Research on Remote Monitoring System Based on Web

0 Introduction
In recent years, with the development of computer technology, control technology, communication technology and network technology, remote monitoring systems have achieved rapid development and are widely used in various aspects of industry and commerce, such as production, detection, monitoring, etc. Web-based remote monitoring systems refer to the use of TCP/IP technology through the Internet, allowing management or dispatchers to see real-time information on the production site, and to achieve remote scheduling, command decision-making, and remote online configuration and fault diagnosis of production equipment. Applying Web technology to remote monitoring systems not only simplifies operations, extends the scope of management, but also reduces software upgrade and maintenance costs. This article mainly discusses the application of a Web-based remote monitoring solution in aquaculture.

l Overall structure of the system
The Web-based remote monitoring system can be divided into three subsystems: field monitoring (intelligent terminal), monitoring center (including communication module, database server, Web server) and client. On the one hand, the intelligent terminal is responsible for collecting the operating status data of various equipment on the field and transmitting it to the monitoring center; on the other hand, it receives the control command of the monitoring center and takes corresponding actions. The communication module of the monitoring center completes the data transmission task with the field controller, the Web server completes the interaction with the client and the field subsystem, and the database is used to store the real-time data obtained on the field. The client subsystem is implemented by the browser and is the part that the user interacts with directly. It accepts the user's input, obtains monitoring data from the monitoring center or sends control commands through the monitoring center.
The remote monitoring system in aquaculture mainly monitors water temperature, pH value, dissolved oxygen and water level. The field monitoring computer is connected to the field monitoring instrument through RS 485, and the remote monitoring computer and the field monitoring computer are connected through the Internet (or GPRS, wireless, dial-up Internet access), so that the remote monitoring computer can monitor the real-time situation on the field at any time. The hardware structure of the whole system is shown in Figure 1.

The remote monitoring computer monitors the changes in the field parameters of the controlled object and queries some historical data; the field monitoring computer sends the detected real-time data and automatically monitors the field monitoring instrument to the remote according to the requirements of the remote monitoring computer user; the core of the field monitoring instrument is the programmable logic controller (PLC), which realizes the measurement of the monitored parameters. The actual data of the controlled object is detected by the sensors corresponding to the controlled parameters, amplified by the conditioning circuit, uploaded to the PLC after isolation circuit and A/D conversion, and the control quantity of the system is calculated by the PID controller in the PLC, and the control quantity is then sent to the actuator by the D/A conversion module of the PLC or the I/O port of the PLC.

2 System software structure modules
The remote monitoring system software includes: on-site monitoring system software, remote service software, Web pages and Web applications.
2.1 On-site monitoring system software The
on-site monitoring system runs in the on-site monitoring computer. Its functions are mainly divided into five parts: human-machine interface, real-time monitoring, data management, communication module and system maintenance: the human-machine interface displays the operating results of other modules of the system to the user, enabling the operator to accurately, quickly and conveniently understand the various environmental parameters of the on-site monitoring system and the operating status of the equipment, and to issue control instructions in a timely manner; the real-time monitoring module is responsible for the communication management between the on-site monitoring computer and various sensors and controllers. Its function is to display the real-time monitoring parameters in a dynamic and static manner, convert the voltage value of the detection parameter into actual dissolved oxygen, temperature, pH value and water level according to its corresponding algorithm, and read the actual value of the corresponding parameter from the lower computer at regular intervals, and judge the activity status and living environment of the organisms in the fish pond based on the collection of the breeding site image; the network communication is mainly responsible for communicating with the server through the Internet connection. The basic principle of this part is to establish a TCP/IP connection between the on-site monitoring equipment and the server.
2.2 Remote service software
The remote service software mainly includes remote user interface, network communication module, database access module and system management module. The network communication module exchanges data with the network communication module of the on-site intelligent monitoring device layer. The human-machine interface provides a friendly human-machine interaction environment for system configuration and administrators. The database access module will call the database storage procedure to save the data sent by the on-site intelligent monitoring device layer, and provide data query function for the on-site intelligent monitoring device layer, so as to notify the on-site intelligent monitoring device layer of the user's changes to the on-site device status. The management and maintenance module is mainly responsible for system configuration and parameter setting.
2.3 Web pages and Web applications
When users access the corresponding site through a Web browser, the Web application runs on the server side and responds to the user's operation. This part includes user management (user registration, identity authentication, permission management, etc.), state configuration (by configuring the parameters of the on-site equipment, controlling the operation of the equipment's operating data, querying information according to various conditions, downloading in multiple formats), and data representation (including data format, graphs, tables, curves, etc.).
2.4 Web database access
The various parameters collected by the on-site monitoring computer are stored in the form of a database on the Web server or database server. Through the writing of the corresponding script language, this information is placed on the Web page and provided to the logged-in user for real-time monitoring. This system uses ASP.NET to implement the writing of Web dynamic pages, and uses ADO in it to access the database. The corresponding script program is analyzed as follows:
(1) Configure the database connection string in the Web.Config file

(3) Display the data in the query result set by binding it to the GridView control

3 Conclusion
The Web-based remote monitoring system makes full use of modern network communication technology, database technology, and network security technology to achieve remote access and control of industry. With the continuous development of network and computer technology, the theory and practice of automatic control technology have been continuously enriched and updated. The application of network technology in industrial control sites has become more and more extensive and the scale has become larger and larger, which has greatly improved the reliability and production efficiency of industrial control. However, in order to fully realize the reliability of remote monitoring, further research is needed on the structure of the remote monitoring system, Web database access technology, and network communication technology.