What is OPC? | Open Platform Communications

What is open platform communications (OPC)?

OPC is open connectivity in industrial automation. Interoperability is supported by non-proprietary open standards specifications. The first OPC standard specification resulted from the collaboration of leading worldwide automation suppliers and Microsoft. Originally based on Microsoft's OLE COM and DCOM technologies, the specification defined a standard set of objects, interfaces, and methods for use in process control and manufacturing automation software applications to facilitate interoperability. Today, there are hundreds of OPC Data Access servers and clients.

What is an OPC server and how does it work?

Wondering if OPC is a client/server technology? It is. One application acts as the server providing data, and the other as a client using data. OPC is an industrial communication standard that enables data exchange between multi-vendor devices and control applications without proprietary restrictions.

What are the benefits of OPC adoption?

OPC adoption offers several key benefits including interoperability, open solutions, and freedom of choice. Automation suppliers can provide solutions that are truly open, which in turn gives users more choices in automation applications. This is an exciting time in the industry—with OPC adoption, automation professionals around the globe are realizing the advantages of incorporating OPC into their industrial applications.

History of OPC

In 1994, experts from a spectrum of industrial disciplines formed the OPC Foundation. The Foundation's goal was developing a single client/server specification that allows vendors to develop applications that share data in a fast, robust fashion, and eliminate proprietary schemes that forced vendors to duplicate development efforts. The OPC Foundation released the first specification, Data Access Specification 1.0a, in 1996. Using this specification, vendors quickly developed client/server software.

The Data Access specification eliminated the need for application vendors to develop proprietary communications drivers—an effort that often outweighed application development. OPC technology focuses vendor efforts almost exclusively on the client application. The Data Access specification defines how both the client and the server application interface are constructed. If the specification is followed properly, a client vendor knows any OPC server for an industrial device can provide the connectivity needed for data access. Issues like time to market or reliability no longer restrict OPC applications.

Historically, end users needed to select solutions based on communication driver availability or vendor willingness to develop them. OPC gives end users the ability to select best-of-breed software to solve application problems. The user can choose from a variety of OPC server vendors to address a new driver requirement or remedy performance issues. Application vendors can focus on continuously improving core products without the disruption of addressing communication issues and needs.

OPC classic specifications

OPC Data Access (OPC DA)

OPC Data Access (OPC DA) is a specification developed by the OPC Foundation. At a high level, an OPC server is comprised of several objects: the server, the group, and the item. Groups provide a way for clients to organize data while items represent connections to data sources within the server. This defines the path for real-time data exchange between a client and server using universal protocols.

OPC Alarms and Events (OPC AE)

With high volumes of automation and data in today’s manufacturing environment, OPC Alarms and Events (OPC AE) notify IT about alarms, audit events, provide advance warning of equipment failures or maintenance needs, and optimize operations when alarms occur to keep systems online.

OPC Historical Data Access (OPC HDA)

OPC Historical Data Access (OPC HDA) allows organizations to access their historical process data. Historical OPC data can be helpful for optimizing operations, analyzing performance, or conducting audits and regulatory checks.

OPC Unified Architecture (OPC UA)

OPC Unified Architecture (UA) is a platform independent architecture that incorporates all the components of the OPC Classic specifications into one framework. This style of service-oriented architecture (SOA) integrates distributed software components and ensures interoperability and communications. A multi-layer approach to OPC architecture offers platform independence, security, the ability to add new features, information modeling, and functional equivalence.