Rockwell Automation 1771-IFE , D17716.5.90 USER MNL. ANALOG INPUT Module User Manual
Page 35
Module Configuration
Chapter 4
4-6
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 polar 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 or 12-bit binary. 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:
1.
Inserting minimum and maximum scaled values in the appropriate
configuration words
2.
If any of the minimum or maximum values are negative, set the
appropriate sign bits in the minimum or maximum sign bit word
3.
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