A method for correcting measurement errors of ultrasonic water meters

Abstract

The present invention relates to the field of flow detection technology, and discloses a method for correcting measurement errors of ultrasonic water meters. The technical solution includes the following steps: S1, using the time difference method to calculate the instantaneous flow value of the ultrasonic water meter; S2, calculating the expected flow error E1 caused by the flow change; S3, calculating RE; S4, judging whether RE exceeds the threshold value in the meter. The present invention solves the problem of increased measurement error caused by flow changes, which is particularly obvious for situations where the flow changes in the metering process are large, the frequency is high, the test time is short, and the measurement frequency is low. The measurement accuracy can be improved without changing the measurement frequency of the ultrasonic water meter, and the measurement frequency can be reduced while ensuring the measurement accuracy requirement, thereby increasing the life of the water meter. The present invention can effectively adapt to various actual water use conditions and optimize the actual use effect of the ultrasonic water meter.

Description

Technical Field

[0001] The present invention relates to the technical field of flow detection, and in particular to a method for correcting measurement errors of an ultrasonic water meter. Background Art

[0002] Due to the limitation of measurement frequency, during the actual measurement process of ultrasonic water meters, when the instantaneous flow changes, within a sampling period, the cumulative flow value is still calculated by multiplying the previous instantaneous flow by the sampling period. Therefore, when the ultrasonic water meter measurement time is short, the instantaneous flow changes greatly, the frequency is high, and the measurement frequency is low, the error here is particularly obvious, resulting in a large flow error, which seriously affects the measurement accuracy of the ultrasonic water meter.

[0003] The current solution to this error is mainly to increase the measurement frequency of the ultrasonic water meter. However, considering the actual use of the ultrasonic water meter, there are large flow fluctuations, multiple flow rate adjustments and short measurement times. The measurement frequency cannot be increased indefinitely, and this error will always exist. Summary of the Invention

[0004] In view of the shortcomings and defects of the existing technology, the present invention provides a method for correcting the measurement error of an ultrasonic water meter, which can effectively reduce the measurement error caused by instantaneous flow changes, effectively improve the measurement accuracy without changing the measurement frequency of the ultrasonic water meter, and reduce the measurement frequency while maintaining the measurement accuracy.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] A method for correcting measurement errors of an ultrasonic water meter comprises the following steps:

[0007] S1, according to the measurement signal of the ultrasonic water meter, the instantaneous flow value v of the ultrasonic water meter is calculated using the time difference method and recorded;

[0008] S2, during the normal operation of the ultrasonic water meter, when the instantaneous flow value changes, a measurement error will occur. The error value is δ = (v1-v2)(Tx). Calculate the expected flow error E1 caused by the flow change:

[0009]

[0010] Where E1 represents the expectation, T represents the ultrasonic water meter sampling period, which is the reciprocal of the measurement frequency f, x is the time when the instantaneous flow changes, v1 and v2 represent the flow values ​​before and after the change, respectively, and P(x) represents the probability that the instantaneous flow value changes at time x;

[0011] S3, according to the flow error expectation, the error degree value RE is obtained:

[0012]

[0013] Where V1 represents the cumulative flow value within the sampling period, V1 = v1T; T is the ultrasonic water meter sampling period; v1 and v2 represent the instantaneous flow values ​​before and after the change respectively;

[0014] S4, judging whether the RE value exceeds the preset threshold range. If so, it is considered that the flow rate has changed during the metering cycle and flow rate correction is required;

[0015] The flow correction scheme is to replace the real instantaneous flow change time x with the fixed time y to minimize the error expectation within the measurement cycle. The error expectation of this process is:

[0016]

[0017] Where E2 represents the error expectation after flow correction, T represents the ultrasonic water meter sampling period, which is the reciprocal of the measurement frequency f, v1 and v2 represent the flow values ​​before and after the change, respectively, and P(x) represents the probability that the instantaneous flow value changes at time x. The optimal value of y that minimizes the error expectation E2 is y0.

[0018] S5, use the corrected cumulative flow value V2 = v1y0 + v2 (T-y0) to replace the original V1 value in the table to calculate the cumulative flow; if the calculated RE value does not exceed the preset threshold range, it is considered that the flow has not changed during the metering cycle, and no correction is made, and the cumulative flow value is still calculated based on V1.

[0019] Furthermore, in step S2, P(x), i.e., the probability distribution estimation method of the instantaneous flow change moment x, can use normal distribution or average distribution;

[0020] Furthermore, in step S3, when either of the instantaneous flow rates v1 and v2 is 0, i.e., when the valve is opened or closed, the RE value is not calculated and the flow correction is performed directly;

[0021] Furthermore, in step S4:

[0022] When the ultrasonic water meter leaves the factory, the preset threshold range is [-σ, σ]. When the RE value is within ±σ, the water flow is considered stable and the fluctuation is within the normal range. Otherwise, the flow rate is considered to have changed. σ is the measurement accuracy of the ultrasonic water meter.

[0023] As the service time of ultrasonic water meters increases, the preset threshold range is [σ-Δσ,σ+Δσ], where Where t represents the current service time, t1 represents the theoretical service time, Δσ represents the change in threshold, σ t It represents the measurement accuracy of ultrasonic water meter when the service time is t, and c is the aging constant.

[0024] The beneficial technical effects of this invention include effectively reducing flow measurement errors caused by instantaneous flow variations, significantly improving the measurement accuracy of ultrasonic water meters, particularly in situations where flow variations are large, frequent, or the measurement frequency is low. Furthermore, while maintaining measurement accuracy, the measurement frequency can be reduced, extending the metering life of the ultrasonic water meter. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is the overall flow chart of the present invention.

[0026] Figure 2 Schematic diagram of flow rate change and flow rate correction in an embodiment of the present invention. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0028] Example: Figure 1 As shown, a method for correcting measurement errors of an ultrasonic water meter includes the following steps:

[0029] S1, the measurement accuracy of the ultrasonic water meter used in the experiment is Class 2, the measurement frequency is 1 Hz, T is 1 s, and based on the measurement signal of the ultrasonic water meter, the instantaneous flow values ​​v1 and v2 of the ultrasonic water meter are calculated using the time difference method and recorded as 3.12 L / h and 4.04 L / h respectively;

[0030] S2, in the normal operation of the ultrasonic water meter, when the instantaneous flow value changes, the flow error expectation caused by the flow change is calculated, and RE is used to determine whether it exceeds the meter threshold. The calculation scheme is as follows:

[0031] In the flow rate change measurement cycle, the error caused by the flow rate change is δ = (v1-v2)(Tx), x is the flow rate change moment, the value range is one measurement cycle, and its probability distribution is considered to be average distribution, then the probability Therefore, the expected error caused by flow rate change is:

[0032]

[0033] Where E1 represents the expectation, T represents the ultrasonic water meter sampling period, which is the reciprocal of the measurement frequency f, v1 and v2 represent the flow values ​​before and after the change, respectively, and Δv represents v1-v2. This error is related to the measurement frequency of the water meter and is particularly obvious when the instantaneous flow rate changes greatly or the change frequency is high.

[0034] S3, calculate the RE value of the instantaneous flow values ​​of v1 and v2 twice before and after. The calculation method is as follows:

[0035]

[0036] Where E1 represents the expected error, V1 represents the cumulative flow value of the instantaneous flow value within the sampling period, V1 = 8.67E-4 (L), the RE value is calculated to be -14.7%, and the preset range in the table is [-2%, 2%]. If it exceeds this range, flow compensation is performed, i.e., step S4;

[0037] S4, calculate the corrected flow value V2 based on the recorded instantaneous flow changes v1 and v2. The calculation scheme is as follows:

[0038] Assume that the flow value changes at a certain time y within the period T, and the flow changes from v1 to v2. If its probability distribution is also considered to be average distribution, then the probability The corrected flow error expectation is:

[0039]

[0040] Depend on It can be seen that when time That is, the correction time is the middle value T mid When , the expected error is the smallest, and the expected error is E2 indicates that the error is reduced by half compared to the original error.

[0041] Therefore, when there is a flow change and RE is greater than the threshold in the table, the minimum error is taken, such as Figure 2 As shown, the actual change is taken at the middle of T, that is, the correction time is T mid , the instantaneous flow rate within T is The calculation method for cumulative flow correction at this time is: The calculated cumulative flow rate correction value V2 is 9.92E-4 (L);

[0042] During this measurement cycle, the original cumulative flow value V1 was 8.67E-4 (L), with a calculated RE value of -14.7%. The corrected cumulative flow value V2 was 9.92E-4 (L), a change of 14.4%. During this flow rate change test cycle, the original expected error was 0.46, while the corrected error was 0.23, reducing the error by half. During this measurement process, when the ultrasonic water meter test duration is short, the flow rate changes are large and frequent, and the water meter measurement frequency is low, the measurement error of the water meter will be greater, further demonstrating the necessity of using this method.

[0043] The above embodiments are illustrations of specific implementation methods of the present invention, rather than limitations of the present invention. Technicians in the relevant technical fields may make various transformations and changes to obtain corresponding equivalent technical solutions without departing from the spirit and scope of the present invention. Therefore, all equivalent technical solutions should be included in the patent protection scope of the present invention.

Claims

1. A method for correcting measurement errors of ultrasonic water meters, characterized in that: The following steps are involved: S1, according to the measurement signal of the ultrasonic water meter, the instantaneous flow value v of the ultrasonic water meter is calculated using the time difference method and recorded; S2, during the normal operation of the ultrasonic water meter, when the instantaneous flow value changes, a measurement error will occur. The error value is δ = (v1-v2)(Tx). Calculate the expected flow error E1 caused by the flow change: Where E1 represents the expectation, T represents the ultrasonic water meter sampling period, which is the reciprocal of the measurement frequency f, x is the time when the instantaneous flow changes, v1 and v2 represent the flow values ​​before and after the change, respectively, and P(x) represents the probability that the instantaneous flow value changes at time x; S3, according to the flow error expectation, the error degree value RE is obtained: Where V1 represents the cumulative flow value within the sampling period, V1 = v1T; T is the ultrasonic water meter sampling period; v1 and v2 represent the instantaneous flow values ​​before and after the change respectively; S4, judging whether the RE value exceeds the preset threshold range. If so, it is considered that the flow rate has changed during the metering cycle and flow rate correction is required; The flow correction scheme is to replace the real instantaneous flow change time x with the fixed time y to minimize the error expectation within the measurement cycle. The error expectation of this process is: Where E2 represents the error expectation after flow correction, T represents the ultrasonic water meter sampling period, which is the reciprocal of the measurement frequency f, v1 and v2 represent the flow values ​​before and after the change, respectively, and P(x) represents the probability that the instantaneous flow value changes at time x. The optimal value of y that minimizes the error expectation E2 is y0. S5, use the corrected cumulative flow value V2 = v1y0 + v2 (T-y0) to replace the original V1 value in the table to calculate the cumulative flow; if the calculated RE value does not exceed the preset threshold range, it is considered that the flow has not changed during the metering cycle, and no correction is made, and the cumulative flow value is still calculated based on V1.

2. The method for correcting measurement errors of ultrasonic water meters according to claim 1, characterized in that: In step S2 , P(x), i.e., the probability distribution estimation method of the instantaneous flow rate change moment x, can use normal distribution or average distribution.

3. The method for correcting measurement errors of ultrasonic water meters according to claim 1, characterized in that: In the calculation of the RE value in step S3, when one of the instantaneous flow rates v1 and v2 is 0 and the other is not 0, that is, when the valve is opened or closed, the RE value is not calculated and the flow correction is performed directly.

4. The method for correcting measurement errors of ultrasonic water meters according to claim 1, wherein: The threshold range of the ultrasonic water meter in step S4 is preset to [-σ, σ] when the ultrasonic water meter leaves the factory. When the RE value is within ±σ, it is considered that the water flow fluctuates normally, otherwise it is considered that the flow rate has changed, where σ is the measurement accuracy of the ultrasonic water meter; As the service time of ultrasonic water meters increases, the preset threshold range is [σ-Δσ,σ+Δσ], where Where t represents the current service time, t1 represents the theoretical service time, Δσ represents the change in threshold, σ t It represents the measurement accuracy of ultrasonic water meter when the service time is t, and c is the aging constant.

5. The method for correcting measurement errors of ultrasonic water meters according to claim 1, characterized in that: As described in step S4, after the flow rate is corrected, the flow rate measurement error caused by the instantaneous flow rate change is reduced, so that the measurement frequency of the ultrasonic water meter can be reduced while the measurement accuracy remains unchanged, thereby increasing the life of the ultrasonic water meter.

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