The process industry’s view of fieldbus is similar to that of the discrete world, but with some physical differences because the process environment often involves explosive or incendiary processes. Power also must be delivered over the network cable - often over distances of 100s of metres!

For these reasons a PI 'Profile' known as PROFIBUS PA is used in process automation. This meets the ‘Intrinsically Safe’ (IS) and bus-powered requirements defined by IEC 61158-2, the fieldbus standard used throughout process automation. A PROFIBUS PA fieldbus network can connect up to 32 devices per 'segment' depending on type and application. 

PROFIBUS PA and PROFIBUS DP use an identical communications protocol and connecting them together is achieved easily using a simple coupler device. 

This gives PROFIBUS a big advantage in process applications because the same fieldbus can cover discrete (factory) and process applications. Most process plants have discrete functions (e.g. pumps, conveyors, actuators and robotic systems) working alongside plant instruments such as pressure and temperature transmitters, so having a single fieldbus for both means big cost savings.

We refer to this as the ‘hybrid’ capability of PROFIBUS, and you will hear us mention this elsewhere in this site. The 'hybrid' nature of PROFIBUS means it has become the clear fieldbus leader in process automation with approximately 4.8 connected devices by the end of 2008. Of these, over 800,000 met the PROFIBUS PA Profile.

TEN REASONS FOR USING PROFIBUS

• It's the preferred fieldbus for end users and it's used in the largest number of applications worldwide.
• There's huge vendor and product choice.
• Openness and interoperability allow easy changes and updates.
• The protocol is optimized for factory and process control using standardized interfaces, and therefore it's ideal for hybrid applications.
• Less hardware is needed, which means less weight and space, also lower installation and life cycle costs.
• There's easy and consistent integration of functional safety and motion control in both factory and process automation enviroments.
• There's flexible media redundancy.
• There's tightly-managed technology development, including test & certification processes.
• It's supported by PI, the world’s largest fieldbus organization.
• There's easy migration to PROFINET.