Rockwell Automation 1756-HIST2G Historian ME 2.1 - Manual (Page 94)

F ACTORY T ALK H ISTORIAN ME M ODULE U SER ’ S G UIDE
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
Typical Value - provides an example of a reasonable value for this point. For a
numeric tag, it must be greater than or equal to the zero, and less than or equal to
the zero plus the span.

Point Source - identifies a point as belonging to a particular interface. When you
configure an interface, you specify a point source for that interface. All the points
that belong to that interface must use that point source code as the value for the
Point Source attribute.
The default point source is FTME. Other options include T (for the Totalizer
utility subsystem in PI) and C (for the Performance Equation tags.)

Scan Rate - a period of time in seconds, which tells FactoryTalk Historian ME
how often to collect the data. Go to the Manage Points tab and Edit Scan
Class(es)
page to define scan rates for scan classes. For Trigger Input and Output
scan types, it is recommended that the scan rate be defined as two seconds or
longer.

Span Value - value for the difference between the top of the range and the bottom
of the range. It is required for all numeric data type points.

Zero Value - indicates the lowest value possible. A zero is required for all
numeric data type points.
E XCEPTION F ILTERING P OINT P ROPERTIES
The FactoryTalk Historian ME exception-reporting specification determines when to
send data to the Snapshot subsystem. The exception-reporting specification consists
of a deviation (Exception Deviation), a minimum time (Exception Min), and a
maximum time (Exception Max).
The Exception Filtering section contains the following fields:
Field Description Default Value
Exception Min Specifies the minimum time span between
exceptions, expressed as dd hh mm ss.
0 seconds
Exception Max Specifies the maximum time span between
exceptions, expressed as dd hh mm ss.
10 minutes
Exception
Deviation
Specifies in engineering units how much a
value may differ from the previous value
before it is considered to be a significant
value.
0.25 engineering
units