Feature: Fieldbus


Will competing Fieldbus technologies ever evolve into open-source architecture?


By Neil Ballinger, Head of EMEA, EU Automation I


n 1999, the IEC 61158 European standard set the parameters for industrial communication networks, accommodating all competing Fieldbus systems and delineating eight protocol sets,


known as “types”. More than 20 years later, competing systems still exist. T e permanence of several competing


Fieldbus technologies meant that the original plan to achieve a unifi ed communications mechanism was never realised. T e applications of Fieldbus are so diverse that a common system seemed unfeasible; but, has this lack of unity been detrimental to Fieldbus? To answer this question, we need to go


back to the basics. Fieldbus is a group of industrial computer network protocols used for real-time distributed control. It is a way of connecting industrial equipment, forming network topologies such as star, ring, daisy-chain, tree and others. Prior to Fieldbus, machines were


connected using RS-232 serial connections, which allow only two devices to communicate. With increasing


36 October 2021 www.electronicsworld.co.uk


digitalisation in factories, Fieldbus gradually replaced point-to-point connection between a machine and its controller. Fieldbus is not a connection type as such, but a description used to indicate a group of protocols, such as ControlNet in the Allen Bradley family, Modbus, Profi Bus, EtherCAT, HART and many more. In Fieldbus, multiple machines are


connected to a connection point, which is in turn connected to a programmable logic controller (PLC). T is system, compared to RS-232 connections, reduces wiring complexity and costs. To allow communication, the factory’s PLCs need a communications protocol compatible with the fi eld devices. Manufacturers don’t necessarily need a protocol from the same brand as their PLC – for example, Profi Bus can connect with all PLCs from the Allen Bradley family. However, some protocols do not play well with others. T is complicates things for users, who have to research the best protocols to ensure that all their equipment can communicate.


Industrial Ethernet While the Fieldbus market remains segmented, industrial Ethernet has grown in popularity. In fact, research by industrial communication specialist HMS Networks suggests that industrial Ethernet has overtaken traditional Fieldbus systems in terms of new installed nodes. For now, it seems unlikely that


competing Fieldbus technologies will ever evolve into an open-source architecture. But, in the meantime, industrial Ethernet is outperforming Fieldbus, because it off ers higher speed, increased connection distance and the capacity to connect more nodes. Nevertheless, the issue of complexity


remains. T e original aim of industrial Ethernet was unifi cation of the communications infrastructure, but, at the moment, the number of Ethernet solutions on the market is even higher than that of Fieldbus. T is complexity makes comparison of diff erent systems diffi cult for end users, but it also means that there are more options available to industrial system designers.


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46