Retrieving Timeseries Data

Historian Multi provides a single client for querying multiple historians. This overview captures shared details for read and aggregation methods.

Timestamp Formats Accepted

Most read methods accept timestamps as:

• Python datetime objects
• Epoch seconds (int or float) or epoch milliseconds (int)
• Strings parsed by dateparser (e.g. "2024-01-01 00:00:00")
• Relative strings like "now" or "1 hour ago"

The library converts timestamps to epoch milliseconds before sending requests.

Methods

• getCurrentDataPoints
• getInterpolatedPoints
• getInterpolatedRange
• getRawDatapoints
• getClosestRawPoint
• getAggregates
• getAggregateIntervals

Output Format Examples

JSON (default)

Single tag responses are simplified to a list of points (or a single point). Multi-tag responses return a dictionary keyed by tag.

RAW

{
  "results": {
    "DEMO_02TI301.PV": {
      "dataPoints": [{ "timestamp": 1704067200000, "value": 38.0, "status": "OK" }]
    }
  }
}

DataFrame (df)

                     DEMO_02TI301.PV  DEMO_02TI201.PV
2024-01-01 00:00:00             38.0             42.0
2024-01-01 01:00:00             37.5             41.7

String (string)

Returns a JSON string of the results.