National Instruments DAQCard-1200 - Manual (Page 35)

Chapter 3 Signal Connections
© National Instruments Corporation 3-13 DAQCard-1200 User Manual
Figure 3-6. Single-Ended Input Connections for Grounded Signal Sources
Common-Mode Signal Rejection Considerations
Figures 3-3 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 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
diff
= V
in+
– V
in–
) and the gain setting of the
instrumentation amplifier. In unipolar mode, the differential input range is
0 to 10 V. In bipolar mode, the differential input range is –5 to +5 V.
V
in–
should remain within a range of –6 to 6 V in bipolar mode and –6 to
ACH 0
Vm
Measured
Voltage
AGND
AISENSE/AIGND
Vs
Vcm
–
–
+
+
–
+
–
+
Front I/O Connector DAQCard-1200 in NRSE Input Configuration
1
2
3
8
9
11
ACH 1
ACH 2
ACH 7
Common-Mode
Noise
Ground-
Referenced
Signal
Source