5-54 Field Control™ Genius® Bus Interface Unit User’s Manual – October 1999 GFK-0825F
5
Input Scaling
The 8-Point Grouped Analog Voltage Input Module performs its own scaling (unlike conventional
Field Control analog modules, whose scaling is performed by the BIU).
Scaling can be used to define a linear relationship between a channel's input voltage in millivolts
(mV) and the value in engin eering units returned to th e BIU. Th e default scaling config ur ation
provides values from -10,000 to 10,000 for an input voltage range of -10V (low span value) to 10V
(high span value).
To scale a channel, choose a high and low point and enter the actual input value (span) and a
corresponding engin eer ing units value for each. D urin g operation, the module wil l use these values
to convert input voltages into digital values that represent engineering units. Scaling does not
increase the resolution of the data, but it does transform the values returned to the BIU into more
convenient units.
If the scaled data falls below the minimum for engineering units, the module returns the minimum
engineering units value (-32767). If the scaled data rises above the maximum for engineering units,
the module returns the maximum engineering units value (32767).
The illustration below shows the module's default scaling.
The first scaling screen shows the engineering units value that is considered equivalent to the low
span (actual) value. Engineering units may be from -32767 to 32767.
S:2 CH1 ENG LO
-1 0000
< > chg entr
-15000
-10000
-5000
0
5000
10000
15000
-15000 -10000 -5000 0 5000 10000 150 00
In
p
ut Volta
g
e in millivol ts
Hi
g
h Point
Low Po in t
10250
-10250