Signal Connections
Chapter 3
SCXI-1124 User Manual
3-6
© National Instruments Corporation
Figure 3-4 shows how to connect a DAC channel as a current output using an external loop
supply.
SCXI-1124
0-20 mA
ISINK
+
-
GND
SCXI-1124
0-20 mA
a. Floating supply and floating load connection
OR
load
load
+
-
V
EXT
V
EXT
SCXI-1124
GND
b. VEXT with high common-mode voltage
ISINK
c. Load with high common-mode voltage
+
V
EXT
-
load
I
V
CM
+
-
High
CMV
SCXI-1124
V
CM
+
-
High
CMV
load
+
V
EXT
-
I
I
ISINK
I
GND
0-20 mA
0-20 mA
GND
ISINK
Figure 3-4. DAC Channel Connection as Current Output, External Loop Supply
When you use an external supply, the order that the supply and load are in does not matter as
long as you do not create a second loop through which current flows. If both your supply and
load are grounded, you must connect your signals as shown in Figure 3-5a. The circuit in
Figure 3-5b does not work.
