Sound velocity calculation method based on ultrasonic metering and ultrasonic water meter

Abstract

The invention relates to the technical field of ultrasonic measurement, in particular to a sound velocity calculation method based on ultrasonic measurement and an ultrasonic water meter, the sound velocity calculation method based on ultrasonic measurement is applied to the ultrasonic water meter, and a public model with multiple piecewise functions is established according to different temperature intervals; and calculating the sound velocity of the ultrasonic pulse working in the set temperature interval, and establishing a single table correction model to correct the common model with the plurality of piecewise functions. The ultrasonic water meter adopts the sound velocity calculation method. The method is reasonable in design, facilitates the reasoning and obtaining of the sound velocity value, and facilitates the improvement of the sound velocity calculation precision.

Description

Technical Field

[0001] The present invention relates to the technical field of ultrasonic measurement, and in particular to a sound velocity calculation method based on ultrasonic measurement and an ultrasonic water meter. Background Art

[0002] In the measurement process of ultrasonic water meters, accurate measurement of the speed of sound in water at different temperatures is a very important task, which is directly related to the accuracy of flow measurement.

[0003] In order to save device costs and improve product market competitiveness, many ultrasonic water meter manufacturers have adopted the practice of omitting temperature sensors in the production process. On the one hand, this can significantly reduce costs, and on the other hand, it can avoid adding additional temperature sensor installation locations, which is beneficial to reducing the volume of the water meter and reducing battery loss, thereby helping to increase the service life of the ultrasonic water meter. At this time, the speed of sound is usually calculated by inference calculation to obtain the instantaneous flow value.

[0004] In addition, based on the relationship between the sound velocity and the sound path L of the ultrasonic pulse in the ultrasonic water meter, the sound velocity is calculated by inference calculation. However, due to the differences in installation size and process, the actual value of the sound path L of different ultrasonic water meters will deviate from the theoretical value. The method of setting a fixed sound path L in the prior art often leads to a large error in the sound velocity calculation. In some cases, the error between the theoretical sound velocity obtained by inference calculation and the actual sound velocity can reach more than 2%, which seriously hinders the improvement of the measurement accuracy of ultrasonic water meters.

[0005] As shown in the patent document entitled A water flow temperature measurement method based on ultrasonic water meter and ultrasonic water meter with application number 202011022714.4, the actual propagation distance of the ultrasonic wave is converted by distance error compensation, and the sound velocity of the ultrasonic wave is calculated based on the actual propagation time. However, in actual application, the patent's assumptions about the consistency of installation dimensions and processes cannot be achieved in the actual process. At the same time, since the ultrasonic wave will lose part of its waveform during the oscillation process, the distance compensation value in the patent often cannot be presented as a constant, but has a certain coupling relationship with the sound velocity. Therefore, there is a certain error in the calculated sound velocity.

[0006] As shown in the patent document entitled "A temperature measurement method suitable for ultrasonic water meters" with application number 202410448132.4, a water temperature calculation model is established in combination with the sound path length. The input of the temperature calculation model is the absolute flight time, and the output is the corrected water temperature. The water temperature calculation model also uses the compensation ratio value of the designed sound path length value for calculation during the calculation process. The algorithm is relatively complex to implement, and the compensation ratio coefficient referenced in the calculation remains unchanged within a fixed temperature range. If too few temperature ranges are selected, certain errors will often be introduced, and accurate sound speed output cannot be achieved. Summary of the invention

[0007] The present invention discloses a sound velocity calculation method based on ultrasonic measurement and an ultrasonic water meter, which solves the technical problem that the method of obtaining the sound velocity by inference by a fixed sound path L in the prior art has low calculation accuracy, and has the technical effect of facilitating the inference to obtain the sound velocity value and facilitating the improvement of the sound velocity calculation accuracy. The technical scheme adopted is as follows: A sound velocity calculation method based on ultrasonic measurement, applied to ultrasonic water meters, comprises the following steps: 1) Prepare multiple ultrasonic water meters of the same specification. Preferably, multiple ultrasonic water meters are placed on a calibration table; 2) In the set temperature interval △T1, obtain the temperature values ​​t11 and t12, and obtain the corresponding sound speeds C11 and C12 by table lookup method, where C11=1468+3.68(t11-10)-0.0279(t11-10)², C12=1468+3.68(t12-10)-0.0279(t12-10)²; 3) Obtain the average value of the uplink and downlink time of ultrasonic pulses of multiple ultrasonic water meters within the set temperature range △T1 A function of the inverse of the speed of sound 1 / C; 4) Fitting the function to establish a common model for calculating the speed of sound; 5) The sound velocity calculation public model is saved in the ultrasonic water meter to infer the ultrasonic pulse sound velocity of the ultrasonic water meter working in the temperature range △T1.

[0008] Based on the above technical solution, the number of the ultrasonic water meters is at least 8 to 10.

[0009] On the basis of the above technical solution, the least square method is used to fit the function to obtain a common model for calculating the speed of sound as a first-order function: ; k is the slope coefficient of the fitting function, and b is the intercept of the fitting function; Based on the above technical solution, the ΔT1 is not greater than 10°C.

[0010] On the basis of the above technical solution, the average value of the up and down time of the ultrasonic pulse is obtained within the set temperature range △T2. Function 2 with the inverse of the speed of sound 1 / C; … In the set temperature range △TN, get the average value of the ultrasonic pulse up and down time The function N is the inverse of the speed of sound 1 / C; The temperature intervals △T1, △T2...△TN are independent of each other and together form an applicable temperature interval △T corresponding to the ultrasonic water meter. The sound velocity calculation public model is expanded into a public model with multiple piecewise functions.

[0011] On the basis of the above technical solution, a temperature sensor is used to collect and obtain the temperature values ​​t11 and t12, and the collection accuracy of the temperature sensor is at least 0.1°C.

[0012] On the basis of the above technical solution, the temperature values ​​t11 and t12 are respectively close to the two end values ​​of the temperature interval ΔT1.

[0013] On the basis of the above technical solution, a plurality of ultrasonic water meters of the same specification are placed on a calibration table, and the temperature range ΔT1 is an integer multiple of the temperature control accuracy of the calibration table.

[0014] Based on the above technical solution, a single table correction model is established, including the following steps: 1) Prepare a single ultrasonic water meter, which works within a set temperature range △T1; 2) Obtain the current working temperature value t1 of the single ultrasonic water meter, and obtain the sound speed C1=1468+3.68(t1-10)-0.0279(t1-10)² by looking up the table; preferably, the temperature value t1 is the middle value of the set temperature interval △T1; 3) Call the public model as described above. When C=C1, the calculation is obtained ; 4) Read the measured value SUM(T) of the uplink and downlink time of the ultrasonic pulse of the single ultrasonic water meter at this time; 5) Calculate the acquisition time and the correction value ; 6) Obtain the sound velocity function of the single ultrasonic water meter after optimization, that is, the single meter correction model: ; Preferably, in order to reduce the randomness of the correction value △t1, a number of temperature values ​​t1, t2, t3 ... tn can be evenly spaced in the set temperature interval △T1, and the average value of the correction value of the corresponding time can be calculated. , the further optimized single table correction model is: ; The single meter correction model for sound velocity calculation is stored in the ultrasonic water meter to infer the ultrasonic pulse sound velocity of the ultrasonic water meter working in the temperature range ΔT1.

[0015] Accordingly, the corresponding optimized single-table correction model for sound velocity calculation is obtained in the set temperature range △T2, △T2...△TN and saved in the ultrasonic water meter.

[0016] Or the correction value △t1 of the temperature interval △T1 is applied to the set temperature intervals △T2, △T3...△T3 to simplify the calculation.

[0017] An ultrasonic water meter, using the above-mentioned sound velocity calculation method based on ultrasonic measurement, comprises a measuring part, wherein the measuring part comprises: The storage unit is used to store the sound speed calculation model in different temperature ranges; the sound speed calculation model can adopt a public model for sound speed calculation or a single table correction model.

[0018] An acquisition unit, which acquires the current measured value of the uplink and downlink time of the ultrasonic pulse of the ultrasonic water meter, so as to acquire the current sound velocity value; A reading unit, used to read the current measured value of the uplink and downlink time difference of the ultrasonic pulse of the ultrasonic water meter; The calculation unit measures and obtains the current instantaneous flow value.

[0019] Beneficial effects: The present invention is reasonably designed, and a public model for calculating the speed of sound is created. The uplink and downlink time of the ultrasonic pulse and the inverse of the speed of sound are used as independent variables and dependent variables. The linear function formed after fitting simplifies the model, facilitates reasoning calculation, and is conducive to improving the measurement efficiency of the ultrasonic water meter; on the other hand, for different temperature intervals, a public model with multiple piecewise functions is formed, so that the public model more accurately describes the relationship between time and the inverse of the speed of sound, which is conducive to improving the accuracy of the estimated speed of sound; on the other hand, the public model uses the average value of the uplink and downlink time of the ultrasonic pulse, that is, when the public model is created, multiple water meters are used, and the uplink and downlink time of the ultrasonic pulse and the average value are used, which fully considers the actual situation that the actual value of the sound path of the ultrasonic water meter will deviate from the theoretical value due to the differences in installation size and process, which is conducive to improving the accuracy of the estimated speed of sound again. In the present invention, in view of the fact that the ultrasonic water meter usually has a large applicable temperature range value, the applicable temperature range value of the ultrasonic water meter is divided into multiple temperature intervals, and then the public model is expanded into a function with multiple segments, which is also conducive to ensuring the accuracy of the speed of sound calculation.

[0020] In addition, the present invention fully considers the calibration efficiency issue, and establishes a single meter correction model after the public model is established. When water meters are mass-produced and calibrated, only a single meter correction is required, and the speed of sound in water can be obtained quickly and accurately.

[0021] The present invention fully considers the consistency of the actual value of the sound path of the ultrasonic water meter and the discreteness of the processing and assembly errors. On the basis of establishing a common model, a single-meter correction model is established. For each ultrasonic water meter, the difference between the time and theoretical calculated value and the actual measured value in the common model is used as a correction value, which is beneficial to further improve the accuracy of the estimated sound velocity, and further helps to improve the measurement accuracy of instantaneous flow and cumulative flow.

[0022] That is, in the invention, a reasonable public model and a single-table correction model are established, and the speed of sound is estimated by combining the two. The algorithm is simple and can greatly improve the accuracy of the estimated speed of sound, which is conducive to reducing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only one embodiment of the present invention, and for ordinary technicians in this field, other implementation drawings can be derived from the provided drawings without creative work.

[0024] Figure 1 : A schematic diagram of the steps of establishing a common model with multiple piecewise functions and a corresponding single-table correction model method in the present invention; Figure 2 : Take multiple temperature points in different temperature ranges, use the corresponding public model to calculate the error of the sound velocity compared with the sound velocity read by the calibration table, and use the corresponding single-meter correction model to calculate the error of the sound velocity compared with the sound velocity read by the calibration table; DETAILED DESCRIPTION As a prior art, the main components of an ultrasonic water meter include an ultrasonic pipe section, a transducer, and a circuit part. The ultrasonic transducer is placed at a corresponding position inside the ultrasonic water meter pipe section. The ultrasonic metering chip transmits pulses of fixed amplitude through the ultrasonic transducer in the upstream and downstream directions at a certain time interval, and determines the upstream and downstream time according to the amplitude of the pulse and the zero crossing point. During the metering process, the ultrasonic water meter mainly calculates the instantaneous flow rate through the time difference data of the upstream and downstream, and then integrates the instantaneous flow rate through the sampling time to obtain the cumulative water consumption. In the process of calculating the instantaneous flow rate, some commonly used formulas are derived as follows: Assume that the sound path of the ultrasonic water meter is L, the sound speed is C, and the water flow rate is v; The time taken to receive the signal in the uplink direction is: ; The time taken to receive the signal in the downlink direction is: ; Among them, Sis the compensation value of the measurement time, which is a constant.

[0025] because , the calculation formula of the uplink and downlink propagation time difference of ultrasonic pulse can be simplified as: ; By transforming the above formula, we can get ; The calculation formula of the instantaneous flow rate in the final ultrasonic pipe section ; Among them, due to C>>V, the uplink and downlink propagation time of the ultrasonic pulse is: ; That is, the up-and-down time of the ultrasonic pulse can be expressed as the inverse of the speed of sound / C is a function of the independent variable, specifically: A sound velocity calculation method based on ultrasonic measurement, applied to ultrasonic water meters, comprises the following steps: 1) Multiple ultrasonic water meters are placed on the calibration table, and the number of ultrasonic water meters is at least 8 to 10. In this embodiment, the number of ultrasonic water meters is 8 and the same specifications are marked as Ⅰ, Ⅱ, Ⅲ, Ⅳ, Ⅴ, Ⅵ, Ⅵ, Ⅶ, and Ⅷ respectively; wherein the applicable temperature range of the 8 ultrasonic water meters is △T=50℃, such as 0~50℃. Among them, multiple ultrasonic water meters are placed in a static water environment to avoid complex electromagnetic interference around them. In other embodiments of the present invention, the number of ultrasonic water meters may be more.

[0026] The calibration table is a prior art and will not be described in detail here. In this embodiment, the temperature control accuracy of the calibration table is 1°C.

[0027] 2) In the set temperature range △T1, in this embodiment, △T1 is 0~10℃, including 0℃, which is an integer multiple of the temperature control accuracy of the calibration table, which is convenient for measurement.

[0028] 3) Obtain temperature values ​​t11 and t12. In this embodiment, temperature values ​​t11 and t12 are respectively close to the two end values ​​of temperature interval △T1. Specifically, adjust the water flow temperature so that the temperature value around the 8 ultrasonic water meter pipes on the calibration table is consistent with the set temperature value t11. When the temperature value around the 8 ultrasonic water meter pipes on the calibration table reaches the set temperature value t11, collect the precise temperature reflected by the temperature sensor inside the calibration table, where the temperature reflected by the temperature sensor is accurate to 0.1°C; Afterwards, according to the temperature value t11, the corresponding sound speed C11 is obtained by table lookup method, that is, C11=1468+3.68(t11-10)-0.0279(t11-10)², and then the inverse of the sound speed at this time is obtained; wherein, obtaining the corresponding sound speed by temperature value table lookup method is a prior art and will not be repeated here.

[0029] The time and data output by the ultrasonic water meter communication line are used to obtain the average uplink and downlink times of the ultrasonic pulses of the eight ultrasonic water meters at the temperature value t11. In this embodiment, the average value of the time is expressed in nanoseconds (ns), and a first data set of the average uplink and downlink times of the acoustic pulses and the inverse of the speed of sound is established.

[0030] Adjust the water flow temperature again to make the temperature around the 8 ultrasonic water meter pipes on the calibration table consistent with the set temperature t12. When the temperature around the 8 ultrasonic water meter pipes on the calibration table reaches the set temperature t12, collect the precise temperature reflected by the temperature sensor inside the calibration table. The temperature reflected by the temperature sensor is accurate to 0.1°C. Afterwards, according to the temperature value of t12, the corresponding sound speed C12 is obtained by table lookup method, that is, C12=1468+3.68(t12-10)-0.0279(t12-10)², and then the inverse of the sound speed at this time is obtained; By using the time and data output by the ultrasonic water meter communication line, the average value of the uplink and downlink times of the ultrasonic pulses of 8 ultrasonic water meters when the temperature value t12 is obtained. In this embodiment, the average value of the time is expressed in nanoseconds (ns), and a second group of data of the average value of the uplink and downlink times of the acoustic pulses and the inverse of the speed of sound is established; in other embodiments of the present invention, more temperature values ​​such as t13, t14, etc. can be obtained within the set temperature interval △T1.

[0031] 4) Obtain the average uplink and downlink time of the ultrasonic pulses of 8 ultrasonic water meters within the set temperature range △T1 A function of the inverse of the speed of sound 1 / C; 5) Fitting the function 1 to establish a common model for calculating the speed of sound. In this embodiment, the least squares method is used to fit the function 1 to obtain a common model for calculating the speed of sound that is a first-order function: ; k is the slope coefficient of the fitting function, and b is the intercept of the fitting function.

[0032] In order to cover the applicable temperature range △T of ultrasonic water meter to a greater extent, in the set temperature range In △T2, in this embodiment, △T2 is 10~20℃, including 10℃, and the above method is used to obtain the average value of the up and down time of the ultrasonic pulse Function 2 with the inverse of the speed of sound 1 / C; … Similarly, within the set temperature range △TN, the average value of the up and down time of the ultrasonic pulse is obtained. A function N of the inverse of the speed of sound 1 / C; in this embodiment, N=5.

[0033] In this embodiment, the temperature intervals △T1, △T2...△TN are independent of each other and together form an applicable temperature interval △T corresponding to the ultrasonic water meter, so that a plurality of segmented public models can be obtained to improve applicability.

[0034] 6) The sound velocity calculation public model is saved in the ultrasonic water meter to infer the ultrasonic pulse sound velocity of the ultrasonic water meter working in the temperature range △T1, △T2, △T3...△T5.

[0035] Further establish a single table correction model, including the following steps: 1) Place the single ultrasonic water meter on the calibration table, such as placing the ultrasonic water meter marked as Ⅰ on the calibration table. Similarly, place the single ultrasonic water meter in a normal temperature static water environment to avoid complex electromagnetic wave interference around it. The water temperature at the water meter pipe section is within the set temperature range △T1 and the temperature remains constant; 2) The temperature sensor inside the calibration table collects the current temperature value t1, and obtains the sound speed at this time C1=1468+3.68(t1-10)-0.0279(t1-10)² by looking up the table; 3) Call the corresponding public model as above, when C=C1, calculate and obtain , that is, the theoretical value of the uplink and downlink time of the ultrasonic pulse of the single ultrasonic water meter; 4) Read the measured value SUM(T) of the uplink and downlink time of the ultrasonic pulse of the single ultrasonic water meter at this time; 5) Calculate the acquisition time and the correction value ; 6) Obtain the sound velocity function of the single ultrasonic water meter after optimization, that is, the single meter correction model: ; In this embodiment, in order to reduce the randomness of the correction value △t1, a plurality of temperature values ​​can be evenly spaced in the set temperature interval △T1. , , … , calculate the average value of the correction value of the corresponding time and , the further optimized single table correction model is: ; The correction value of the single meter correction model for sound velocity calculation is stored in the internal storage chip of the ultrasonic water meter to infer the ultrasonic pulse sound velocity of the ultrasonic water meter working in the temperature range △T1. In addition, to further simplify the operation, the correction value is used for all piecewise functions, which greatly reduces the workload of single meter correction. When leaving the factory, it is only necessary to correct the public model used by the water meter at room temperature, so as to achieve rapid factory delivery and improve production efficiency.

[0036] In this embodiment, within the set temperature range △T1, if Figure 2 As shown, the horizontal axis is temperature, and the vertical axis is the error percentage of the sound velocity calculated value compared to the value read by the calibration table. The blue curve above is the error degree of the sound velocity calculated by the corresponding single-meter correction model compared to the sound velocity read by the calibration table when multiple temperature points are taken in different temperature intervals; the orange curve below is the error degree of the sound velocity calculated by the corresponding public model compared to the sound velocity read by the calibration table when multiple temperature points are taken in different temperature intervals. Among them, the adjacent temperature points are connected by a straight line.

[0037] It can be seen that compared with the public model, the error of the corrected single water meter sound velocity is within 3‰, which can greatly improve the water meter measurement accuracy.

[0038] In other embodiments of the present invention, correction values ​​of corresponding single-meter correction models may also be obtained in set temperature intervals ΔT2, ΔT3, ... ΔT5, and stored in the internal storage chip of the ultrasonic water meter.

[0039] An ultrasonic water meter, using the above-mentioned sound velocity calculation method based on ultrasonic measurement, includes a metering part, the metering part includes: The storage unit is used to store the sound speed calculation model in different temperature ranges; the sound speed calculation model adopts a public model for sound speed calculation or a single table correction model.

[0040] An acquisition unit, which acquires the current measured value of the uplink and downlink time of the ultrasonic pulse of the ultrasonic water meter, so as to acquire the current sound velocity value; A reading unit, used to read the current measured value of the uplink and downlink time difference of the ultrasonic pulse of the ultrasonic water meter; The calculation unit measures and obtains the current instantaneous flow value.

[0041] The present invention is described above by way of examples, but the present invention is not limited to the above specific embodiments, and any changes or modifications made based on the present invention belong to the scope of protection claimed by the present invention.

Claims

1. A method for calculating the speed of sound based on ultrasonic measurement, characterized in that: Applied to ultrasonic water meter, including the steps: 1) Prepare multiple ultrasonic water meters of the same specifications; 2) In the set temperature interval △T1, obtain the temperature values ​​t11 and t12, and obtain the corresponding sound speeds C11 and C12 by table lookup method, where C11=1468+3.68(t11-10)-0.0279(t11-10)², C12=1468+3.68(t12-10)-0.0279(t12-10)²; 3) Obtain the average value of the uplink and downlink time of ultrasonic pulses of multiple ultrasonic water meters within the set temperature range △T1 A function of the inverse of the speed of sound 1 / C; 4) Fitting the function to establish a common model for calculating the speed of sound; 5) The sound velocity calculation public model is saved in the ultrasonic water meter to infer the ultrasonic pulse sound velocity of the ultrasonic water meter working in the temperature range △T1.

2. The method for calculating the speed of sound based on ultrasonic measurement according to claim 1, characterized in that: The number of the ultrasonic water meters is at least 8 to 10.

3. The method for calculating the speed of sound based on ultrasonic measurement according to claim 1, characterized in that: The least square method is used to fit the function to obtain the common model for calculating the sound velocity as a first-order function: ； k is the slope coefficient of the fitting function, and b is the intercept of the fitting function.

4. The method for calculating the speed of sound based on ultrasonic measurement according to claim 1, characterized in that: The ΔT1 is not greater than 10°C.

5. The method for calculating the speed of sound based on ultrasonic measurement according to claim 1, characterized in that: In the set temperature range △T2, get the average value of the ultrasonic pulse up and down time Function 2 with the inverse of the speed of sound 1 / C; … In the set temperature range △TN, get the average value of the ultrasonic pulse up and down time The function N is the inverse of the speed of sound 1 / C; The temperature intervals △T1, △T2...△TN are independent of each other and together form an applicable temperature interval △T corresponding to the ultrasonic water meter. The sound speed calculation public model is expanded into a public model with multiple piecewise functions.

6. The method for calculating the speed of sound based on ultrasonic measurement according to claim 1, characterized in that: The temperature values ​​t11 and t12 are acquired by using a temperature sensor, and the acquisition accuracy of the temperature sensor is at least 0.1°C.

7. The method for calculating the speed of sound based on ultrasonic measurement according to claim 6, characterized in that: The temperature values ​​t11 and t12 are respectively close to the two end values ​​of the temperature interval ΔT1.

8. The method for calculating the speed of sound based on ultrasonic measurement according to claim 1, characterized in that: A plurality of ultrasonic water meters of the same specification are placed on a calibration table, and the temperature range ΔT1 is an integer multiple of the temperature control accuracy of the calibration table.

9. The method for calculating the speed of sound based on ultrasonic measurement according to any one of claims 1 to 7, characterized in that: Establishing a single table correction model includes the following steps: 1) preparing a single ultrasonic water meter, and the single ultrasonic water meter operates within a set temperature range △T1; 2) Obtain the current working temperature value t1 of the single ultrasonic water meter, and obtain the sound speed C1=1468+3.68(t1-10)-0.0279(t1-10)² by looking up the table; 3) Call the public model, when C=C1, calculate and obtain ; 4) Read the measured value SUM(T) of the uplink and downlink time of the ultrasonic pulse of the single ultrasonic water meter at this time; 5) Calculate the acquisition time and the correction value ; 6) Obtain the sound velocity function of the single ultrasonic water meter after optimization, that is, the single meter correction model: ； The single meter correction model for sound velocity calculation is stored in the ultrasonic water meter to infer the ultrasonic pulse sound velocity of the ultrasonic water meter working in the temperature range ΔT1.

10. An ultrasonic water meter, characterized in that: The method for calculating the speed of sound based on ultrasonic measurement as claimed in any one of claims 1 to 9 comprises a measuring unit, wherein the measuring unit comprises: A storage unit, used for storing sound velocity calculation models in different temperature ranges; An acquisition unit, which acquires the current measured value of the uplink and downlink time of the ultrasonic pulse of the ultrasonic water meter, so as to acquire the current sound velocity value; A reading unit, used to read the current measured value of the uplink and downlink time difference of the ultrasonic pulse of the ultrasonic water meter; The calculation unit measures and obtains the current instantaneous flow value.

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