National Instruments E Series - Manual (Page 55)

Chapter 4 Signal Connections
 National Instruments Corporation 4-19 DAQCard E Series User Manual
Single-Ended Connections for Floating Signal
Sources (RSE Configuration)
Figures 4-6 shows how to connect a floating signal source to a channel
on a DAQCard configured for RSE mode.
Single-Ended Connections for Grounded Signal
Sources (NRSE Configuration)
To measure a grounded signal source with a single-ended
configuration, you must configure your DAQCard in the NRSE input
configuration. The signal is then connected to the positive input of the
DAQCard PGIA, and the signal local ground reference is connected to
the negative input of the PGIA. The ground point of the signal should,
therefore, be connected to the AISENSE pin. Any potential difference
between the DAQCard ground and the signal ground appears as a
common-mode signal at both the positive and negative inputs of the
PGIA, and this difference is rejected by the amplifier. If the input
circuitry of a DAQCard were referenced to ground, in this situation as
in the RSE input configuration, this difference in ground potentials
would appear as an error in the measured voltage.
Figure 4-6. Single-Ended Input Connections for Nonreferenced or Floating Signals
V
s
+
+
+
-
-
-
V
m
Measured
Voltage
Floating
Signal
Source
ACH<0..15>
AIGND
Instrumentation
Amplifier
I/O Connector
AISENSE
Selected Channel in RSE Configuration
PGIA
Input Multiplexers