Fieldbuses in General

Stepping from analog to digital communication means a major paradigm shift.

In control systems that do not rely on a fieldbus, there is a clear divide between the devices and the controls; the tasks of each are separated. Only analog values (measured data) are transferred between devices and controllers, and this communication is one-way. From a personnel perspective, this typically meant that an instrumentation technologist was responsible for the field devices, and a control engineer scales the (4-20mA) analog values coming into the control system accordingly.

Analog system: one-way communication

In a fieldbus system, the instruments are an integral part of the system, and the control engineer has full control over field devices. From the engineer’s point of view, there is now no distinction between the instruments and the control system. It is an integrated whole. Having the instruments as part of the control system is a major paradigm shift as it gives the instrument a role that in the past had been reserved for the control system. Conversely, the instrument technologist needs access to the control system for set up and monitoring of the instruments. The communication is no longer analog, but digital; no longer one-way, but two-way. And with this shift, we now have a network, and different topologies are possible.

Fieldbus system: two-way digital communication

Benefits of using a digital fieldbus (PROFIBUS)

  • Plant Asset Management – Information from process instruments and sensors and actuators are available in the controller.
  • Engineering and Documentation – Engineering is simpler, and the documentation is far less complicated as hundreds of separate wires are reduced to just a single cable.
  • Installation – With less hardware, installation is easier and faster.
  • Commissioning – Devices can sequentially be brought online, one by one, with start-up initiated from a central location.
  • Process Variables – The diagnostic information and status bytes available tell the user if they can trust the process variable or not.
  • Manufacturing Flexibility – As demand shifts, changes in manufacturing can be implemented rapidly.
  • Maintenance and Operations – With the powerful diagnostics of a fieldbus come improved availability and reduced downtime.

Learn more about fieldbuses and their value with this white paper: Why use a Fieldbus?

Why Use a Fieldbus?