1 Overview
As an important parameter of modern industrial control, flow is increasingly showing its importance. The metal tube float flowmeter is used to continuously measure the volumetric flow of liquid and gas in the closed pipeline. The structure is firm and reliable, and can adapt to the flow measurement in various occasions. Therefore it is widely used in flow measurement and industrial process control. Only by selecting the right model can the production system achieve the best performance.
VisualBasic is one of the powerful development software developed by Microsoft Corporation. It has been praised by a large number of programmers for its friendly interface, easy entry and short development cycle. In addition, the Visual Basic system has strong database management capabilities. Using data controls and database management windows, you can directly create or process dynamic databases and provide powerful data storage and retrieval capabilities.
This paper takes VB as a development platform, aiming at the shortcomings of the selection system interface in the DOS environment that is not flexible, fast, and user-friendly. The design scheme of the selection system with friendly interface and good combination with the network is given.
2 System Structure and Function Introduction
The system has established a friendly Windows-based instrument selection system man-machine interface, and adopted the VB6.0 DHTML (Dy-namicHTML) design tool in the design, which makes the software and the network have a good combination. After the user logs in to the system, the model of the metal tube float meter that meets the requirements can be obtained by selecting and inputting the parameters. The system will give the best choice based on the user's parameters. The user can then choose whether to print the instrument selection result form and enter a comment for easy review. The system is mainly divided into the following four modules: login module, parameter selection and data processing, display results and give advice, print modules. The system has administrator rights settings. For each company's individual needs, you can choose whether to set encryption or lock. After entering the system, users enter relevant parameters according to their own needs, and then the system performs data processing in the background. If the value entered by the user is not within the specification range of the manufacturer, a prompt message will be given; if it is within the specification range of the manufacturer, all models conforming to the user's requirements will be given. If the user has other special requirements, it can be written in a note and submitted to the manufacturer. Program flow chart shown in Figure 1.
Figure 1 program flow diagram system back-end database using SQLServer format database. The open data connection (OpenDataBaseConnectivity) provided by Visual Basic, ie, ODBC function, can be directly accessed and used to establish and connect a back-end large-scale network database. In the program flowchart program of Figure 1, a structured query language-SQL data standard is used to directly access the database on the Server. The system provides simple object-oriented database operations instructions, multi-user database access locking mechanism, network database SQL retrieval and query functions; and provides a SQL network interface for the database running on a stand-alone machine to facilitate rapid in a distributed environment And effectively achieve the customer server's link and establishment.
3 Data processing
Manufacturers can only use water and air to represent general liquids and gases at the time of flow design and calibration, and the "selection sample" provides selected flow rates in terms of water and air. Float meter for different media and different conditions (such as gas pressure and temperature, etc.). According to the measurement principle, although the float stays at the same height during measurement, the flow value it represents is different. To accurately select the flowmeter specifications and use the instrument well on site, it is necessary to know the relationship between them and the flow rate. Conversion (even flow measurement also requires flow conversion at tabulation and calibration). Therefore, the conversion of traffic in the background data processing is the key link.
The basis for the conversion is twofold: the theoretical calculation formula of the float flowmeter and the state equation of the ideal gas.
In the formula:
Q is the volume flow;
α is the flow coefficient;
Fn is the annular gap area between the maximum diameter of the float and the cross section of the same height cone;
g is the acceleration of gravity;
Vy is the volume of the float;
Ρf is the density of the float;
Ï is the density of the measured fluid;
A is the maximum cross-sectional area of ​​the float.
The units in the formula are cm, g, and s.
The state equation of the ideal gas:
In the formula:
P0, P1 are absolute pressures in two states;
T0, T1 are absolute temperatures (K) in two states;
V0, V1 are the volumes in two states.
The influence of the compression factor is neglected here, ie the situation where the pressure is not high and the accuracy is not high. Otherwise, the denominators on both sides of the equation are multiplied by the compression factors Z0, Z1, respectively.
(1) The following two relationships can be derived from the equation of state of the ideal gas:
1) Traffic relationship
2) Density relationship
In the formula:
M is the quality of the medium;
Ï is the density of the medium;
Q is the flow of media.
After conversion, the corresponding modules of the program will be screened and model-matched in the dynamic database in the background according to the obtained conversion data, and the model of the best float flow meter that meets the requirements of the user or is close to the user's requirements is given. If there is no model that meets the user's requirements, the corresponding prompt will be given.
4 Conclusion
With the increasing complexity and automation of the production process, new, higher and more requirements will be proposed for flow measurement and control, such as 5~7m extra large diameter and extra-large flow measurement; ultra-small flow measurement; molten steel and other high-temperature media The flow measurement; liquid nitrogen and other ultra-low temperature media flow measurement. This requires a more convenient, quick and accurate selection system to match the production and ordering of products. The design of this system is based on the link between the network and the dynamic database to facilitate the timely upgrade and improvement of the system. It provides favorable conditions for product model updates and timely product promotion. If some of these parameters and databases are changed, this system model can also be extended to other production areas.
references
1 Liu Jianwu. Using VB to develop wireless communication programs. China Instruments, 2001, (2).
2 Wang Jianmin. Object-oriented programming a VisualBasic6.0. Machinery Industry Press, 2001,12.
3 Shao Zhongwu et al. Data Acquisition System. Shandong Petroleum University Press, 1998: 42~48.
4 Wang Yi, Li Yang. ORM implementation of dynamic database. Computer age, 2007, (7).
5 Zhou Jun. Flow meters and their selection. China Instruments, 2001, (1).
As an important parameter of modern industrial control, flow is increasingly showing its importance. The metal tube float flowmeter is used to continuously measure the volumetric flow of liquid and gas in the closed pipeline. The structure is firm and reliable, and can adapt to the flow measurement in various occasions. Therefore it is widely used in flow measurement and industrial process control. Only by selecting the right model can the production system achieve the best performance.
VisualBasic is one of the powerful development software developed by Microsoft Corporation. It has been praised by a large number of programmers for its friendly interface, easy entry and short development cycle. In addition, the Visual Basic system has strong database management capabilities. Using data controls and database management windows, you can directly create or process dynamic databases and provide powerful data storage and retrieval capabilities.
This paper takes VB as a development platform, aiming at the shortcomings of the selection system interface in the DOS environment that is not flexible, fast, and user-friendly. The design scheme of the selection system with friendly interface and good combination with the network is given.
2 System Structure and Function Introduction
The system has established a friendly Windows-based instrument selection system man-machine interface, and adopted the VB6.0 DHTML (Dy-namicHTML) design tool in the design, which makes the software and the network have a good combination. After the user logs in to the system, the model of the metal tube float meter that meets the requirements can be obtained by selecting and inputting the parameters. The system will give the best choice based on the user's parameters. The user can then choose whether to print the instrument selection result form and enter a comment for easy review. The system is mainly divided into the following four modules: login module, parameter selection and data processing, display results and give advice, print modules. The system has administrator rights settings. For each company's individual needs, you can choose whether to set encryption or lock. After entering the system, users enter relevant parameters according to their own needs, and then the system performs data processing in the background. If the value entered by the user is not within the specification range of the manufacturer, a prompt message will be given; if it is within the specification range of the manufacturer, all models conforming to the user's requirements will be given. If the user has other special requirements, it can be written in a note and submitted to the manufacturer. Program flow chart shown in Figure 1.
Figure 1 program flow diagram system back-end database using SQLServer format database. The open data connection (OpenDataBaseConnectivity) provided by Visual Basic, ie, ODBC function, can be directly accessed and used to establish and connect a back-end large-scale network database. In the program flowchart program of Figure 1, a structured query language-SQL data standard is used to directly access the database on the Server. The system provides simple object-oriented database operations instructions, multi-user database access locking mechanism, network database SQL retrieval and query functions; and provides a SQL network interface for the database running on a stand-alone machine to facilitate rapid in a distributed environment And effectively achieve the customer server's link and establishment.
3 Data processing
Manufacturers can only use water and air to represent general liquids and gases at the time of flow design and calibration, and the "selection sample" provides selected flow rates in terms of water and air. Float meter for different media and different conditions (such as gas pressure and temperature, etc.). According to the measurement principle, although the float stays at the same height during measurement, the flow value it represents is different. To accurately select the flowmeter specifications and use the instrument well on site, it is necessary to know the relationship between them and the flow rate. Conversion (even flow measurement also requires flow conversion at tabulation and calibration). Therefore, the conversion of traffic in the background data processing is the key link.
The basis for the conversion is twofold: the theoretical calculation formula of the float flowmeter and the state equation of the ideal gas.
In the formula:
Q is the volume flow;
α is the flow coefficient;
Fn is the annular gap area between the maximum diameter of the float and the cross section of the same height cone;
g is the acceleration of gravity;
Vy is the volume of the float;
Ρf is the density of the float;
Ï is the density of the measured fluid;
A is the maximum cross-sectional area of ​​the float.
The units in the formula are cm, g, and s.
The state equation of the ideal gas:
In the formula:
P0, P1 are absolute pressures in two states;
T0, T1 are absolute temperatures (K) in two states;
V0, V1 are the volumes in two states.
The influence of the compression factor is neglected here, ie the situation where the pressure is not high and the accuracy is not high. Otherwise, the denominators on both sides of the equation are multiplied by the compression factors Z0, Z1, respectively.
(1) The following two relationships can be derived from the equation of state of the ideal gas:
1) Traffic relationship
2) Density relationship
In the formula:
M is the quality of the medium;
Ï is the density of the medium;
Q is the flow of media.
After conversion, the corresponding modules of the program will be screened and model-matched in the dynamic database in the background according to the obtained conversion data, and the model of the best float flow meter that meets the requirements of the user or is close to the user's requirements is given. If there is no model that meets the user's requirements, the corresponding prompt will be given.
4 Conclusion
With the increasing complexity and automation of the production process, new, higher and more requirements will be proposed for flow measurement and control, such as 5~7m extra large diameter and extra-large flow measurement; ultra-small flow measurement; molten steel and other high-temperature media The flow measurement; liquid nitrogen and other ultra-low temperature media flow measurement. This requires a more convenient, quick and accurate selection system to match the production and ordering of products. The design of this system is based on the link between the network and the dynamic database to facilitate the timely upgrade and improvement of the system. It provides favorable conditions for product model updates and timely product promotion. If some of these parameters and databases are changed, this system model can also be extended to other production areas.
references
1 Liu Jianwu. Using VB to develop wireless communication programs. China Instruments, 2001, (2).
2 Wang Jianmin. Object-oriented programming a VisualBasic6.0. Machinery Industry Press, 2001,12.
3 Shao Zhongwu et al. Data Acquisition System. Shandong Petroleum University Press, 1998: 42~48.
4 Wang Yi, Li Yang. ORM implementation of dynamic database. Computer age, 2007, (7).
5 Zhou Jun. Flow meters and their selection. China Instruments, 2001, (1).
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