In a recent data integration project, Siemens engineers in Copenhagen, Denmark were able to connect equipment and instrumentation running in a high-security facility to a remote monitoring location, using the OPC DataHub.

The goal was to allow technicians access to the machines they needed to work on, without breaching security or permitting any non-authorized personnel on site.

“The OPC DataHub is running very well,” said Carsten, the project leader. “We do a lot of this kind of data integration, and there will be other projects. We have chosen the right solution.”

Software Toolbox, Cogent's sales and technical partner for North America, knows that one size cannot fit all when it comes to off-the-shelf automation software. Since 1996 they have provided hundreds of speciality products to thousands of customers--end users, system integrators, OEMs, and large automation suppliers. Software Toolbox is a Charter Member of the OPC Foundation, and is fully involved in product testing to ensure reliable interoperability.

"Cogent's commitment to OPC interoperability and certification is evident in the OPC DataHub, and meets the high standards we set for our diverse client base," said John Weber, President of Software Toolbox. "The OPC DataHub has proven its value time and again in a wide range of industrial automation applications."

OPC tunnelling is an excellent way to network OPC and avoid the hassles of DCOM. You just connect an OPC DataHub to your OPC server, and configure a tunnel to another OPC DataHub on your OPC client machine. But sometimes people ask: are there any limitations on how much data I can send across the tunnel?

Here are some general considerations:

• Performance of the OPC DataHub does not depend on the number of points (tags) in the system, but rather on the number of data changes per second that are processed. We have tested the OPC DataHub at 100,000 changes per second in ideal conditions, but a more realistic number would be 20,000 to 30,000 changes per second in the steady state.
• Although theoretically you are limited only by the amount of memory, systems with over 100,000 or 150,000 tags will experience some slowdowns.
• The initial connection time can vary depending on the OPC server you are using. Once the connection is made, though, the tunnel will perform at about the same efficiency as a local OPC connection.

With these in mind, here are a couple of suggestions for maximizing performance:

• If the CPU is overloaded, you can add more processing power. The multi-threaded architecture of the OPC DataHub will benefit from running on up to 4 cores.
• For large numbers of tags, you can slow down the data update rates for the connection between the OPC server and the OPC DataHub, which will reduce the processing load, as well as reducing network bandwidth.