Method for obtaining operating parameters of an ultrasonic flowmeter

Abstract

The present application relates to gas flow rate measurement, and particularly provides a method for obtaining working parameters of an ultrasonic flowmeter, comprising the following steps: A1. adjusting the working temperature and the working frequency of a first transducer at zero flow rate, corresponding multiple frequencies to the same temperature, and a second transducer outputting multiple parameters corresponding to the working temperature and the frequency; A2. obtaining an evaluation value according to the multiple parameters, the evaluation value corresponding to the working temperature and the frequency; A3. finding the maximum value in the multiple evaluation values corresponding to the same temperature, and the frequency corresponding to the maximum value being taken as the preferred frequency corresponding to the working temperature; and A4. establishing a data point and saving the same, the data point comprising the working temperature, the preferred frequency and the evaluation value. The present application has the advantages of accurate measurement and the like.

Description

Technical Field

[0001] This invention relates to ultrasonic flow velocity detection, and particularly to a method for obtaining the operating parameters of an ultrasonic flow meter. Background Technology

[0002] The flue gas ultrasonic flow meter includes a drive analysis unit, a transmitting transducer, a receiving transducer, and related structural components. The drive analysis unit emits ultrasonic waves through the transmitting transducer. The emitted ultrasonic waves propagate through the air medium to the receiving transducer and are received by the receiving transducer. By calculating the time difference between the ultrasonic wave emission from the transmitting transducer and the ultrasonic wave reception from the receiving transducer, the current air velocity can be calculated.

[0003] The working principle of ultrasonic transducers is based on the piezoelectric effect or magnetostriction effect. High temperature environments significantly affect the performance of ultrasonic transducers. In a flue gas ultrasonic flowmeter with a given structure, high temperature mainly affects the dielectric constant of the internal ultrasonic transducer. Increased temperature causes the resonant frequency of the piezoelectric crystal to drift, affecting the imaging resolution. Of course, high temperature can also cause the matching layer (such as epoxy resin) to soften, change the acoustic impedance, and reduce energy transmission efficiency, etc.

[0004] When the transmission matching frequency of the drive circuit is inconsistent with the resonant frequencies of the transmitting and receiving transducers, the electrical energy to acoustic energy conversion efficiency is significantly reduced, resulting in a weakening of the transmitted and received ultrasonic intensity. This leads to a significant change in the signal quality of the flue gas ultrasonic flowmeter, ultimately causing abnormal instrument measurements.

[0005] To address the above problems, the existing solutions are mainly as follows:

[0006] 1. Material selection: High-temperature piezoelectric materials use bismuth layered ceramics, such as BiT, or single crystal materials, such as GaPO4. Electrodes are made of platinum or gold, and encapsulation materials are made of high-temperature epoxy resin or ceramic shells.

[0007] 2. Thermal management design, such as active cooling methods such as micro fans or liquid cooling channels, passive heat dissipation methods such as copper or aluminum heat sinks and heat sink structure design, and heat source isolation using aerogel or multi-layer reflective foil.

[0008] 3. Structural optimization, such as using high-temperature stress design or high-temperature solder.

[0009] 4. Signal compensation techniques, such as temperature sensor integration and wide-temperature-range calibration.

[0010] The above methods can largely solve the problem of high-temperature application of ultrasonic transducers, but the cost and difficulty of solving them place high demands on the technical skills of enterprises and technicians, making their application in flue gas ultrasonic flow meters very difficult. Summary of the Invention

[0011] To address the shortcomings of the existing technical solutions, this invention provides a method for obtaining the operating parameters of an ultrasonic flowmeter.

[0012] The objective of this invention is achieved through the following technical solution:

[0013] A method for obtaining operating parameters of an ultrasonic flowmeter, wherein the ultrasonic flowmeter includes a first transducer and a second transducer; the method includes the following steps:

[0014] A1. At zero flow rate, adjust the operating temperature and the operating frequency of the first transducer. The same temperature corresponds to multiple frequencies. The second transducer outputs multiple parameters corresponding to the operating temperature and frequency.

[0015] A2. An evaluation value is derived based on the multiple parameters, and the evaluation value corresponds to the operating temperature and frequency;

[0016] A3. Find the maximum value among multiple evaluation values ​​corresponding to the same temperature, and take the frequency corresponding to the maximum value as the preferred frequency corresponding to the working temperature;

[0017] A4. Establish and save data points, including operating temperature, preferred frequency, and evaluation value.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] Based on the method of the present invention, the transmission matching frequency of the driving circuit and the resonant frequency of the transmitting transducer and the receiving transducer can be kept in a better matching state in real time at different temperatures, so as to offset the influence of high temperature on the ultrasonic transducer. It can also optimize the transmission and receiving frequencies under different working conditions and under different aging and contamination conditions of the sensor. Attached Figure Description

[0020] The disclosure of this invention will become more readily understood with reference to the accompanying drawings. It will be readily understood by those skilled in the art that these drawings are merely illustrative of the technical solutions of this invention and are not intended to limit the scope of protection of this invention. In the drawings:

[0021] Figure 1 This is a flowchart illustrating the method for obtaining the product according to an embodiment of the present invention;

[0022] Figure 2 This is a partial structural schematic diagram of the ultrasonic flow meter according to an embodiment of the present invention;

[0023] Figure 3 This is a schematic diagram of the signal at 30.2℃ and 80kHz;

[0024] Figure 4This is a schematic diagram of the signal at 30.2℃ and 90kHz;

[0025] Figure 5 This is a schematic diagram of the signal at 30.2℃ and 100kHz;

[0026] Figure 6 This is a schematic diagram of multiple parameters in the output signal. Detailed Implementation

[0027] Figures 1-6 The following description illustrates optional embodiments of the invention to teach those skilled in the art how to implement and reproduce the invention. Some conventional aspects have been simplified or omitted to explain the technical solutions of the invention. Those skilled in the art should understand that variations or substitutions derived from these embodiments will be within the scope of the invention. Those skilled in the art should understand that the following features can be combined in various ways to form multiple variations of the invention. Therefore, the invention is not limited to the following optional embodiments, but is defined only by the claims and their equivalents.

[0028] Example 1.

[0029] The method for obtaining the operating parameters of the ultrasonic flowmeter in this embodiment of the invention is as follows: Figure 1 As shown, the method for obtaining the information includes the following steps:

[0030] like Figure 2 As shown, the ultrasonic flow meter includes a first transducer 21 and a second transducer 22, which are mounted on the connecting rod 11.

[0031] A1. At zero flow rate, adjust the operating temperature and the operating frequency of the first transducer 21, with multiple frequencies corresponding to the same temperature.

[0032] like Figures 3-5 As shown, the second transducer 22 outputs multiple parameters corresponding to the operating temperature and frequency.

[0033] A2. An evaluation value is derived based on the multiple parameters, and the evaluation value corresponds to the operating temperature and frequency.

[0034] A3. Find the maximum value among multiple evaluation values ​​corresponding to the same temperature, and use the frequency corresponding to the maximum value as the preferred frequency corresponding to the working temperature.

[0035] A4. Establish and save data points, including operating temperature, preferred frequency, and evaluation value.

[0036] To adapt to different measurement environment temperatures, the method further includes the following steps:

[0037] A5. Construct an analysis model based on the data points.

[0038] A6. In the application, the ambient temperature is obtained, and the preferred frequency corresponding to the ambient temperature is output using the analysis model, which is used as the operating frequency of the first transducer. The second transducer outputs multiple parameters corresponding to the ambient temperature and the preferred frequency to obtain the actual flow rate.

[0039] To refine the analysis model and adapt it to each instrument, the method further includes the following steps:

[0040] A7. Determine whether the actual flow rate is zero.

[0041] If the flow rate is not zero, continue the measurement.

[0042] If the flow rate is zero (if the deviation between the actual flow rate and zero is less than the threshold, the actual flow rate is zero), proceed to the next step.

[0043] A8. Determine whether the measured ambient temperature is the same as the working temperature in step A1.

[0044] If the result is yes, obtain the actual evaluation values ​​corresponding to the multiple parameters output in step A6, replace the evaluation values ​​in the data points corresponding to the working temperature in step A4 with the actual evaluation values, and update the analysis model.

[0045] If the result is negative, obtain the actual evaluation values ​​corresponding to the multiple parameters output in step A6. Using the actual evaluation values, the measured ambient temperature, and the preferred frequency output in step A6, establish new data points and save them, and update the analysis model.

[0046] To obtain the optimal frequency more scientifically, the parameters further include the normalized signal-to-noise ratio (SNR), received wave amplitude (H), received wave duration (CT), and ultrasonic flight jitter (σ). TOF .

[0047] To obtain a better evaluation, the evaluation value Q is further defined as follows:

[0048] Q = a·SNR + b·H + c·CT + d·σ TOF a, b, c, and d are weights, and a + b + c + d = 1.

[0049] Example 2.

[0050] An example of the application of the method for obtaining the working parameters of an ultrasonic flowmeter according to Embodiment 1 of the present invention in flue gas velocity monitoring.

[0051] In this application example, such as Figure 1 As shown, the method includes the following steps:

[0052] A1. Before leaving the factory, the ultrasonic flow meter undergoes testing, specifically:

[0053] At zero flow rate, adjust the operating temperature (ambient temperature) of the first transducer 21 and the second transducer 22, with a temperature change range of [-20℃-100℃] and a change step of 2℃.

[0054] At each temperature point, the circuit drives the alternating voltage frequency of the first transducer 21, with a frequency variation range of [80kHz-120kHz] and a variation side length of 1kHz.

[0055] like Figures 3-5 As shown, the current temperature is 30.2℃, and the frequencies are 80kHz, 90kHz, and 100kHz. Green represents the transmitted signal of the first transducer 21, blue represents the output voltage signal of the second transducer 22, and yellow represents the positive half-envelope wave of the output signal after half-wave rectification and low-pass filtering.

[0056] like Figure 6 As shown, multiple parameters corresponding to the operating temperature and frequency are obtained from the output of the second transducer 22. These parameters are as follows:

[0057] 1. Signal-to-noise ratio (SNR).

[0058] The ADC acquires the output signal s(t) (including noise) of the second transducer 22.

[0059] Locate the main peak time window [t1,t2] of the received original wave.

[0060] Calculate the power of the original received wave signal:

[0061] μ noise The noise mean (which can be calculated from the no-signal mean of the received signal when no ultrasonic wave is emitted), t s =t2-t1+1.

[0062] Calculate the noise power by selecting the sample noise s from the signal-free region after the delay segment of the original received wave signal in the above formula. noise (t).

[0063] , t s =t4-t3+1, where t3 is the start time of the no-signal zone in the delay segment, and t4 is the end time of the no-signal zone in the delay segment.

[0064] Calculate SNR: .

[0065] 2. Ultrasonic flight jitter σ TOF The calculation method is as follows:

[0066] like Figure 6 As shown, the time it takes for an ultrasonic wave to travel from the first transducer 21 to the second transducer 22 and form the first main peak in the fluid is defined as the flight time.

[0067] The standard deviation of the TOF measured 10 consecutive times was used as σ. TOF .

[0068] 3. The received wave amplitude H and received wave duration CT are calculated by analyzing the envelope of the original signal, such as... Figure 6 As shown.

[0069] For example, at a temperature of 30.2℃ and frequencies of 80kHz, 90kHz, and 100kHz, the parameters are shown in Table 1.

[0070] Table 1 shows the parameters at different operating frequencies at the same temperature.

[0071] .

[0072] Because the four parameters mentioned above have different dimensions, there are significant differences, such as flight jitter σ. TOF The values ​​of H are in μs (e.g., 0.8 μs) and mV (e.g., 1000 mV). The two values ​​differ greatly. If they are directly used in the weighted scoring method for calculation, the parameters will be overwhelmed by the difference in dimensions. Therefore, it is necessary to normalize the data of the above four parameters (key characteristic indicators).

[0073] The amplitude H and duration CT are normalized using the Min-Max normalization method, as shown in the following formula.

[0074] .

[0075] The SNR (signal-to-noise ratio) is normalized using a log-linear transformation method, as shown in the following formula:

[0076] .

[0077] All three parameters mentioned above are considered better the larger they are, but σ TOF The evaluation of flight jitter parameter should be as low as possible, so the Min-Max normalization method, which takes the reciprocal, should be used. The formula is as follows:

[0078] X 正向 =1 / X.

[0079] In the original Min-Max normalization method, X is X 正向 Substitute the values ​​into the calculation.

[0080] At 30.2℃, there are 40 frequency points. Based on the experimental results, the normalized min and max values ​​of the above four key characteristic indicators can be obtained, as shown in Table 2.

[0081] Table 2 shows the min and max values ​​of multiple parameters after normalization.

[0082] .

[0083] A2. An evaluation value is derived based on multiple normalized parameters, and the evaluation value corresponds to the operating temperature and frequency.

[0084] The evaluation value Q = 0.35·SNR + 0.15·H + 0.15·CT + 0.35·σ TOF .

[0085] For example, at a temperature of 30.2℃, the evaluation values ​​for each frequency (80kHz, 90kHz, and 100kHz) are as follows:

[0086] Q(80kHz, 30.2℃)=0, Q(90kHz, 30.2℃)=0.4701, Q(100kHz, 30.2℃)=0.7547.

[0087] A3. Find the maximum value among multiple evaluation values ​​corresponding to the same temperature, and use the frequency corresponding to the maximum value as the preferred frequency corresponding to the working temperature.

[0088] A4. Establish and save the data points, which include operating temperature, preferred frequency, and evaluation value, as shown in Table 3.

[0089] Table 3 shows the parameters (operating temperature, optimization frequency, and evaluation value) for each data point.

[0090] .

[0091] A5. Based on the data points, learn a Bayesian optimization (BO) analysis model.

[0092] A6. In field applications, the ambient temperature is obtained, and the preferred frequency corresponding to the ambient temperature is output using the analysis model. This frequency is used as the operating frequency of the first transducer. The second transducer outputs multiple parameters corresponding to the ambient temperature and the preferred frequency to obtain the actual flow rate.

[0093] For example, if the ambient temperature measured by the ultrasonic flowmeter is 25.1℃, and the optimal frequency for the ultrasonic transducer at this temperature is predicted to be 107.4kHz according to the analysis model, and this frequency is used as the operating frequency of the first transducer 21, then the second transducer 22 obtains the signal-to-noise ratio (SNR), received wave amplitude (H), received wave duration (CT), and ultrasonic wave flight jitter (σ) at the current temperature. TOF Meanwhile, the instrument measured the current flow velocity as 0.53 m / s.

[0094] The ambient temperature measured by the ultrasonic flowmeter is 31.2℃. Based on the analysis model, the optimal frequency for the ultrasonic transducer at this temperature is predicted to be 105.4kHz. Using this frequency as the operating frequency of the first transducer 21, the second transducer 22 obtains the signal-to-noise ratio (SNR), received wave amplitude (H), received wave duration (CT), and ultrasonic wave flight jitter (σ) at the current temperature. TOF Meanwhile, the instrument measured the current flow velocity as 0.11 m / s, which is less than the flow velocity threshold of 0.2 m / s, and the current flow velocity is zero.

[0095] The ambient temperature measured by the ultrasonic flowmeter is 30.2℃. Based on the analysis model, the optimal frequency for the ultrasonic transducer at this temperature is predicted to be 105kHz. Using this frequency as the operating frequency of the first transducer 21, the second transducer 22 obtains the signal-to-noise ratio (SNR), received wave amplitude (H), received wave duration (CT), and ultrasonic wave flight jitter (σ) at the current temperature. TOF Meanwhile, the instrument measured the current flow velocity as 0.14 m / s, which is less than the flow velocity threshold of 0.2 m / s, and the current flow velocity is zero.

[0096] A7. Determine whether the actual flow rate is zero.

[0097] If the flow rate is not zero, continue the measurement.

[0098] If the actual flow velocity of 0.53 m / s is not zero, the ultrasonic flow meter will continue to measure at the preferred frequency.

[0099] If the flow rate is zero (if the deviation between the actual flow rate and zero is less than the threshold, the actual flow rate is zero), proceed to the next step.

[0100] A8. Determine whether the measured ambient temperature is the same as the working temperature in step A1.

[0101] If the result is yes, obtain the actual evaluation values ​​corresponding to the multiple parameters output in step A6, replace the evaluation values ​​in the data points corresponding to the working temperature in step A4 with the actual evaluation values, and update the analysis model.

[0102] If the result is negative, obtain the actual evaluation values ​​corresponding to the multiple parameters output in step A6. Using the actual evaluation values, the measured ambient temperature, and the preferred frequency output in step A6, establish new data points and save them, and update the analysis model.

[0103] For example, if the ambient temperature is 30.2℃ and the operating temperature in step A1 is the same, then based on the multiple parameters of the second transducer 22 in A6 (signal-to-noise ratio SNR, received wave amplitude H, received wave duration CT, and ultrasonic flight jitter σ), TOFThe actual evaluation value is obtained and replaced with the evaluation value in the data point corresponding to the working temperature in step A4, and the analysis model is updated.

[0104] Since the ambient temperature of 31.2℃ is different from the operating temperature in step A1, the actual evaluation value is obtained based on multiple parameters of the second transducer 22 in A6. The actual evaluation value, the currently measured ambient temperature of 31.2℃, and its corresponding preferred frequency are used as new data points to update the analysis model.

Claims

1. A method of obtaining operating parameters of an ultrasonic flow meter, the ultrasonic flow meter comprising a first transducer and a second transducer; characterized by, The obtaining method comprises the following steps: A1. At zero flow rate, adjusting the working temperature and the working frequency of the first transducer, the same temperature corresponding to multiple frequencies, the second transducer outputting multiple parameters corresponding to the working temperature and the frequency; the multiple parameters are respectively normalized signal-to-noise ratio SNR, received amplitude H, received wave duration CT and ultrasonic wave flight jitter σ TOF ; A2. obtaining an evaluation value according to the plurality of parameters, the evaluation value corresponding to the working temperature and the frequency; A3. finding the maximum value in the plurality of evaluation values corresponding to the same temperature, and the frequency corresponding to the maximum value is taken as the preferred frequency corresponding to the working temperature; A4. establishing and saving a data point, the data point comprising the working temperature, the preferred frequency and the evaluation value; The receiving amplitude H and the receiving wave duration CT are obtained by analyzing the envelope wave of the original signal output by the second transducer TOF The ultrasonic flight jitter σ is obtained by obtaining the time of flight, which is the time difference between the ultrasonic wave output by the first transducer and the first main peak formed by the second transducer; and the standard deviation of multiple time of flight measurements is the ultrasonic flight jitter σ TOF .

2. The obtaining method of claim 1, wherein, The obtaining method further comprises the following steps: A5. constructing an analysis model according to the data of the data point; A6. in the application, obtaining a measured ambient temperature, outputting the preferred frequency corresponding to the measured ambient temperature by using the analysis model, and taking the preferred frequency as the working frequency of the first transducer, and the second transducer outputs a plurality of parameters corresponding to the measured ambient temperature and the preferred frequency, and obtaining the actual flow rate.

3. The obtaining method of claim 2, wherein, The obtaining method further comprises the following steps: A7. judging whether the actual flow rate is zero; if the flow rate is not zero, continue to measure; if the flow rate is zero, proceed to the next step; A8. judging whether the measured ambient temperature is the same as the working temperature in step A1; if the result is yes, obtaining an actual evaluation value corresponding to the plurality of parameters outputted in step A6, replacing the evaluation value in the data point corresponding to the working temperature in step A4 with the actual evaluation value, and updating the analysis model; if the result is no, obtaining an actual evaluation value corresponding to the plurality of parameters outputted in step A6, establishing a new data point by using the actual evaluation value, the measured ambient temperature and the preferred frequency outputted in step A6, saving the new data point, and updating the analysis model.

4. The obtaining method according to claim 3, wherein, In step A7, if the deviation between the actual flow rate and zero is less than a threshold value, the actual flow rate is zero.

5. The obtaining method of claim 1, wherein, The evaluation value Q is: Q = a • SNR + b • H + c • CT + d • σ TOF where a, b, c and d are weights, a + b + c + d = 1.

6. The obtaining method according to claim 5, wherein, a=0.35, b=0.15, c=0.15, d=0.

35.

7. The obtaining method of claim 1, wherein, The normalization of the amplitude and the duration adopts the Min-Max normalization method, the normalization of the signal-to-noise ratio adopts the logarithmic linear conversion normalization method, and the normalization of the flight jitter adopts the Min-Max normalization method after taking the reciprocal.

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