OPC Meaning – OLE for Process Control – The software connector for automation
The most important basic technology from Microsoft COM / OLE is used to exchange data between applications.Microsoft has the operating systems Windows 10, Windows 8
OLE for Process Control (OPC) is based on this technology. Most important goal of the OPC activities is to create a uniform software interface based on the known Microsoft technology easy to use for users as well as for Automation system provider is easy to implement.
In the September 1996 the OPC Foundation was founded in the USA. Owns today the OPC Foundation already has around 150 members, including all major members worldwide active manufacturers of automation systems such as Fisher-Rosemount, Siemens, Trebing & Himstedt, Rockwell Automation, ABB, Wonderware, National Instruments and Honywell.
Especially the end customers of the OPC Technology expects significant benefits, shows the remarkably high proportion of over 20% end customers in the OPC Foundation.
Microsoft also documents with theMembership fully supports this standard. In no other Organization have such bundled resources in development capacity,along with global marketing.
At the Hanover Fair in 1998, 17 companies presented their OPC based Products and controlled a factory models.
Implementation of the OPC specification in Products went so quickly that neither company interests nor the established ones Standardization bodies could keep pace. OPC was on the first day
Fast lane and has not been viewed by corporate strategists or technology discussions slowed down what was often doomed to many other technologies
Advantages of OPC technology
In addition to the goal of generally simplifying the connection of applications OPC offers manufacturing and process engineering with business / office applications a number of other advantages.
Dissolve the manufacturer dependency for hardware and software
The prior art is characterized in that today for the connection of Process hardware a special driver for data exchange with the PC application enables.
OPC offers a standard interface, regardless of the specific one Application. For the hardware manufacturer, this means that he only needs one Implement OPC server interface.
The manufacturers of software products such as Visualizations, measuring systems etc. only have to be done via an OPC client Interface.
The end customer, in turn, can freely choose between the choose different providers of hardware and software components and rely on Concentrate functional selection criteria and do not pay attention to whether the one suitable driver is available.
Plug & Play configuration of data exchange
With OPC, the configuration of the data exchange becomes hardware or between Applications greatly simplified. If there is an OPC server, this is the first then the data (tags) of the OPC server, in the usual Microsoft Explorer style selected with a mouse click. The tags can be structured into groups, so that only the data that is really of interest is exchanged. The conserves resources in the PC.
Multi-client access and data distribution
Each OPC server is able to process requests from several clients. Should data be used multiple times, for example by a visualization, as even from a database, different software packages can be based on the data of the Access OPC servers. No manufacturer-specific agreement is required for this or additional implementation. The OPC server uses Microsoft for this
Functions of the operating system (COM technology) that every OPC server “inside”Has.Network capability and internet / intranet In addition to the COM technology,
OPC uses DCOM (Distributed COM) to To achieve network capability.
This means that there are not only data sources (OPC servers),which are available on the local PC, but all servers of the network as remote data source available. Remote operator stations, multi-user systems,
Access to distributed data sources, no problem with OPC. The OPC clients notice not even if it is a local or remote data source. OPC or DCOM hides the difference
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How OPC Sever –OPC Client work?
The OPC concept is designed for use at the cell and control level. Here make the OPC server process data available.
OPC clients and OPC servers are currently PC-based systems with a Microsoft Windows operating system
OPC defines objects that are described by object interfaces. In the OPC server there are two versions of the object interfaces that are created by an OPC client can be addressed (picture 2):
The COM custom interface
The OLE automation interface
The COM interface is used by function-oriented languages, such as C ++. Script languages such as Visual Basic,be communicated.
An OPC server consists of three hierarchically graded objects:
An OPC server maps the real objects to items. These items are inside of the OPC server clearly. The client organizes the items in one or more OPC groups
The IOPCServer interface is the main interface of an OPC server. Next It primarily serves functions for status information and error handling Manage private groups through clients. Are particularly interesting however the optional interfaces. With IOPCServerPublicGroups the server can Provide clients with items.
IOPCServerBrowseServerAddressSpace allows you to search the server on his existing items. The clients no longer have to syntax the items know. In addition to relieving items syntax, this function enables
Transfer of the server configuration.Process variables no longer have to be set several positions can be defined (e.g. fieldbus connection, PLC, visualization),but are passed on to the requesting clients by servers.
IPersistFile gives clients the ability to configure the server save or reload. For example, when the system starts up Configuration done from a central point.
OPC Group objects enable the grouping of items and their items Data exchange between the OPC server and the OPC client.
IOPCGroupStateMgt is used for status management of private groups. So can the update times or the tolerance bands of a group are changed.
With the IOPCItemMgt interface, the client is able to create a group of items add or remove.
Synchronous and asynchronous interfaces are available for data access.
So control systems can only include alarm values and the data of the displayed page read at short intervals
The OPC item object is part of the automation interface. It makes it possible Manage the status, the required data type and the reading or write access to the item
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