Abstract: Several oil depot explosions in China have highlighted the importance and urgency of real-time monitoring and timely information feedback for oil depots. Based on the current situation in China and an analysis of some physical parameters affecting oil depot safety, this paper proposes a solution for oil depot monitoring using fiber optic sensors and PROFIBUS and the Internet as transmission media. This solution enables real-time, remote, and automatic monitoring of the oil depot's status and timely feedback of crucial safety parameters via the Internet. Keywords: optical fiber sensor, PROFIBUS network, remote monitoring, data acquisition Research On Remote Monitoring System Used In Oil Warehouse Abstract: Several oil warehouses have been detonated in our country, making people pay more attention to the safety status of oil warehouses. This article provides a method to monitor oil warehouses from a distance through a PROFIBUS network and the Internet. It is based on the use of optical fiber sensors and the analysis of data that has an effect on oil warehouse safety. This method can realize real-time monitoring, automation, and real-time feedback of state parameters. Keywords: optical fiber sensor, PROFIBUS network, remote monitoring, data acquisition 1 Introduction Oil warehouses are commonly found in petroleum, chemical, and mining enterprises. These oil warehouses are important fuel bases for these enterprises and a crucial production link. The construction scale of various oil warehouses is increasing, and the cost is also rising. To ensure the safety of oil warehouses, it is necessary to collect real-time data on the physical parameters that affect oil warehouse safety and realize automated management of oil warehouses. Timely monitoring of oil depot tank status parameters such as liquid level, temperature, pressure, and oil/gas concentration can significantly improve the efficiency of oil depot intake, storage, and management, greatly enhancing safety and thus having wide application value. Real-time monitoring of these parameters allows for real-time display and alarm setting on intelligent instruments, triggering audible and visual alarms when limits are exceeded. Furthermore, these status values ​​can be transmitted via the internet, allowing authorized managers to view the depot's safety parameters from anywhere via a browser, enabling unattended remote monitoring. 2. Acquisition of Oil Depot Status Parameters Oil depot tank areas are generally the most dangerous parts of a storage facility, requiring extremely high safety standards. Oil is flammable and explosive, necessitating stringent explosion-proof requirements. Electrical instruments are insufficient for safe detection of liquid level and temperature. Fiber optic sensors, however, measure various physical quantities by observing changes in the physical characteristics of light propagating through optical fibers under different physical states, such as interference, diffraction, polarization, and reflection. They offer a very high safety factor in flammable and explosive areas. Therefore, fiber optic sensors are used to measure physical parameters such as liquid level, temperature, and pressure. 2.1 Liquid Level Status Parameters Oil storage equipment in oil depots typically uses tanks with extremely high safety parameters. Monitoring the liquid level is a crucial parameter for oil depot production and safety management. Based on comprehensive consideration, the GY-IB fiber optic level gauge is selected, as it offers an extremely high safety factor in flammable and explosive environments. [align=center] Figure 1: Schematic diagram of the level gauge communication interface[/align] 2.2 Temperature Status Parameters Temperature signals are obtained from GCM-type fiber optic temperature sensors. These signals are converted into 4-20mA analog signals via safety barriers or explosion-proof transmitters and sent to the AI ​​interface of the PLC's ET200S module. [align=center] Figure 2: Temperature transmitter to PLC principle[/align] 2.3 Oil and Gas Concentration Status Parameters The tank area of ​​an oil depot is a key area for fire and explosion prevention. Combustible gas alarm devices are used to detect the concentration of combustible gases in the tank area, triggering an alarm before reaching a dangerous level. This is a powerful means of fire prevention, explosion prevention, and prevention of oil and gas leaks. Based on the specific circumstances, the ES2OOOT-C series combustible gas alarm device is selected. The combustible gas alarm signal is a standard 4-20mA DC signal, which can be connected to the PLC through a safety barrier. [align=center] Figure 3 Combustible Gas Alarm Signal Measurement Principle Diagram[/align] 3 Overall Architecture of Remote Monitoring System 3.1 System Structure Since oil tanks in oil depots are widely distributed, even in different areas, to obtain the oil storage and safety status parameters of the entire oil depot, it is necessary to install corresponding sensors for each oil tank and oil and gas concentration fire alarm devices for the oil tank area, forming a complete sensor network. The data acquisition system responsible for collecting this sensor information must be a distributed system, and this data acquisition system must have long-distance data acquisition and transmission capabilities. Finally, the use of a certain communication method is also very important for the entire system. Based on the above considerations, the system structure diagram is as follows: [align=center] Figure 4 Oil Depot Remote Monitoring Structure Diagram[/align] The core control system consists of a Siemens S7-400 PLC and a depot monitoring PC (Profibus-DP Class 1 master device). Its DP port exchanges real-time data with the bus module ET200S via a DP cable. The ET200S collects the main monitoring parameters of the system through field detection elements and sensor systems, and transmits the collected data to the central controller through a Profibus-DP fieldbus network with a maximum speed of 12 Mbit/s. The controller processes the data according to specific process requirements and then transmits the control data to the ET200S through the Profibus-DP network, realizing the control flow of each field monitoring element. The depot monitoring PC is responsible for monitoring the Profibus-DP slave devices and obtaining various monitoring data. This data is written to the database for the WEB server to request data, while remote clients request data from the WEB server through the Internet, thereby realizing remote monitoring of the oil depot. 3.2 System Hardware Composition The system hardware consists of two parts: a data acquisition part composed of sensors and PLCs, and a data transmission and processing part composed of servers and clients. Sensors are one of the key components of the entire system. Since the oil depot is a flammable and explosive site, our selection must meet certain safety standards. We chose fiber optic liquid level sensors, GCM-type fiber optic temperature sensors, and ES2000T-C point-type combustible gas detectors suitable for flammable and explosive environments to acquire the oil depot's status parameters. A distributed data acquisition system using a Profibus-DP network is constructed at the field level PLC level, using the Profibus communication protocol to achieve data transmission between PLCs. Profibus-DP is a device bus, mainly used for complex field devices and distributed I/O. Its physical structure is RS-485, with a transmission rate of 9.6kb/s to 12Mb/s. The maximum transmission distance can be extended to 10KM with repeaters, and up to 127 stations can be connected. At the management level, PLCs and PCs form an Ethernet network, responsible for field-level monitoring and display of acquired data. 3.3 Software Composition The software can be divided into two parts: data acquisition and data transmission. The data acquisition part is responsible for acquiring real-time data transmitted from sensors and monitoring elements to the PLC. The data acquisition software was developed using KingSCADA industrial control configuration software. It includes a main control monitoring screen, real-time trend curves, historical trend curves, alarm records, and timely writes the monitored tank level, temperature, and oil and gas concentration, among other status parameters, into the database. The data transmission software adopts a B/S (Browser/Server) architecture, a modification or improvement of the C/S (Client/Server) architecture that emerged with the rise of Internet technology. In this architecture, the user interface is implemented through a web browser (such as Internet Explorer, Netscape, etc.), with minimal transaction logic implemented on the browser side and the main transaction logic implemented on the server side, forming a so-called three-tier architecture. This greatly simplifies the system configuration load on the client side, reduces the cost and workload of system maintenance and upgrades, and lowers the overall cost for the user. The data flow is as follows: [align=center] Figure 5 Data Flow Diagram[/align] This software is an ASP.NET application developed using Visual C# in the Microsoft Developer Studio development environment. ASP.NET is a technology that embeds scripting languages ​​on the server side to achieve dynamic data interaction. Server-side scripts can be used to establish database connections and retrieve data from the database based on specific conditions, then store the results in ordinary HTML code. These server-side scripts are independent of any browser or user platform. 4. Conclusion The remote monitoring system for the oil depot is a distributed system integrating monitoring, control, and management. The system described in this paper is based on fiber optic sensors, uses Profibus and Ethernet to form the system's communication network, and employs a PLC as the system's underlying control station to complete real-time data acquisition and process control of the production process. Through the combination of Web database technology and ASP technology, the safety status parameters and alarm parameters of the oil depot can be viewed via the Internet, realizing remote monitoring of the oil depot. References: [1] Zhang Zhipeng, W.A. Gambling. Principles of Fiber Optic Sensors [M]. Beijing: China Metrology Press, 1991. 175-184 [2] Liao Yanbiao. Recent Development of Fiber Optic Sensors. Vol.13, No.3, June 2000. 27-29 [3] Liang Changyin, Sun Guang. Multi-channel Oil Level Measurement System Based on Fiber Optic Sensors [J]. Microcomputer Information, 2005, 21(3): 26-29 [4] Introduction to PROFIBUS Networks. SIEMENS AG, 1997 [5] ET ZOOM Distributed I/O Device Manual. SIEMENS AG, 1997 [6] Zheng Yujun, et al. VISUAL C# Case Tutorial. Beijing Hope Electronic Press, 2002. [7] Qiming Studio (ed.). MIS System Development and Application. People's Posts and Telecommunications Press, 2005