PLC suppliers are worried by turbulent market conditions and an uncertain future, says a new report on the global market for PLCs. This market is being hit by a variety of factors including rapid changes in computing and communications technologies, the global economic slowdown, a strong user acceptance of open systems, and a growing threat from industrial PCs, the ARC Advisory Group suggests.

The report* predicts that the overall PLC market will revive slowly during the period to 2006, but that sales of particular types of PLCs, software and services could expand rapidly - or decline.

For example, as "nano" PLCs (with up to 32 I/O) add networking capabilities, and "micro" PLCs (with up to 128 I/O) become more powerful, there will be a growing trend to replace large PLCs with networks of smaller PLCs. The attractions of this approach include reliability, scalability and simplified wiring.

According to ARC, the industrial PC is not yet a threat to PLCs and should be regarded as an ally, providing the hardware and software components to upgrade "traditional" PLCs.

Similarly, smart sensors and actuators are not challenging PLCs yet although the increasing processing power of field-level devices makes it possible to create complex automation systems with fewer PLCs than were needed previously, ARC warns.

* PLC worldwide outlook, market analysis and forecast through 2006.