Rockwell Automation 1791-XXXX ANALOG BLOCK I/O - Manual (Page 17)

Introducing Block I/O
Chapter 1
1-10
You can choose one of three scaling methods:
binary counts
default scaling
user scaling
User scaling is not available when you select discrete transfer mode.
The following table shows the output signals produced by various module
data values entered in each of the three scaling methods. In the user scaling
column, S
max
was set to 5000 and S
min
was set to 0000.
Module Data
Output Signal
Binary Counts
Scaling
Default
Scaling
User
Scaling
Approx. +10.25V 8395 10250 5062
+10V 8191 10000 5000 (Smax)
0.000V 0000 00000 2500
-10.00V -8192 -10000 0000 (Smin)
Approx. -10.25V -8396 -10250 -0062
Current Outputs - 1791ĆN4C2 and 1791ĆNDC
A simplified schematic of a 0 to 20mA output channel is shown below.
2
Opto
Isolation
DAC Digital
Output
I
OUTS
I
OUT
I
RET
2
Note: Schematic does not show overvoltage protection circuits.
High Side
Current
Monitor
-15V
+15V
12505-I
Isolated Analog
Output Common
Isolated Analog
Output Common
The 0 to 20mA output provides 13 bits of resolution and is capable of
driving loads as large as 1k ohm.