Rockwell Automation 1756-HIST2G FactoryTalk Historian ME 2.2 - Manual (Page 232)

F ACTORY T ALK H ISTORIAN ME U SER ’ S G UIDE
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Typical value
Enter a reasonable value for a point. For a numeric tag, it must be greater than or
equal to the value of the Zero property, and less than or equal to the value of the
Zero property plus the value of the Span property.
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Zero
Enter the lowest value possible. This attribute is required for all numeric data type
points. It does not have to be the same as the instrument zero, but that is usually a
logical choice.
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Span
Enter the difference between the top and the bottom of the range. This attribute is
required for all numeric data type points. For float16 point types, Span is used
with Zero for scaling values in the archive. Span must be a positive value. If the
value for a point type float16 point is greater than the top of range, it is recorded
in the archive as “Over Range”. For other point types, Zero and Span do not affect
the values recorded in the archive. The span is also used when defining a