National Instruments Module SCXI-1125 - Manual (Page 20)

Chapter 2 Connecting Signals
© National Instruments Corporation 2-3 SCXI-1125 User Manual
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 ride
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