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Version: v3

OPC Classic™

OPC Classic™ (HDA/DA) is a communication protocol used in the industrial world and developed by the OPC Foundation. This technology has been replaced by OPCUA but is still widely used in the industry. To use OPC UA™ in OIBus, see the OPC UA connector documentation.

An HDA server allows to retrieve the history of data over a more or less long period, while a DA server allows to retrieve only the most recent value of a tag.

Only OPC in HDA mode is supported by OIBus. This connector uses the OIBus Agent.

caution

The OIBus Agent must be installed on a Windows machine.

Specific settings​

OIBus exchanges commands and data with the HDA agent through a TCP server/client communication. Therefore, several fields must be filled to make OIBus communicate with the OIBus Agent:

  • Remote agent URL: Specify the URL of the remote OIBus agent, e.g., http://ip-address-or-host:2224.
  • Connection timeout: Set the timeout for establishing a connection.
  • Retry interval: Time to wait before retrying connection.
  • Server host: Address of the OPC server (from the remote OIBus agent machine).
  • Server name: Name of the OPC server (e.g. Matrikon.OPC.Simulation).

Throttling settings​

For South connectors capable of historical data retrieval, you have the flexibility to request data in intervals. These intervals can vary in size, depending on factors such as the chosen scan mode or the presence of prolonged network failures.

To handle such scenarios, the throttling settings enable you to divide large intervals into smaller sub-intervals, each no longer than the specified Max read interval (in seconds). These sub-intervals are requested with a delay defined by the Read delay setting (in milliseconds).

In certain situations, adding an overlap to the query can be beneficial. You can achieve this by configuring the overlap field (in milliseconds): it will subtract this specified number of milliseconds from the @StartTime variable of the subsequent query.

Item settings​

When configuring each item to retrieve data in JSON payload, you'll need to specify the following specific settings:

  • Node ID: The Node ID corresponds to the path of the data within the appropriate namespace on the OPC server.
  • Aggregate: Aggregate the retrieved values over the requested interval (be sure that the server supports the aggregate).
  • Resampling: When aggregate is different from Raw, it is possible to resample the retrieved values at the requested interval.
Compatibility with the OPC server

It's important to note that not all aggregation and resampling options are supported by OPC servers. To avoid compatibility issues, it's recommended to use Raw aggregation and None resampling whenever possible.

The name of the item will serve as a reference in JSON payloads, specifically in the pointID field for the North application.