Method for Determining the First Wave Threshold of an Ultrasonic Flow Meter Based on a TDC Chip

Abstract

This invention relates to a method for determining the first-wave threshold of an ultrasonic flow meter, specifically a method for determining the first-wave threshold of an ultrasonic flow meter based on a TDC chip. The technical solution of this invention is as follows: Initialize the first-wave threshold of the TDC chip; the TDC chip sends an excitation signal to an upstream or downstream transducer; the TDC chip receives echo signals returned from the downstream or upstream transducer; continuously measure eight flow rates, with ultrasonic time-of-flight jumps occurring in at least three of the measurements, and calculate the amplitude A of the first sine wave in the echo signals received by the TDC chip that exceeds the first-wave threshold; increase the first-wave threshold of the TDC chip until a TDC chip timeout occurs; for amplitudes with the same or similar values ​​among the calculated amplitudes, only one amplitude is retained, and wave_set1 is calculated as the first-wave threshold when the ultrasonic flow meter is operating.

Description

Technical Field

[0001] This invention relates to a method for determining the first wave threshold of an ultrasonic flow meter, specifically a method for determining the first wave threshold of an ultrasonic flow meter based on a TDC chip. Background Technology

[0002] In the ultrasonic water meter industry, the transducer plays a crucial role. It is the foundation of ultrasonic metering and determines the accuracy of the measurement.

[0003] Currently, in the ultrasonic water meter industry, the waveform of ultrasonic water meters can affect the accuracy of measurement in many ways. For example, air bubbles can cause waveform attenuation and result in inaccurate measurement, while scale buildup on the reflector or transducer after long-term use of the pipe section can also lead to inaccurate measurement due to waveform attenuation.

[0004] To determine whether a waveform is attenuating or increasing, the industry currently uses a half-wavelength ratio method, which compares the pulse width of the first wave with the theoretical pulse width of a standard transducer. The magnitude of this ratio determines whether the waveform is attenuating or increasing. This step primarily aims to ensure the correct waveform selection during the initialization phase, preventing slight waveform changes under normal conditions from causing waveform skipping in ultrasonic water meters. However, this method has the following problems: Generally, before waveform stability is achieved, the waveform ratio is almost 1:2:3 (e.g., amplitudes of 30mV, 60mV, and 90mV respectively). When air bubbles suddenly appear in the pipe section, the amplitude attenuates, potentially resulting in the second wave having the same height as the first wave (30mV), and the third wave having the same height as the second wave (60mV). In this case, the measured half-wavelength ratio will not change, making it impossible to accurately determine whether the waveform has changed. Summary of the Invention

[0005] The purpose of this invention is to address the aforementioned problems by providing a method for determining the first wave threshold of an ultrasonic flow meter based on a TDC chip.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0007] A method for determining the initial wave threshold of an ultrasonic flow meter based on a TDC chip, comprising:

[0008] S102. Initialize the first wave threshold of the TDC chip;

[0009] S104, TDC chip sends excitation signals to upstream or downstream transducers.

[0010] S106, the TDC chip receives echo signals returned from downstream or upstream transducers.

[0011] S108. If eight flow rates are continuously measured, and at least three of the measurements show an ultrasonic time-of-flight jump, then proceed to step S110; otherwise, proceed to step S104.

[0012] S110. Calculate the amplitude A of the first sine wave whose amplitude exceeds the first wave threshold in the echo signal received by the TDC chip using the following formula;

[0013]

[0014]

[0015] In the formula, A is the amplitude, wave_set is the first wave threshold, Wwave_set is the pulse width corresponding to the first wave threshold, and W0 is the standard half-wave pulse width of the echo signal received by the TDC chip.

[0016] S112. Increase the first wave threshold of the TDC chip and execute step S104 until a TDC chip timeout occurs.

[0017] S114. For amplitude values ​​that are the same or similar in the calculated amplitude values, only one amplitude value is retained, and wave_set1 is calculated using the following formula as the first wave threshold when the ultrasonic flow meter is working.

[0018] wave_set1 = (A2 - A1) * 0.3 + A1

[0019] In the formula, A1 is the smallest value among the remaining values, and A2 is the second smallest value among the remaining values.

[0020] Preferably, in step S112, the increase in the first wave threshold is 50%-80% of the amplitude A of the first sine wave whose amplitude exceeds the first wave threshold in the echo signal received by the TDC chip.

[0021] The beneficial effects of this invention are as follows:

[0022] 1. This invention utilizes ultrasonic time-of-flight jumps as a trigger source and uses the trigonometric function principle to calculate the amplitude A of the first sine wave in the echo signal received by the TDC chip that exceeds the first wave threshold. By continuously changing the first wave threshold of the TDC chip, multiple different amplitudes A can be obtained until the TDC chip times out. For amplitudes with the same or similar values ​​among the calculated amplitudes, only one amplitude is retained. The obtained amplitude is used to calculate wave_set1, which is used as the first wave threshold when the ultrasonic flow meter is working. That is, the ultrasonic time-of-flight jump is used as a trigger source, and the peak values ​​of each peak of the sine wave are calculated using the trigonometric function principle, thereby determining the attenuation or increase of the waveform.

[0023] 2. Set the first wave threshold of the ultrasonic flow meter to be slightly higher than the smallest value among the remaining amplitudes (for amplitudes with the same or similar values ​​among the calculated amplitudes, only one amplitude is retained, and the remaining amplitudes are much lower than the second smallest value among the remaining amplitudes); in this way, even if the waveform attenuates, the frequency of re-determining the first wave threshold of the ultrasonic flow meter can be reduced as much as possible, saving power consumption. Attached Figure Description

[0024] Figure 1 This is a diagram of the TDC chip and its peripheral circuits according to the present invention.

[0025] Figure 2 This is a schematic diagram of the first-wave threshold determination method of the present invention. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, a clear and complete description will be provided below in conjunction with the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the protection scope of the present invention.

[0027] This invention primarily utilizes the principles of trigonometric functions to reconstruct a sine wave using the formula Asin(x). It uses a TDC chip to set the first wave threshold (wave_set) to reconstruct the peak of the sine wave at that threshold. Assuming the first wave threshold of the TDC chip is 10mV, the resulting half-wave ratio is 0.4 (meaning the ratio of the pulse width corresponding to the current first wave threshold to the standard half-wave pulse width is 0.4). Then, using the formula... The x value is calculated to determine the position of the first wave threshold of the TDC chip in the current wave. Then, the amplitude A is calculated to be 12mV using the formula Asin(54°)=10mV.

[0028] Using this principle, multiple amplitude values ​​can be obtained by continuously changing the first-wave threshold of the TDC chip. Based on the transducer's characteristics, when the number of excitations (square waves sent by the TDC chip) is sufficient, the transducer oscillation will inevitably reach a peak amplitude. This can be understood as follows: when the transducer (in this case, a receiving transducer) receives the first wave, it generates an oscillation of intensity X. When it receives the second wave, the oscillation of the first wave has not yet ended. Because the first and second waves are in phase, they can be superimposed, resulting in an intensity of 2X. However, the maximum intensity the transducer can oscillate is only Y, which is when nX > Y (where n is the nth wave received by the transducer). The transducer can only exhibit an oscillation of Y. Therefore, the final amplitude value must be Y. When the first-wave threshold of the TDC chip exceeds the Y value, the signal amplitude cannot be read, resulting in a TDC chip timeout.

[0029] like Figure 2 As shown in this embodiment, a method for determining the first-wave threshold of an ultrasonic flow meter based on a TDC chip is presented. This method is based on a loop formed by the TDC chip, an upstream transducer, and a downstream transducer. Specifically, in this example, the TDC chip used is an MS1030 ultrasonic flow measurement chip. Figure 1 The UP pin is connected to the signal line (usually the red line) of the upstream transducer, and the AGND pin is connected to the ground line (usually the white line) of the upstream transducer; Figure 1 The middle pin DOWN is connected to the signal line (usually the red line) of the downstream transducer, and the pin AGND is connected to the ground line (usually the white line) of the downstream transducer, forming a loop.

[0030] Example 1

[0031] This embodiment describes a method for determining the first-wave threshold of an ultrasonic flowmeter based on a TDC chip, specifically including:

[0032] S102. Initialize the first wave threshold of the TDC chip;

[0033] The S104 and TDC chips send excitation signals to the upstream transducer. The upstream transducer, acting as a transmitting transducer, vibrates after receiving the excitation signal and radiates sound waves into the medium. The downstream transducer, acting as a receiving transducer, is affected by the sound waves in the medium, causing the mechanical vibration system of the downstream transducer to vibrate. This causes a corresponding change in the electric or magnetic field in the energy storage element of the downstream transducer, resulting in an echo signal corresponding to the sound signal being generated at the electrical output terminal of the downstream transducer.

[0034] S106, the TDC chip receives the echo signal returned from the downstream transducer;

[0035] S108. If eight flow rates are continuously measured, and at least three of the measurements show an ultrasonic time-of-flight jump, then proceed to step S110; otherwise, proceed to step S104.

[0036] S110. Calculate the amplitude A of the first sine wave whose amplitude exceeds the first wave threshold in the echo signal received by the TDC chip using the following formula;

[0037]

[0038]

[0039] In the formula, A is the amplitude; wave_set is the first wave threshold; Wwave_set is the pulse width corresponding to the first wave threshold, which can be directly read from the register of the TDC chip (the TDC chip records the rise time and fall time of the echo signal / sine wave corresponding to the first wave threshold, and stores the difference between the two times in the register as the pulse width corresponding to the first wave threshold); W0 is the standard half-wave pulse width of the echo signal received by the TDC chip. This standard half-wave pulse width is related to the oscillation frequency of the standard transducer or the transducer under test. Assuming that the oscillation frequency of the standard transducer or the transducer under test is 1 MHz, the standard half-wave pulse width is 0.5 microseconds.

[0040] S112. Increase the first wave threshold of the TDC chip and execute step S104 until a TDC chip timeout occurs; the increase in the first wave threshold is 50%-80% of the amplitude A of the first sine wave in the echo signal received by the TDC chip that exceeds the first wave threshold. For example, it can be selected as 70% of the amplitude A of the first sine wave in the echo signal received by the TDC chip that exceeds the first wave threshold.

[0041] S114. For amplitude values ​​that are the same or similar in the calculated amplitude values, only one amplitude value is retained, and wave_set1 is calculated using the following formula as the first wave threshold when the ultrasonic flow meter is working.

[0042] wave_set1 = (A2 - A1) * 0.3 + A1

[0043] In the formula, A1 is the smallest value among the remaining values, and A2 is the second smallest value among the remaining values.

[0044] The initial threshold of the ultrasonic flow meter during operation is set slightly higher than the smallest amplitude A1 among the remaining amplitudes (for amplitudes with the same or similar values ​​among the calculated amplitudes, only one amplitude is retained, and the remaining amplitudes are the smallest), and much lower than the second smallest amplitude A2 among the remaining amplitudes. In this way, even if the waveform attenuates, the frequency of re-determining the initial threshold of the ultrasonic flow meter during operation can be reduced as much as possible, thus saving power consumption. To facilitate understanding, an example is given below: Assume A1 is 30mV and A2 is 60mV. According to the method in this embodiment, the initial wave threshold (wave_set1) of the ultrasonic flowmeter is set to 39mV. If, after two years of operation, the waveform attenuates and the peak of the second wave in the echo signal is 45mV (still greater than the value of wave_set1), then there is no need to redetermine the initial wave threshold of the ultrasonic flowmeter. Conversely, if the initial wave threshold of the ultrasonic flowmeter is set close to A2, for example, to 50mV, after two years of operation, the waveform attenuates and the peak of the second wave in the echo signal is 45mV, which is less than the initial wave threshold of the ultrasonic flowmeter. In this case, it is necessary to redetermine the initial wave threshold of the ultrasonic flowmeter, which will increase the power consumption of the ultrasonic flowmeter.

[0045] For amplitude values ​​that are the same or similar, the standard is generally that the difference should not exceed 5mV. For example, if the calculated amplitude values ​​are 10mV, 10mV, 11mV, 20mV, 21mV, 21mV, 30mV, 30mV, 31mV, and 31mV, then delete one of the values ​​of 10mV, 11mV, 21mV, and 21mV, and one of the values ​​of 30mV, 31mV, and 31mV, and keep only the three values ​​of 10mV, 20mV, and 30mV.

[0046] Of course, within the scope of options available to those skilled in the art, the aforementioned steps S104 and S106 can also be replaced by the following steps:

[0047] The S104 and TDC chips send excitation signals to the downstream transducers. The downstream transducers, acting as transmitting transducers, vibrate after receiving the excitation signals and radiate sound waves into the medium. The upstream transducers, acting as receiving transducers, are affected by the sound waves in the medium, causing the mechanical vibration system of the upstream transducers to vibrate. This causes a corresponding change in the electric or magnetic field in the energy storage element of the upstream transducers, resulting in an echo signal corresponding to the sound signal being generated at the electrical output terminal of the upstream transducers.

[0048] The S106 TDC chip receives the echo signal returned from the upstream transducer.

[0049] The preferred embodiments of the present invention have been described, and various changes or modifications made by those skilled in the art will not depart from the scope of the present invention.

Claims

1. A method for determining the first wave threshold of an ultrasonic flow meter based on a TDC chip, characterized by include: S102. Initialize the first wave threshold of the TDC chip; S104, TDC chip sends excitation signals to upstream or downstream transducers; S106, the TDC chip receives echo signals returned from downstream or upstream transducers; S108. If eight flow rates are continuously measured, and at least three of them show ultrasonic time-of-flight jumps, then proceed to step S110. Otherwise, proceed to step S104; S110. Calculate the amplitude A of the first sine wave whose amplitude exceeds the first wave threshold in the echo signal received by the TDC chip using the following formula; In the formula, A is the amplitude, wave_set is the first wave threshold, Wwave_set is the pulse width corresponding to the first wave threshold, and W0 is the standard half-wave pulse width of the echo signal received by the TDC chip. S112. Increase the first wave threshold of the TDC chip and execute step S104 until a TDC chip timeout occurs. S114. For amplitude values ​​that are the same or similar in the calculated amplitude values, only one amplitude value is retained, and wave_set1 is calculated using the following formula as the first wave threshold when the ultrasonic flow meter is working. wave_set1 = (A2 - A1) * 0.3 + A1 In the formula, A1 is the smallest value among the remaining values, and A2 is the second smallest value among the remaining values.

2. The method of claim 1, wherein: In step S112, the increase in the first wave threshold is 50%-80% of the amplitude A of the first sine wave whose amplitude exceeds the first wave threshold in the echo signal received by the TDC chip.

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