Rockwell Automation FactoryTalk Historian SE DataLink 4.2 User Guide - Manual (Page 54)

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FactoryTalk Historian DataLink User Guide
46
Minimum Percent
Good Specify the minimum percentage of good data (page 25) required in
each time range to calculate and return a value. Insufficient good
data is substituted as a placeholder when a value is not returned.
Timestamps Select show start time to display the Start time of each interval
used to calculate a value. Start times are added in a column to the
left or a row above calculated values.
Select show end time to display the End time of each interval used
to calculate a value. End times are added in a column to the left or a
row above calculated values.
For Maximum, Minimum and Range calculations, select show
min/max time to display time stamps corresponding to minima
and/or maxima over each interval used to calculate a value:
 For Minimum and Maximum calculations, the time stamp of the
corresponding value is displayed.
 For Range functions, both time stamps are displayed.
Percent Good Select show percent good to display the percentage of time for
which good values are returned over the total time range of the array.
Percent good values are typically added in a column to the right or a
row below retrieved values.
Good values are event values determined to be valid by the
FactoryTalk Historian server, and not in an error state. The
percentage of good values helps in assessing the reliability of
calculations built on FactoryTalk Historian point values, particularly if
calculated values are to be used in further calculations.
Special Notes You can use a FactoryTalk Historian Expression (page 91) instead of a
tag name for this function.
Reference a range of tag names to display sampled values for each.
Note that by default, values are displayed in rows for a column of
referenced tags, and in columns for a row of referenced tags.
For Maximum or Minimum calculations with specified intervals, time
stamps indicate the start time of each calculation interval.
Time stamps cannot be displayed for Total, Standard Deviation,
Average, Count or Mean calculations when the interval is unspecified.
The PIAdvCalcVal() function is used to retrieve a single value if you
do not specify an interval; otherwise the PIAdvCalcDat() function is
used to retrieve multiple interval values. Function names including
'Exp' and 'Fil' are used for calculations that include PI Expressions and
Filter Expressions, respectively.