Rockwell Automation 1771-IFF/A,D17716.5.116 FAST ANALOG INPUT MODULE - Manual (Page 56)

6-6
Publication 1771Ć6.5.116 - June 1996
Your module can perform linear conversion of unscaled data to
engineering units, (for example; gallons/minute, degrees C, degrees
F and pounds/square inch). Unscaled data in the module has a range
of 0 through 4095 for the unipolar ranges (0 to 5V dc/0 to 20mA and
1 to 5V dc/4 to 20mA); and -4095 to +4095 (8190) for the bipolar
ranges (+5V/+20mA and +10V). BTW words 6 through 37 are the
scaling words for channels 1 through 16. Channel 1 minimum
scaling values are set in word 6, and maximum scaling values are set
in word 7. Channel 2 minimum scaling values are set in word 8, and
maximum scaling values are set in word 9, and so on for the other
channels.
The format of this data is 4-digit BCD. The resolution at the module
of scaled values is the same as for unscaled data: one part in 4095 for
0 to 5V dc/0 to 20mA and 1 to 5V dc/4 to 20mA ranges; and one part
in 8190 for the +5V/+20mA and +10V ranges. Resolution at the
processor, however, is determined by the scaled ranges (i.e., if 0 =
minimum and 500 = maximum, resolution is now 1 part in 500).
Each input channel can be scaled independently of the other
channels.
Note: To achieve the 0 to +10V range you must use bipolar scaling.
Select the +10V range and scale for + the actual intended range. If
you need 0 to 100 gpm, set scaling values at -100 and +100. You will
effectively be creating a 0 to 10V range that is scaled from 0 to 100.
Implementing the Scaling Feature
You implement the scaling feature by:inserting minimum and
maximum scaled values in the appropriate configuration words using
BCD format.
C. If any of the minimum or maximum values are negative, set
the appropriate sign bits in the minimum or maximum sign
bit word
D. If a single channel is scaled, all channels must be scaled, and
all 37 configuration words must be written to the module.
Scaling Ranges
The maximum range of the scaling values is +9999 BCD. These
values must be entered in BCD.
Typically, invalid values are “minimum greater than maximum,” or
“minimum equal to maximum.” If invalid values are entered into
the scaling words, the corresponding input in the BTR data will
be zero and the invalid scaling bit will be set.
Scaling