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Tag changes at the Edge are published each time the Qualified Value (Value, Timestamp and Quality) changes.

If you believe that you are missing tag change events in the data published by the MQTT modules, the recommended approach is:

  • Set up a History Storage Provider at the Edge
  • Configure the tag history as shown below to historize tag change events

Edge Tag History Configuration

History must be enabled on the Edge tag with these three settings required:

  • Deadband Style set to Discrete
  • Sample Mode set to On Change
  • Min Time Between Samples set to 0



Deadband Style must be set to Discrete for all tag datatypes. This ensures that a change is registered any time the value moves +/- the specified amount from the last stored value.

If left at the default Auto setting, Ignition will determine the deadband style based on the tag datatype. See this Ignition Configuring Tag History Deadband and Analog Compression for details on how the Analog and Discrete Deadband Styles differ. 



When you identify missing tag change events in the published data, you can then query the History Storage Provider to see if these values exist in the database.



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