Variable History

Variable history shows logged values as a table. It looks at the same data as the trend graphic; the difference is that it gives you the numbers rather than the curve.

In the right-hand panel you choose the project, optionally a connection, and then the variables; give a start and end date and press Search.

The order matters: the variable list does not fill until a project is chosen, because variables belong to a project. Choosing a connection is an optional narrowing — a way to shorten a long variable list.

Four resolutions

The tabs at the top of the panel decide the resolution the values come back at:

Tab	What it returns
Raw	The logged values themselves, unsummarised
Interval	Summarised at an interval you choose
Hourly	An hourly summary
Daily	A daily summary

Narrow the range first, then switch to Raw

Raw returns every record in the range. On a variable logged once a second, a day is hundreds of thousands of rows. Finding what you are after with Hourly or Daily and then switching to Raw over that narrow range is both faster and more readable.

When a table beats a chart

A trend graphic shows the shape; this screen gives you the value. When you need the exact second and value at which an alarm fired, a figure for a shift report, or the moment a device stopped sending, the table is the more direct answer.

Related

• Trend Graphic — the same data as a chart
• Variables — the logging configuration