Rockwell Automation 1756-HIST2G Historian ME 2.1 - Manual (Page 91)

5 • M ANAGING P OINTS
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
Descriptor - defines the base point attribute that can be used to provide a textual
description of a point. The Descriptor is a common attribute to display in various
client applications and user reports.

Extended Description - only used with Trigger Input or Output tags. Use this field
to specify:
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EVENT = <tag name> <condition>
where <condition> is Increment, Decrement, Nonzero, Any, or Anychange
Or
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TRIG = <tag name>
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Instrument Tag - indicates the controller from which the data is coming. If you
replace a controller with a different one that measures the same process value, it is
usually best to continue using the same point. Edit the point as required so that it
will collect the new data.
The format of the instrument tag name is:
[<controllerprojectname>_1_<controllerslotnumber>][<controllertagname>]
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Source Tag - only used with Trigger Input or Output tags. Use this field for the
trigger name.

Type - specifies the data type of the point values. Changing a point’s data type
causes the Archive subsystem to close the current archive record and start a new
one with the new type information in the header. For points collected
automatically, use the point type that most closely matches the point type in the
source system.
When defining multiple triggers, make sure that each event calls a different tag
name.