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5-46 Field Control™ Genius® Bus Interface Unit User’s Manual
–
October 1999 GFK-0825F
5
Input Scaling
The following screens can be used to set up custom scaling values. The 16-Point Grouped Analog
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 current in microAmps
(µA) and the value in engineering units returned to the BIU. The default scaling configuration
provides values from 4,000 to 20,000 for an input current range of 4mA (low span value) to 20mA
(high span value).
To scale a channel, choose a high and low point and enter the actual input value (span) and a
corresponding engineering units value for each. During operation, the module will use these values
to convert input currents 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. The “Open Wire” diagnostic bit is enabled if actual input current value used for
the “Low Point” is greater than 2 milliamps.
If the scaled data falls below the minimum for engineering units, the module returns the minimum
engineering units value (-32768). 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.
24000
20000
16000
12000
8000
4000
4000 20000 24000
Input Current in MicroAmps (Span)
Low Point
25000
25000
High Point
Overrange
0
Engineering Units
The first scaling screen shows the engineering units value that is considered equivalent to the low
span (actual) value. Engineering units may be from -32768 to 32767.
S:4 CH1 EU L
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