Rockwell Automation 1756-HIST2G FactoryTalk Historian ME 2.2 - Manual (Page 114)

F ACTORY T ALK H ISTORIAN ME M ODULE U SER ’ S G UIDE
104
In the preceding illustration, values A, D, and C are reported to the FactoryTalk
Historian ME server. Value A is the last reported value, and values B and C fall
within the exception deadband. However, value D falls outside the deadband, so the
Data Collection service reports value D as well as the previous value (in this case,
value C).
The Data Collection service uses the point’s Exception Deviation (ExcDev),
Exception Min (ExcMin), and Exception Min (ExcMax) attributes to decide whether
to report the new value to the FactoryTalk Historian ME server:
Field Description
ExcDev Determines how much a point's value needs to change before the
Data Collection service sends it to the FactoryTalk Historian ME
server. For example, a 12 bit A/D converter can never be more
precise than 1 part in 4096.
is the
last
reported
value. A
TIME
TEMPERATURE
ExcMax
ExcDev
ExcDev
The value DD falls outside the
deadband so the Data Collection
service reports it and the previous
value to FactoryTalk Historian ME.
D