Rockwell Automation FactoryTalk Historian SE DataLink 4.2 User Guide - Manual (Page 45)

3
●
FactoryTalk Historian DataLink Functions
●
●
●
●
●
37
Filter Expression Add a filter expression to filter event values using a mathematical
expression, eliminating data for which the expression evaluates as
false. The filter expression is applied to the raw data from FactoryTalk
Historian (and not values that result from the calculation itself).
For example, the simple filter expression:
sinusoid < 70
would remove all values over 70 from the calculation. You can also
use any valid FactoryTalk Historian performance equation in the filter
expression to build more complex expressions to remove atypical
peaks in data values, for example.
Select mark as filtered to substitute
Filtered as a placeholder for
each value or block of values filtered from the array based on the
filter
expression (page 91).
Boundary Type Specify a boundary type to determine how to handle data values near
the start and end times of the value range:
 Inside (default)
Returns values at start and end times, if they exist, or the nearest
values occurring within the range.
 Outside
Returns the closest values occurring immediately outside the
range.
 Interpolated
Returns interpolated values at start and end times.
 Auto
Interpolated, but using Inside behavior for tags with step
attributes set on Windows-based FactoryTalk Historian servers.
Count of Values Normally the first row or column of the array includes the count of
values retrieved for the time range. Select hide count to hide the
count of values and show only retrieved values in the array.