Computer Solutions Like many
marriages, that of fieldbus with IT and/or other fieldbuses is fraught with flare-ups and breakdowns, but ultimately both parties know they have no option but to try and make it work, asserts Boris Sedacca.
Factory networking unites with IT
F
rom motor control to process calibration in explosive environments, there are almost as many types of fieldbus
as there are applications, and some applications will host multiple fieldbus environments without a specific site standard.
The Sellafield nuclear reprocessing plant in the UK for example uses Modbus with operator panels for pump control as well as IP67 Profibus nodes. It mixes PLCs from Rockwell Allen Bradley and Siemens, not to mention Schneider Modicon.
The wired connections between devices and groups of devices at the physical layer of all fieldbuses will normally come from specialist terminal suppliers such as Phoenix Contact and the three Ws – Wago, Weidmuller and Wieland.
In fact the Interbus serial bus system developed by Phoenix Contact connects sensors and actuators in accordance with IEC 61158 specifications for industrial computer network protocols used for real-time distributed control.
There is a wide variety of competing fieldbus standards, principally AS-Interface, CAN,
Fig. 1. Some industrial plants host multiple fieldbus environments. Wired connections between devices and groups of devices at the physical layer of all fieldbuses will normally come from specialist terminal suppliers.
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EtherCAT, Foundation fieldbus, Interbus, LonWorks, Modbus, Profibus BitBus, CompoNet and SafetyBUS p, let alone underlying industrial automation communication protocols such as HART, AS-i, DeviceNet and EtherNet/IP.
“Before we launched the first slice I/O at the Hanover Fair in 1995, all fieldbus products would have been a base and a block of I/O for eight or 16 channels, or maybe four analogue channels, but you could not mix them,” recalls Derek Lane, automation manager at Wago and deputy chairman of the Profibus Group.
“It has always been the automotive sector that has pushed fieldbus and PLC developments, like when General Motors issued its
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