Open Platform Communications (OPC): Understanding OPC Server Technology

Kepware has years of experience developing reliable, easy-to-use OPC technologies. Learn about the evolution of OPC standards—from the OPC Foundation launch to the adoption of OPC UA today.

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.

cs-data-center-750x500

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.

Why Was OPC Designed?

OPC technology was developed by the OPC Foundation to reduce duplicate efforts required from hardware manufacturers, by simplifying industrial devices and application communication protocols within the larger distributed control system. It supports easy data exchange between SCADA, HMI, PLC, and other critical systems.

2col-750x500

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

The OPC Classic specifications were developed using Microsoft’s COM/DCOM to foster smooth communication between applications and devices on distributed networks. These specifications cover data transfer, alarms and events, and historical data, and offer a wide range of tools for people who prefer "off-the-shelf" products.

  • 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)

    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.

dpm-750x500

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.

digital-manufacturing-750x500

ThingWorx Kepware Server

Kepware's goal within the OPC environment is to be a leading provider of the server component by providing reliable, easy-to-use products. ThingWorx Kepware Server is built upon years of development efforts in communications driver development and OPC technology.