Error evaluation and correction method for ultrasonic flowmeter

Abstract

The application provides an ultrasonic flowmeter error evaluation and correction method, which comprises the following steps: (1) establishing a pipeline model; (2) evaluating flow velocity error; (3) establishing an ultrasonic flowmeter measurement error correction model; and (4) outputting the corrected ultrasonic flowmeter flow error. The application provides a flow velocity correction coefficient under non-standard test conditions relative to standard test conditions, and can be used in the measurement of ultrasonic flowmeters under non-standard test conditions in water pipe networks. At this time, a long straight pipe section does not need to be provided, the space and cost requirements are low, the measurement error of the flowmeter can be within ±0.5% through the provided error correction model, and the accuracy is high. The ultrasonic flowmeter error evaluation and correction method provided by the application is not affected by the installation mode of the ultrasonic flowmeter and the type of the flow resistance element, and is suitable for a wide range of conditions.

Description

Technical Field

[0001] This application belongs to the field of pipeline flow measurement technology, and in particular relates to a method for error evaluation and correction of ultrasonic flow meters. Background Technology

[0002] Water balance testing is a fundamental step in water-saving optimization analysis, providing crucial information for exploring effective water-saving approaches, developing targeted water-saving measures, and improving the water efficiency of equipment and facilities. Currently, ultrasonic flow meters are commonly used for flow measurement in water balance testing. While ultrasonic flow meters offer advantages such as low pressure loss, high measurement accuracy, and no interference with the measured medium, the presence of flow obstructions in the pipeline, such as bends, valves, and pumps, can interfere with fluid flow, causing various flow pattern changes, such as secondary flow disturbances. Asymmetric flow field distributions and radial velocity components can alter the direction and velocity of ultrasonic wave propagation, thus affecting flow measurement accuracy. To improve measurement accuracy, commonly used methods include:

[0003] (1) Strict standard testing conditions are adopted, requiring the on-site measuring points to have sufficiently long straight pipe sections, horizontal flow direction, or bottom-up flow, etc., to ensure that the fluid flow state is not affected as much as possible. However, more than 80% of the measuring points in refining and chemical enterprises do not meet the above standard testing conditions. This method has high requirements for space and cost and is not suitable for practical application scenarios.

[0004] (2) Due to the limitations of standard testing conditions, adding a rectifier is a relatively effective means. Since the shape, structure, and installation method of the rectifier directly affect its working performance, rectifiers used in engineering applications often need to be designed for specific occasions, resulting in inconsistent flow conditioner structures and performance. In addition, unreasonable shapes and structures and non-standard installation methods can lead to turbulent flow fields downstream of the rectifier, failing to achieve the rectification effect.

[0005] (3) Using a multi-channel ultrasonic flow meter for measurement can better adapt to changes in flow field morphology and improve measurement accuracy. However, for small-diameter ultrasonic flow meters, it is difficult to adopt a multi-channel solution due to space limitations, and most can only use a single-channel layout.

[0006] Currently, no reports have been found regarding error correction techniques for widely used single-channel ultrasonic flow meters. Existing technologies mainly focus on the flow velocity distribution within pipelines and the influence of errors.

[0007] Application content

[0008] To overcome the aforementioned deficiencies in the prior art, this invention proposes a method for evaluating and correcting the error of ultrasonic flowmeters under non-standard testing conditions. This method can quickly establish a pipeline model by combining a mechanism model based on Python with a finite element model. It is applicable to situations where there are complex flow obstructions in the pipeline, such as bends, valves, and pumps, and can achieve rapid and accurate evaluation and correction of the measurement error of ultrasonic flowmeters, thereby improving the accuracy of flow measurement.

[0009] This invention proposes a method for evaluating and correcting errors in ultrasonic flow meters, the improvement of which lies in that the method includes...

[0010] (1) Establish a pipeline model;

[0011] (2) Evaluate the flow velocity error;

[0012] (3) Establish a measurement error correction model for ultrasonic flowmeters;

[0013] (4) Output the corrected flow error of the ultrasonic flow meter.

[0014] Preferably, step (1) includes

[0015] A pipeline model is established based on a mechanistic model and a finite element model using Python. The mechanistic model obtains the flow characteristics of the flow obstruction component, and the finite element model includes the flow obstruction component and the pipeline.

[0016] Preferably, step (2) includes

[0017] 2-1 Obtain the average velocity along the fluid flow direction on the ultrasonic propagation path and the stable velocity value of the fluid returning to a fully developed state, and calculate the flow velocity error of the ultrasonic flow meter according to the uncorrected error calculation formula of the ultrasonic flow meter;

[0018] 2-2 Change the location of the ultrasonic flow meter to obtain multiple data points measured by the ultrasonic flow meter;

[0019] 2-3 Using the distance between the ultrasonic flow meter and the flow obstruction element as a variable, the error curve of the ultrasonic flow meter is obtained.

[0020] Furthermore, the formula for calculating the uncorrected flow velocity error of the ultrasonic flow meter is expressed as follows:

[0021]

[0022] v1 = k1 × v x (2)

[0023]

[0024] In the formula, ε1 is the uncorrected flow velocity error of the ultrasonic flow meter; v1 is the measured flow velocity of the ultrasonic flow meter, in m / s; vs is the flow velocity setpoint, in m / s; k1 is the flow velocity correction coefficient for the model; vx is the average velocity along the fluid flow direction on the ultrasonic propagation path, in m / s; and vm is the stable flow velocity value, in m / s.

[0025] Preferably, step (3) includes

[0026] 3-1 Based on the flow velocity measurement value v1 and the flow velocity set value vs of the ultrasonic flow meter, the ratio of the flow velocity set value to the flow velocity measurement value of the ultrasonic flow meter is defined as the flow velocity correction coefficient k2 of the ultrasonic flow meter.

[0027]

[0028] The corrected flow rate is calculated using the flow velocity correction coefficient k2, the flow velocity measurement value v1, and the pipe cross-sectional area S.

[0029] q2=k2×v1×S (5)

[0030] 3-2 The relationship between the flow velocity correction coefficient k2 and the distance is fitted to obtain the flow error correction model of the ultrasonic flow meter.

[0031] The flow error correction model for ultrasonic flow meters can be expressed as follows:

[0032] k2 = AZ 5 +BZ 4 +CZ 3 +DZ 2 +EZ+F (6)

[0033] Y = X × k2 (7)

[0034] In the formula, A, B, C, D, E, and F are fitting parameters; Y is the corrected flow rate value of the ultrasonic flow meter; Z is the distance between the measuring point and the flow obstruction element; and X is the flow rate measurement value of the flow meter.

[0035] Furthermore, in the data fitting of the relationship between the flow rate correction coefficient k2 and the distance, the distance is the distance between the measurement point and the flow obstruction.

[0036] Furthermore, Z is the distance between the measuring point and the flow obstruction element, where the measuring point is the midpoint of the flow meter along the pipeline axis.

[0037] Preferably, step (4) includes obtaining the corrected flow value Y using the ultrasonic flow meter error correction model, and then obtaining the corrected ultrasonic flow meter flow error.

[0038] The formula for calculating flow error is:

[0039]

[0040] In the formula, ε2 represents the flow error of the corrected ultrasonic flow meter.

[0041] Preferably, flow meter error correction models are provided under different conditions based on different combinations of flow obstruction type and ultrasonic flow meter installation location.

[0042] Furthermore, the upstream and downstream of the flow meter are both bends, or the upstream and downstream of the flow meter are both valves, or the upstream of the flow meter is a bend and the downstream is a valve, or the upstream of the flow meter is a valve and the downstream is a bend.

[0043] The technical solutions provided by the embodiments of the present invention may include the following beneficial effects:

[0044] This invention provides a method for evaluating and correcting the error of ultrasonic flow meters under non-standard testing conditions. It provides a flow velocity correction coefficient for non-standard testing conditions relative to standard testing conditions. This method can be used in ultrasonic flow meter measurement applications under non-standard testing conditions in water pipe networks. In this case, it does not require a sufficiently long straight pipe section, and has low requirements for space and cost. The provided error correction model can keep the flow meter measurement error within ±0.5%, with high accuracy.

[0045] The ultrasonic flowmeter error evaluation and correction method provided by this invention is applicable to various scenarios, including when both upstream and downstream of the flowmeter are bends, when both upstream and downstream of the flowmeter are valves, when the upstream of the flowmeter is a bend and the downstream is a valve, and when the upstream of the flowmeter is a valve and the downstream is a bend, etc. It is not affected by the installation method of the ultrasonic flowmeter or the type of flow obstruction, and has a wide range of applicable conditions.

[0046] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit the invention. Attached Figure Description

[0047] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0048] Figure 1 This is a schematic flowchart of a specific embodiment of an ultrasonic flow meter error evaluation and correction method according to this application;

[0049] Figure 2 This is a schematic diagram of an ultrasonic flow meter measurement system according to a specific embodiment of an ultrasonic flow meter error evaluation and correction method based on this application.

[0050] Figure 3This is a schematic diagram showing the influence of the channel arrangement, pipe diameter, and distance on the measurement error of an ultrasonic flow meter according to a specific embodiment of an ultrasonic flow meter error evaluation and correction method based on this application.

[0051] Figure 4 This is a schematic diagram comparing the errors before and after correction for pipe diameters of 0.1m and 0.2m, according to a specific embodiment of an ultrasonic flow meter error evaluation and correction method based on this application.

[0052] Figure 5 This is a schematic diagram showing the influence of the channel arrangement, pipe diameter, and distance on the measurement error of an ultrasonic flow meter according to a specific embodiment of an ultrasonic flow meter error evaluation and correction method based on this application.

[0053] Figure 6 This is a schematic diagram showing the influence curves of valve opening and distance on the measurement error of an ultrasonic flow meter according to a specific embodiment of an ultrasonic flow meter error evaluation and correction method based on this application.

[0054] Figure 7 This is a schematic diagram comparing the corrected error with the original error of a pipe with a diameter of 0.5m and a valve opening of 45°, according to a specific embodiment of an ultrasonic flow meter error evaluation and correction method based on this application.

[0055] Figure 8 This is a schematic diagram comparing the corrected error with the original error of a pipe with a diameter of 0.5m and a valve opening of 60°, according to a specific embodiment of an ultrasonic flow meter error evaluation and correction method based on this application.

[0056] Among them, 1 is a fluid conveying device, 2 and 3 are flow obstruction components, 4 is a test pipe, and 5 is an ultrasonic flow meter;

[0057] The same or similar reference numerals in the accompanying drawings represent the same or similar parts. Detailed Implementation

[0058] To better understand and explain this application, a further detailed description will be provided below with reference to the accompanying drawings. This application is not limited to these specific embodiments. Rather, any modifications or equivalent substitutions made to this application should be covered within the scope of the claims.

[0059] It should be noted that numerous specific details are provided in the following detailed embodiments. Those skilled in the art should understand that this application can be implemented without these specific details. In the various detailed embodiments given below, principles, structures, and components well known in the art are not described in detail in order to highlight the main points of this application.

[0060] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0061] This invention addresses the problems existing in the prior art, such as... Figure 1 , Figure 2 As shown, a method for evaluating and correcting the error of ultrasonic flowmeters under non-standard testing conditions is proposed. This method can quickly build a pipeline model by combining the mechanism model and the finite element model based on Python. It is applicable to situations where there are complex flow obstructions such as bends, valves, and pumps in the pipeline, so as to realize the rapid and accurate evaluation and correction of the measurement error of ultrasonic flowmeters, thereby improving the accuracy of flow measurement.

[0062] Example 1:

[0063] Taking the ultrasonic flowmeter in the upstream flow field of a bend as an example, the effects of channel arrangement, pipe diameter, and distance between the flowmeter and the bend on the flowmeter measurement error were evaluated. The upstream pipe length was set to 20D, and the downstream pipe length was set to 50D (D is the pipe diameter in meters). The ultrasonic flowmeter channel arrangement was the V-method for pipe diameters of 0.1m and 0.2m, and the Z-method for other pipe diameters.

[0064] The curves showing the influence of channel arrangement, pipe diameter, and distance on the measurement error of ultrasonic flowmeters are shown below. Figure 3 .Depend on Figure 3 The following conclusions can be drawn: (1) The measurement error of the ultrasonic flow meter decreases as the distance between it and the downstream bend increases. This is because the degree of disturbance of the flow field by the bend gradually decreases as the distance between the ultrasonic flow meter and the bend increases; (2) The measurement error of the flow meter when the pipe diameter is 0.1m and 0.2m is greater than the error when the pipe diameter is in the range of 0.3m to 0.6m; (3) When the pipe diameter is in the range of 0.3m to 0.6m, the error measurement curves basically coincide, so the same formula can be used for correction. Similarly, the same formula can be used for correction when the pipe diameter is 0.1m and 0.2m.

[0065] Taking a horizontal bend as an example, a flow meter flow error correction model was established. The error correction model for different pipe diameters is as follows:

[0066] When the pipe diameter is 0.1m and 0.2m:

[0067] Y = (-0.0062Z) 4 +0.0555Z 3 -0.1849Z 2 +0.2736Z+0.8469)×X

[0068] When the pipe diameter is 0.3m to 0.6m:

[0069] Y = (0.0047Z) 4 -0.0383Z 3 +0.1149Z 2 -0.1510Z+1.0739)×X

[0070] Y represents the corrected flow rate value of the ultrasonic flow meter, Z represents the distance between the measurement point (the midpoint of the flow meter along the pipe axis) and the flow obstruction, and X represents the flow measurement value of the flow meter.

[0071] Figure 4 This is a comparison chart of the errors before and after correction for pipe diameters in the ranges of 0.1m and 0.2m. Figure 4 It can be seen that the corrected errors are all stable within ±0.1%, and the error correction effect of the model is very significant.

[0072] Example 2:

[0073] Taking the ultrasonic flow meter in the upstream flow field of a butterfly valve as an example, the upstream pipe length is set to 20D, and the downstream pipe length is set to 50D (D is the pipe diameter, unit: m). The influence of valve opening and pipe diameter on the flow meter measurement error is analyzed, and finally, a flow measurement error correction model is established using model data.

[0074] Figure 5 This graph shows the variation of ultrasonic flowmeter measurement error with the distance between the flowmeter and the downstream valve under different pipe diameter conditions, with a valve opening of 45° and an inlet flow velocity of 1 m / s. Specifically, the ultrasonic flowmeter channel arrangement is the V-method for pipe diameters of 0.1 m and 0.2 m, and the Z-method for other pipe diameters. Figure 5 It is known that, under the same inlet flow velocity and valve opening conditions, the arrangement of the flow meter channel and the pipe diameter will affect the flow meter measurement error. Asymmetrical flow velocity distribution or the presence of a radial velocity component will cause measurement error in ultrasonic flow meters.

[0075] Figure 6 This graph shows the impact of valve opening on the measurement error of an ultrasonic flow meter when the pipe diameter D = 0.5 m and the inlet flow velocity is 1 m / s. The valve disturbs the flow field upstream of it, especially when the valve opening is small, resulting in strong lateral flow near the valve. Figure 6 It can be seen that the ultrasonic flowmeter has a relatively large measurement error within the range of 0 to 1.5D (D is the pipe diameter) upstream of the valve. As the distance between the flowmeter and the valve increases, the measurement error gradually decreases. Therefore, we can conclude that as the valve opening and the distance between the ultrasonic flowmeter and the valve increase, the degree of flow field disturbance gradually decreases, and the flowmeter measurement error gradually decreases.

[0076] Taking a pipe diameter of 0.5m as an example, the error correction model for the ultrasonic flowmeter at different valve openings is as follows:

[0077] When the valve opening is 15°: Y = (-0.416Z) 4 +2.302Z 3 -4.651Z 2 +4.083Z-0.326)×X

[0078] When the valve opening is 45°: Y = (-0.053Z) 4 +0.350Z 3 -0.833Z 2 +0.837Z+0.708)×X

[0079] When the valve opening is 60°: Y = (-0.139Z) 4 +0.707Z 3 -1.280Z 2 +0.957Z+0.765)×X

[0080] When the valve opening is 90°: Y = (-0.008Z) 4 -0.032Z 3 +0.034Z 2 +0.013Z+0.975)×X

[0081] When the valve opening is 45°, the flow error correction model for different pipe diameters is as follows:

[0082] When the pipe diameter is 0.1m:

[0083] Y = (2.142Z) 5 -11.793Z 4 +34.232Z 3 -55.231Z 2 +46.920Z-15.375)×X

[0084] When the pipe diameter is 0.2m:

[0085] Y = (0.115Z) 5 -1.287Z 4 +5.739Z 3 -12.703Z 2 +13.965Z-5.106)×X

[0086] When the pipe diameter is 0.3m: Y=(-0.031Z) 4 +0.245Z 3 -0.673Z 2 +0.762Z+0.700)×X

[0087] When the pipe diameter is 0.4m: Y = (-0.042Z)4 +0.304Z 3 -0.767Z 2 +0.806Z+0.707)×X

[0088] When the pipe diameter is 0.5m: Y = (-0.053Z) 4 +0.350Z 3 -0.833Z 2 +0.837Z+0.708)×X

[0089] When the pipe diameter is 0.6m: Y = (-0.056Z) 4 +0.365Z 3 -0.857Z 2 +0.847Z+0.712)×X

[0090] To compare the changes in error before and after the correction, simulations of the error before and after the correction were performed. Figure 7 This is a comparison chart showing the corrected error and the original error for a pipe with a diameter of 0.5m and a valve opening of 45°. Figure 7 It can be seen that the corrected error is stable within ±0.1%. Figure 8 This is a comparison chart showing the corrected error and the original error for a pipeline with a diameter of 0.5m and a valve opening of 60°. Figure 8 It can be seen that the corrected error is stable within ±0.5%.

[0091] Example 3:

[0092] Error correction models for ultrasonic flowmeters with different types and installation positions of flow obstruction components were established, and the corrected errors were all stable within ±0.5%.

[0093] (1) The error correction model when both upstream and downstream of the flow meter are bends is:

[0094] Y = (-3.613 × 10 8 Z 5 +5.239×10 -6 Z 4 -2.879×10 -4 Z 3 +7.46×10 -3 Z 2 -9.233×10 -2 Z+1.477)×X

[0095] (2) The error correction model when both upstream and downstream of the flow meter are valves is:

[0096] Y = (-5.694 × 10 -9 Z 5 +9.206×10-7 Z 4 -5.785×10 -5 Z 3 +1.790×10 -3 Z 2 -2.909×10 -2 Z+1.235)×X

[0097] (3) The error correction model for the flow meter when the upstream is a bend and the downstream is a valve is:

[0098] Y = (-1.522 × 10 -10 Z 5 +4.130×10 -9 Z 4 -4.120×10 -6 Z 3 +1.967×10 -4 Z 2 -6×10 -3 Z+1.117)×X

[0099] (4) The error correction model when the upstream of the flow meter is a valve and the downstream is a bend is:

[0100] Y = (3.478 × 10 -8 Z 5 +4.365×10 -6 Z 4 -2.095×10 -4 Z 3 +4.765×10 -3 Z 2 -5.251×10 2 Z+1.276)×X

[0101] (6) The error correction model for the flow meter when the upstream is a pump and the downstream is a bend is:

[0102] Y = (-1.314 × 10 -8 Z 5 +1.738×10 -6 Z 4 -8.940×10 -5 Z 3 +2.286×10 -3 Z 2 -3.05×10 -2 Z+1.177)×X

[0103] (7) The error correction model when the upstream of the flow meter is a pump and the downstream is a valve is:

[0104] Y = (2.573 × 10 -9 Z5 -3.003×10 -7 Z 4 +1.335×10 -5 Z 3 -2.823×10 -4 Z 2 +2.884×10 -3 Z+0.9897)×X

[0105] (8) The error correction model for the flow meter with an upstream bend and a downstream pump is:

[0106] Y = (1.982 × 10 -8 Z 4 -4.895×10 -6 Z 3 +3.854×10 -4 Z 2 -1.266×10 -2 Z+1.157)×X

[0107] It should be noted that although the operations of the method of this application are described in a specific order in the accompanying drawings, this does not require or imply that these operations must be performed in that specific order, or that all the operations shown must be performed to achieve the desired result. On the contrary, the steps depicted in the flowchart can be executed in a different order. Additionally or alternatively, certain steps may be omitted, multiple steps may be combined into one step, and / or one step may be broken down into multiple steps.

[0108] Those skilled in the art will understand that any computer system with suitable programming means is capable of executing the steps of the methods of this application contained in a computer program product. Although most of the specific embodiments described in this specification focus on software programs, alternative embodiments that implement the methods provided in this application in hardware are also within the scope of protection claimed in this application.

[0109] It will be apparent to those skilled in the art that this application is not limited to the details of the exemplary embodiments described above, and that this application can be implemented in other specific forms without departing from the spirit or essential characteristics of this application. Therefore, the embodiments should be considered exemplary and not restrictive, and the scope of this application is defined by the appended claims rather than the foregoing description. All variations within the meaning and scope of equivalents of the claims are included within this application. No reference numerals in the claims should be construed as limiting the scope of the claims. Furthermore, it is clear that the word "comprising" does not exclude other components, units, or steps, and the singular does not exclude the plural. Multiple components, units, or devices recited in the claims may also be implemented by a single component, unit, or device through software or hardware.

[0110] The above-disclosed embodiments or specific implementations are only a part of the embodiments or specific implementations of this application and should not be construed as limiting the scope of the rights of this application. Equivalent changes made in accordance with the claims of this application shall still fall within the scope of this application.

Claims

1. A method for evaluating and correcting errors in an ultrasonic flow meter, characterized in that, The method includes (1) Establishing a pipeline model, specifically including: establishing a pipeline model based on a mechanism model and a finite element model using Python, wherein the mechanism model obtains the flow characteristics of the flow obstruction component, and the finite element model includes the flow obstruction component and the pipeline; (2) Evaluate the flow velocity error, specifically including: 2 1. Obtain the average velocity along the fluid flow direction on the ultrasonic propagation path and the stable velocity value of the fluid returning to a fully developed state, and calculate the flow velocity error of the ultrasonic flow meter according to the uncorrected error calculation formula of the ultrasonic flow meter; 2 2. Change the location of the ultrasonic flow meter to obtain multiple data points measured by the ultrasonic flow meter; 2 3. Using the distance between the ultrasonic flow meter and the flow obstruction element as a variable, the error curve of the ultrasonic flow meter is obtained; (3) Establish an ultrasonic flowmeter measurement error correction model, specifically including: 3-1 Based on the flow velocity measurement value v1 and the flow velocity set value vs of the ultrasonic flow meter, the ratio of the flow velocity set value to the flow velocity measurement value of the ultrasonic flow meter is defined as the flow velocity correction coefficient k2 of the ultrasonic flow meter. 3-2 The relationship between the flow velocity correction coefficient k2 and the distance is fitted to obtain the flow error correction model of the ultrasonic flow meter; The flow error correction model for ultrasonic flow meters can be expressed as follows: In the formula, A, B, C, D, E, and F are fitting parameters; Y is the corrected flow rate value of the ultrasonic flow meter; Z is the distance between the measuring point and the flow obstruction; X is the flow rate measurement value of the flow meter; K 2z This is the flow velocity correction factor when the distance between the measuring point and the flow obstruction is Z; (4) Output the corrected flow error of the ultrasonic flow meter.

2. The method for evaluating and correcting errors in an ultrasonic flowmeter according to claim 1, characterized in that, The formula for calculating the uncorrected flow velocity error of the ultrasonic flow meter is expressed as follows: In the formula, ε1 is the uncorrected velocity error of the ultrasonic flow meter; v1 is the measured velocity value of the ultrasonic flow meter, in m / s; v s The flow rate setpoint is in m / s; k1 is the flow rate correction factor for the model; v x The average velocity of the ultrasonic wave along the direction of fluid flow along its propagation path, in m / s; v m This is the steady-state flow velocity value, in m / s.

3. The method for evaluating and correcting errors in an ultrasonic flowmeter according to claim 1, characterized in that, Z is the distance between the measuring point and the flow obstruction element, where the measuring point is the midpoint of the flow meter along the pipeline axis.

4. The method for evaluating and correcting errors in an ultrasonic flowmeter according to claim 1, characterized in that, Step (4) includes obtaining the corrected flow value Y using the ultrasonic flow meter error correction model, and then obtaining the corrected ultrasonic flow meter flow error. The formula for calculating flow error is: In the formula, ε2 represents the flow error of the corrected ultrasonic flow meter.

5. The method for evaluating and correcting errors in an ultrasonic flowmeter according to claim 1, characterized in that, Flowmeter error correction models are provided under different conditions based on different combinations of flow obstruction type and ultrasonic flowmeter installation location.

6. The method for evaluating and correcting errors in an ultrasonic flowmeter according to claim 1 or 5, characterized in that, The upstream and downstream of the flow meter are both bends, or the upstream and downstream of the flow meter are both valves, or the upstream of the flow meter is a bend and the downstream is a valve, or the upstream of the flow meter is a valve and the downstream is a bend.

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