What is Fieldbus? The Concept of Fieldbus

According to the definition of IEC standard of International Electrotechnical Commission and Fieldbus Foundation FF: Fieldbus is a digital, bidirectional transmission, multi-branch structure communication network connecting intelligent field devices and automation systems.

The essential meaning of fieldbus is expressed in the following aspects.

(1) Field communication network, Fieldbus, as a digital communication network, has been extended to the field equipment in the production site, so that the one-way parallel transmission of analog signal transmission or switch signal of point-to-point type has been changed into the two-way serial digital transmission of multi-point and one-line.

(2) Field device interconnection, Field devices refer to sensors, transmitters and actuators, etc. located at the production site. These field devices can be directly interconnected in the field through the field bus to exchange information with each other. In the computerized decentralized control system, the field devices cannot exchange information directly with each other.

(3) Interoperability The so-called interoperability refers to the ability of devices from different manufacturers to communicate with each other and to complete functions in a multi-factory environment. It is reflected in 1.the freedom of the user to choose the device, and this choice is independent of the supplier, control system and communication protocol; 2.the ability of the manufacturer to add new and useful functions; 3.the absence of proprietary protocols and special customization of driver software and upgrade software.

(4) Decentralized function blocks The fieldbus control system decentralizes the function blocks to be executed in the field instruments, thus eliminating the process control stations in the traditional computerized centralized control system. For example, a fieldbus transmitter can run a Pm control function block in addition to the functions of a general transmitter. Similarly, in addition to the functions of general actuators, fieldbus actuators can also run control function blocks and output characteristic compensation blocks, and even realize the functions of self-calibration of valve characteristics and self-diagnosis of valve faults.

(5) Fieldbus power supply In addition to transmitting information, fieldbus can also complete the function of power supply for field devices. The bus power supply not only simplifies the installation and wiring of the system, but also realizes the intrinsically safe system through the matching safety gate, which lays the foundation for the application of the fieldbus control system in the flammable and explosive environment.

(6) Open interconnection network Fieldbus is an open interconnection network, which can be interconnected with the same layer network or different layer network. Fieldbus protocol is a completely open protocol, which is an open, standardized and standardized communication protocol. This means that fieldbus devices from different manufacturers, as long as they conform to the fieldbus protocol, can be connected into a system through the fieldbus network to realize comprehensive automation.