Chapter 3
Signal Connections
© National Instruments Corporation
3-7
SCXI-1124 User Manual
uncontrolled
loop
current
+
-
load
SCXI-1124
V
EXT
0-20 mA
+
-
load
I
I
ISINK
GND
ISINK
GND
SCXI-1124
DOES NOT
WORK
a. Correct
b. Incorrect
V
EXT
Figure 3-5. Current Loop Connection, Load and External Supply Both Grounded
Chassis Ground Connections
The front signal connector also has a chassis ground pin. If you have any floating channels
(channels that are not already referenced to ground from your signal connections) that you want
to reference to earth ground, connect the isolated ground of the channel to the chassis ground pin.
Do not use this pin as a safety earth ground because the ground trace cannot handle the
potentially large currents that result when the channel is shorted to high voltage. Use the strain
relief tab on the terminal block for the safety earth ground.
Rear Signal Connector
Note: If you are using the SCXI-1124 with a National Instruments DAQ board and cable
assembly, you do not need to read the remainder of this chapter. If you are also using
the SCXI-1180 feedthrough panel, the SCXI-1343 rear screw terminal adapter, or the
SCXI-1351 one-slot cable extender with the SCXI-1124, read this section.
Figure 3-6 shows the SCXI-1124 rear signal connector pin assignments.