National Instruments NI USB-621x - Connecting Ground-Referenced Signal Sources

Chapter 5 Connecting AI Signals on the USB-6210/6211 Devices
© National Instruments Corporation 5-9 NI USB-621x User Manual
connection is shared with all channels rather than being cabled in a twisted
pair with the AI+ signal.
Using the DAQ Assistant, you can configure the channels for RSE or NRSE
input modes. Refer to the Configuring AI Ground-Reference Settings in
Software section of Chapter 4, Analog Input, for more information about
the DAQ Assistant.
Using Referenced Single-Ended (RSE) Connections for Floating Signal
Sources
Figure 5-6 shows how to connect a floating signal source to the NI 621x
device configured for RSE mode.
Figure 5-6. RSE Connections for Floating Signal Sources
Using the DAQ Assistant, you can configure the channels for RSE or NRSE
input modes. Refer to the Configuring AI Ground-Reference Settings in
Software section of Chapter 4, Analog Input, for more information about
the DAQ Assistant.
Connecting Ground-Referenced Signal Sources
What Are Ground-Referenced Signal Sources?
A ground-referenced signal source is a signal source connected to the
building system ground. It is already connected to a common ground point
with respect to the device, assuming that the computer is plugged into the
same power system as the source. Non-isolated outputs of instruments and
devices that plug into the building power system fall into this category.
Selected Channel in RSE Configuration
PGIA
Input Multiplexers
–
+
–
Floating
Signal
Source
V
s
I/O Connector
AI GND
AI SENSE
AI <0..
n >
+
Programmable Gain
Instrumentation
Amplifier
Measured
Voltage
V
m
–
+