OPCUA

OPCUA technology is a protocol for accessing data in read or write mode.The data is organized in a tree-like address space and is referenced with aunique address.OPCUA is a modern standard for OPC HDA / DA technologies and is often embedded natively in industrial controllers.

OPCUA embeds two variants of the protocol: HA (Historical Access) and DA(Data Access). The first mode allows access to a history of values over atime interval for the requested points (data), while the second modeaccesses the values at each moment requested.

OIBus integrates the two OPCUA variants in read-only mode (datafeedback only). Each mode has its own connector.

OPCUA HA (Historian Access)

The OIBus OPCUA_HA connector communicates with an OPCUA server thathas HA mode enabled. If the OPCUA server does not have HA mode enabled or installed, the connection will fail.

The following fields must be filled in:

  • The server address with the name at the end of the address (the endpoint in the example below)
  • The username and password in case of authentication

The server category also allows you to refine some parameters associated with the network:

  • Retry interval: duration between two connection attempts in case of loss
  • Max read interval: the request interval is divided into sub-intervals, especially in the event of an activity recovery, to lighten the connection.
  • Read interval delay: Time delay between two successive reads to allow OIBus to insert the requested data in the cache. It is useful to increase it in case of a large number of requested values.
  • Max return values: maximum number of values returned by a request (the request is then split)
  • Read timeout: time before the connection expires during a read request.

Finally, the scan group allows you to indicate how the data should be aggregated on the specified scan mode. For example, if the scan mode every10Seconds is specified, the values are aggregated according to the method indicated by steps of 10 seconds.

opcua-ha

The points can be listed by clicking on the “points” button. A pointId corresponds to the address of the data on the OPCHDA server.

OPCUA DA (Data Access)

The OPCUA_DA connector is a lighter version of the OPCUA_HA connector because it does not manage history requests. You just have to fill in the following fields:

  • The server address with the name at the end of the address (the endpoint in the example below)
  • The username and password in case of authentication
  • Retry interval: duration between two connection attempts in case of loss
opcua-da