Install

Start by downloading the “OPC UA” package available in the Apps Manager.

Once the package has finished installing, the “OPCUA - Read” node will be available in your Data Flow Manager. Drag and drop the node into your flow.

Creating a Connection

Double click the node to open it.

• Connection: Used to create a connection configuration to the OPCUA server.
• Name: Changes the name of the node as shown in the Data Flows Manager. Has no effect on the query nor the connection.

To connect the node to the server, make sure that “Add new OPCUA-Connector…” is selected in the Connection field, and click the pencil icon next to it to start creating a new OPCUA Connection configuration.

• Endpoint: The IP address or URL of the server being pulled from.
• Name: Determines the name of the configuration. Does not affect the connection.

• SecurityPolicy: Determines the form of encryption used.
• SecurityMode: Choose the security mode.
• Use Login: Allows a connection to the server using a username and password.

• Initial Delay: Sets a delay before a connection is made.
• Requested Timeout: Determines how many seconds the node will wait for a response before timing out.

Once the fields have been filled, the configuration should be all set. Click “Update” to add the node configuration and then “Deploy” at the top-right of the window to save your changes. If the connection has been created, the node should have a green status symbol and say “online”.

Selecting Tags

The next tab of the OPCUA node is Tags Selection.

This is where tags from the server are selected. The top list shows tags that are currently selected for extraction, while the bottom list can be used to search for tags that need to be added to the extraction list.

There are multiple methods to add tags to the extraction list. Near the bottom left of the extraction list, there is an “Add a tag” button. This will create a new, blank entry in the extraction list. The full tag path needs to be entered in the “Node Id” field, and the “Name” field determines what the name of the tag will be when extracted to the IOT server. Make sure that the “Name” field is unique for each tag entry or else tags will overwrite each other.

The ”import” and “export” buttons at the top of the extraction list can also be used to set tags to be extracted. The “export” button will download a Tab Separated file to your machine of the tags that are currently set to be extracted, and the “import” button accepts a Tab Separated file and sets it to be the extraction list. Keep in mind that the “import” button will overwrite the current extraction list, so it is important to export the current list first before importing a new one.

The “Tag discovery” section on the bottom can also be used for adding tags to the extraction list. By clicking the magnifying glass icon, it will show available scopes that may contain tags. Clicking the magnifying glass again with a scope selected will search further for sub-scopes. Once you have reached the scope where tags are, click the “discover” button to reveal selectable tags. “Recursive discover” can be selected to search through every sub-scope for additional tags.

Once a required tag is found in the discovery panel, a name can be entered for it, and it can then be brought up into the extraction list using the arrow button next to it.

When every required tag has been added to the extraction list, click “Done” and deploy the changes to save the list.

Subscribe mode

OPC UA Subscribe mode is managed using the node dedicated to this method:

The subscribe mode is a method to read data from a server which differ from the read. Read method is triggered manually (or automatically with a trigger node) and gives us data when asked. Subscribe mode gives us data when data is published by the system (a PLC, a sensor, ...)

However we can configure how we would like to be notified when data is published, we can manage advanced settings to specify how we want to sample data or publish it on our node. Here are a list of the advanced settings we have in this node:

Example:

Publish interval= 5000: A message is published out of the node every 5 seconds
Sampling interval= 2000: A maximum of one value every 2 seconds is sampled for tags
Queue size= 3: Only 3 values are kept in buffer and pushed out of the node
Discard oldest= true: Oldest values are deleted, the newests are published

here is how the data is extracted with this strategy VS how it was generated by the sensor