Chapter 2
Connecting Signals
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National Instruments Corporation
2-3
Floating Signal
In cases where both signal lines at the transducer end are floating and no
common-mode voltage exists, establish an earth connection at the
SCXI-1125 by connecting the negative input line to chassis ground in the
terminal block, as shown in Figure 2-2. This eliminates noise that can be on
the floating signal. If the floating signal is not configured like Figure 2-2,
the noise can couple to the chassis ground through the amplifier and exhibit
a differential mode signal that can be amplified by the amplifier.
Connecting the signal to chassis ground breaks the isolation barrier.
Figure 2-2.
Connecting a Floating Signal
Module
+
–
+
+
–
I
V
out
V
s
