Fieldbus is often mentioned in industries such as electrical, but not everyone has an understanding of fieldbus technology. In order to improve everyone’s understanding of field bus, this article will introduce the definition of field bus technology, and discuss the connection between field bus and PLC at the end.

1. Fieldbus technology

Fieldbus (Fieldbus) is an industrial data bus that has developed rapidly in recent years. It mainly solves the digital communication between field devices such as intelligent instruments, controllers, and actuators in industrial fields, as well as these field control devices and advanced control systems. information transfer between them. Because of a series of outstanding advantages such as simple, reliable, economical and practical field bus, it has been highly valued by many standard groups and computer manufacturers.

Fieldbus (Fieldbus) is an industrial communication system that connects a large number of field-level devices and operation-level devices in an automation system. It is generally defined as: an open, digital, two-way serial, multi-node communication bus for intelligent field devices and automation systems.

Fieldbus (Fieldbus) was developed internationally in the late 1980s and early 1990s, and is used for field intelligent equipment interconnection communication networks in the fields of process automation, manufacturing automation, and building automation. It serves as the basis of the factory’s digital communication network, which communicates the connection between the production process site and the control equipment and its connection with the higher control management level. It is not only a basic network, but also an open, new fully distributed control system. This comprehensive technology with intelligent sensing, control, computer, digital communication and other technologies as the main content has attracted worldwide attention and has become a hot spot in the development of automation technology, which will lead to profound changes in the structure and equipment of automation systems. Many powerful and influential companies in the world have successively developed fieldbus technology and products to varying degrees. The working environment of the fieldbus device is at the bottom layer of the process equipment. As a basic communication network at the factory equipment level, it is required to have the characteristics of simple protocol, strong fault tolerance, good security and low cost: it has certain time certainty and high real-time performance. It also has the characteristics of stable network load, mostly short frame transmission and frequent information exchange. Due to the above-mentioned characteristics, the field bus system has the characteristics of different upper-layer high-speed data communication networks from network structure to communication technology.

The field bus system is generally referred to as the fifth generation control system, also known as FCS – field bus control system. People generally refer to the pneumatic signal control system PCS before the 1950s as the first generation, the 4-20mA and other electric analog signal control systems as the second generation, the digital computer centralized control system as the third generation, and the 70th generation. The distributed distributed control system DCS since the middle of the 1990s is called the fourth generation. The field bus control system FCS, as a new generation control system, on the one hand, breaks through the limitation of the DCS system using a dedicated communication network, adopts an open and standardized solution, and overcomes the defects caused by the closed system; on the other hand, the DCS system The centralized and decentralized distribution system structure has become a new type of fully distributed structure, and the control function is completely delegated to the site. It can be said that openness, decentralization and digital communication are the most significant features of fieldbus systems.

Second, the connection between fieldbus technology and PLC

The field bus control system distributes the control station function of the DCS to the field control equipment, and the basic functions of automatic control can be realized only by the field bus equipment.

After using the fieldbus, the operator can realize remote monitoring in the central control room, adjust the parameters of the field equipment, and can also predict the fault and find the fault point through the self-diagnosis function of the field equipment.

The combination of PLC and field bus can form a cheap and powerful distributed control system.

PLC and field bus are inseparable, and field bus itself is developed by major PLC manufacturers, such as Siemens’ PROFIBUS and AS-i.Rockwell Automation Company’s ControINet and DeviceNet. PLCs from mainstream manufacturers can be connected to various major fieldbus networks.