Cyclic self-calibration flow online detection method and system

Abstract

The invention relates to the technical field of flow detection, in particular to a circulating self-calibration flow online detection method and system.The circulating self-calibration flow online detection method comprises the steps that preset standard meters are connected in parallel to form a flow detection system, and the piston measuring range and the standard meter flow measuring range in the flow detection system are collected; comparing and analyzing whether the flow measuring range of the standard meter is within the piston measuring range; if yes, indicating the piston to perform flow calibration on the to-be-detected standard meter; and if not, carrying out iterative calibration according to a preset flow circulation self-calibration strategy so as to improve the measurement range of the flow detection system. The method has the advantages that the detection range effect of the standard meter in large-flow detection is improved, and meanwhile the detection uncertainty can be reduced.

Description

Technical Field

[0001] The present application relates to the technical field of flow detection, and in particular to a method and system for online detection of cyclic self-calibration flow. Background Art

[0002] Flow standard devices are widely used in the actual evaluation of flow meters, especially the standard meter method, which has the advantages of mature technology and high work efficiency in flow detection of large-diameter equipment.

[0003] In the related art, the detection device used in the standard meter method is usually equipped with a high-precision piston, and its accuracy standard is transmitted to the standard meter. Since the volume of the piston should not be too large, the range of flow detection is limited. In order to increase the range, multiple standard meters are usually connected in parallel to increase the range.

[0004] With respect to the above-mentioned related technologies, when a plurality of standard meters are connected in parallel to increase the detection range, when the detection range increases, the number of standard meters used increases accordingly, which increases the device cost and the installation workload. Summary of the invention

[0005] In order to solve the technical problems in the above-mentioned related technologies, the present application provides a cyclic self-calibration flow online detection method.

[0006] In a first aspect, the present application provides a method for online detection of cyclic self-calibration flow, which adopts the following technical solution: A cyclic self-calibration flow online detection method, comprising: The preset standard meter is connected in parallel to form a flow detection system, and the piston range in the flow detection system and the flow measurement range of the standard meter are collected; Compare and analyze whether the flow measurement range of the standard meter is within the piston range; If so, the piston is instructed to perform flow calibration against the standard meter; If not, an iterative calibration is performed using a preset flow cycle self-calibration strategy to improve the measurement range of the flow detection system.

[0007] By adopting the above technical solution, multiple standard meters are connected in parallel to form a flow detection system with a higher flow detection range. At the same time, the flow detection system is self-circulatingly calibrated and iterated to further improve the range of the flow detection system.

[0008] Optionally, the flow cycle self-calibration strategy includes: When the indicating piston transfers flow to each standard meter in the flow detection system, the flow range of each standard meter is consistent with the transfer limit of the piston; Close the piston and adjust the regulating valve of the standard meter until the flow range of the standard meter reaches the preset upper limit value; The flow meter preset in the flow detection system satisfies the preset switching condition, and the flow meter is cyclically switched as the meter to be tested and the standard meter. The switching condition is whether the flow meter completes the flow point range calibration of the next standard meter.

[0009] By adopting the above technical solution, the flow detection system transmits the detection accuracy of the piston to each standard meter, so that the flow range of each standard meter remains consistent, thereby reducing the detection accuracy error in the flow detection process and improving the accuracy of the flow detection value. At the same time, by adjusting the detection upper limit value when the standard meter is switched from the meter being tested to the standard meter, the measurement range can be improved.

[0010] Optionally, when the flow meter is used as the meter to be tested and the standard meter to be cyclically switched, it also includes: The error calculation of the meter under test is performed to determine the relative error of the meter under test. The error calculation adopts the following formula: (1) (2) in, Indicates the relative error of the meter under test. Indicates the cumulative flow volume of the meter under test. Indicates the cumulative test time of the meter under test. Indicates the piston flow value, Indicates the effective diameter of the piston, represents the material expansion coefficient of the piston, Indicates the water temperature in the piston cylinder.

[0011] By adopting the above technical solution, the relative error of the standard meter is calculated, so that when the standard meter is cyclically self-calibrated according to the calculation result, the flow detection error can be known in time, which is helpful for error analysis based on the relative error.

[0012] Optionally, also include: The combined standard uncertainty of the standard table after the value transfer is calculated using the following formula: (3) in, represents the uncertainty of the standard table, Indicates the uncertainty of the standard meter at this flow point, Indicates the repeatability of the test table.

[0013] By adopting the above technical solution, the uncertainty of the standard meter is calculated during the cyclic self-calibration process, so that the accuracy of flow detection during the cyclic self-calibration process can be judged according to the uncertainty, which is helpful to analyze the reliability of the detection result.

[0014] Optionally, the uncertainty calculation also includes: Collect the number of times the value is transferred and synthesized, and calculate and correct the uncertainty; The revised calculation formula is as follows: (4) in, Indicates the number of times the value is passed.

[0015] By adopting the above technical solution, during the cyclic transfer detection accuracy process of the standard table, the number of repeated transfers is used as an influencing factor for the calculation to adjust the calculation formula, so that the uncertainty calculation of the standard table is more accurate.

[0016] Optionally, the error calculation for the meter under test includes: The outer wall temperature value and the ambient temperature value of the piston are detected at a preset minimum detection frequency. When the ambient temperature value is within a preset normal temperature range, a preset temperature transfer calculation strategy and the outer wall temperature value are used for calculation to determine the water flow temperature value of the piston inner cylinder. The temperature transfer calculation strategy is calculated using the following formula: (5) in, q is the heat flux density between the water flow in the piston cylinder and the inner wall of the piston cylinder, h 1 is the convection heat transfer coefficient, which is calculated based on the Nusselt number corresponding to the forced convection heat transfer in the tube. T in is the inner wall temperature of the piston cylinder. Based on the analysis of heat conduction between the inner and outer walls of the piston cylinder, we can get: (6) in, k represents the thermal conductivity of the piston cylinder, δ Indicates the wall thickness of the piston cylinder, T out is the temperature of the outer wall of the piston cylinder, which can be collected by a temperature sensor. Based on the natural convection heat transfer analysis between the outer wall of the piston cylinder and the ambient air, we can get: (7) in, h 2 is the natural convection heat transfer coefficient between the outer wall of the piston cylinder and the ambient air, which is calculated based on the Nusselt number corresponding to natural convection. T ambis the ambient temperature. Based on formula (7), the value of the heat flux density q can be calculated. Combining formulas (5) to (7), we can get: (8) Based on formula (8), the temperature of the water flow in the piston cylinder can be calculated more accurately based on the temperature of the outer wall of the piston cylinder.

[0017] By adopting the above technical solution, when calculating the water flow temperature value of the water flow in the piston cylinder, factors such as the heat transfer temperature gradient ratio, the specific heat capacity coefficient and the thermal conductivity coefficient are integrated to make the calculation result of the water flow temperature value more accurate, thereby helping to improve the calculation reliability of the relative error of the tested meter. At the same time, there is no need to place the temperature sensor in the piston cylinder, which helps to reduce the difficulty of structural design and reduce the inconvenience of installation.

[0018] Optionally, when collecting the outer wall temperature value, include: Collect the piston movement frequency of the piston and match it with the interference weight ratio corresponding to the piston movement frequency in the preset temperature interference database; Calculating based on the interference weight ratio and the water flow temperature value to determine the water flow temperature correction value; The water flow temperature value is replaced and updated based on the water flow temperature correction value.

[0019] By adopting the above technical solution, when collecting the outer wall temperature value, the interference weight ratio of the water flow temperature value in the cylinder is searched and corrected according to the piston movement frequency due to the water flow brought by the piston movement, making the detection of the outer wall temperature value more realistic.

[0020] Optionally, the piston movement frequency can be collected by: Based on the movement frequency collection and analysis during the piston movement, the piston movement frequency is determined, and a pause in the movement frequency collection is issued, and the pipeline flow output by the piston is detected at the same time; Calculate the flow rate change rate based on the pipeline flow rate, and compare and analyze whether the flow rate change rate is greater than a preset reference water flow change rate; If it is less than or equal to, the acquisition of piston change rate is suspended; If it is greater, the piston movement frequency is collected again and updated.

[0021] By adopting the above technical solution, the water flow rate change rate in the pipeline is analyzed when collecting the piston movement frequency, and the piston frequency collection and control is performed based on the comparative relationship between the water flow rate change rate and the reference water flow rate change rate, so as to reduce unnecessary frequent piston frequency detection when the water flow rate change rate is not obvious.

[0022] In the second aspect, the present application provides a cyclic self-calibration flow online detection system, which adopts the following technical solution: A cyclic self-calibration flow online detection system, comprising: The acquisition module connects the preset standard meter in parallel to form a flow detection system, and collects the piston range in the flow detection system and the flow measurement range of the standard meter; Flow analysis module, used to compare and analyze whether the flow measurement range of the standard meter is within the piston range; If so, the piston is instructed to perform flow calibration against the standard meter; If not, the cyclic calibration module is instructed to perform iterative calibration using a preset flow cycle self-calibration strategy to improve the measurement range of the flow detection system.

[0023] By adopting the above technical solution, the standard meters are connected in parallel to form a flow detection system, which can improve the flow detection range while allowing the flow system to form a closed loop through cyclic self-calibration, so that the accuracy can be transmitted to each other between the standard meters, which helps to maintain the measurement accuracy of the flow detection system.

[0024] In summary, the present application includes at least one of the following beneficial technical effects: 1. Connect multiple standard meters in parallel to form a flow detection system with a higher flow detection range. At the same time, perform self-circulation calibration iteration on the flow detection system to further improve the flow detection system's range; 2. When calculating the water flow temperature value of the water flow in the piston cylinder, the heat transfer temperature gradient ratio, specific heat capacity coefficient, thermal conductivity coefficient and other factors are integrated to make the calculation result of the water flow temperature value more accurate, thereby helping to improve the calculation reliability of the relative error of the meter under test. At the same time, there is no need to put the temperature sensor into the piston cylinder, which helps to reduce the difficulty of structural design and installation inconvenience; 3. When collecting the piston movement frequency, the water flow rate change rate in the pipeline is analyzed, and the piston frequency collection and control is performed based on the comparative relationship between the water flow rate change rate and the reference water flow rate change rate, so as to reduce unnecessary frequent piston frequency detection when the water flow rate change rate is not obvious. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a method flow chart of steps S100 to S202 in this application.

[0026] Figure 2 It is a method flow chart of steps S2021 to S2026 in this application.

[0027] Figure 3 It is a method flow chart of steps S300 to S302 in this application.

[0028] Figure 4 It is a method flow chart of steps S3011 to S30122 in this application.

[0029] Figure 5 It is a system diagram of the cyclic self-calibration flow online detection system in this application. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of this application more clear, the following Figure 1-Figure 5 It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0031] The embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0032] The embodiment of the present application discloses a cyclic self-calibration flow online detection method, which connects multiple standard meters in parallel to form a flow detection system with a higher flow detection range, and simultaneously performs self-cyclic calibration iterations on the flow detection system to further improve the range of the flow detection system.

[0033] Reference Figure 1 The method flow of the cyclic self-calibration flow online detection method includes the following steps: Step S100: connecting preset standard meters in parallel to form a flow detection system, and collecting the piston range in the flow detection system and the flow measurement range of the standard meter; The standard meter is a standard flow meter. The flow range of a single standard meter is a fixed value. When multiple standard meters are connected in parallel, the flow detection system formed in parallel can have a larger flow measurement range, which helps to adapt to a large range of flow devices for flow detection. The flow measurement range of the standard meter represents the total measurement value of the flow detection system, and the piston range represents the range corresponding to the piston configured in the flow detection system. In this embodiment, a high-precision piston is configured in the detection device, and the piston precision standard is transferred to the standard meter. The piston is used as the primary standard in the flow detection system and the starting flow generator.

[0034] In this embodiment, the nominal volume of the piston is 40L, and the measurement range is 0.012 to 4.0 cubic meters per hour. Different standard meters have different measurement ranges, and the specific measurement range of the standard meter is set according to the actual situation, and multiple standard meters connected in parallel are all standard meters of the same type.

[0035] Step S200: Compare and analyze whether the flow measurement range of the standard meter is within the piston range; Step S201: If yes, instruct the piston to calibrate the flow rate of the standard meter; When the measuring range of the standard meter is within the piston range, the piston is not likely to produce errors or affect the measurement accuracy when measuring the flow rate. In this case, the indicating piston can be used to calibrate the flow rate of the standard meter.

[0036] Step S202: If not, perform iterative calibration using a preset flow cycle self-calibration strategy to increase the measurement range of the flow detection system.

[0037] If the measurement range of the standard meter is not within the piston range, it means that the flow measurement range has exceeded the piston range. At this time, the measurement accuracy of the standard meter is prone to deviation. The standard meter is iterated through a pre-set flow self-circulation calibration strategy so that the measurement accuracy is repeatedly transmitted within the flow measurement system. The specific flow cycle self-calibration strategy is further explained in subsequent steps.

[0038] Reference Figure 2 , the flow cycle self-calibration strategy includes: Step S2021: instructing the piston to transfer flow to each standard meter in the flow detection system respectively, so that the flow range of each standard meter is consistent with the transfer limit of the piston; When the piston, as the primary standard, transmits the flow to each subsequent standard meter, the flow value detected by each standard meter for the output flow is the same, thereby making the flow range of each standard meter consistent.

[0039] Step S2022: closing the piston and adjusting the regulating valve of the standard meter until the flow range of the standard meter reaches a preset upper limit value; After the piston transfers the flow to the standard meter, the measurement range of each standard meter in the flow detection system is further improved by closing the piston and adjusting the flow range of the standard meter to the upper limit value, so that the overall measuring range of the standard meter is larger than the measuring range of the piston, thereby reducing the risk of large measurement errors.

[0040] Step S2023: Whether the preset flow meter in the flow detection system meets the preset switching condition, the flow meter is cyclically switched as the meter to be tested and the standard meter, and the switching condition is whether the flow meter has completed the flow point range calibration of the next standard meter.

[0041] In the self-circulation process, by switching the multiple standard meters in the flow measurement system between the meter to be tested and the standard meter, each standard meter can both perform measurements and be the object to be measured. Therefore, in the repetitive process, the repeatability of the standard meter is selected, that is, the repeatability of the standard meter used in parallel is small, the deviation value is not large or the deviation performance is close within the same horizontal range, which can improve the calculation accuracy of uncertainty.

[0042] When the flow meter is switched between the meter to be tested and the standard meter, it also includes: Step S2024: Calculate the error of the meter under test to determine the relative error of the meter under test. The error calculation adopts the following formula: (1) (2) in, Indicates the relative error of the meter under test. Indicates the cumulative flow volume of the meter under test. Indicates the cumulative test time of the meter under test. Indicates the piston flow value, Indicates the effective diameter of the piston, represents the material expansion coefficient of the piston, Indicates the water temperature in the piston cylinder.

[0043] Step S2025: Calculate the synthetic standard uncertainty of the standard table after the value transfer, using the following formula: (3) in, represents the uncertainty of the standard table, Indicates the uncertainty of the standard meter at this flow point, Indicates the repeatability of the test table.

[0044] When calculating uncertainty, also include: Step S2026: collecting the number of times the value is transferred and synthesized, and calculating and correcting the uncertainty; The revised calculation formula is as follows: (4) in, Indicates the number of times the value is passed.

[0045] The error calculation for the meter under test includes: The outer wall temperature value and the ambient temperature value of the piston are detected at a preset minimum detection frequency. When the ambient temperature value is within a preset normal temperature range, a preset temperature transfer calculation strategy and the outer wall temperature value are used for calculation to determine the water flow temperature value of the piston inner cylinder. The temperature transfer calculation strategy is calculated using the following formula: (5) in, q is the heat flux density between the water flow in the piston cylinder and the inner wall of the piston cylinder, h 1 is the convection heat transfer coefficient, which is calculated based on the Nusselt number corresponding to the forced convection heat transfer in the tube. T inis the inner wall temperature of the piston cylinder. Based on the analysis of heat conduction between the inner and outer walls of the piston cylinder, we can get: (6) in, k represents the thermal conductivity of the piston cylinder, δ Indicates the wall thickness of the piston cylinder, T out is the temperature of the outer wall of the piston cylinder, which can be collected by a temperature sensor. Based on the natural convection heat transfer analysis between the outer wall of the piston cylinder and the ambient air, we can get: (7) in, h 2 is the natural convection heat transfer coefficient between the outer wall of the piston cylinder and the ambient air, which is calculated based on the Nusselt number corresponding to natural convection. T amb is the ambient temperature. Based on formula (7), the value of the heat flux density q can be calculated. Combining formulas (5) to (7), we can get: (8) Based on formula (8), the temperature of the water flow in the piston cylinder can be calculated more accurately based on the temperature of the outer wall of the piston cylinder.

[0046] Reference Figure 3 , when collecting the outer wall temperature value, including: Step S300: collecting the piston movement frequency of the piston and matching the interference weight ratio corresponding to the piston movement frequency in the preset temperature interference database; When the piston is in motion and continuously reciprocates in the cylinder to provide pressure, a certain temperature will be generated and interfere with the water flow temperature in the cylinder. Different piston movement frequencies will produce corresponding interference ratios, which are defined as interference weight ratios. In order to make the calculation accuracy of water flow temperature values ​​higher, a temperature interference database is established, and different interference weight ratios and corresponding piston movement frequencies are stored in the database. When the piston movement frequency is input, the corresponding interference weight ratio is automatically searched and output.

[0047] Step S301: Calculating based on the interference weight ratio and the water flow temperature value to determine the water flow temperature correction value; By multiplying the interference weight ratio and the water flow temperature value, the affected temperature difference can be obtained, and then the corrected water flow temperature can be obtained by subtracting the temperature difference from the water flow temperature, which is defined as the water flow temperature correction value.

[0048] Step S302: replacing and updating the water flow temperature value based on the water flow temperature correction value.

[0049] By replacing the water flow temperature difference and the water flow temperature value, the calculation accuracy when calculating the relative error is higher.

[0050] Reference Figure 4 , when collecting the piston movement frequency, it includes: Step S3011: performing motion frequency collection and analysis based on the piston motion to determine the piston motion frequency, and issuing a signal to pause the motion frequency collection, while detecting the pipeline flow output by the piston; When the reciprocating frequency of the piston changes, the pipeline flow rate will change accordingly, indicating that the water temperature in the piston cylinder will change to a certain extent. Therefore, by monitoring the pipeline flow rate, it is possible to know whether the piston movement frequency has changed. Among them, the collection of the piston movement frequency is suspended after the initial collection of the piston movement frequency to reduce the frequent collection frequency.

[0051] Step S3012: performing calculation based on the pipeline flow to determine the flow change rate, and comparing and analyzing whether the flow change rate is greater than a preset reference water flow change rate; The reference water flow rate indicates that the pipeline flow fluctuation is small. The difference between the two pipeline flows detected in the set cycle unit time is calculated and divided by time, and the resulting value is defined as the flow rate change rate. By comparing the flow rate change rate with the reference water flow rate change rate, it can be determined whether the water flow output from the piston has changed significantly in unit time.

[0052] Step S30121: If it is less than or equal to, suspend collecting the piston change rate; If the flow rate change rate is less than or equal to the reference water flow change rate, it means that the movement frequency of the piston has not changed significantly at this time. In order to reduce frequent detection activities, the collection of the piston change rate is suspended.

[0053] Step S30122: If it is greater than, re-collect and update the piston movement frequency.

[0054] If the flow rate change rate is greater than the reference water flow change rate, it means that the reciprocating frequency of the piston has changed significantly at this time. In this case, the piston movement frequency is collected again, thereby improving the accuracy of calculating the temperature in the piston cylinder, which helps to further improve the calculation reliability of the relative error.

[0055] Based on the same inventive concept, an embodiment of the present invention provides a cyclic self-calibration flow online detection system, comprising: The acquisition module connects the preset standard meter in parallel to form a flow detection system, and collects the piston range in the flow detection system and the flow measurement range of the standard meter; Flow analysis module, used to compare and analyze whether the flow measurement range of the standard meter is within the piston range; If so, the piston is instructed to perform flow calibration against the standard meter; If not, the cyclic calibration module is instructed to perform iterative calibration using a preset flow cycle self-calibration strategy to improve the measurement range of the flow detection system.

[0056] Reference Figure 5 The flow detection system formed in parallel includes a water tank, a circulating water pump, a pressure-stabilizing tank, a high-precision piston, a controller, a test station, a pneumatic switch valve, a standard meter and a pneumatic control valve. The water pump provides water flow as a flow source. The circulating water pump is connected between the pressure-stabilizing tank and the water tank. The controller controls the high-precision piston to form a pressure difference by controlling the start of the servo motor, thereby transmitting the water flow in the water tank in turn through the circulating water pump, the pressure-stabilizing tank, the test station, the pneumatic switch valve, the standard meter and the pneumatic control valve, and finally flows back to the water tank to form a closed-loop flow detection device.

[0057] Those skilled in the art can clearly understand that for the convenience and simplicity of description, only the division of the above-mentioned functional modules is used as an example. In actual applications, the above-mentioned functions can be assigned to different functional modules as needed, that is, the internal structure of the device is divided into different functional modules to complete all or part of the functions described above. The specific working process of the system, device and unit described above can refer to the corresponding process in the aforementioned method embodiment, and will not be repeated here.

[0058] An embodiment of the present invention provides a computer-readable storage medium storing a computer program that can be loaded by a processor and execute a cyclic self-calibration flow online detection method.

[0059] Computer storage media include, for example, various media that can store program codes, such as USB flash drives, mobile hard disks, read-only memories (ROM), random access memories (RAM), magnetic disks or optical disks.

[0060] Based on the same inventive concept, an embodiment of the present invention provides an intelligent terminal, including a memory and a processor, wherein the memory stores a computer program that can be loaded by the processor and execute a cyclic self-calibration flow online detection method.

[0061] Those skilled in the art can clearly understand that for the convenience and simplicity of description, only the division of the above-mentioned functional modules is used as an example. In actual applications, the above-mentioned functions can be assigned to different functional modules as needed, that is, the internal structure of the device is divided into different functional modules to complete all or part of the functions described above. The specific working process of the system, device and unit described above can refer to the corresponding process in the aforementioned method embodiment, and will not be repeated here.

[0062] The above are all preferred embodiments of the present application, and are not intended to limit the protection scope of the present application. Any feature disclosed in this specification (including the abstract and drawings), unless otherwise stated, can be replaced by other equivalent or alternative features with similar purposes. That is, unless otherwise stated, each feature is only an example of a series of equivalent or similar features.

Claims

1. A cyclic self-calibration flow online detection method, characterized in that: include: The preset standard meter is connected in parallel to form a flow detection system, and the piston range in the flow detection system and the flow measurement range of the standard meter are collected; Compare and analyze whether the flow measurement range of the standard meter is within the piston range; If so, the piston is instructed to perform flow calibration on the standard meter to be checked; If not, an iterative calibration is performed using a preset flow cycle self-calibration strategy to improve the measurement range of the flow detection system.

2. The cyclic self-calibration flow online detection method according to claim 1 is characterized in that: The flow cycle self-calibration strategy includes: When the indicating piston transfers flow to each standard meter in the flow detection system, the flow range of each standard meter is consistent with the transfer limit of the piston; Close the piston and adjust the regulating valve of the standard meter until the flow range of the standard meter reaches the preset upper limit value; The flow meter preset in the flow detection system satisfies the preset switching condition, and the flow meter is cyclically switched as the meter to be tested and the standard meter. The switching condition is whether the flow meter completes the flow point range calibration of the next standard meter.

3. The cyclic self-calibration flow online detection method according to claim 2 is characterized in that: When the flow meter is used as the meter to be tested and the standard meter to be switched cyclically, it also includes: The error calculation of the meter under test is performed to determine the relative error of the meter under test. The error calculation adopts the following formula: （1） （2） in, Indicates the relative error of the meter under test. Indicates the cumulative flow volume of the meter under test. Indicates the cumulative test time of the table under test. Indicates the piston flow value, Indicates the effective diameter of the piston, represents the material expansion coefficient of the piston, Indicates the water temperature in the piston cylinder.

4. The cyclic self-calibration flow online detection method according to claim 3 is characterized in that: Also includes: The combined standard uncertainty of the standard table after the value transfer is calculated using the following formula: （3） in, represents the uncertainty of the standard table, Indicates the uncertainty of the standard meter at this flow point, Indicates the repeatability of the test table.

5. The cyclic self-calibration flow online detection method according to claim 4 is characterized in that: When calculating uncertainty, also include: Collect the number of times the value is transferred and synthesized, and calculate and correct the uncertainty; The revised calculation formula is as follows: （4） in, Indicates the number of times the value is passed.

6. The cyclic self-calibration flow online detection method according to claim 3 is characterized in that: The error calculation for the meter under test includes: The outer wall temperature value and the ambient temperature value of the piston are detected at a preset minimum detection frequency. When the ambient temperature value is within a preset normal temperature range, a preset temperature transfer calculation strategy and the outer wall temperature value are used for calculation to determine the water flow temperature value of the piston inner cylinder. The temperature transfer calculation strategy is calculated using the following formula: （5） in, q is the heat flux density between the water flow in the piston cylinder and the inner wall of the piston cylinder, h 1 is the convection heat transfer coefficient, which is calculated based on the Nusselt number corresponding to the forced convection heat transfer in the tube. T in is the inner wall temperature of the piston cylinder. Based on the analysis of heat conduction between the inner and outer walls of the piston cylinder, we can get: （6） in, k represents the thermal conductivity of the piston cylinder, δ Indicates the wall thickness of the piston cylinder, T out is the temperature of the outer wall of the piston cylinder, which can be collected by a temperature sensor. Based on the natural convection heat transfer analysis between the outer wall of the piston cylinder and the ambient air, we can get: （7） in, h 2 is the natural convection heat transfer coefficient between the outer wall of the piston cylinder and the ambient air, which is calculated based on the Nusselt number corresponding to natural convection. T amb is the ambient temperature. Based on formula (7), the value of the heat flux density q can be calculated. Combining formulas (5) to (7), we can get: （8） Based on formula (8), the temperature of the water flow in the piston cylinder can be calculated more accurately based on the temperature of the outer wall of the piston cylinder.

7. The cyclic self-calibration flow online detection method according to claim 6 is characterized in that: When collecting the outer wall temperature value, include: Collect the piston movement frequency of the piston and match it with the interference weight ratio corresponding to the piston movement frequency in the preset temperature interference database; Calculating based on the interference weight ratio and the water flow temperature value to determine the water flow temperature correction value; The water flow temperature value is replaced and updated based on the water flow temperature correction value.

8. The method for online detection of cyclic self-calibration flow according to claim 7, characterized in that: When collecting piston movement frequency, include: Based on the movement frequency collection and analysis during the piston movement, the piston movement frequency is determined, and a pause in the movement frequency collection is issued, and the pipeline flow output by the piston is detected at the same time; Calculate the flow rate change rate based on the pipeline flow rate, and compare and analyze whether the flow rate change rate is greater than a preset reference water flow change rate; If it is less than or equal to, the acquisition of piston change rate is suspended; If it is greater, the piston movement frequency is collected again and updated.

9. A cyclic self-calibration flow online detection system, characterized in that: include: The acquisition module connects the preset standard meter in parallel to form a flow detection system, and collects the piston range in the flow detection system and the flow measurement range of the standard meter; Flow analysis module, used to compare and analyze whether the flow measurement range of the standard meter is within the piston range; If so, the piston is instructed to perform flow calibration against the standard meter; If not, the cyclic calibration module is instructed to perform iterative calibration using a preset flow cycle self-calibration strategy to improve the measurement range of the flow detection system.

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