Safe Data Transmission, Long Distances: Fiber Optic Link for Profibus Communications

Fiber optic link for Profibus communications

In the chemical, petrochemical and pharmaceutical industries as well as in the oil and gas sector, explosion hazards must be avoided by suitable means at all times. For this purpose measurement and control installations rely on Remote I/O more and more. These employ PROFIBUS which makes use of fiber optic links to bridge long distances at high speed.


Reliable, economical operation

Plants built over a wide area often employ redundancy in their control system because of the high economic importance to maintain production. Since high speed PROFIBUS only permits the use of copper cable for short distances fiber optic links offer an ideal alternative.

There are three main differences with copper cables which make fiber optic links the right choice in process control applications.

  • Fiber optic links ensure full galvanic isolation between the plant area and the control room
  • Low energy levels of light cannot generate sparks or hot surfaces
  • Electromagnetic fields cannot cause interference in the fibers unlike in data transmission via copper cables

New Zone 1 Fiber Optic Link in GRP enclosure
New Zone 1 Fiber Optic Link in GRP enclosure

Furthermore the fiber optic links profibus-repeater presented here offers some additional features. It can be used in a point to point application as well as in a redundant ring. It is capable of detecting Profibus faults and can induce a redundancy line change automatically. At the Zone 1 plant level of the Remote I/O station conventional bus cables are used. As the RS485 link is not intrinsically safe the cable must be wired in a similar way to power cables as to satisfy increased safety requirements.


Summary

Fiber optic technologies are the key to bus systems extending into the hazardous area. This enables improved efficiencies achieved in other branches of automation to be transferred to process automation without restriction. Fiber optic installations will continue to rise significantly especially as investments are being undertaken to extend the plant life by modernizing control systems.


Serviceline Information

Products

Links

Download Article