OPC Based Client for Process Control

Abstract

OLE for Process Control (OPC), which stands for Object Linking and Embedding (OLE) for Process Control, is the original name for a standard specification developed in 1996. The standard specifies the communication of real-time plant data between control devices from different manufacturers. The OPC technology is based on the COM and DCOM technologies. COM and DCOM technologies are developed by Microsoft Windows Operating System. OPC technology defines objects, interfaces and methods to control process. It also serves manufacturing automation applications to facilitate interoperability. OPC Data access is the most common OPC specification. OPC Data Access is used to read and write real-time data. OPC servers provide a method for many different software packages to access data from a process control device, such as a PLC (Programmable Logic Controller) or DCS (Distributed Control System).Traditionally, any time a package needed access to 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 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.