Profibus (Process Field Bus) is a widely used communication protocol in industrial automation and process control systems. It was developed by the German company Siemens in the 1990s and has become an industry standard for connecting various devices in the field of factory automation and process control.
Profibus supports both serial and Ethernet-based communication. There are two main variants of Profibus:
- Profibus DP (Decentralized Peripherals): Profibus DP is the most common variant of Profibus and is used for communication between a PLC (master) and field devices (slaves) in factory automation applications. It is a high-speed, robust, and deterministic protocol suitable for real-time control and monitoring. Profibus DP typically uses RS-485 or fiber optic cables as the physical layer, with transmission speeds of up to 12 Mbps.
- Profibus PA (Process Automation): Profibus PA is specifically designed for process control applications, such as those found in the chemical, oil and gas, and pharmaceutical industries. It is used to connect instruments, such as sensors, actuators, and analyzers, in hazardous areas where intrinsic safety is required. Profibus PA uses a two-wire transmission scheme and operates at lower speeds compared to Profibus DP, typically up to 31.25 kbps.
Profibus utilizes a master-slave architecture, where the master device (typically a PLC or DCS) initiates communication with one or more slave devices. The protocol supports cyclic and acyclic communication. In cyclic communication, the master device polls the slave devices at regular intervals to read or write process data. Acyclic communication allows for on-demand communication between the master and slave devices for parameterization, diagnostics, or special requests.
Profibus provides various diagnostic and control functions, allowing for device configuration, monitoring, and troubleshooting. It offers features such as cyclic redundancy check (CRC) for data integrity, device addressing for identification, and built-in diagnostics for detecting communication faults.
One of the notable advantages of Profibus is its wide industry support, with many manufacturers offering Profibus-compatible devices. This ensures interoperability and allows for easy integration of devices from different vendors into a Profibus network.
Profibus has been largely superseded by newer protocols such as PROFINET, which is an Ethernet-based successor to Profibus. PROFINET offers higher speeds, greater flexibility, and enhanced functionality while maintaining compatibility with Profibus devices.
Profibus has been widely adopted in various industrial sectors and continues to be used in many applications, especially in existing installations where Profibus networks are already established.