Creating an OPC-UA Tag

After creating a tag on an OPC-UA device, you need to tell Koios which node in the OPC-UA server this tag represents. You can configure these fields during creation or afterwards on the tag's Configuration tab.

Protocol Fields

Namespace

The namespace index that identifies which part of the server's address space the node belongs to.

• Namespace 0 is the standard OPC-UA namespace (built-in server nodes)
• Namespace 1 is typically the server's own application namespace
• Higher namespaces are used by add-ons or companion specifications

The browser fills this in automatically. If entering manually, use the numeric namespace index (e.g. 2).

Identifier

The node's identifier within its namespace. This is the specific address of the data point you want to read or write.

• The format depends on the Identifier Type — it could be a number, a string path, a GUID, or a byte string
• Example (numeric): 1001
• Example (string): Boiler.Temperature.PV

Identifier Type

The format of the node's identifier.

• Default: Numeric

Data Type

The expected data type of the node's value. Koios uses this to correctly interpret the raw bytes returned by the server.

Using the Node Browser

The OPC-UA node browser connects to the server in real time and lets you navigate the address space visually.

1. Open the tag's Configuration tab and click Browse
2. The browser displays the server's node tree as expandable folders
3. Navigate to the node you want and select it
4. The Namespace, Identifier, Identifier Type, and Data Type are all populated automatically
5. Click Apply to save the selection

After Configuration

1. Save the tag configuration
2. Test the tag — click

   Test

   to verify Koios can read a value from this node (see Testing a Tag)
3. Enable the tag — flip the enable switch to start collecting data