Summary: This article mainly introduces the construction of a real-time data acquisition and WEB publishing system for a large-scale station under Shengli Oilfield Gathering and Transportation Company. It includes the overall system design, the technologies used, the problems encountered, and the solutions. The upper-level configuration software used is PCAUTO from Beijing Sanwei Force Control. The main technologies applied include OPC, DDE, NETDDE, distributed real-time database, and RS485 bus smart meter reading. Keywords: Data acquisition system, PCAUTO, OPC, DDE 1.1 Basic Introduction The Gudao compressor station under the Gathering and Transportation Company has an annual natural gas processing capacity of 200 million cubic meters and an annual light hydrocarbon production of over 13,000 tons, making it a relatively large compressor station. It has positions for 500,000 cubic meters of natural gas, SW64 compressors, secondary pressurization, centrifuges, gas distribution, coal-fired boilers, and power distribution. Specifically: the 500,000-unit station uses a Honeywell S9000 DCS control system with IFix6.0 as the upper-level configuration software and WIN98 as the operating system; the SW64 station uses a Cooper RR controller with INTouch as the upper-level configuration software and WINNT4.0 as the operating system; the secondary booster station uses an Omron controller with IFix6.0 as the upper-level configuration software and WIN98 as the operating system; the centrifuge station uses a Henghe CS1000 DCS control system with Henghe's own configuration software and WINNT4.0 as the operating system; the gas distribution station uses a SIXNET ST-GT-1210 controller with PCAUTO from Beijing Sanwei Likong as the upper-level configuration software and WIN2000 as the operating system; the coal boiler station control system uses a Mitsubishi PLC with MCGS from Beijing Kunlun Tongtai as the upper-level configuration software and WIN2000 as the operating system; and the power distribution station is equipped with a Xuji power distribution protection system and monitoring system. 1.2 Real-time Data Acquisition System Functional Design The PCAUTO software from Beijing Sanwei Likong Company is used as the configuration software for the data acquisition system. Real-time data from various control systems is collected via an intra-station LAN using fiber optic transmission and transmitted to the Likong server located in the compressor station dispatch room. This server is equipped with dual network cards and is connected to the Shengli Oilfield WAN. Real-time data is then published via the web on the oilfield network. Simultaneously, real-time data can be stored at fixed points in the source data system currently under construction in the oilfield, generating various reports. 1.3 Data Acquisition System Functional and Scheme Design PCAUTO from Beijing Sanwei Likong is selected as the system configuration software. It is responsible for acquiring readings from configuration software such as iFix, INTouch, MCGS, Henghe CS1000, Xuji, and Likong PCAUTO, as well as intelligent instruments supporting RS-485. The system functional network topology diagram is as follows: 1.4 System Application Technology Introduction 1.4.1 OPC Introduction OPC is an open standard for industrial control based on Microsoft's OLE/COM technology and using a client/server model. OPC establishes a unified software interface standard between industrial control equipment and application software. It primarily addresses the interaction between monitoring programs and their data sources. Using OPC technology, field devices and their drivers can be encapsulated to form an OPC server. The OPC server collects data from the devices and communicates with OPC client applications to exchange data, as shown in Figure 1. The OPC server shields the field-level device drivers; client application developers only see the unified interface provided by the OPC server and do not need to worry about the field device drivers. As long as the client application conforms to the OPC interface specification, it can exchange data with the OPC server. Similarly, hardware manufacturers only need to develop a driver for the hardware they produce and then write an OPC server according to the OPC standard. All client applications developed according to the OPC standard can then interact with the hardware device without writing additional device drivers. In this way, in industrial field monitoring and control systems, process or equipment monitoring programs (or monitoring configuration software) can easily interact with the OPC server of field devices via industrial Ethernet to obtain the required field data. On the one hand, the monitoring program can read data from the OPC server cache to obtain process or device operating parameters and implement effective monitoring. On the other hand, for device data with high real-time requirements, the monitoring program can directly read data from the device. If users need to expand the functionality of the monitoring software, they can directly configure the customized OPC package into the existing software without worrying about the underlying device drivers, making software deployment easier. 1.4.2 Introduction to DDE Dynamic Data Exchange (DDE) is an abbreviation for Dynamic Data Exchange. It was proposed by Microsoft and is currently mainly used on Win98 and WinNT4.0 operating systems, with compatibility only provided on newer operating systems. DDE is based on the Windows message mechanism. Two Windows applications "dialogue" by exchanging messages to complete data requests, responses, and transmissions. These two programs are called "Server" and "Client," respectively. The Server is the data provider, and the Client is the data requester and receiver. The DDE Server is a program that maintains data that other Windows programs may use, while the DDE Client is a program that obtains this data from the Server. Once a connection is established between the "Server" and the "Client," the "Client" will be immediately notified when the data in the "Server" changes. The data connection channel established via DDE is bidirectional, meaning the "Client" can not only read data from the "Server" but also modify it. DDE communication primarily occurs between two Windows applications. Most current Windows-based applications still support DDE, but its disadvantages are also obvious: low communication efficiency and slow data refresh when the amount of data is large. 1.4.3 Distributed Application of ForceControl Regional Real-Time Database. The real-time database is a core component of the configuration software. The real-time database operating system performs various operations on the database, including: real-time data processing, historical data storage, statistical data processing, alarm processing, and data service request processing. ForceControl's real-time database system is also a distributed database system. Since many situations require storing databases on different computers geographically distributed in different locations, a physically distributed but logically centralized database is achieved through a computer network, possessing distributed transparency. Databases created with ForceControl have data physically distributed across different geographical locations or different computers in the same location, but the user is unaware of the data distribution during operation. What users see is not a distributed database, but a centralized database with a global data schema. When building the ForceControl distributed database, the ForceControl system supports network communication methods including: TCP/IP network, serial communication (RS232/422/485), and telephone dial-up network. Performance features of ForceControl's database and management system: A truly distributed structure, supporting both C/S and B/S applications; the distributed database structure can be used to build enterprise applications of various sizes; the real-time database system has high reliability and data integrity; it provides powerful enterprise-level real-time information system client application tools; its flexible expansion structure can meet various user needs; high-speed data storage and retrieval functions; the real-time database is a separate process and can run separately from the HMI; it achieves millisecond-level data acquisition and time synchronization with the acquisition unit; it saves data with a high compression ratio, enabling massive storage of historical data; it supports standards such as OPC, DDE, ODBC, and ActiveX; it can read and write process data from DCS, PLC, and other SCADA systems. 1.4.4 Reading Data from Smart Instruments on the RS485 Bus Some workstations have numerous smart instruments installed, such as gas flow meters. These instruments integrate digital circuits, enabling them to perform some data processing functions and store data in their registers. They also support RS485 data transmission. Therefore, we categorize these smart instruments into one or more RS485 networks, connecting the ForceControl server to the network as the master. Other instruments on the bus act as slaves. The master sends commands to the slaves via the bus according to the communication protocol to read data from their registers. If there are more than two RS485 networks, multiple serial port cards are installed on the server. Then, the I/O drivers for the smart instruments are configured in ForceControl PCAUTO. If a driver for these instruments cannot be found, a custom driver can be written according to the RS485 communication protocol provided by the instrument manufacturer, mimicking the driver format provided by ForceControl. Afterward, simple configuration settings can be performed in ForceControl PCAUTO to read the smart instrument readings. 1.5 System Construction Process 1.5.1 Yokogawa CS1000 System Data Retrieval There are two access methods for data interaction between OPC clients and OPC servers: synchronous and asynchronous. The synchronous method is relatively simple to implement. The client sends a read/write request to the server and then waits for the server to return information. This method is suitable when the client data is small and the amount of data exchanged with the server is relatively small. However, when there is network congestion or a large number of clients accessing the system, it will cause a decrease in system performance efficiency. The asynchronous method is more complex to implement. After the client sends a read/write request to the server, the server immediately returns information indicating that the request has been accepted. The client can then perform other processing. When the server completes the read/write operation, it notifies the client program of the operation completion by calling a callback function and transmits the corresponding information. Therefore, the asynchronous method is more efficient, can avoid blocking of large data requests from multiple clients, and can maximize the saving of CPU and network resources. Yokogawa's OPC data interaction is asynchronous, requiring the registration of several related dynamic link library files with the operating system on the client computer to complete the data interaction between the OPC client and server. Then, define the I/O device in ForceControl PCAUTO, add an OPC Client, configure the IP address, and refresh to find the OPC Server in the CS1000 computer system corresponding to the IP address. The configuration process is shown in the following figure: After configuring the OPC Client, add the corresponding data points in the ForceControl database configuration, as shown in the following figure: This completes the configuration of the Yokogawa CS1000's OPC in ForceControl PCAUTO, and data in the Yokogawa CS1000 system can be synchronized. One of the screens after configuration is shown below: 1.5.2 OPC Data Acquisition Process of Mitsubishi PLC for Thermal Medium Furnace Mitsubishi PLCs are relatively universal, and there are many OPC Server programs that support this hardware. We chose KepServer software. This program supports many hardware devices and can publish the real-time data acquired from the underlying devices in the form of an OPC Server after establishing communication with the hardware, and interact with other software to complete functions such as upper-level monitoring and parameter setting. The configuration process is shown in the following figure: After configuring the OPC Server, add an I/O device in ForceControl PCAUTO and then add a database point in the ForceControl PCAUTO real-time database configuration. The screen after configuration is as follows: 1.5.3 Retrieving IFIX Data via DDE The IFIX software supports Microsoft's DDE dynamic data exchange. Our design involves installing a ForceControl system on the monitoring machine at the work station, using ForceControl to interact with IFIX via DDE, and then using ForceControl PCAUTO's network data source function to indirectly retrieve real-time data from the server. First, a DDE Server module in IFIX must be started and set to start simultaneously with IFIX so that IFIX can support DDE programs while running. Then, add a DDE I/O device in ForceControl PCAUTO: Then add a database point in the ForceControl PCAUTO real-time database configuration. The screen after configuration is as follows: 1.5.4 Retrieving INTouch Data via NETDDE NETDDE is a method of data interaction via DDE over a network. Before using NETDDE, some DDE-related configurations must be performed on the two computers, such as adding DDE sharing and trust sharing settings. See the following figure for specific settings: [align=center] [/align] Then add database points in the real-time database configuration of ForceControl PCAUTO. The screen after configuration is as follows: 1.5.5 Retrieving Smart Meter Readings The key to retrieving smart meter readings is finding a suitable I/O driver. For common meters, ForceControl generally supports them. Then add the driver for this meter in ForceControl's I/O devices, and then set up the points in the database. For some uncommon meters, you can find their original 485 communication protocol and develop your own driver using the driver development SDK package provided by ForceControl. Below are the relevant parameter diagrams of several meters we read via 485: