses after echo processing reduces the interference of echo signal distortion; and the determination of the time point greatly improves the accuracy of the measurement. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of echo interference;

[0017] Figure 2 This is a flowchart illustrating the method of an embodiment of this application;

[0018] Figure 3 This is a schematic diagram of waveform detection;

[0019] Figure 4 This is a hardware block diagram of an embodiment of this application. Detailed Implementation

[0020] The technical solution of the present invention will be further described in detail below with reference to the figures, but the scope of protection of the present invention is not limited to the following description.

[0021] This application provides a method for measuring the time of flight of an ultrasonic flowmeter using the ringing method, such as... Figure 2 As shown, it includes:

[0022] Step 1: Prediction step. Prediction is performed before the formal ringing method measurement to determine the amplification factor of the echo circuit and the magnitude of the first threshold voltage.

[0023] Step 1_1: The two circuits generate excitation signals with the same number of pulses in succession to excite the ultrasonic transducer.

[0024] Step 1_2: After the ultrasonic transducer amplifies the received echo signal, the amplification factor of the echo circuit is adjusted according to the peak value of the echo signal.

[0025] Step 1_3: The timing circuit generates the same number of pulses again to excite the transmitting ultrasonic transducer, and the receiving ultrasonic transducer receives the reflected wave signal. The peak voltage of the amplified reflected wave signal is measured and recorded as the interference threshold. The first threshold voltage is adjusted according to the relationship between the interference threshold and the first threshold voltage.

[0026] Step 2: Formal measurement to obtain the flight time of the entire ringing method measurement process.

[0027] Step 2_1: During the formal measurement, determine the number of pulses C of the echo signal and the preset number of pulses C. d If the comparison meets the rules, it is used as the excitation signal for the ringing method measurement; otherwise, the measurement is repeated.

[0028] Step 2_2: After the number of cycles of the ringing method measurement is reached, take the time points t1, t2 and t3 corresponding to the three points of the echo signal obtained by the last amplification and filtering, and determine whether the rules are met. If the rules are met, the flight time is obtained through the time measurement circuit. If the rules are not met, the measurement is repeated.

[0029] Furthermore, in step 1_1, the timing circuit first excites the transmitting ultrasonic transducer, and while the receiving ultrasonic transducer receives the echo signal, the conditioning circuit excites the transmitting ultrasonic transducer again.

[0030] Furthermore, step 1_2 involves adjusting the peak consistency of the echo signals excited by the timing circuit and the conditioning circuit, specifically:

[0031] Adjust the amplification factor according to the relationship between the peak value of the collected echo signal and the target peak value. If the target peak value is greater than the peak value of the echo signal, increase the amplification factor of the echo circuit, and vice versa. Adjust the circuit amplification factor of the echo signal to keep the peak values ​​of the echo signals of the timing circuit and the conditioning circuit consistent. The target peak value is generally 2V.

[0032] Furthermore, the reflected wave signal in step 1_3 is the signal after the ultrasonic signal has been reflected two or more times in the pipeline.

[0033] Furthermore, the steps in step 1_3 to adjust the first threshold voltage according to the interference threshold are as follows:

[0034] If the interference threshold is less than the first threshold voltage and the difference is less than V o If the interference threshold is less than the first threshold voltage and the difference is greater than V, then no action is taken; otherwise, the interference threshold is less than the first threshold voltage and the difference is greater than V. o If the interference threshold is greater than the first threshold voltage, then the first threshold voltage is equal to the interference threshold plus V. o V oGenerally, 100mV is used. The first threshold voltage is determined after repeating steps 1-3 three times without any adjustment.

[0035] Furthermore, in step 2_1, the number of pulses whose amplitude after amplification and filtering of the echo signal is higher than the first threshold voltage is denoted as the pulse count C, and the pulse count is preset to C. d It will change with the number of pulses of the excitation signal, and is set to 5 by default.

[0036] Furthermore, the rule for step 2_1 is: C = C d If the conditions are met, the pulse signal will be used as the excitation signal for the ringing method measurement; otherwise, the measurement will be repeated.

[0037] Furthermore, in step 2_2: as Figure 3 As shown, the echo signal obtained by the final amplification and filtering of the ringing method is compared with the first threshold voltage and the second threshold voltage. Here, t1 and t2 are the time points corresponding to the first and second intersection points of the first threshold voltage and the processed echo signal, and t3 is the time point corresponding to the first intersection point of the second threshold voltage and the processed echo signal after t1.

[0038] The further step 2_2 uses the following rule: T default -T e ≤t1+t3-2t2≤T default +T e T default T represents the preset time interval, while T represents the theoretical time interval. e This is a time error caused by external factors such as voltage fluctuations.

[0039] This application also provides a time-of-flight measurement system for an annular ultrasonic flowmeter, comprising:

[0040] The prediction module is used to determine the amplification factor of the echo circuit and the magnitude of the first threshold voltage.

[0041] The excitation signal determination module is used to determine whether a pulse signal can be used as the excitation signal for ringing method measurement by comparing the number of pulses after echo processing.

[0042] The time point determination module is used to determine three time points after the ringing method has been cycled a certain number of times, based on the comparison between the echo signal obtained by the final amplification and filtering and the first threshold voltage and the second threshold voltage.

[0043] The decision-making module is used to determine the relationship between the three time points mentioned above. If the rules are met, the flight time is obtained through the time measurement circuit; otherwise, the measurement is repeated.

[0044] This application also provides hardware circuits, such as... Figure 4 As shown, the timing circuit transmits an excitation signal to excite ultrasonic transducer 1 via a switching circuit. Ultrasonic transducer 2 receives the echo, amplifies and filters it, and then compares the processed signal with a first threshold voltage and a second threshold voltage to obtain a pulse signal. This pulse signal, obtained through the second threshold voltage comparison, is then used by a conditioning circuit to excite the ultrasonic transducer again. The counting circuit counts the pulse signal obtained from the first threshold voltage comparison once per measurement. The cycle measurement terminates when the number of cycles reaches a set value N; that is, the last measurement sends a stop signal to the timing chip, completing one measurement cycle.

[0045] The functions of some circuits in the above technical solution are as follows: the conditioning circuit counts the pulses of the echo and ensures that the number of pulses for each excitation signal is the same; the timing circuit acquires the flight time; and the switching circuit switches between the transducer, filter circuit, and conditioning circuit.

[0046] The effects of the above technical solution are as follows: The predicted value alters the amplification factor of the echo circuit, achieving consistent adjustment of the echo signal peak value; dynamically adjusting the first threshold voltage eliminates the influence of the reflected wave signal; waveform judgment in the formal measurement reduces interference from echo signal distortion; and timing point judgment greatly improves measurement accuracy.

[0047] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for measuring the time of flight of an annular ultrasonic flowmeter, characterized in that... The method includes the following steps: Determine the amplification factor of the echo circuit and the magnitude of the first threshold voltage; By comparing the number of pulses after echo processing, it can be determined whether the pulse signal can be used as the excitation signal for ringing method measurement; After the number of cycles of the ringing method measurement is reached, the three time points are determined by comparing the echo signal obtained by the final amplification and filtering with the first threshold voltage and the second threshold voltage. Determine the relationship between the three time points mentioned above. If the rules are met, the flight time is obtained through the time measurement circuit; otherwise, the measurement is repeated. The three specific time points are: The echo signal obtained by the final amplification and filtering of the ringing method is compared with the first threshold voltage and the second threshold voltage. The first time point t1 is the time point corresponding to the first intersection of the first threshold voltage and the processed echo signal; the second time point t2 is the time point corresponding to the second intersection of the first threshold voltage and the processed echo signal; the second time point t3 is the time point corresponding to the first intersection of the second threshold voltage and the processed echo signal taken after the first time point t1. The rules are as follows: T default -T e ≤t1+t3-2t2≤T default +T e ; Where T default T is the preset time interval. e This represents the time error.

2. The method for measuring the time of flight of an ultrasonic flowmeter using the ringing method according to claim 1, characterized in that: The specific steps for determining the amplification factor of the echo circuit and the magnitude of the first threshold voltage are as follows: Step 1_1: The timing circuit and the conditioning circuit generate excitation signals with the same number of pulses in succession to excite the ultrasonic transducer. Step 1_2: After the ultrasonic transducer amplifies the received echo signal, it adjusts the amplification factor of the echo circuit according to the peak value of the echo signal to keep the peak value of the echo signal of the timing circuit and the conditioning circuit consistent. Step 1_3: The timing circuit generates the same number of pulses again to excite the transmitting ultrasonic transducer and the receiving ultrasonic transducer to receive the reflected wave signal. The peak voltage of the amplified reflected wave signal is measured and recorded as the interference threshold. The first threshold voltage is adjusted according to the relationship between the interference threshold and the first threshold voltage.

3. The method for measuring the time of flight of an ultrasonic flowmeter using the ringing method according to claim 2, characterized in that: In steps 1 and 2, if the target peak value is greater than the echo signal peak value, the amplification factor of the echo circuit is increased; otherwise, it is decreased.

4. The method for measuring the time of flight of an ultrasonic flowmeter using the ringing method according to claim 2, characterized in that: In steps 1-3, the reflected wave signal is the interference signal after the ultrasonic signal is reflected twice or more in the pipeline.

5. A method for measuring the time of flight of an ultrasonic flowmeter using the ringing method according to any one of claims 2 to 4, characterized in that: The adjustment of the first threshold voltage in step 1_3 is as follows: If the interference threshold is less than the first threshold voltage and the difference is less than the set threshold, no action is taken. Otherwise, if the interference threshold is less than the first threshold voltage and the difference is greater than the set threshold, or if the interference threshold is greater than the first threshold voltage, the first threshold voltage is set to equal the interference threshold plus the set threshold.

6. The method for measuring the time of flight of an ultrasonic flowmeter using the ringing method according to claim 1, characterized in that: The number of pulses C obtained from the amplified and filtered echo signal is compared with the preset number of pulses C. d Comparison, if C is with C d If they are not equal, then remeasure; if C and C d If they are equal, then they are used as the excitation signal for the ringing method measurement.

7. The method for measuring the time of flight of an ultrasonic flowmeter using the ringing method according to claim 1, characterized in that: The second threshold voltage is set to 0 potential.

8. A time-of-flight measurement system for an annular ultrasonic flowmeter, characterized in that, include: The prediction module is used to determine the amplification factor of the echo circuit and the magnitude of the first threshold voltage. The excitation signal determination module is used to compare the number of pulses after echo processing and determine whether the pulse signal can be used as the excitation signal for ringing method measurement. The time point determination module is used to determine three time points after the ringing method has been cycled a certain number of times, based on the comparison between the echo signal obtained by the final amplification and filtering and the first threshold voltage and the second threshold voltage. The decision-making module is used to determine the relationship between the three time points mentioned above. If the rules are met, the flight time is obtained through the time measurement circuit; otherwise, the measurement is repeated. The three specific time points are: The echo signal obtained by the final amplification and filtering of the ringing method is compared with the first threshold voltage and the second threshold voltage. The first time point t1 is the time point corresponding to the first intersection of the first threshold voltage and the processed echo signal; the second time point t2 is the time point corresponding to the second intersection of the first threshold voltage and the processed echo signal; the second time point t3 is the time point corresponding to the first intersection of the second threshold voltage and the processed echo signal taken after the first time point t1. The rules are as follows: T default -T e ≤t1+t3-2t2≤T default +T e ; Where T default T is the preset time interval. e This represents the time error.

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