Realising the benefits of change

As new fieldbus technologies and connectivity standards are adopted, so the options for tackling transmission speed, capacity and distance issues are increasing. The trick is converting from one transport medium to another without re-engineering

The emergence of Ethernet, together with fibre optic and wireless technologies, is increasing the number of connections available to the operators of process plants. Since data integrity is paramount and software re-engineering expensive, more and more process engineers are now turning to new technology that converts data from one transport medium to another.

Traditionally the control strategy of the process industries was based on serial wiring, which was simple to implement. As a result many of today's process products, from chemicals and crisps to oil and textiles, rely on automation using the RS232, RS422 or RS485 protocols.

While serial communications such as these remain hugely important in industrial automation, another technology is rapidly gaining ground. This is the TCP/IP communication protocol, running on Ethernet cabling. And alongside this new protocol, the automation scene is being further complicated by two other emerging technologies - fibre optics and wireless.

Fibre optic cable can transport serial data or TCP/IP data. As fibre optics can send signals over distances, this is a very useful technology for linking process plants and sites that are many kilometres apart. There are also other advantages with this technology. Firstly, huge amounts of data can be sent and received at the speed of light. Secondly, the data travels as light waves and is not affected by the electromagnetic noise that is a particular problem associated with process plants in the utility sector.

Then there are the new wireless technologies. In a way these parallel the 'hardwired' world and include wireless serial connections such as the much-heralded Bluetooth and also wireless Ethernet.

Ideal combinations For process engineers, this produces an increasingly complex range of options at the interfaces where the different systems interconnect. And each combination will have its own particular benefit. For example, a conversion from serial communication using copper cables to serial over a fibre link would be useful where speed and distance are important issues.

If a whole process plant network needs speeding up when traffic is heavy and the distance involved is no more than 2km, then changing from an Ethernet cable to a multi-mode fibre cable would be a sensible option to consider. Choosing a single-mode fibre cable instead would increase the useful distance to 100km.

A straight swap from a serial cable to an Ethernet cable would enable greater distances and provide multiple messaging over one cable. If the option were to change from a wireless serial link to an Ethernet link, equipment would become more easily portable without the time and expense associated with recabling.

While the options are many and often appear confusing, the process industries are primarily concerned with two issues - data integrity and the cost associated with any re-engineering of its existing software.

To provide solutions to these issues, Digi developed its Connectware range, providing process companies with a vital tool in their automation strategies. Connectware includes a whole range of options for converting from one data transport medium to another while maximising the speed, integrity and benefits from data and control networks.

Fibre transceivers and converters, serial to Ethernet concentrators, and hubs are available across a wide variety of operating systems platforms. These can connect virtually any equipment into a cohesive information and management network for the modern process plant, while at the same time ensuring that the data remains unchanged as it travels from instrument to server.

 

Conversion Strategies
Convert from	Convert to	Benefits
Serial cable	Ethernet cable	Enables greater distance and provides multiple messaging over one cable. Multiple devices can be monitored centrally
Serial over copper	Serial over fibre	Great for improving distance and speed. Fibre cables are not affected by electro magnetic interference
Ethernet cable	multi-mode fibre cable	Speeds up the whole network when network traffic is heavy. Maximum distance is about 2km
Ethernet cable	Single-mode fibre cable	Enables distances of up to 100km at the speed of light
Serial output	Wireless serial or Ethernet	Makes equipment easily portable without the need for recabling. Removes wiring tangles

Entrix
h102@industrialnetworking.co.uk