_historian

Messages for our historian feature

  2 minute read  

Topic structure

flowchart LR topicStart["umh.v1..."] --> _historian _historian --> |Optional| tagName _historian --> |Optional| tagGroup tagGroup --> tagName classDef mqtt fill:#00dd00,stroke:#333,stroke-width:4px; class umh,v1,enterprise,_historian mqtt; classDef optional fill:#77aa77,stroke:#333,stroke-width:4px; class site,area,productionLine,workCell,originID,tagGroup,tagName optional; tagGroup -.-> |1-N| tagGroup click topicStart href "../"

Message structure

Our _historian messages are JSON containing a unix timestamp as milliseconds (timestamp_ms) and one or more key value pairs. Each key value pair will be inserted at the given timestamp into the database.

Show JSON Schema

Examples:

{
    "timestamp_ms": 1702286893,
    "temperature_c": 154.1
}

{
    "timestamp_ms": 1702286893,
    "temperature_c": 154.1,
    "pressure_bar": 5,
    "notes": "sensor 1 is faulty"
}

If you use a boolean value, it will be interpreted as a number.

Tag grouping

Sometimes it makes sense to further group data together. In the following example we have a CNC cutter, emitting data about it’s head position. If we want to group this for easier access in Grafana, we could use two types of grouping.

  1. Using Tags / Tag Groups in the Topic: This will result in 3 new database entries, grouped by head & pos.

    Topic: umh/v1/cuttingincorperated/cologne/cnc-cutter/_historian/head/pos

    {
 "timestamp_ms": 1670001234567,
  "x": 12.5,
  "y": 7.3,
  "z": 3.2
}

    This method allows very easy monitoring of the data in tools like our Management Console or MQTT Explorer, as each new / will be displayed as a Tree.

What’s next?

Find out how the data is stored and can be retrieved from our database.

Last modified January 22, 2024: Update version (074cc23)