National Instruments NI 6120 - Manual (Page 48)

Chapter 4 Connecting Signals
NI 6115/6120 User Manual 4-10 ni.com
Figure 4-3. Pseudodifferential Input Connections on the NI 6120
for Ground-Referenced Signals
With this type of connection, the PGIA rejects both the common-mode
noise in the signal and the ground potential difference between the signal
source and the device ground, shown as V
cm
in Figures 4-2 and 4-3.
+
–
V
m
100 pF* 1 M*
50 Ω 0.1 µF
High-Frequency
Common Mode Choke
ACH0+
ACH0–
ACH0GND
PGIA
Instrumentation
Amplifier
*10 k Ω 40 pf for ranges > ±10 V
Ground-
Referenced
Signal
Source
AC Coupling
Common-
Mode
Noise and
Ground
Potential
Measured
Voltage
V
s
V
cm
+
–
+
–
+
–