Chapter 2 Hardware Overview ofthe NI PXI-7831R
© National Instruments Corporation 2-9 NI PXI-7831R User Manual
Figure 2-5. Differential Input Connections for Ground-Referenced Signals
With this connection type, the instrumentation amplifier rejects both the
common-mode noise in the signal and the ground potential difference
between the signal source and the NI PXI-7831R ground, shown as Vcm
in Figure 2-5. In addition, the instrumentation amplifier can reject
common-mode noise pickup in the leads connecting the signal sources to
the device. The instrumentation amplifier can reject common-mode signals
as long as V+in and V–in (input signals) are both within their specified input
ranges. Refer to Appendix A, Specifications, for more information about
input ranges.
Differential Connections for Nonreferenced or Floating Signal Sources
Figure2 -6 shows how to connect a floating signal source to a channel on
the NI PXI-7831R configured in DIFF input mode.
DIFF Input Mode Selected
–
+
–
+
–
+
–
+
Vcm
Vs
Ground-
Referenced
Signal
Source
Common-
Mode
Noise and
Ground
Potential
I/O Connector
AISENSE
AIGND
VmMeasured
Voltage
Instrumentation
Amplifier
x8 Channels
AI+
AI–