OLE for process control
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OLE for Process Control (OPC) is the original name for a standard developed in 1996 by an industrial automation industry task force. The standard specified the communication of real-time plant data between control devices from different manufacturers.
The original standard was based on the OLE COM and DCOM technologies developed by Microsoft Corporation for the MS Windows operating system family. The standard is now maintained by the OPC Foundation and has been renamed the OPC Data Access standard.
OPC was designed to bridge Windows based applications and process control hardware and software applications. It is an open standard that permits a consistent method of accessing field data from plant floor devices. This method remains the same regardless of the type and source of data.
OPC servers provide a method for many different software packages to access data from a process control device, such as a PLC or DCS. Traditionally, any time a package needed access data from a device, a custom interface, or driver, had to be written. The purpose of OPC is to define a common interface that is written once and then reused by any business, SCADA, HMI, or custom software packages.
Once an OPC server is written for a particular device, it can be reused by any application that is able to act as an OPC client. OPC servers use Microsoft’s OLE technology (also known as the Component Object Model, or COM) to communicate with clients. COM technology permits a standard for real-time information exchange between software applications and process hardware to be defined.