Thursday, September 1, 2011

Bridging Concepts of OPC Server

It is not probable for two Servers of OPC to correspond with each other out of the box except the supplier additional Server of non-OPC abilities to the software of OPC Server. OPC is according to architecture of Client/Server. Consequently, an application of OPC Client such as Management system, Production system, HMI, Historian, etc, it makes demands to swap over data with a Server of OPC. The Server of OPC reacts to these demands. But, note that a Server of OPC can only react to demands; the Server of OPC can not make applications. It means, Servers of OPC can only perform what they are telling. So, two Servers of OPC can not swap over the data with each other straightly because every waits for an application from the other, and while Servers of OPC don’t make demands, no data transmit will take position.

This is correct for any architecture of Client/Server based system in universal and OPC particularly. The only method for two Servers of OPC to correspond is to include an application of Client OPC offer a connection between the two servers, therefore becoming an “OPC Bridge.” The Bridge of OPC attaches two or more Servers of OPC jointly. The Bridge of OPC demands data from one Server OPC, and writes the data to the other server of OPC. All products of OPC Bridge pursue this idea. Integrators have to get 3 steps to setup the transfer of data:

1. Setup the Bridge of OPC to link to the servers of OPC. The Servers of OPC to which the link connects are set by the Integrator.
2. Setup the Bridge of OPC to interpret data from one Server of OPC, and write it to another Server of OPC. The Integrator preselects the particular data to transmit.
3. Setup the Bridge of OPC to repeatedly perform the above pattern.

Connecting to Servers of OPC
The initial step to setup a Bridge of OPC is linking to the Servers of OPC. The products of OPC Bridge characteristically allow Integrators with the following methods to attach to Servers of OPC:

1. Graphical User Interface (GUI) allows Integrators to graphically surf the local PC and another PCs on the network.
2. Manually Configuration allows Integrators to acquire fast access to recognized resources of OPC.

Most applications of OPC Bridge give both techniques above and allow Integrators to choose the most proficient method to create the connection of OPC Server.

Mapping OPC Bridge Items
Integrators have to choose the source and target of every data item after making the first connection to the Servers of OPC. The applications of OPC Bridge characteristically allow Integrators to complete this as below:

1. The interface of graphical allows Integrators to graphically choose every source item and the target of the data.
2. Importing files of data allows Integrators to make a configuration file with an application for example Microsoft Excel and import the file into the bridge for heap configuration.

It may look the method of graphical configuration is an proficient way to construct the Bridge of OPC; but, consider that mainly data transmits move thousands items from a Server of OPC to another. Setting up every data item independently is both error prone and time-consuming. Consequently, if you have to shift many data, they suggest choosing a Bridge of OPC that allows you to make standard files of configuration, for instance a file of Comma Separated Value (CSV), with a tool of mass-configuration for example Microsoft Excel.

Execution of OPC Bridge
When the Integrator develops the Bridge of OPC, they have to execute automatically. This automation approaches in some dissimilar flavors:

1. Standard application of Windows with precise startup: The Bridge of OPC begins only when someone clearly chooses it. This mode of startup may be suitable for testing reasons, but not for manufacture because this way needs manual interference to start the OPC Bridge operation.
2. Standard application of Windows with regular startup: The Bridge of OPC begins when a detailed user logs on to Windows. Whilst this technique does not involve manual interference, it does need a precise logon account.
3. A Service of Windows is a particular application that is setup to carry out with the identity of System. It performs as the Operating System itself. This is the mainly attractive way to operate the Bridge of OPC. This application can start automatically as fast as Windows boots up and does not need a particular user to log on to the PC. The Bridge of OPC is after that capable to immediately start sending out data with minimum interruption. Implementation as a Windows Service is pleasing even if the project wants particular User Accounts to connect to remote PCs.

The majority applications of OPC Bridge can perform in all of the modes listed, nevertheless, when choosing a Bridge of OPC, they suggest that you select a product that can operate as a Service of Windows.


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