CN107655552B - A correction method of ultrasonic water meter flow velocity based on non-measurement section propagation time difference and zero drift error - Google Patents

Abstract

A method for correcting flow velocity of an ultrasonic water meter based on the propagation time difference and zero drift error of the non-measurement section, which includes the following steps: accurately measuring the time sum of forward and reverse flow at a reference temperature, and calculating the time sum of the non-measurement section through multiple sampling averages ;According to the time difference of multiple measurements of reference temperature, minimum temperature, and maximum temperature, calculate the reference zero drift and calibration zero drift; during real flow measurement, the non-measurement period time can be shielded, the time difference of the measurement period can be calibrated, and the actual temperature zero drift can be removed , perform temperature inverse calculation and Reynolds number compensation. The present invention calculates the effective time difference of the measuring section and the error of the non-measuring section through static water measurement at a single point temperature, and solves the error caused by the processing and assembly of the base meter and the transducer; by establishing the zero drift and temperature curve, the zero drift value is effectively removed, Reduce the error caused by insufficient resolution of the timing chip, perform temperature compensation and correction through real-flow measurement and back-calculate temperature, and perform a precise calibration at the factory. The measurement algorithm is simple in actual measurement and the measurement accuracy is high.

Description

A correction of flow velocity of ultrasonic water meter based on propagation time difference and zero drift error of non-measurement section method

technical field

The invention belongs to the technical field of water meter measurement and detection, in particular to an ultrasonic water meter flow velocity correction method based on non-measurement section propagation time difference and zero drift error.

Background technique

At present, the factors affecting the error of the ultrasonic water meter are the nonlinearity of the average velocity of the line and the average velocity of the surface, the error of processing and assembly, the error of the non-measurement section, the influence of the roughness of the inner wall of the pipeline, the error caused by the temperature change under normal pressure, and the insufficient resolution of the TDC timing. Error, error caused by unstable echo at the end of timing, fluid interference in the pipeline, error caused by characteristic correction, vibration in the pipeline and error caused by unsatisfactory installation conditions.

Some error factors can be corrected by piecewise linearity, or fitting straight line correction, increasing timing resolution, designing filter circuits to obtain more reliable stop waves, adding rectifiers, adding straight pipe sections before and after, adding temperature sensors, or using accurate temperature inverse calculations, etc. Most of the errors introduced by zero drift and non-measurement sections are forcibly repaired by external detection equipment or correction coefficient correction, and no better solution is mentioned.

The current general practice is that the sound path L of the pipeline depends on the processing accuracy of the pipe manufacturer. The actual measured sound path of the ultrasonic waves includes the center distance between the two reflecting surfaces and twice the center distance between the transducer and the reflecting surface. Due to the installation of the transducer and its own size error, the actual waveform reflection position of the internal reflection surface of the pipeline is different, causing assembly errors. The temperature change is compensated by using an external temperature sensor, or by using a more advanced timing chip (internal integrated temperature measurement unit) to compensate for the difference between the temperature and the actual temperature during actual measurement, which brings hardware costs Increase; the error generated by the resolution of the TDC timing chip itself is the zero drift. Usually, the zero drift is tested separately through external components. There is no better solution without changing the original base meter structure and without external equipment.

Contents of the invention

Aiming at the deficiencies of the existing technology, the present invention provides a method that does not change the structure of the existing base meter, does not increase the cost, and has no external auxiliary measuring equipment, accurately calculates the actual measurement sound path through an algorithm, establishes zero drift and temperature change curves, and adopts segmented The method of calibration realizes the accurate measurement of the household ultrasonic water meter.

Technical scheme of the present invention is:

The invention provides a method for correcting flow velocity of an ultrasonic water meter based on non-measurement section propagation time difference and zero-drift error. The method includes the following steps: S1, the step of calculating the non-measurement section propagation time; S2, establishing the relationship curve between zero-drift error and temperature Step; S3, calculating the instantaneous linear velocity.

Further, step S1 is specifically:

Step S1-1, the calibration station sends a calibration instruction and a reference temperature T _r to the ultrasonic water meter;

Step S1-2, using the ultrasonic water meter to carry out multiple samplings, the sum of forward and reverse flow propagation times of zero flow at the reference temperature Tr, to obtain the average value _{SumTof Tr} of multiple samplings;

Step S1-3, using the following formula to calculate the propagation time E _S of the non-measurement section:

E _S ＝SumTof _r -2×(L ₀ +L _d )/C _r

Among them: T _r represents the reference temperature, SumTof _r is the average value of the sum of the forward and reverse flow propagation times of zero flow measured by the ultrasonic wave at the reference temperature T _r , L ₀ represents the effective length of the measuring tube, and L _d represents the effective measuring tube Diameter, C _r represents the supersonic speed at the reference temperature T _r , obtained by looking up the table.

Further, step S2 includes the following steps:

Step S2-1, according to the reference temperature T _r and the temperature range (T _i , T _j ) measured by the ultrasonic water meter, define the temperature range T _i < T _r ≤ T _j ;

Step S2-2, Obtain the measured zero drift value of zero flow at three temperature points T _i , T _r , T _j

Step S2-3, calculating the reference zero drift value of the reference temperature T _r

Among them: K(T _j ,T _i ) represents the slope of the temperature value and the corresponding measurement zero drift value;

Step S2-4, under the water meter working condition, obtain the measured zero drift value of the measured temperature T _m

Step S2-5, calculating the reference zero drift value of the measured temperature T _m

Step S2-6, establishing zero drift error The relationship curve with the measured temperature T _m of the water meter working condition:

Among them: T _m represents the actual measured temperature when the ultrasonic water meter is working normally; Indicates the reference zero drift value at temperature T _m ; Indicates the measurement zero drift value at temperature T _m .

Further, in step S2-2 and step S2-4, measure zero drift value The calculation steps are: corresponding to the three temperature points, measure the forward and reverse flow time difference of zero flow at the corresponding temperature point several times, and calculate the measurement zero drift value of the corresponding temperature point respectively

Among them, N _χ represents the number of measurements at the corresponding temperature, Δt _χ represents the difference between forward and reverse flow of zero flow at the k-th measurement of the corresponding measurement temperature point, and Δt _χavg represents the zero flow rate of the corresponding measurement temperature point The average value of the difference between forward and reverse flow. (The standard deviation can explain the discreteness of the measurement points, and is closely related to the timing resolution of the timing chip itself, so the standard deviation is taken as the zero drift guide value).

Further, step S3 specifically includes:

Step S3-1, the ultrasonic water meter works normally, and calculates the supersonic velocity C _T ;

Among them: L ₀ is the length of the effective measuring tube, L _d is the diameter of the effective measuring tube, (L ₀ +L _d ) is the effective measuring sound path, SumTof _T is the difference between the forward and countercurrent propagation time of the ultrasonic wave at the temperature T in actual work and, SumTof _T ＝t _up +t _dwon , t _up , t _dwon represent forward and reverse flow propagation time respectively; E _S represents non-measurement segment propagation time;

Step S3-2, obtain the actual temperature T according to the supersonic C _T look-up table; (sound velocity and temperature relationship table)

Step S3-3, calculating the instantaneous linear velocity V _L ;

Among them, K(L _d , L _D ) represents the diameter reduction coefficient between the effective measuring pipe diameter L _d and the water pipe diameter L _D , K _ΔT represents the temperature compensation coefficient of the actual temperature T, C _T represents the supersonic speed, and Δt represents the actual working temperature of the ultrasonic wave. The difference between forward and countercurrent propagation time at temperature T, E _Om(Adapt) represents the zero drift error.

Further, after step S3, step S4 is also included: performing flow calibration through segmental correction.

Beneficial effects of the present invention:

Under the premise of not changing the structure of the base meter and adding auxiliary measuring equipment, the present invention only needs one accurate measurement at a constant temperature to obtain the error of the non-measurement section, improve the accuracy of the measurement section during actual flow measurement, and reduce the The error caused by the non-measurement section can effectively correct the processing and assembly error; measure the time difference and standard deviation at three temperature points, calculate the reference zero drift, establish the zero drift and temperature curve, and use the standard deviation to detect the discreteness of the TDC timing chip measurement. Dynamically measure the change characteristics of zero drift with temperature to reduce errors caused by insufficient resolution of timing chips.

The present invention proposes a method of removing non-measurement period time and zero drift, so that the measurement of effective measurement period is more accurate. After a factory calibration, the actual measurement temperature is reversed to perform Reynolds number compensation, and the effective measurement time difference is calculated. The flow velocity is corrected by the segmented correction method, which greatly improves the measurement accuracy of the water meter.

Although the present invention has been described with reference to the accompanying drawings, various modifications and changes will occur to those skilled in the art. The equivalents of various modifications and changes of the present invention are all within the scope of the claims of the present invention.

The technology not involved in the present invention is the same as the prior art or can be realized by using the prior art, so it will not be described in detail in the present invention.

Other features and advantages of the present invention will be described in detail in the detailed description that follows.

Description of drawings

The above and other objects, features and advantages of the present invention will become more apparent by describing the exemplary embodiments of the present invention in more detail with reference to the accompanying drawings, wherein, in the exemplary embodiments of the present invention, the same reference numerals generally represent same parts.

Figure 1 Structural diagram of the measuring tube.

Figure 2 Zero drift and temperature curves.

Figure 3 Calibration algorithm flow chart.

Detailed ways

Preferred embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although preferred embodiments of the invention are shown in the drawings, it should be understood that the invention may be embodied in various forms and should not be limited to the embodiments set forth herein.

A method for correcting flow velocity of an ultrasonic water meter based on non-measurement section propagation time difference and zero drift error, the method comprising the following steps:

S1, the step of calculating the propagation time of the non-measurement segment;

Step S1-1, the calibration station sends a calibration instruction and a reference temperature T _r to the ultrasonic water meter;

Step S1-2, using an ultrasonic water meter to sample the sum of the forward and reverse flow propagation times _SumTof Tr of zero flow at the reference temperature _Tr ;

Step S1-3, using the following formula to calculate the propagation time E _S of the non-measurement section:

E _S ＝SumTof _r -2×(L ₀ +L _d )/C _r

Among them: T _r represents the reference temperature, SumTof _r is the average value of the sum of the forward and reverse flow propagation times of zero flow measured by the ultrasonic wave at the reference temperature T _r , L ₀ represents the effective length of the measuring tube, and L _d represents the effective measuring tube Diameter, C _r represents the supersonic speed at the reference temperature T _r , obtained by looking up the table.

S2, the step of establishing the relationship curve between zero drift error and temperature;

Step S2-1, according to the reference temperature T _r and the temperature range (T _i , T _j ) measured by the ultrasonic water meter, define the temperature range T _i < T _r ≤ T _j ;

Step S2-2, Obtain the measured zero drift value of zero flow at three temperature points T _i , T _r , T _j

Step S2-3, calculating the reference zero drift value of the reference temperature T _r

Among them: K(T _j ,T _i ) represents the slope of the temperature value and the corresponding measurement zero drift value;

Step S2-4, under the water meter working condition, obtain the measured zero drift value of the measured temperature T _m

Step S2-5, calculating the reference zero drift value of the measured temperature T _m

Step S2-6, establishing zero drift error The relationship curve with the measured temperature T _m of the water meter working condition:

Among them: T _m represents the actual measured temperature when the ultrasonic water meter is working normally; Indicates the reference zero drift value at temperature T _m ; Indicates the measurement zero drift value at temperature T _m .

S3, calculating the instantaneous linear velocity;

Step S3-1, the ultrasonic water meter works normally, and calculates the supersonic velocity C _T ;

Among them: L ₀ is the length of the effective measuring tube, L _d is the diameter of the effective measuring tube, (L ₀ +L _d ) is the effective measuring sound path, SumTof _T is the difference between the forward and countercurrent propagation time of the ultrasonic wave at the temperature T in actual work and, SumTof _T ＝t _up +t _dwon , t _up , t _dwon represent forward and reverse flow propagation time respectively; E _S represents non-measurement segment propagation time;

Step S3-2, obtain the actual temperature T according to the supersonic velocity C _T look-up table;

Step S3-3, calculating the instantaneous linear velocity V _L ;

Among them, K(L _d , L _D ) represents the diameter reduction coefficient between the effective measuring pipe diameter L _d and the water pipe diameter L _D , K _ΔT represents the temperature compensation coefficient of the actual temperature T, C _T represents the supersonic speed, and Δt represents the actual working temperature of the ultrasonic wave. The difference between forward and countercurrent propagation time at temperature T, E _Om(Adapt) represents the zero drift error.

When implementing it:

In this embodiment, the measurement of an ultrasonic water meter in a DN15 copper pipe section is taken as an example, the reference temperature T _r =25°C is taken, and the effective measurement pipe length L ₀ =0.045m as shown in FIG. 1 . The effective measuring tube diameter L _d =0.011m, the actual inner diameter L _D of the base meter =0.017m. The distance between the centers of the reflecting surfaces of the two transducers is L _t =0.063m.

The following steps calibrate measurements for zero flow:

1) SumTofi of the forward and reverse flow propagation times of N times of continuous sampling ( _N≥32 ) of zero flow.

2) Calculate the average value of N SumTof _Tr

3) When T _r ＝25℃, C _r ＝1496.6m/s, so E _S ＝ _SumTofavg -2×(L ₀ +L _d )/C _r gets the non-measurement period E _S .

4) Temperature grade T50, T _i = 1°C < T _r ≤ T _j = 50°C, measure the forward and reverse flow time difference Δt _j of T _j zero flow, and the forward and reverse flow time difference Δt _i of T _i , measure N times at three temperature points (N≥32) time difference value, record the time difference of N times at three temperature points and calculate the average value, according to the formula Zero drift when T _j is calculated Zero drift at T _i Therefore the reference zero drift According to the reference zero drift, take the difference between the actual measured zero drift and the reference zero drift to calibrate the actual zero drift, so the zero drift curve at the actual temperature is

It can be seen from the above formula that the actual zero drift is a function of the temperature and the measured zero drift. It is necessary to calculate the measured zero drift during real flow measurement and inversely calculate the temperature.

The following are real flow measurements:

5) In practical application, _{SumTof T} , t _up , t dwon are obtained from the measurement. From Fig. 1, it can be seen that the sound path L=L ₀ +L _d , and the supersonic velocity can be calculated The actual temperature T can be found through the relationship between sound velocity and temperature.

6) Substituting the zero drift and temperature curve according to the temperature T obtained in step 5, performing calibration according to the actual zero drift and temperature relationship in step S2, and obtaining E _Om(Adapt) , as shown in Figure 2, under some temperature points, Measured zero drift and calibration zero drift curve.

7) Actual zero drift is substituted into the flow velocity calculation formula Where L is the effective measurement sound path.

8) Judging which flow velocity segment the current line flow velocity V _L is in, and calling different calibration equations for flow velocity correction.

Table 1 Part of temperature point measurement zero drift and calibration zero drift comparison table

temperature(℃) Measurement zero drift (ns) Calibration zero drift (ns) 0.1 0.0266351 0.025031107 1 0.038379 0.036832983 5 0.031137 0.029848652 10 0.0296148 0.028648539 15 0.039592 0.038947826 20 0.028828 0.028505913 25 0.0292474 0.0292474 30 0.052954 0.053276087 35 0.029888 0.030532173 40 0.0275011 0.02846736 45 0.043885 0.045173347 50 0.037035 0.038645434

Having described various embodiments of the present invention, the foregoing description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and alterations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments.

Claims (2)

1. A method for correcting ultrasonic water meter flow velocity based on non-measurement section propagation time difference and zero drift error, characterized in that the method comprises the following steps: S1, calculating the step of non-measurement section propagation time; S2, establishing the relationship between zero drift error and temperature The step of the curve; S3, calculating the instantaneous linear velocity; Step S1 is specifically: Step S1-1, the calibration station sends a calibration instruction and a reference temperature T _r to the ultrasonic water meter; Step S1-2, using an ultrasonic water meter to sample the sum of the forward and reverse flow propagation times _SumTof Tr of zero flow at the reference temperature _Tr ; Step S1-3, using the following formula to calculate the propagation time E _S of the non-measurement section: E _S ＝SumTof _r -2×(L ₀ +L _d )/C _r Among them: T _r represents the reference temperature, SumTof _r is the average value of the sum of the forward and reverse flow propagation times of zero flow measured by the ultrasonic wave at the reference temperature T _r , L ₀ represents the effective length of the measuring tube, and L _d represents the effective measuring tube Diameter, C _r represents the supersonic speed at the reference temperature T _r , obtained by looking up the table; Step S2 comprises the following steps: Step S2-1, according to the reference temperature T _r and the temperature range (T _i , T _j ) measured by the ultrasonic water meter, define the temperature range T _i < T _r ≤ T _j ; Step S2-2, Obtain the measured zero drift value of zero flow at three temperature points T _i , T _r , T _j Step S2-3, calculating the reference zero drift value of the reference temperature T _r Among them: K(T _j ,T _i ) represents the slope of the temperature value and the corresponding measurement zero drift value; Step S2-4, under the water meter working condition, obtain the measured zero drift value of the measured temperature T _m Step S2-5, calculating the reference zero drift value of the measured temperature T _m Step S2-6, establishing zero drift error The relationship curve with the measured temperature T _m of the water meter working condition: Among them: T _m represents the actual measured temperature when the ultrasonic water meter is working normally; Indicates the reference zero drift value at temperature T _m ; Indicates the measured zero drift value at temperature T _m ; In step S2-2 and step S2-4, measure the zero drift value The calculation steps are: corresponding to each temperature point, measure the forward and reverse flow time difference of zero flow at the corresponding temperature point several times, and calculate the measurement zero drift value of the corresponding temperature point respectively Among them, N _χ represents the number of measurements at the corresponding temperature, Δt _χ represents the difference between forward and reverse flow of zero flow at the k-th measurement of the corresponding measurement temperature point, and Δt _χavg represents the zero flow rate of the corresponding measurement temperature point The average value of the difference between forward and reverse flow; Step S3 specifically includes: Step S3-1, the ultrasonic water meter works normally, and calculates the supersonic velocity C _T ; Among them: L ₀ is the length of the effective measuring tube, L _d is the diameter of the effective measuring tube, (L ₀ +L _d ) is the effective measuring sound path, SumTof _T is the difference between the forward and countercurrent propagation time of the ultrasonic wave at the temperature T in actual work and, SumTof _T ＝t _up +t _dwon , t _up , t _dwon represent forward and reverse flow propagation time respectively; E _S represents non-measurement segment propagation time; Step S3-2, obtain the actual temperature T according to the supersonic velocity C _T look-up table; Step S3-3, calculating the instantaneous linear velocity V _L ; Among them, K(L _d , L _D ) represents the diameter reduction coefficient between the effective measuring pipe diameter L _d and the water pipe diameter L _D , K _ΔT represents the temperature compensation coefficient of the actual temperature T, C _T represents the supersonic speed, and Δt represents the actual working temperature of the ultrasonic wave. The difference between forward and countercurrent propagation time at temperature T, E _Om(Adapt) represents the zero drift error. 2. According to claim 1, a method for correcting ultrasonic water meter flow velocity based on non-measurement section propagation time difference and zero drift error, characterized in that after step S3, it also includes step S4: according to the interval where the linear flow velocity is located, call the corresponding calibration The equation corrects the flow rate, calculates the instantaneous flow rate and compares it with the standard value, and uses the zero drift value for flow correction.