Chapter 4 Connecting Signals
© National Instruments Corporation 4-11 NI 6115/6120 User Manual
Connections for Nonreferenced or Floating Signal Sources

Figures 4-4 and 4-5 show how to connect a floating signal source to a

channel on the NI 6115 and NI 6120, respectively.

Figure 4-4. Differential Input Connections on the NI6115
for Nonreferenced Signals
+
ACH0 Connections Shown
PGIA
1 M*
100 pf*
10 nf
Bias
Resistor
(see text)
AC Coupling
Vm
I/O Connector
Bias
Current
Return
Paths
Floating
Signal
Source
Instrumentation
Amplifier
Measured
Voltage
ACH0GND
ACH0–
ACH0+
+
*10 kΩ40 pf for ranges > ±10 V
Vs
+
Common-Mode
Choke