Understand the OPC UA Standard
- Last UpdatedSep 12, 2024
- 2 minute read
OPC UA defines a common infrastructure model to facilitate the exchange of data between OPC UA-supported systems and devices, using OPC UA-defined and vendor-defined data types. The OPC UA Service uses OPC UA to exchange data.
About Classic OPC and OPC UA
OPC UA is a parallel standard to the classic OPC standard. It does not replace the classic OPC standard, but complements it by addressing its limitations.
Classic OPC
OPC originally stood for OLE (Object Linking and Embedding) for Process Control. Later, the OPC Foundation dropped the acronym and identified “OPC” as a word in its own right.
OLE is a Microsoft technology that allows an application to export content in the form of an object to another application, and then import it with additional content. Typically, the changes in the main file automatically update the application or document that references it. With OLE, the visual display of data from other applications is possible within a host application, even when the host application cannot generate such content by itself.
OPC provides a common interface for real-time communication between different control devices and related software products from different technology vendors.
There are several different OPC specifications for different communication functions, the primary specifications being Data Access (OPC DA), Historical Data Access (OPC HDA), and Alarms and Events (OPC AE).
OPC UA
OPC UA unifies the different classic OPC specifications by means of a unified architecture. It retains all the classic OPC functionalities while leveraging the services technology. It also provides robust, reliable, high-performance communication, suitable for automation.
OPC UA supports binary encoding for high-performance data exchange, and incorporates a number of other improvements.
Comparing OPC UA with Classic OPC
OPC UA differs significantly from its predecessor, OPC. The table below explains the key differences between classic OPC and OPC UA.
|
Classic OPC |
OPC UA |
|---|---|
|
Uses the COM/DCOM technology of Microsoft to communicate. It does not have configurable time-outs. It depends on the DCOM time-out, which is configured in the system. |
Uses a services architecture to export data, which improves the ease of communication and connectivity. |
|
Is dependent on Windows operating systems. |
Is platform independent and can connect to a wide variety of devices and platforms. |
|
Has limited security. |
Has built-in security. |
|
No built-in capabilities to handle problems, such as lost messages. |
Has built-in capabilities to handle problems, such as lost messages. |
For more information on OPC UA, see http://www.opcfoundation.org.
Understanding the OPC UA Connectivity
OPC UA provides connectivity to a variety of servers, clients, and devices across various operating systems to exchange data. It connects to third-party data sources.
An OPC UA Server is a discoverable software resource with a well-defined service description. Any OPC UA Client can search, bind, and connect to the OPC UA Server service. The Service Oriented Architecture (SOA) is a set of patterns for creating loosely-coupled services that provide flexibility and responsiveness for software components to leverage the functionalities of one another.
About OPC UA Connectivity Capabilities
OPC UA connects to data sources at every level of the industrial automation hierarchy. It connects to controllers, sensors, HMI products, manufacturing systems, and planning systems. The diagram below illustrates the levels to which OPC UA servers and clients can connect.