Chapter 3
Signal Connections
©
National Instruments Corporation
3-7
The input signal range of an SCXI-1120 input channel is ±5 V/ G
total
referenced to its negative input, where G
total
is equal to the product of the
first-stage and second-stage gains. In addition, the input channels are
overvoltage protected to 250 V
rms
with power on or off at a maximum of
4.5 mA
rms
sink or source.
♦
SCXI-1120D
When connecting AC-coupled signals to the SCXI-1120D, you do not need
to add the external resistor, as the SCXI-1120D provides a DC path
internally. Refer to Figures 3-6 and 3-7 for further details.
Figure 3-6.
AC-Coupled Signal Connection for the SCXI-1120D with
High Common Mode Voltage
Figure 3-7.
Floating AC-Coupled Signal Connection for the SCXI-1120D
Temperature Sensor Connection
Pins C2 and C4 are dedicated for connecting to a terminal block
temperature sensor. The temperature sensor is not isolated and is
referenced to the chassis ground. The connection is overvoltage protected
to ±25 VDC with power on and ±15 VDC with power off.
Module
+
-
+
+
-
I
out
V
s
V
+
-
cm
V
High
CMV
511 k
Ω
511 k
Ω
+
-
+
+
-
I
out
V
s
V
511 k
Ω
511 k
Ω
