National Instruments SCB-68 - Manual (Page 34)

Chapter 3 Connecting Signals
SCB-68 Shielded Connector Block User Manual 3-6 ni.com
Differential Connections for Ground-Referenced
Signal Sources
Figure 3-2 shows how to connect a ground-referenced signal source to a
channel on the DAQ device configured in DIFF input mode.
Figure 3-2. 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 DAQ device ground, shown as V
cm
in
Figure 3-2.
–
+
–
+
V
cm
V
s
Ground-
Referenced
Signal
Source
Common-
Mode
Noise and
Ground
Potential
I/O Connector
AIGND
PGIA
–
+
–
+
Instrumentation
Amplifier
Measured
Voltage
V
m
ACH+ or ACH< i>
ACH– or ACH< i+8>
AISENSE*
Measurement Device Configured in DIFF Input Mode
*AISENSE is not present on all devices.