Rockwell Automation 1746-NI8 SLC 500 Analog Input Modules User Manual - Manual (Page 48)

5–7 Channel Configuration, Data, and Status
Publication 1746Ć6.8 - April 1997
Voltage/Current Range Resolution
per LSB
Number of
Significant Bits
Decimal
Representation
0 to 20 mA 0 to 16,384 14 bits
4 to 20 mA 3,277 to 16,384 13.67 bits 1.22070 uA
-20 mA to +20 mA -16,384 to +16,384 15 bits
0 to 1 mA 0 to 1000 10 bits
1 uA
➀
➀
This data format is not supported by the 1746ĆNI4 module, but is available for the 1746ĆNI8 module.
User defined scaling count (Class 3 operation only) allows the
output image data words 8 and 9 (or words 10 and 11) to be selected
to represent low scale and high scale limits. The module uses these
limits and scales proportionately between them. For example, if
words 8 and 9 are selected to represent low and high scaling ranges
(data format select bits = 100 binary), and word 8 contains 0000 hex
(0 decimal), and word 9 contains 4E20 hex (20000 decimal), this
would represent the range of values that the voltage or current
readings would be scaled into. The lowest voltage or current reading
would be scaled to 0, and the highest voltage or current reading
would be scaled to 20000, with other readings scaled proportionately
between them.
If the module is in Class 1 mode and you attempt to configure for
user defined proportional counting, a configuration error will be
generated.
Using ScaledĆforĆPID and Proportional Counts
The scaled-for-PID and proportional count selections provide the
highest display resolution, but also require you to manually convert
the channel data to “real” units.