Rockwell Automation FactoryTalk Historian SE DataLink 4.2 User Guide - Manual (Page 52)

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FactoryTalk Historian DataLink User Guide
44
Calculation Mode The following calculations are provided:
 Total

Minimum

Maximum
 Standard deviation
 Range

Average
 Count
 Mean
All calculation modes are time-weighted except for the Mean function,
which is an event-weighted version of the Average function.
Calculation Basis Select either a time- or event-weighted basis for the calculation:

Calculations are time-weighted by default. Each event value is
weighted for purposes of the calculation by the duration of time
over which the event applies.
 Event-weighted calculations weigh each event value equally. At
least one event (two for standard deviation calculations) must
exist within a time range for a successful calculation.
Conversion Factor The conversion factor is used for Total calculations where the time
unit of the point calculated is not the same as the server default time
unit. A conversion factor may be necessary to convert to the units
desired for the calculation from the server default of units per day.
The following table illustrates the use of conversion factors for points
using different units of flow. Note that a conversion factor of one
means that the conversion factor is not needed, and that units cannot
be specified.
Flow unit Conversion Factor needed to match server default
(units/day)
Units/day 1.0
Units/hour 24
Units/minute 1440
Units/second 86400