National Instruments Data Acquisition Device E Series - Manual (Page 60)

Chapter 2 Analog Input
© National Instruments Corporation 2-27 E Series User Manual
Single-Ended Connections for Floating Signal Sources
(RSE Configuration)
Figure 2-11 shows how to connect a floating signal source to a channel
configured for RSE mode.
Figure 2-11. Single-Ended Connections for Floating Signal Sources
(RSE Configuration)
Single-Ended Connections for Grounded Signal Sources
(NRSE Configuration)
To measure a grounded signal source with a single-ended configuration,
you must configure your device in the NRSE input configuration. Connect
the signal to the positive input of the PGIA, and connect the signal local
ground reference to the negative input of the PGIA. The ground point of the
signal, therefore, connects to the AI SENSE pin, as shown in Figure 2-12.
Any potential difference between the device 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 device were referenced to ground, as it is in the RSE input
configuration, this difference in ground potentials would appear as an error
in the measured voltage.
Selected Channel in RSE Configuration
PGIA
Input Multiplexers
–
+
–
Floating
Signal
Source
V
s
I/O Connector
AIGND
AI SENSE
AI
+
Programmable Gain
Instrumentation
Amplifier
Measured
Voltage
V
m
–
+