© National Instruments | 4-17
M Series User Manual
Using Referenced Single-Ended (RSE) Connections for
Floating Signal Sources
Figure 4-9 shows how to connect a floating signal source to the M Series device configured for
RSE mode.
Figure 4-9. RSE Connections for Floating Signal Sources
Note (NI USB-62xx BNC Devices) To measure a floating signal source on USB
BNC devices, move the switch under the BNC connector to the FS position.
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 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.
The difference in ground potential between two instruments connected to the same building
power system is typically between 1 and 100 mV, but the difference can be much higher if power
distribution circuits are improperly connected. If a grounded signal source is incorrectly
measured, this difference can appear as measurement error. Follow the connection instructions
for grounded signal sources to eliminate this ground potential difference from the measured
signal.
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
–
+
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