Fieldbus issues

What is a field bus? By definition, a field bus is an open, fully digital, two-way, multi-station communication system used to connect field electrical devices, field instruments, and field equipment with the main system in the control room. Fieldbus standards specify how data is exchanged between a certain number of field devices within a control system. The transmission medium for data can be wires and cables, optical fibers, telephone lines, radio, and so on. Put simply, a field bus is a bus technology used in the field. The wiring method for traditional control systems is a parallel connection style, with the PLC controlling various electrical components; each component has an I/O port, and two wires are required to connect them together for control and/or power supply purposes. When the number of electrical components controlled by a PLC reaches dozens or even hundreds, the wiring of the entire system becomes very complex, prone to errors, and makes construction and maintenance quite inconvenient. To this end, people are considering how to combine so many wires together, using a single wire to connect all devices; all data and signals flow along this wire, while control and communication between devices can be configured as desired. Thus, this wire naturally came to be called a bus, just like the concept of a bus within a computer. Since the control objects are all located in industrial and mining sites, unlike computers which are usually used indoors, this type of bus is called a field bus.

A field bus is a digital, two-way, multi-branch communication network that connects intelligent field devices to automation systems; its key feature is its ability to support full digital communication in a two-way, multi-node, bus-based format. The fieldbuses currently in use include: AnyBus, CAN, Profibus, Fieldbus, WorldFIP, P-NET, LonWorks, INTERBUS, DNET, CNET, LIGHTBUS, MODBUS, CC-LINK. On an FF bus, generally a maximum of 12 instruments can be connected per segment, and the maximum distance from a segment to an instrument should be 120 meters

You can download information on the FF bus at www.fieldbus.org! For other buses, you can go to the corresponding official websites to download the materials!

Theoretically, a FF bus segment can support up to 16 devices, Profibus PA can handle up to 32 devices, and Modbus can support up to 255 slaves. In practice, the actual number of connected devices depends on the specific circumstances and requires calculation; it is related to parameters such as current and instrument power.