Cogent Real-Time Systems, developer of the OPC DataHub, has partnered with the OPC Training Institute (OPCTI), the largest OPC training company in the world, to include the OPC DataHub in its hands-on classes.

"OPCTI uses the OPC DataHub to illustrate concepts for OPC tunneling and bridging," said Randy Kondor, President of OPCTI. "Using the OPC DataHub, students are able to overcome DCOM configuration problems by establishing a tunnel between multiple computers. In addition, the OPC DataHub is used to bridge two OPC Servers so that data can transfer from one to the other. This enables students to simulate transferring data between control systems."

For the best possible tunneling connection, the OPC DataHub's configuration options provide several ways to improve data throughput rates.

For example, on the slave side of the tunnel, you can:

• Specify a read-only connection, if the slave is only receiving data.
• Use binary mode transmission, with possible CPU gains of up to 50%.
• Set the heartbeat timeout to 0, particularly useful over very slow networks.

And on the master side of the tunnel you can configure how the DataHub maintains its queue of old values, and how it buffers data to be sent to the slave. In brief, if you find your tunneling connection to be a bit slow, there's a good chance you can speed it up.

A customer of BitCtrl Systems in Leipzig, Germany wanted to connect a new OPC-enabled Siemens PLC running SINAUT (a Siemens-protocol) to an existing system running on the QNX real-time operating system, using a combination of permanent and dialed connections.

The OPC DataHub connects to the Siemens software as an OPC client, and then mirrors the data over a network connection to a Cascade DataHub running on a QNX computer. BitCtrl wrote a custom driver to connect their FlexCtrl product to the Cascade DataHub on the QNX computer. FlexCtrl can now use the data from the new Siemens control system to perform further calculations and display new graphics, independent of the type of the connection. The new system adds 5,000 new data points to the existing system, in several steps.