Rockwell Automation 1756-HIST2G FactoryTalk Historian ME 2.2 - Manual (Page 94)

F ACTORY T ALK H ISTORIAN ME M ODULE U SER ’ S G UIDE
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Trigger Input - triggered input tags are used to collect a data point after a
particular triggering event has occurred. For trigger input tags,
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Output - triggered output tags are used to output (write-back) a data point to a
controller after a particular triggering event has occurred.
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High Speed - high speed tags are scanned and the data event (with value and
timestamp) is logged at the specified scan time interval.
In general, high speed tags are intended for fast Data Collection speeds with
scan rates of 10 ms. The Data Collection interface will not put the point on
scan if it is configured at a rate slower than 0.5 seconds.
The module will not allow high speed tags to be created with a scan rate
slower than 500ms, or advised or polled tags to be created with a scan rate
faster than 500ms.
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Scan On - identifies active tags. Points with this flag set to ON and with a point
source attribute set to FTME are considered active tags. Points with this flag set to
OFF will not update.
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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.
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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.)
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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.
See “Trigger Point Configuration Examples” for a Trigger Input tag configuration
sample.
See “Trigger Point Configuration Examples” for an Output tag configuration
sample.