Rockwell Automation 1756-HIST2G Historian ME 2.1 - Manual (Page 306)

F ACTORY T ALK H ISTORIAN ME M ODULE U SER G UIDE
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ExcDev The base attribute that specifies exception deviation in
engineering units. ExcDev specifies the deadband or how
much a new value must differ from the previous value sent to
the Snapshot subsystem on the FactoryTalk Historian ME
server in order to determine whether the new value is
significant and should also be sent.
ExcMax The base attribute that specifies exception maximum time, in
seconds. ExcMax is the maximum time difference from the last
sent event before the next event will be sent. ExcMax thus
effectively limits the length of time that events can be
discarded because their values did not exceed exception
deviation.
ExcMin The base attribute that specifies exception minimum time, in
seconds. ExcMin is the minimum time difference from the last
sent event before the next event is eligible to be sent. Thus, the
send rate of events for the associated point can be at most one
event every ExcMin seconds.
Exception Deviation See ExcDev.
Exception Maximum See ExcMax.
Exception Minimum See ExcMin.
Exception Reporting
The process, executed internally by Data Collection, of
sending events to the Snapshot subsystem on the FactoryTalk
Historian ME server only when there has been a significant
change in the monitored value. Significance is determined with
a simple deadband algorithm.
Exception Specification The three base attributes that control the exception reporting
process for a particular point: ExcDev, ExcMax, and ExcMin.
Although it is technically not included in the specification,
Span affects ExcDev.
FactoryTalk Historian
ME server
The set of several software subsystems packaged together that
constitute a single logical server application capable of storing
time-series data from distributed data sources and serving this
same data to client applications in real-time.
FactoryTalk Security A set of security services are fully integrated into the
FactoryTalk Directory.
Term Definition