Rockwell Automation FactoryTalk Historian SE 4.0 Live Data Interface User Guide - Manual (Page 28)

Chapter 5 Point Configuration
28 Rockwell Automation Publication HSELD-UM024A-EN-E–September 2013
Item Description
Compression
Minimum
(CompMin) A point is archived if the elapsed time since the previous time the
point was saved is greater than or equal to the minimum time, and
the value has changed by more than the deviation. For data points
associated with interfaces that send exception reports, set
CompMin to 0.
Compression
Maximum
(CompMax) A point is archived if the elapsed time since the previous time the
point was saved is greater than the maximum time. The
recommended maximum time specification is one work shift (for
example, 8 hours). Duplicate values will be archived if the elapsed
time exceeds CompMax. You typically set CompMax to the same
value for all points in the system.
NOTE
For information on compression testing, refer to "Exception Reporting
and Compression Testing" in the FactoryTalk Historian SE Server
Reference Guide, available in the Common Files\Rockwell\Help folder
in your Program Files directory.
For each data point, you can set the following three attributes to
configure its exception reporting specification:
Item Description
Exception Deviation
(ExcDev): Specifies in engineering units how much a point's value must
change before the interface considers it a significant value, and
sends it to the server. As a general rule, you should set the
exception slightly smaller than the precision of the instrument
system.
Exception Minimum
(ExcMin): Specifies a limit on how frequently the interface can report values
to the server. For example, if you want the interface to wait full ten
minutes before reporting a new value to the server, then you would
set the ExcMin attribute to ten minutes. ExcMin is typically set to
zero.
Exception Maximum
(ExcMax): Specifies a limit on how long the interface can go without reporting
a value to the Historian server. After the ExcMax time period, the
interface sends the next new value to the server, regardless of
whether the new value is different from the last reported value.
Exception Reporting