OPC

OPC is the name for a set of standards for communicating real time plant data between control devices from different manufacturers. Its goal is for application developers to develop using a standard API and then be able to connect to different devices without having to write a communications driver for that particular device themselves. A good analogy made by the OPC Foundation is that OPC fills a need in automation similar to that provided by printer drivers in the Windows operating system.

There is a market place for a variety of OPC related products. The OPC Foundation Vendor List is one of the directories available for identifying whether the control device you need to communicate to has OPC software available for it. There are a variety of different OPC software product types. One key product type is an OPC Server. The OPC MetaBridge implementation communicates to OPC Servers to extract data and make it available to MacroView MetaServer client programs. OPC servers can be thought of as a device driver for control devices. The term server is used as OPC information is served to client programs and a communications network is often involved.

There are a number of different OPC specifications for different types of data. The OPC specifications that are supported by the OPC MetaBridge application are:

The OPC Data Access specification deals solely with real time current data and is often abbreviated as OPC DA. The OPC Alarms and Events specification provides applications access to alarm and event information generated by a control device on a real time basis. It is often abbreviated as OPC AE. There are many other OPC specifications and these available for download at the OPC Foundation web site. The OPC MetaBridge application supports OPC DA Version 2.x and 3.x for real time data value transfer. It supports OPC AE Version 1.x for event data transfer.