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Ground-
+
Referenced
V
Signal
s
–
Source
Common-Mode
Noise
+
V
cm
–
Front I/O
Connector
© National Instruments Corporation
1
ACH 0
2
ACH 1
3
ACH 2
8
ACH 7
9
AISENSE/AIGND
11
AGND
DAQCard-1200 in NRSE Input Configuration
Figure 3-6. Single-Ended Input Connections for Grounded Signal Sources
Common-Mode Signal Rejection Considerations
Figures 3-4 and 3-6 show connections for signal sources that are already
referenced to some ground point with respect to the DAQCard-1200.
In these cases, the instrumentation amplifier can reject any voltage caused
by ground-potential differences between the signal source and the
DAQCard-1200. In addition, with differential input mode connections, the
instrumentation amplifier can reject common-mode noise pickup in the
leads connecting the signal sources to the DAQCard-1200.
The common-mode input range of the DAQCard-1200 instrumentation
amplifier is the magnitude of the greatest common-mode signal that can be
rejected.
The common-mode input range for the DAQCard-1200 depends on the size
of the differential input signal (V
instrumentation amplifier. In unipolar mode, the differential input range is
0 to 10 V. In bipolar mode, the differential input range is from –5 to +5 V.
V
should remain within a range of –6 to +6 V in bipolar mode and
in–
+
–
= V
– V
diff
in+
3-13
Chapter 3
Connecting the Signals
+
Measured
V
m
Voltage
–
) and the gain setting of the
in–
DAQCard-1200 User Manual
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