History

Control how a tag's values are recorded over time and clean up old data.

THMI keeps a history of tag values so you can analyze them over time — most visibly in trends. Enable history on a tag to record it, and control how it’s stored.

What gets recorded

By default every change is recorded. With custom preferences you can refine this:

• Deadband — the minimum difference between two consecutively logged values. A larger deadband stores fewer points and ignores small fluctuations (noise).
• Aggregate values — instead of logging raw changes, store one summarized value per interval. Choose:
  • a function — average, min, max, sum, count, first, last, median, range, or a percentile (50th, 75th, 90th, 95th); and
  • a request interval — how long each aggregated value covers (in seconds).

Recomputing history

If you change how a calculated tag works, you can recompute history to recalculate its aggregated past values. (Source tags must have history enabled for this to be possible.)

History cleanup

To keep storage in check, history cleanup removes old data: