Fluid working condition determination method and flow measurement method and device thereof

Abstract

The invention discloses a fluid working condition determination method and a flow measurement method and device thereof, and the method comprises the steps: detecting the maximum amplitude of an ultrasonic signal, calculating a series of standard deviation values of the maximum amplitude, and judging whether the fluid contains bubbles or not through the standard deviation values; the amplification coefficient of the ultrasonic signal is adjusted according to the condition that the fluid contains the bubbles, so that the condition that the ultrasonic signal is disordered due to the bubbles is avoided, and the stability and accuracy of flow measurement are improved.

Description

Technical Field

[0001] The present invention relates to an ultrasonic flowmeter, and in particular to a method for determining a fluid working condition used in ultrasonic flowmeter technology, a flow measurement method, and a measuring device. Background Art

[0002] Ultrasonic flowmeter is a device that measures flow by detecting the acceleration and deceleration effect of the fluid flow on the ultrasonic beam (or ultrasonic pulse). The time difference method is widely used in the field of ultrasonic flow measurement. Its principle is to calculate the flow velocity of the fluid by measuring the difference between the propagation time of the ultrasonic signal in the fluid in the downstream and the propagation time in the upstream, and then calculate the flow rate of the fluid. Specifically, Figure 8 As shown, the flow meter has a pipe section 51, and piezoelectric vibrators 52 and 53 are respectively set upstream and downstream of the pipe section 51. The piezoelectric vibrators 52 and 53 transmit and receive ultrasonic waves to each other, and the controller 53 measures the ultrasonic waves along the direction of fluid flow (see Figure 8 The propagation time of the ultrasonic wave propagating between the two piezoelectric vibrators in the direction of fluid inflow (indicated by arrow A and the direction of fluid outflow (indicated by arrow B)) and the propagation time of the ultrasonic wave propagating between the two piezoelectric vibrators in the direction opposite to the fluid flow are measured. When the ultrasonic wave propagates in the downstream direction, the propagation speed is accelerated by the fluid flow speed, and when the ultrasonic wave propagates in the reverse direction, the propagation speed is slowed down by the fluid flow speed. The flow velocity and flow rate of the fluid can be calculated based on the difference between the measured upstream and downstream propagation times. The pipe section 51 of the ultrasonic flowmeter can be as follows: Figure 8 In the broken line shape shown, the piezoelectric vibrators 52 and 53 are respectively arranged at the upstream and downstream ends of the broken line pipe section, so that the piezoelectric vibrator can be completely shielded by the pipe section to avoid contact between the fluid in the pipe section and the piezoelectric vibrator, and to avoid mutual corrosion and contamination between the two; and the ultrasonic wave can be propagated in the medium basically in a straight path, which can reduce the energy loss caused by passing through the medium interface.

[0003] The threshold method is often used in ultrasonic flowmeters to measure the propagation time of ultrasonic waves. The ultrasonic waveform generated by each excitation of the piezoelectric vibrator is a spindle-shaped wave with an envelope shape. The ultrasonic signal has a series of zero-crossing points that cross the zero axis from negative to positive. When the peak of the detected waveform signal exceeds the threshold line, the first zero-crossing point after the peak is taken as the timing point, thereby measuring the corresponding propagation time. Using this method, the downstream propagation time of the ultrasonic wave in the fluid and the upstream propagation time of the ultrasonic wave in the fluid can be calculated respectively. The flow velocity of the fluid is then calculated based on the difference between the downstream and upstream propagation times. However, during the flow measurement process, because the fluid being measured may not be a pure liquid and may contain substances such as bubbles, the propagation of the ultrasonic wave in the fluid will be affected by the interference of bubbles and other substances, resulting in large fluctuations in the ultrasonic signal waveform. This makes the timing points calculated by the threshold method inaccurate, resulting in flow measurement errors.

[0004] In addition, in existing ultrasonic flow meters, it is usually necessary to amplify the ultrasonic signal to meet the needs of subsequent flow measurement processing of the ultrasonic signal. However, when the ultrasonic signal waveform fluctuates greatly due to interference from substances such as bubbles, it will cause the amplification factor used to control the amplification factor of the ultrasonic signal to be frequently adjusted, causing the waveform amplitude of the ultrasonic signal to oscillate more vigorously, resulting in a decrease in the measurement accuracy of the ultrasonic flow meter. Summary of the Invention

[0005] In order to solve the problem of existing ultrasonic flowmeters that propagation in the fluid may be affected by interference from substances such as bubbles, resulting in large fluctuations in the ultrasonic signal waveform, which makes the timing point calculated by the threshold method inaccurate and leads to errors in flow measurement, the present invention provides a fluid working condition determination method and flow measurement method and measurement device that can effectively determine whether there are bubbles in the fluid, maintain reasonable adjustment of the amplification factor and accurate flow measurement, while avoiding frequent adjustment of the amplification factor and avoiding aggravated oscillation of the waveform amplitude, thereby improving the flow measurement accuracy.

[0006] The specific technical solution adopted by the present invention to solve the above technical problems is: a method for determining fluid working conditions, characterized in that it includes the following determination steps: A1. Initialize the system; A2. Receive ultrasonic signals, receiving ultrasonic signals propagating in the fluid; A3. Preprocess the ultrasonic signal. This includes amplifying the ultrasonic signal and acquiring the ADC waveform. A4 detects the maximum amplitude data of this signal, and performs maximum amplitude detection on the ultrasonic signal preprocessed in step A3 above; A5. Store the maximum amplitude data of the signal, store the detected maximum amplitude, and accumulate the stored value; A6 determines whether the number of stored values ​​meets the first set value. If so, the standard deviation of the amplitude data consisting of multiple maximum amplitude detection values ​​is calculated. Otherwise, it returns to step A2 above and executes the subsequent steps in sequence. A7. Determine whether the calculated standard deviation data value is greater than a first set standard deviation threshold. If so, determine that the fluid operating condition is a bubble condition; if not, determine that the fluid operating condition is a normal condition.

[0007] By preprocessing, storing, and calculating the standard deviation of the ultrasonic maximum signal amplitude data and comparing it with the first set standard deviation threshold, the fluid working condition can be determined, and whether the fluid contains bubbles can be effectively determined. This can provide relevant effective calculation and measurement execution basis for the subsequent reasonable adjustment of the amplification factor and accurate flow measurement.

[0008] Preferably, in the above steps A5 to A7, the amplitude data consisting of multiple maximum detected amplitudes are recorded as an amplitude sequence. After performing a standard deviation calculation on the amplitude sequence, the amplitude sequence is recorded as The amplitudes in the sequence are replaced with the newly detected amplitudes in a first-in, first-out fashion, and the standard deviation calculation is performed again on the amplitude sequence to obtain the newly calculated standard deviation data. This improves the real-time reliability and effectiveness of standard deviation data acquisition.

[0009] Preferably, in step A4, the waveform determination unit detects the maximum amplitude of the pre-processed ultrasonic signal, and transmits and stores the detected maximum amplitude data to form an amplitude sequence, thereby improving the accuracy, reliability and effectiveness of the determination of the pre-processed ultrasonic signal.

[0010] Another invention object of the present invention application is to provide a fluid flow measurement method, which is characterized in that: after receiving the ultrasonic signal, it is amplified and the amplification factor of the ultrasonic signal is adjustable; using the fluid working condition determination method of the above-mentioned claims 1 to 3, when the fluid working condition is determined to be a bubble working condition, the amplification factor of the ultrasonic signal is not adjusted.

[0011] Preferably, it is characterized in that the following measuring steps are specifically performed: B1. Initialize the system; B2. Receive ultrasonic signals, receiving ultrasonic signals propagating in the fluid; B3. Preprocessing the ultrasonic signal, preprocessing the ultrasonic signal, including ultrasonic signal amplification and ADC waveform acquisition; B4. Determine whether the processed signal meets the set requirements. The ultrasonic signal pre-processed in step B3 is determined to meet the set requirements. If it is determined to meet the set requirements, the following steps B5 to B10 and B11 to B16 are executed in sequence; if it is determined that it does not meet the set requirements, return to step B2 above and loop through step B2 and the following steps; B5. If the above step B4 determines that the set requirements are met, the maximum amplitude data of the signal is detected, and the maximum amplitude detection of the ultrasonic signal pre-processed in step B3 is performed; B6. Store the maximum amplitude data of the signal. This data is stored and the number of detected maximum amplitudes is accumulated. B7 determines whether the storage quantity satisfies the first set value. After the number of stored items in step B6 is accumulated to the first set number, the storage quantity satisfies the first set number to determine; B8 standard deviation calculation, the above step B7 determines whether the first set number is satisfied, the standard deviation of the amplitude data consisting of a plurality of detection amplitudes is calculated; B9. If the above step B7 does not satisfy the first set number, return to step B2 and loop through the above steps B2 to B7; B10 determines whether the calculated standard deviation data value is greater than the first set standard deviation threshold, the standard deviation data calculated in B8 is compared with the first set standard deviation threshold to determine the fluid condition; if the judgment is yes, the fluid condition is determined to be a bubble condition; if the judgment is no, the fluid condition is determined to be a normal condition; B11. If the above step B4 determines that the setting requirements are met, when executing the above step B5, the signal after processing is also determined to meet the setting requirements and steps B11 to B16 are executed simultaneously; B12. Determine whether the processed signal meets the set requirements. If so, execute the task of storing the signal. B13. Determine whether the number of stored signals is two and continuous. Determine whether the number of stored signals after processing meets the set requirement of two and continuous. and signal When all are determined to be ultrasonic signals that meet the set requirements, cross-correlation calculation is performed; B14. In step B12 above, if the ultrasonic signal is determined to be not in compliance with the set requirements, the previous signal is cleared and the process returns to step B2 above to loop through steps B5 to B10 and steps B11 to B16 above, and then determines whether the next signal meets the set requirements until step B12 above is executed to determine whether two consecutive signals meet the set requirements. and signal All are judged to be ultrasonic signals that meet the set requirements; B15. In step B10 above, when the received fluid operating condition is identified as a bubble condition, the amplification factor is maintained unchanged; B16. In step B10 above, when the received fluid operating condition is identified as a normal operating condition, the first set amplitude range is compared with the average value of the amplitude data. If the average value of the amplitude data is within the first set amplitude range, the amplification factor is determined to be reasonable at this time, and the amplification factor is maintained unchanged. If the average value of the amplitude data is not within the first set amplitude range, the amplification factor is determined to be unreasonable at this time, and an adjustment factor is obtained based on the ratio of the middle value of the first set amplitude range to the maximum value of the detected amplitude, and the amplification factor is adjusted accordingly based on the adjustment factor. It can meet the reasonable adjustment of the amplification factor under different working conditions, avoid excessive adjustment of the amplification factor, and avoid the intensified oscillation of the waveform amplitude, thereby realizing accurate flow measurement.

[0012] Preferably, in the above step B16, when the first set amplitude range is compared with the average value of the amplitude data, the method for determining whether the average value of the amplitude data is within the first set amplitude range is to determine whether the processed signal meets the following set requirement steps: C1: Detect the maximum amplitude of the signal and compare it with the signal amplitude range. If the detected maximum amplitude is within the signal amplitude range, enter step D2, otherwise clear the signal. or signal , and clear the previous signal or signal , and return to step B2 above; C2: Record the signal or signal The maximum amplitude and the horizontal coordinate corresponding to the maximum amplitude are compared with the maximum amplitude and the horizontal coordinate corresponding to the maximum amplitude of the previous ultrasonic signal. If the maximum amplitude difference and the amplitude horizontal coordinate difference are both less than the set range, the fixed point is extrapolated forward and backward with the horizontal coordinate position of the maximum amplitude as the center, and the area between the front and rear points is used as the effective waveform judgment area of ​​the signal; if the maximum amplitude difference / amplitude horizontal coordinate difference is greater than the set range, the previous signal is cleared. or signal , and return to step B2 above; C3: Use the positive and negative set thresholds to convert the part of the signal located in the valid waveform judgment area into high and low levels, and count the duration and number of high and low levels, and compare them with the set time range and set number range of high and low levels. If the counted duration and number of high and low levels are both within the set time range and set number range of high and low levels, then it is determined that the processed signal is an ultrasonic signal that meets the set requirements, and the subsequent operations of the above step B13 are executed; otherwise, return to the above step B2.

[0013] Preferably, when the step B10 is executed to determine whether the fluid working condition is normal, the steps B13 to B16 and the following amplification factor determination, adjustment, propagation time calculation and flow rate measurement methods are executed; D1. Determine whether the fluid working condition is normal; perform the following steps D2 to D3 or D4 to D3 according to the fluid working condition; D2. When the fluid working condition is determined to be an abnormal bubble working condition, the fluid propagation time calculation is performed and the amplification factor is maintained unchanged; D3. After performing the fluid propagation time calculation in step D2 above, perform the fluid flow measurement task; D4. When the fluid working condition is determined to be normal, the execution determines whether two adjacent detection amplitudes are within the first set amplitude range; D5. If the values ​​in step D4 are all within the first set amplitude range, the fluid propagation time calculation is performed and the amplification factor is maintained at a reasonable level. D6. After calculating the fluid propagation time in step D5 above, perform the fluid flow measurement task; D7. If the above step D4 determines that none of the values ​​are within the first set amplitude range, the fluid propagation time calculation and the unreasonable amplification factor adjustment tasks are performed; D8. In the above step D7, after performing the fluid propagation time calculation, the fluid flow measurement task is performed.

[0014] Improve the determination of fluid working conditions and amplification factors, and make the flow measurement accurate, reliable, stable and effective.

[0015] Preferably, in the cross-correlation calculation in step B15, the first flow measurement unit and the second flow measurement unit are respectively set in the FPGA processor and the DSP processor, and the FPGA processor is used to execute the functional program in the first flow measurement unit; the DSP processor is used to execute the functional program in the second flow measurement unit; the DSP processor can perform precise calculations on floating-point numbers and has high-precision and efficient processing capabilities. When the DSP processor is used to calculate the propagation time, the cross-correlation calculation data calculated by the FPGA processor can be converted from integer type to floating-point type. This takes into account the large amount of computation required for the amortized cross-correlation method, the parallel processing of fluid working condition detection operations, and the high-precision processing capability for accurately measuring the fluid flow rate, thereby improving processing accuracy, stability, reliability and effectiveness.

[0016] Another invention purpose of the present invention application is to provide a fluid flow measurement device, characterized in that: the fluid operating condition determination method described in one of the above technical solutions and the fluid flow measurement method described in one of the above technical solutions are adopted, and the fluid flow measurement device adopted includes a pipe section, a first piezoelectric vibrator, a second piezoelectric vibrator and a control operation unit, the first piezoelectric vibrator and the second piezoelectric vibrator are respectively attached to the wall surfaces at both ends of the pipe section, and the first piezoelectric vibrator and the second piezoelectric vibrator are respectively electrically connected to the control operation unit; the control operation unit includes a signal control unit, a signal processing unit, a first flow measurement unit and a second flow measurement unit, wherein the first flow measurement unit includes a waveform determination unit, a first operation unit, an operating condition determination unit and a second operation unit, and the second flow measurement unit includes an identification and comparison unit, a time difference operation unit, a flow operation unit, an amplification factor determination unit and an amplification factor adjustment unit; the signal processing unit includes an amplifying unit and an acquiring unit, the signal control unit is used to receive an ultrasonic signal propagating in the fluid, and the signal processing unit is used to receive a signal The control unit transmits the ultrasonic signal and performs preprocessing, which includes ultrasonic signal amplification and ADC waveform acquisition; the waveform judgment unit is used to detect the maximum amplitude and waveform judgment of the ultrasonic signal waveform processed by the signal processing unit, the first operation unit is used to perform standard deviation operation and calculation on the ultrasonic waveform signal after detection and judgment by the waveform judgment unit, the second operation unit is used to perform cross-correlation calculation on two consecutive ultrasonic signals, the working condition judgment unit is used to compare the standard deviation data value calculated by the first operation unit with the first set standard deviation threshold to determine the fluid working condition; the amplification coefficient judgment unit compares the first set amplitude range with the average value of the amplitude data to determine whether the amplification coefficient is reasonable at this time; the amplification coefficient adjustment unit 32 is used to calculate the corresponding adjustment coefficient, and the adjustment coefficient is determined according to the ratio of the middle value of the first set amplitude range to the maximum value of the detected amplitude; the time difference operation unit is used to calculate the propagation time according to the cross-correlation calculation data; the flow operation unit is used to measure the flow rate of the fluid according to the propagation time. Improve the accuracy, reliability, stability and effectiveness of the determination method of fluid working conditions and its fluid flow measurement method, and maintain reasonable adjustment of the amplification factor and accurate flow measurement while avoiding frequent adjustment of the amplification factor and avoiding aggravated oscillation of the waveform amplitude.

[0017] Preferably, the working condition determination unit is provided with a first set standard deviation threshold, and the amplification factor determination unit is provided with a first set amplitude range, thereby improving the reliability and effectiveness of the determination criteria of the working condition determination unit and the amplification factor determination unit.

[0018] The beneficial effects of the present invention are as follows: the present invention provides a method for determining fluid working conditions and a flow measurement method and a measuring device using the above method, by evaluating the standard deviation of the maximum amplitude of the ultrasonic signal, and using the standard deviation to determine whether the fluid contains bubbles; by making targeted settings for the adjustment of the amplification factor under different working conditions, reasonable adjustment of the amplification factor under different working conditions is met, and excessive adjustment of the amplification factor is avoided, as well as the aggravated oscillation of the waveform amplitude is avoided, thereby achieving accurate flow measurement.

[0019] The present invention also provides a configuration scheme based on FPGA and DSP dual processors, which uses the FPGA processor to perform cross-correlation calculations while also performing amplitude sequence The standard deviation calculation and fluid working condition determination fully utilize the parallel processing capability of the FPGA processor and give play to its time-efficiency performance advantage; the DSP processor is used to perform data type conversion and linear interpolation on the cross-correlation calculation data, making full use of the high-precision capability of the DSP processor to improve the flow measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The present invention provides a flow chart of a method for determining a fluid working condition and a flow measurement method thereof, as well as a method for determining a fluid working condition in a measuring device.

[0021] Figure 2 for Figure 1 The fluid operating condition determination method shown is a structural and functional block diagram applied to a flow measurement device.

[0022] Figure 3 This is a method for determining fluid working conditions and its flow measurement method, various bubble density working conditions in the measuring device, and a standard deviation diagram of the ultrasonic signal amplitude under normal working conditions.

[0023] Figure 4 The present invention provides a method for determining a fluid working condition, a flow measurement method thereof, and a schematic structural diagram of a fluid flow measurement device in the measurement device.

[0024] Figure 5 for Figure 4 A flow chart of a method for determining a fluid operating condition and a flow measurement method thereof, and a fluid flow measurement method in a measuring device, applied to the present invention; Figure 6 for Figure 4 and Figure 5 A flow chart of a fluid flow measurement method according to a fluid working condition determination result in the fluid measurement method shown; Figure 7 This is a method for determining fluid working conditions and its flow measurement method, as well as a timing diagram of FPGA control in a measurement device of the present invention; Figure 8 This is a schematic diagram of the structure and principle of a time-of-flight ultrasonic flowmeter in the prior art; Figure 9 It is a waveform diagram of ultrasonic signals processed by a method for determining fluid working conditions and a flow measurement method and a measurement device of the present invention. DETAILED DESCRIPTION

[0025] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] Embodiment 1: Figure 1 and Figure 2 A flow chart of the method for determining fluid working conditions and Figure 1 The method is applied to a structural and functional block diagram of a flow measurement device; Figure 2 As shown ( Figure 2 The flow measuring device includes a pipe section 1, a first piezoelectric vibrator 2, a second piezoelectric vibrator 3 and a control operation unit. The pipe section 1 is arranged in a three-section broken line shape, and the middle section of the pipe section 1 is a straight line. The first piezoelectric vibrator 2 and the second piezoelectric vibrator 3 are respectively attached to the wall surfaces at both ends of the middle section of the pipe section 1 in the axial direction. The first piezoelectric vibrator 2 and the second piezoelectric vibrator 3 do not contact the fluid in the pipe section 1. The first piezoelectric vibrator 2 and the second piezoelectric vibrator 3 will not be corroded by the fluid, nor will they contaminate the fluid. They are particularly suitable for pipeline systems with high cleanliness requirements such as electronic chemicals. The transmission of ultrasonic waves through the wall of the pipe section 1 will cause energy loss. Figure 1 In the device, the first piezoelectric vibrator 2 and the second piezoelectric vibrator 3 are arranged at the axial ends of the straight pipe section 1, so that the ultrasonic wave propagates basically in a straight line between the two piezoelectric vibrators, reducing the energy loss caused by reflection and refraction when passing through the wall of the pipe section 1, which is beneficial to improving the signal quality of the ultrasonic wave and is particularly suitable for the measurement of small flow rates.

[0027] like Figure 2 and Figure 4As shown, in this embodiment, the control operation unit includes a signal control unit 4, a signal processing unit 5, a waveform determination unit 6, a first operation unit 7 and an operating condition determination unit 8; the signal control unit 4 is connected to the first piezoelectric vibrator 2 and the second piezoelectric vibrator 3 respectively through signal lines, and intermittently stimulates the first piezoelectric vibrator 2 or the second piezoelectric vibrator 3 on one side to send an ultrasonic signal through an excitation signal, and the second piezoelectric vibrator 3 or the first piezoelectric vibrator 2 on the other side receives the ultrasonic signal, and the sending and receiving of the ultrasonic signal are continuously switched back and forth between the first piezoelectric vibrator 2 and the second piezoelectric vibrator 3; when the ultrasonic propagation direction is consistent with the direction of fluid flow in the flow measuring device, the signal received by the piezoelectric vibrator is a downstream ultrasonic signal; when the ultrasonic propagation direction is opposite to the direction of fluid flow in the flow measuring device, the signal received by the piezoelectric vibrator is a downstream ultrasonic signal. The signal control unit 4 is provided with an amplifier 11 at the downstream stage, the amplifier 11 is provided with a collection unit 12 at the downstream stage, the collection unit 12 is provided with a waveform determination unit 6 at the downstream stage, the waveform determination unit 6 is provided with a first operation unit 7 and a second operation unit 9 at the downstream stage, the first operation unit 7 is provided with an operating condition determination unit 8 and an amplification factor determination unit 31 at the downstream stage, the operating condition determination unit 8 is provided with an amplification factor determination unit 31 at the downstream stage, the amplification factor determination unit 31 is provided with a time difference operation unit 25 at the downstream stage, the time difference operation unit 25 is provided with a flow rate operation unit 26 at the downstream stage, the amplification factor determination unit 31 is provided with an amplification factor adjustment unit 32 at the downstream stage, and the amplification factor adjustment unit 32 is provided with the amplifier 11 at the downstream stage.

[0028] The signal processing unit 5 includes an amplifier 11 and an acquisition unit 12. The amplifier 11 amplifies the received ultrasonic signal according to the amplification factor, and the amplified ultrasonic signal is transmitted to the acquisition unit 12; the acquisition unit 12 performs ADC waveform acquisition on the received ultrasonic signal at a fixed acquisition frequency, and the processed signal is transmitted to the waveform determination unit 6.

[0029] When measuring flow, if there are bubbles in the fluid, the bubbles will affect the propagation of ultrasonic waves in the fluid, and the ultrasonic signals received by the first piezoelectric vibrator 2 or the second piezoelectric vibrator 3 will be changed due to the interference of the bubbles. When there are bubbles in the fluid, the fluctuation of the amplitude of the ultrasonic signal propagating in the fluid will be more severe than the fluctuation of the amplitude of the ultrasonic signal propagating in normal working conditions. Figure 3 The figure shows the standard deviation of the maximum amplitude of the ultrasonic signal under various bubble density conditions and normal operating conditions. Curves Wave 1, Wave 2, and Wave 3 represent the standard deviation curves of the maximum amplitude of the ultrasonic signal measured under different bubble densities, respectively. Curve Wave 4 is the standard deviation curve of the maximum amplitude of the ultrasonic signal measured under normal operating conditions. It can be seen that the standard deviation of the maximum amplitude of the ultrasonic signal under bubble conditions is significantly greater than the standard deviation of the maximum amplitude of the ultrasonic signal under normal operating conditions. Based on this, the standard deviation value can be used to accurately and effectively determine whether there are bubbles in the fluid.

[0030] Therefore, the waveform determination unit 6 is used to detect the maximum amplitude of the processed signal, and the detected maximum amplitude data is transmitted to the first operation unit 7. The maximum amplitude stored in the first operation unit 7 can form an amplitude sequence. .

[0031] The maximum number of amplitude data that can be stored in the first operation unit 7 can be set to a first set number. In the embodiment of the present invention, the first set number can be selected as ten. When the maximum number of amplitude data stored in the first operation unit 7 accumulates to ten, the amplitude sequence is processed by the first operation unit 7. The standard deviation is calculated and the calculated standard deviation data is transmitted to the operating condition determination unit 8.

[0032] The working condition determination unit 8 is provided with a first set standard deviation threshold value, which can be selected to be equal to or slightly greater than the standard deviation value of the maximum amplitude of the ultrasonic signal under normal fluid working conditions. The working condition determination unit 8 compares the calculated standard deviation data value with the first set standard deviation threshold value. If the calculated standard deviation data value is greater than the first set standard deviation threshold value, the fluid working condition is determined to be a bubble working condition; if the calculated standard deviation data value is not greater than the first set standard deviation threshold value, the fluid working condition is determined to be a normal working condition (see Figure 5 ).

[0033] During the operation of the ultrasonic flowmeter, ultrasonic signals are continuously emitted and received. At the same time, the standard deviation of the maximum amplitude of the ultrasonic signal is calculated and updated based on the latest ultrasonic signal, and the normal fluid working condition is determined. After performing a standard deviation calculation, the amplitude series can be The maximum amplitude data in the sequence are replaced by the newly detected maximum amplitude data in accordance with the first-in-first-out principle, and the amplitude sequence is calculated using the standard deviation calculation unit 18. The standard deviation calculation is performed again to obtain newly calculated standard deviation data, and the fluid working condition is determined again to update the fluid working condition in real time.

[0034] 2) Example 2 Figure 4 A flow chart of a fluid measurement method; Figure 5 for Figure 4 A flow chart of a method for adjusting the amplification factor and calculating the flow rate according to the fluid working conditions in the method; Figure 6 for Figure 4 and Figure 5The method is applied to a structural and functional block diagram of a flow measuring device; in this embodiment, the flow measuring device includes a pipe segment 1, a first piezoelectric vibrator 2, a second piezoelectric vibrator 3 and a control operation unit. The pipe segment 1, the first piezoelectric vibrator 2, and the second piezoelectric vibrator 3 in this embodiment are the same components as the pipe segment 1, the first piezoelectric vibrator 2, and the second piezoelectric vibrator 3 in Example 1, and have the same position layout, and will not be repeated here.

[0035] In this embodiment, the waveform determination unit 6 is used to detect the maximum amplitude of the processed signal, and the detected maximum amplitude data is transmitted to the first operation unit 7. The maximum amplitude stored in the first operation unit 7 can form an amplitude sequence. .

[0036] The maximum number of amplitude data that can be stored in the first operation unit 7 can be set to a first set number. In the embodiment of the present invention, the first set number can be selected as ten. When the maximum number of amplitude data stored in the first operation unit 7 accumulates to ten, the amplitude sequence is processed by the first operation unit 7. The standard deviation is calculated and the calculated standard deviation data is transmitted to the operating condition determination unit 8.

[0037] A first set standard deviation threshold is provided in the operating condition determination unit 8. The first set standard deviation threshold can be selected as the standard deviation value of the maximum amplitude of the ultrasonic signal corresponding to when the fluid operating condition is normal, or a standard deviation value slightly larger than the maximum amplitude of the ultrasonic signal corresponding to when the fluid operating condition is normal. The operating condition determination unit 8 compares the calculated standard deviation data value with the first set standard deviation threshold. If the calculated standard deviation data value is larger than the first set standard deviation threshold, the fluid operating condition is determined to be a bubble condition; if the calculated standard deviation data value is not larger than the first set standard deviation threshold, the fluid operating condition is determined to be a normal condition.

[0038] Stable control of the amplification factor of the ultrasonic signal amplification factor is of great significance for improving the measurement accuracy of the flow measurement device. In the ultrasonic flowmeter, the amplification factor in the signal processing unit 5 is dynamically adjusted according to the waveform amplitude of the received ultrasonic signal to obtain the best ultrasonic signal-to-noise ratio. When in the bubble working state, the amplitude of the received ultrasonic signal is unstable, which will cause the amplification factor to be frequently adjusted, causing the waveform amplitude of the ultrasonic signal to oscillate more, resulting in a decrease in the measurement accuracy of the flow measurement device. Therefore, in this embodiment, an amplification factor determination unit 31 and an amplification factor adjustment unit 32 are respectively provided in the second flow measurement unit and the first flow measurement unit.

[0039] When the current fluid working condition is determined to be a bubble working condition, the amplification factor is maintained unchanged.

[0040] When the current fluid working condition is determined to be a normal working condition, the amplitude data used to calculate the standard deviation data is transmitted to the amplification coefficient determination unit 31; a first set amplitude range is provided in the amplification coefficient determination unit 31; the amplification coefficient determination unit 31 compares the first set amplitude range with the average value of the amplitude data. If the average value of the amplitude data is within the first set amplitude range, it is determined that the amplification coefficient is reasonable at this time and the amplification coefficient is maintained unchanged; if the average value of the amplitude data is not within the first set amplitude range, it is determined that the amplification coefficient is unreasonable at this time, and the corresponding adjustment coefficient is calculated by the amplification coefficient adjustment unit 32. The adjustment coefficient is determined based on the ratio of the middle value of the first set amplitude range to the maximum value of the detected amplitude. The adjustment coefficient is transmitted to the signal processing unit 5, and the signal processing unit 5 adjusts the amplification coefficient accordingly based on the adjustment coefficient.

[0041] During the aforementioned adjustment process of the amplification factor, if the amplification factor value to be adjusted, as determined based on the adjustment factor, is not less than the upper limit of the amplification factor, the amplification factor is directly adjusted to the upper limit; if the amplification factor value to be adjusted, as determined based on the adjustment factor, is less than the upper limit of the amplification factor, the amplification factor is directly adjusted to the value to be adjusted. By only adjusting the amplification factor when the fluid operating condition is determined to be normal, it is possible to maintain reasonable adjustment of the amplification factor while avoiding frequent adjustment of the amplification factor and preventing increased oscillation of the waveform amplitude.

[0042] By adjusting the above operation, the received ultrasonic signal can be stably amplified, whether the fluid is in normal working condition or bubble working condition, effectively ensuring the quality of the ultrasonic signal after amplification and other processing. or signal Perform maximum amplitude detection and use the waveform determination unit 6 to determine the signal or signal It determines whether the ultrasonic signal meets the set requirements, identifies the effective ultrasonic signal, and improves the accuracy of the flow measurement results. or signal After being transmitted to the waveform determination unit 6, the waveform determination unit 6 first detects the maximum amplitude of the signal. The waveform determination unit 6 is provided with a signal amplitude range. The waveform determination unit 6 compares the detected maximum amplitude with the signal amplitude range. If the detected maximum amplitude is within the signal amplitude range, the signal is recorded. or signal The maximum amplitude and the horizontal coordinate corresponding to the maximum amplitude are compared with the maximum amplitude of the previous ultrasonic signal and the horizontal coordinate corresponding to the maximum amplitude. If the maximum amplitude difference and the amplitude horizontal coordinate difference are both less than the set range (the set range can be obtained by placing the calibrated flow meter in the bubble working fluid for testing), the fixed points are extrapolated forward and backward with the horizontal coordinate position of the maximum amplitude as the center, and the area between the front and rear points is used as the effective waveform judgment area of ​​the signal for subsequent use; if the detected maximum amplitude is outside the signal amplitude threshold range, the signal is cleared or signal , and clear the previous signal or signal If the detected maximum amplitude is within the signal amplitude threshold range, but the maximum amplitude difference / amplitude horizontal coordinate difference is greater than the set range, the previous signal is cleared. or signal , re-receive the next ultrasonic signal propagating in the fluid, and repeat the above operation on the signal.

[0043] The waveform determination unit 6 is further provided with positive and negative set thresholds and set time ranges and set number ranges for high and low levels. The positive and negative set thresholds are used to convert the portion of the signal located in the valid waveform determination area into high and low levels, wherein the portion above the positive set threshold or below the negative set threshold is converted into a high level, and the portion below the positive set threshold or above the negative set threshold is converted into a low level. By counting the duration and number of high and low levels and comparing them with the set time range and set number range of high and low levels, if the counted duration and number of high and low levels are both within the set time range and set number range of high and low levels, then the processed signal is determined to be an ultrasonic signal that meets the set requirements; otherwise, the signal is cleared. or signal , receive the next ultrasonic signal propagating in the fluid, and repeat the above operation for the signal.

[0044] Since ultrasonic waves propagating in a fluid medium are easily affected by changes in the fluid environment, resulting in changes in the amplitude of the ultrasonic waveform, the existing ultrasonic measurement method based on threshold and zero-crossing comparison has the problem of easily generating wave jumps, resulting in low accuracy of flow detection results. Therefore, in this embodiment, a flow measurement method based on cross-correlation is adopted to accurately measure the flow rate.

[0045] When judging the signal or signal When the ultrasonic signal meets the set requirements, the signal meeting the set requirements is transmitted to the second operation unit 9. The second operation unit 9 can store an even number of signals meeting the set requirements. In the embodiment of the present invention, the second operation unit 9 can store two signals meeting the set requirements. When two consecutive signals meeting the set requirements are received, and signal After being sequentially stored in the second operation unit 9, the second operation unit 9 is used to perform cross-correlation calculation on two continuous signals; the cross-correlation calculation includes calculating the signal and signal The sum of products between the two is obtained by dividing the signal Data and signals in The data in the table are multiplied and accumulated in pairs, and the first product sum can be directly calculated, which is recorded as the product sum ; Then the signal The data position in the data is relatively offset, and each offset is only offset by 1 data position offset, and the above signal The data and the offset signal in The data in the _ are multiplied and accumulated again, and the sum of the products after the shift can be calculated. By repeating the above offset and subsequent calculation steps, multiple product sums can be obtained. The sums of multiple products are: , ,…, ,in is the data position offset; the sum of products The calculation formula is as follows: ∑ also represents the sum of the products when i=1, 2,…,n.

[0046] Based on the above-mentioned plurality of product sums, the maximum value of the product sum is detected by the second operation unit 9. The sum of the sum and product becomes the maximum data position offset The detected data position offset and the corresponding product sum are recorded as cross-correlation calculation data, and the calculated cross-correlation calculation data are transmitted to the second flow measurement unit.

[0047] The time difference calculation unit 25 in the second flow rate measurement unit calculates the propagation time based on the cross-correlation calculation data to determine the difference in the propagation time of the ultrasonic signal in the forward and reverse directions. More specifically, in the above propagation time calculation process, the corresponding forward and reverse propagation time difference is calculated based on the data position offset of the maximum value of the sum of products. The time difference calculation unit 25 transmits the difference data of the forward and reverse flow propagation times to the flow rate calculation unit 26 .

[0048] The flow calculation unit 26 is provided with a flow rate calculation formula using the difference between the forward and reverse flow propagation times as a variable. The flow rate calculation formula can be selected from the following forms: in is the flow rate, is the speed of ultrasound in the fluid medium, is the distance that the ultrasonic wave propagates in the fluid in pipe section 1; The flow rate calculation unit 26 uses the calculated difference in forward and reverse flow propagation time to calculate the flow rate. Calculate the flow rate of the fluid using the above flow rate calculation formula , and using the calculated flow rate The flow rate of the fluid is calculated based on the known cross-sectional area of ​​pipe segment 1.

[0049] The first set amplitude range is compared with the average value of the amplitude data. If the average value of the amplitude data is within the first set amplitude range, the first set amplitude range is compared with the average value of the amplitude data. If the average value of the amplitude data is not within the first set amplitude range, the first set amplitude range is compared with the average value of the amplitude data.

[0050] 3) Example 3 In the specific implementation process of the above scheme, considering that the cross-correlation method has a large amount of computation, and that it is also necessary to process the fluid condition detection calculation in parallel and accurately calculate the fluid flow rate, the processing capacity of a single chip solution is difficult to meet the above computational requirements at the same time. In this embodiment, the first flow measurement unit and the second flow measurement unit are respectively set in the FPGA processor and the DSP processor, and the FPGA processor is used to execute the functional program in the first flow measurement unit. Figure 7 An FPGA control timing diagram is shown. According to the timing diagram, it can be seen that the operation time involved in the cross-correlation calculation process is long and the amount of calculation is large. In addition, while the FPGA processor is used to perform the cross-correlation calculation, the amplitude sequence is also performed in this embodiment. The calculation of standard deviation and determination of fluid working conditions fully utilize the parallel processing capability of FPGA processor and give full play to its time-efficiency performance advantage.

[0051] Since floating-point operations on FPGA processors are usually implemented using fixed-point or floating-point simulations, the floating-point operation processing capabilities of FPGA processors are weak and inefficient, making it difficult to accurately measure the flow rate of the fluid. In this embodiment, a DSP processor is used to execute the functional program in the second flow measurement unit. The DSP processor can perform precise operations on floating-point numbers and has high-precision and efficient processing capabilities. When the DSP processor is used to calculate the propagation time, the cross-correlation calculation data calculated by the FPGA processor can be converted from integer type to floating-point type.

[0052] Since the cross-correlation calculation data calculated by the FPGA processor are all integers, the actual maximum value of the sum of products is usually at the data position offset and or Therefore, when the FPGA processor detects the maximum value of the sum of products, The sum of the sum and product becomes the maximum data position offset When the data position offset is adjacent to the data position offset, and the sum of the products corresponding to the adjacent data position offset It is detected that the above-detected data position offset and the corresponding product sum are both recorded as cross-correlation calculation data, and the cross-correlation calculation data is transmitted to the DSP processor via the FPGA processor. The DSP processor is used to convert the above-mentioned cross-correlation calculation data from integer type to floating-point type, and linear interpolation is performed between two adjacent data points. The maximum value of the product sum is obtained based on the cross-correlation calculation data after linear interpolation. The maximum value of the product sum calculated by the DSP processor using the above method is closer to the actual maximum value than the maximum value of the product sum calculated by the FPGA processor. Then, the corresponding data position offset is determined based on the maximum value of the product sum calculated by the DSP processor, and the corresponding difference in forward and reverse flow propagation time is calculated based on the data position offset of the maximum value of the product sum. , and then calculate the flow velocity and flow rate of the fluid with high precision.

[0053] The above specific embodiments are used to illustrate the present invention rather than to limit the present invention. Any modifications and changes made to the present invention within the scope of protection of the claims of the present invention shall fall within the scope of protection of the present invention.

[0054] In the description of the positional relationship of the present invention, terms such as "inside", "outside", "up", "down", "left", "right", etc. that indicate orientation or positional relationship are based on the orientation or positional relationship shown in the drawings. They are only for the convenience of describing the embodiments and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, they should not be understood as limiting the present invention.

Claims

1. A method for determining fluid operating conditions, characterized in that: The following steps are included A1. Initialize the system; A2. Receive ultrasonic signals, receiving ultrasonic signals propagating in the fluid; A3. Preprocess the ultrasonic signal. This includes amplifying the ultrasonic signal and acquiring the ADC waveform. A4 detects the maximum amplitude data of this signal, and performs maximum amplitude detection on the ultrasonic signal preprocessed in step A3 above; A5. Store the maximum amplitude data of the signal, store the detected maximum amplitude, and accumulate the stored value; A6 determines whether the number of stored values ​​meets the first set value. If so, the standard deviation of the amplitude data consisting of multiple maximum amplitude detection values ​​is calculated. Otherwise, it returns to step A2 above and executes the subsequent steps in sequence. A7. Determine whether the calculated standard deviation data value is greater than the first set standard deviation threshold. If so, the fluid working condition is determined to be a bubble condition. If the answer is no, the fluid working condition is determined to be normal.

2. The method for determining fluid operating conditions according to claim 1, wherein: In the above steps A5 to A7, the amplitude data consisting of multiple maximum detected amplitudes is recorded as an amplitude sequence , after calculating the standard deviation of the amplitude sequence, the amplitude sequence The amplitudes in the sequence are replaced with the newly detected amplitudes in accordance with the principle of first-in-first-out, and the standard deviation calculation is performed again on the amplitude sequence to obtain the newly calculated standard deviation data.

3. The method for determining fluid operating conditions according to claim 1, wherein: In the above step A4, the waveform determination unit is used to detect the maximum amplitude of the pre-processed ultrasonic signal, and the detected maximum amplitude data is transmitted and stored to form an amplitude sequence.

4. A method for measuring fluid flow, characterized in that: After receiving the ultrasonic signal, it is amplified and processed, and the amplification factor of the ultrasonic signal is adjustable; using the fluid working condition determination method of the above claims 1 to 3, when the fluid working condition is determined to be a bubble working condition, the amplification factor of the ultrasonic signal is not adjusted.

5. The fluid flow measurement method according to claim 4, characterized in that: Perform the following measurement steps: B1. Initialize the system; B2. Receive ultrasonic signals, receiving ultrasonic signals propagating in the fluid; B3. Preprocessing the ultrasonic signal, preprocessing the ultrasonic signal, including ultrasonic signal amplification and ADC waveform acquisition; B4. Determine whether the processed signal meets the set requirements. The ultrasonic signal pre-processed in step B3 is determined to meet the set requirements. If it is determined to meet the set requirements, the following steps B5 to B10 and B11 to B16 are executed in sequence; if it is determined that it does not meet the set requirements, return to step B2 above and loop through step B2 and the following steps; B5. If the above step B4 determines that the set requirements are met, the maximum amplitude data of the signal is detected, and the maximum amplitude detection of the ultrasonic signal pre-processed in step B3 is performed; B6. Store the maximum amplitude data of the signal. This data is stored and the number of detected maximum amplitudes is accumulated. B7 determines whether the storage quantity satisfies the first set value. After the number of stored items in step B6 is accumulated to the first set number, the storage quantity satisfies the first set number to determine; B8. If the first set number of values ​​is satisfied in step B7, the standard deviation of the amplitude data consisting of multiple detection amplitudes is calculated; B9. If the above step B7 does not satisfy the first set number, return to step B2 and loop through the above steps B2 to B7; B10 determines whether the calculated standard deviation data value is greater than the first set standard deviation threshold, the standard deviation data calculated in B8 above is compared with the first set standard deviation threshold to determine the fluid condition; If the judgment is yes, the fluid working condition is determined to be a bubble working condition; if the judgment is no, the fluid working condition is determined to be a normal working condition; B11. If the above step B4 determines that the setting requirements are met, when executing the above step B5, the signal after processing is also determined to meet the setting requirements and steps B11 to B16 are executed simultaneously; B12. Determine whether the processed signal meets the set requirements. If so, execute the task of storing the signal. B13. Determine whether the number of stored signals is two and continuous. Determine whether the number of stored signals after processing meets the set requirement of two and continuous. and signal When all are determined to be ultrasonic signals that meet the set requirements, cross-correlation calculation is performed; B14. In step B12 above, if the ultrasonic signal is determined to be not in compliance with the set requirements, the previous signal is cleared and the process returns to step B2 above to loop through steps B5 to B10 and steps B11 to B16 above, and then determines whether the next signal meets the set requirements until step B12 above is executed to determine whether two consecutive signals meet the set requirements. and signal All are judged to be ultrasonic signals that meet the set requirements; B15. In step B10 above, when the received fluid operating condition is identified as a bubble condition, the amplification factor is maintained unchanged; B16. In step B10 above, if the received fluid operating condition is determined to be normal, the first set amplitude range is compared with the average value of the amplitude data. If the average value of the amplitude data is within the first set amplitude range, the amplification factor is determined to be reasonable and the amplification factor is maintained unchanged. If the average value of the amplitude data is not within the first set amplitude range, it is determined that the amplification coefficient is unreasonable at this time, and the adjustment coefficient is obtained according to the ratio of the middle value of the first set amplitude range to the maximum value of the detection amplitude, and the amplification coefficient is adjusted accordingly according to the adjustment coefficient.

6. The fluid flow measurement method according to claim 4, characterized in that: In the above step B16, when the first set amplitude range is compared with the average value of the amplitude data, the method for determining whether the average value of the amplitude data is within the first set amplitude range is to determine whether the processed signal meets the following set requirements: C1: Detect the maximum amplitude of the signal and compare it with the signal amplitude range. If the detected maximum amplitude is within the signal amplitude range, enter step D2, otherwise clear the signal. and signal , and clear the previous signal or signal , and return to step B2 above; C2: Record the signal and signal The maximum amplitude and the horizontal coordinate corresponding to the maximum amplitude are compared with the maximum amplitude and the horizontal coordinate corresponding to the maximum amplitude of the previous ultrasonic signal. If the maximum amplitude difference and the amplitude horizontal coordinate difference are both less than the set range, the fixed points are extrapolated forward and backward with the horizontal coordinate position of the maximum amplitude as the center, and the area between the front and rear points is used as the effective waveform judgment area of ​​the signal; If the maximum amplitude difference / amplitude horizontal axis difference is greater than the set range, the previous signal is cleared or signal , and return to step B2 above; C3: Use the positive and negative set thresholds to convert the part of the signal located in the valid waveform judgment area into high and low levels, and count the duration and number of high and low levels, and compare them with the set time range and set number range of high and low levels. If the counted duration and number of high and low levels are both within the set time range and set number range of high and low levels, then it is determined that the processed signal is an ultrasonic signal that meets the set requirements, and the subsequent operations of the above step B13 are executed; otherwise, return to the above step B2.

7. The fluid flow measurement method according to claim 4, characterized in that: When the above step B10 is executed to determine whether the fluid working condition is normal, the above steps B13 to B16 and the following amplification factor determination, adjustment, propagation time calculation and flow rate measurement methods are executed; D1. Determine whether the fluid working condition is normal; perform the following steps D2 to D3 or D4 to D3 according to the fluid working condition; D2. When the fluid working condition is determined to be an abnormal bubble working condition, the fluid propagation time calculation is performed and the amplification factor is maintained unchanged; D3. After performing the fluid propagation time calculation in step D2 above, perform the fluid flow measurement task; D4. When the fluid working condition is determined to be normal, the execution determines whether two adjacent detection amplitudes are within the first set amplitude range; D5. If the values ​​in step D4 are all within the first set amplitude range, the fluid propagation time calculation is performed and the amplification factor is maintained at a reasonable level. D6. After calculating the fluid propagation time in step D5 above, perform the fluid flow measurement task; D7. If the above step D4 determines that none of the values ​​are within the first set amplitude range, the fluid propagation time calculation and the unreasonable amplification factor adjustment tasks are performed; D8. In the above step D7, after performing the fluid propagation time calculation, the fluid flow measurement task is performed.

8. The fluid flow measurement method according to claim 4, characterized in that: In the cross-correlation calculation in the above-mentioned step B15, the first flow measurement unit and the second flow measurement unit are respectively set in the FPGA processor and the DSP processor, and the FPGA processor is used to execute the functional program in the first flow measurement unit; the DSP processor is used to execute the functional program in the second flow measurement unit; the DSP processor can perform precise calculations on floating-point numbers and has high-precision and efficient processing capabilities. When the DSP processor is used to calculate the propagation time, the cross-correlation calculation data calculated by the FPGA processor can be converted from integer type to floating-point type.

9. A fluid flow measurement device, characterized in that: The device comprises a control operation unit, which uses the fluid operating condition determination method according to claim 1 to determine the operating condition of the fluid flowing through the fluid flow measurement device.

10. The fluid flow measurement device according to claim 9, characterized in that: The fluid flow measuring device includes a pipe section, a first piezoelectric vibrator, a second piezoelectric vibrator and a control operation unit. The first piezoelectric vibrator and the second piezoelectric vibrator are respectively attached to the wall surfaces at both ends of the pipe section, and the first piezoelectric vibrator and the second piezoelectric vibrator are respectively electrically connected to the control operation unit; the control operation unit includes a signal control unit, a signal processing unit, a first flow measurement unit and a second flow measurement unit; the signal control unit is used to receive ultrasonic signals propagating in the fluid, and the signal processing unit is used to receive ultrasonic signals propagated by the signal control unit and perform preprocessing, and the preprocessing includes ultrasonic signal amplification and ADC waveform acquisition; the first flow measurement unit is used to judge the fluid working condition, and the second flow measurement unit is used to judge and adjust the amplification factor and calculate the fluid flow.

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