Machine data

The most common sources of machine data are programmable logic controllers (PLCs), OPC UA servers, and historians. There are corresponding modules available for the most common systems. In addition, MQTT modules can be useful in some cases.

Working with PLCs

When getting data from PLCs, there's typically no metadata available, only the raw bytes or words. To make this data useful, we must add relevant information to allow the input modules to provide useful data. This is done by defining tags. Examples include specifying the address, data type, and name. This can be done in the module settings, or by providing a list of tags as a resource file referenced from the module. Each module can read any number of tags from the same PLC, but since data is pulled from the PLCs, these modules must be initiated each time you want to read data (for example, by using an Interval module).

OPC UA servers

The OPC UA server provides structured data with corresponding metadata. Tags are referenced by specifying node IDs, either in the module settings or through a resource file. With OPC UA, you have the option to trigger reads using either of the following methods:

• From the flow with the OPC UA Reader module or

• Allowing the OPC UA server to push data to your flow using the OPC UA Subscriber module.

Each time you trigger the Reader module, it retrieves all configured tags in a single message. With the Subscriber module, you will get individual messages for each tag when the value changes, but not more often than the configured publishing interval. You can also subscribe to events from the OPC UA server with the OPC UA Events module.

Note: The available machine connectors are found in the Sources/Industrial category.