Rockwell Automation FactoryTalk Historian SE 3.0 UniInt Interface User Guide - Manual (Page 25)

UniInt Interface User Manual 19
CompDev, CompMin, CompMax, CompDevPercent
These are the compression specifications. CompDev is the compression deviation; CompMin
is the compression minimum time; and CompMax is the compression maximum time.
CompDevPercent and CompDev are related by:
CompDev = CompDevPercent * Span / 100
where Span is defined by the Span Historian point attribute.
The ―swinging door compression‖ algorithm is used to filter the data. The algorithm is
described in the Historian Server Reference Guide manual.
Scan
By default, the Scan attribute has a value of 1, which means that scanning is turned on for the
point. Setting the scan attribute to 0 turns scanning off. If the scan attribute is 0 when the
interface starts, a message is written to the pipc.log and the tag is not loaded by the interface.
There is one exception to the previous statement.
If any Historian Point is removed from the interface while the interface is running (including
setting the scan attribute to 0), SCAN OFF will be written to the Historian Point regardless
of the value of the Scan attribute. Two examples of actions that would remove a Historian
Point from an interface are to change the point source or set the scan attribute to 0. If an
interface specific attribute is changed that causes the tag to be rejected by the interface,
SCAN OFF will be written to the Historian point.
Location4
For interfaces that support scan-based collection of data, Location4 defines the scan class for
the Historian point. The scan class determines the frequency at which input points are
scanned for new values. For more information, see the description of the /f parameter in the
Interface Startup Parameters section beginning page 3.
Zero and Span Attributes
Zero and Span attributes are required for Historian point types of Int16 and Float16 because
the values of Zero and Span attributes affect the data representation in the Archive for these
point types. Zero and Span attributes for other point types may have an affect on the data
collection especially if the compression and exception specifications are specified using the
percentage point attributes. For more information, see Historian Server Reference Guide.
TypicalValue
Although the TypicalValue is only used to document a reasonable value for the Historian
point, it must be specified if its default value will not fall between the Zero and Zero+Span.
Otherwise, creation of the Historian Point will fail. For a numeric tag, it must be greater than