Integral retrieval - wwExpression query example

In this example, the integral of a tag named Speed (measured in m/s), is computed over two 1-minute long intervals (wwResolution = 60000 milliseconds) to measure the distance traveled in meters over the interval.

SELECT StartDateTime, DateTime, TagName, Value, Quality, QualityDetail as QD, wwUnit

FROM History

WHERE TagName = 'Speed'

AND DateTime >= '2020-12-03 10:00'

AND DateTime < '2020-12-03 10:02'

AND wwRetrievalMode = 'Integral'

AND wwResolution = 60000

The results are:

To display the results using a different unit of measure, you can use the wwExpression query parameter with the following syntax:

wwExpression = 'UOM(TagName, target unit)'

For example, the integral of the Speed tag is computed again over two 1-minute long intervals, but this time the value is converted to the distance in centimeters.

SELECT StartDateTime, DateTime, TagName, Value, Quality, QualityDetail as QD, wwUnit

FROM History

WHERE TagName = 'Speed'

AND DateTime >= '2020-12-03 10:00'

AND DateTime < '2020-12-03 10:02'

AND wwRetrievalMode = 'Integral'

AND wwResolution = 60000

AND wwExpression = 'UOM([Speed],cm)'

The results are:

Note: Engineering unit conversion requires the advanced feature license. If your Historian does not have the advanced feature license activated, the results are returned in the original units.