Using Differential Connections For Ground-Referenced Signal Sources - National Instruments NI USB-621x User Manual

Chapter 5 Connecting AI Signals on the USB-6210/6211 Devices

Using Differential Connections for Ground-Referenced Signal Sources

NI USB-621x User Manual
Figure 5-7 shows how to connect a ground-referenced signal source to the
USB-6210/6211 device configured in DIFF mode.
Ground-
+
Referenced
V
Signal
s
–
Source
Common-
+
Mode
V
cm
Noise and
–
Ground
Potential
I/O Connector
Figure 5-7. Differential Connections for Ground-Referenced Signal Sources
With this type of connection, the NI-PGIA rejects both the common-mode
noise in the signal and the ground potential difference between the signal
source and the device ground, shown as V
AI+ and AI– must both remain within ±11 V of AI GND.
AI +
AI –
Input Multiplexers
AI SENSE
AI GND
M Series Device Configured in DIFF Mode
cm
5-12
Instrumentation
Amplifier
+
+
PGIA
Measured
–
V
m
Voltage
–
in the figure.
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