The worldwide market for distributed control systems, personal computer-based systems, and programmable logic controller systems will grow at a compound annual growth rate of 6.6% from about $2.2 billion in 2000 to more than $3 billion in 2005, according to the projections of Venture Development Corp. (VDC), Natick, Mass.

In a report entitled “Global Markets and User Needs for Industrial Distributed/Remote/I/O, Second Edition,” VDC predicts distributed control systems (DCSs) will use thousands of I/O points in large-scale applications prevalent in continuous-process applications, and thus remain the preferred system in that area. However, programmable logic controller (PLC)-based systems are invading process-control markets. Offering batch processing and discrete functions, PLCs can do much that once only DCSs could. VDC also notes another significant trend: the use of hybrid controls that incorporate PLCs into DCSs. DCSs may maintain an advantage in terms of redundancy, however, because of the complexity of large-scale continuous processes.

PC-based control systems also present a challenge to DCSs. Continuing to propel interest in the use of PCs for factory controls is the growing familiarity of people with PCs, including factory equipment operators and maintenance personnel. Also, the flexibility of PC technology lends itself to products, markets, and time frames exhibiting great levels of fluctuation. The technology’s inherent web connectivity is another key selling point whenever enterprise level communications are an issue.

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