An OPC server is a software application that acts as an Application Programming Interface, also known as API, or protocol converter. OPC was designed to provide a common bridge for Windows based software applications and process control hardware. Standards define consistent methods of accessing field data from plant floor devices. An OPC server for one hardware device provides the same methods for an OPC Client to access its data as any and every other OPC server for that same and any other hardware device. The server will connect to a device or a data source such as a database or User interface, and translate the data into a standard-based OPC format. 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.
This method remains the same regardless of the type and source of data. The aim was to reduce the amount of duplicated effort required from hardware manufacturers and their software partners, and from the SCADA and other HMI producers in order to interface the two. In fact, the OPC is all about Open Productivity & Connectivity in industrial automation and the enterprise systems that support industry. There are currently seven standards specifications completed or in development, and all of the OPC servers provide information that is valuable to the enterprise. Once if the information is improperly updated, it could have significant consequences to plant processes.
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 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. The value of OPC is that it is an open standard, which means lower costs for manufacturers and more options for users. Hardware manufacturers need only provide a single OPC server for their devices to communicate with any OPC client. Software vendors simply include OPC client capabilities in their products and they become instantly compatible with thousands of hardware devices, and users can choose any OPC client software they need, resting assured that it will communicate seamlessly with their OPC-enabled hardware.