Overview of OPC

This sub-book describes the use of PcVue as an OPC-DA client, and how to configure the OPC servers it will connect to.

OPC is an acronym for Open Platform Communications (formerly OLE for Process Control).

OPC Classic is a communication standard based on OLE / COM technology.

The OPC concept is based on client/server architecture. PcVue is normally used as an OPC client although it may also be used as an OPC server. It can be simultaneously connected to several OPC servers and/or clients either on the local computer or on remote computer (using DCOM – Distributed COM).

Many manufacturers of industrial controllers now supply an OPC server with their equipment. The OPC server communicates directly with the equipment using the manufacturer’s proprietary protocol. PcVue communicates in turn with the server using OPC.

After connecting to an OPC server, the OPC client can define groups of data in the server. A group is to allow the client to organize the data it requires. In the case of PcVue, it is used to allocate a rate at which the data will be requested from the field device.

OPC XML-DA

OPC XML is a technology that makes plant floor data available using SOAP/XML. OPC XML-DA allows the client and server to communicate using HTTP over an intranet or internet connection.

Configuring Windows when using DCOM

If you are using a remote OPC server (DCOM), it is likely that you will have to make some configuration changes to Windows before communication can be established. As the callback mechanism used by OPC essentially turns the OPC client into a DCOM server and the OPC server into a DCOM client, the configuration changes must be made on all computers that contain an OPC server or OPC client.

Configuring OPC

 PcVue has both OPC client and server capability. To use PcVue as an OPC client you must configure a connection to an OPC server using the tasks available in the Application Explorer.