Chapter 4 Connecting Signals
NI 6115/6120 User Manual 4-10 ni.com
Figure 4-3. Pseudodifferential Input Connections on the NI 6120
forGro und-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 Vcm in Figures4-2 and 4-3.+
–Vm
100 pF* 1 M*
50 Ω0.1 µF
High-Frequency
Common Mode Choke
ACH0+
ACH0–
ACH0GND
PGIA
Instrumentation
Amplifier
*10 kΩ40 pf for ranges > ±10 V
Ground-
Referenced
Signal
Source
AC Coupling
Common-
Mode
Noise and
Ground
Potential
Measured
Voltage
Vs
Vcm
+
–
+
–+
–