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5-96 Field Control™ Genius® Bus Interface Unit User’s Manual
–
October 1999 GFK-0825F
5
Scaling Range
Scaling can be used to define a constant-slope mapping from the value in engineering units sent by
the BIU to a channel's output current. The default scaling configuration (selection 1 on this screen)
provides an output current range of 4mA (low span value) to 20mA (high span value) for
engineering units (AI) values of 4,000 to 20,000.
On this screen, specify the default range used for scaling analog output data. There are three
predetermined range and data scaling combinations (selections 1, 2 and 3).
S:1 CH1 DEF RNG
1
< > tgl entr
The default is 1. Selections 1 or 2 have low span (output current) values which are greater than
3.5mA and therefore enable an "Open Wire" diagnostic bit which is set whenever the output falls
below approximately 2mA. "NONE" is used for display purposes only and cannot be selected if
range 1, 2 or 3 is being used (see next section). If you want to enter different scaling parameters
than those used for selections 1, 2, or 3, change the span and engineering units values from the
scaling screens.
Selection
Data Range = Output current (
µ
A)
1 4000 to 20000 = 4000 to 20000
2 0 to 32000 = 4000 to 20000
3 0 to 32000 = 0 to 20000
none User-configured scaling
The illustration below shows scaling for the default range selections.
Commanded Value in En
g
ineerin
g
Units
Low Point
46771
High Point
Output Current in MicroAmps
Maximum Output (~20.48mA)
20000
10000
4000
0
4000 2000010000