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AS MOST of us know, no single network can meet all the communications needs of all the different types of processes for which we use automation. In many cases, it’s necessary to share information in real time or at least as close to real time as we can manage across these networks, because we’re unable to use one network in our facility.
The most commonly used solution to this challenge is OPC, the Open Process Connectivity managed by the OPC Foundation. You’ll use different flavors of OPC depending on the application and system requirements. To determine which of the seven OPC versions you need, investigate each at the foundation’s web site, and/or consult with your system integrator, who will have experience in this area.
Present versions of OPC are derived from COM and DCOM, the same technology used to link an embedded “Excel” table into a “Word” document, thus having legacy connections with the Windows Operating System. The recently defined OPC-UA (Unified Architecture) is designed to be platform independent.
Despite the fact that OPC is the de facto real-time communications “glue,” like anything else, it has its limitations, including:
Driven by the requirements of the above-mentioned foundations for tight interoperability, and the fact that the joint effort to update EDDL technology includes OPC UA, it’s necessary that, once released, UA address some of the above concerns. OPC UA should be available from several manufacturers later this year, and my expectation is that we will see it demonstrated at ISA Expo 2006, Oct. 17-19, in Houston.
The OPC Foundation, like many other industry associations, followed the lead of the Fieldbus Foundation and formed an End-User Council to channel feedback directly from customers to their organization, and improve their products. If you have any comments on limitations or improvements you would like to see to make OPC more user-friendly, please let me know and I will pass the information along.
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