National Instruments SCB-68A - Using Differential Connections for Ground-Referenced Signal Sources

2-14 | ni.com
Chapter 2 Analog Input and Temperature Sensor Measurements
Using Differential Connections for Ground-Referenced Signal
Sources
Figure 2-10 shows how to connect a ground-referenced signal source to the DAQ device
configured in differential mode.
Figure 2-10. 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
cm
in the figure.
AI+ and AI– must both remain within ±11 V of AI GND.
DAQ Device Configured in Differential Mode
PGIA
–
+
–
+
–
+
–
+
V
cm
V
s
Ground-
Referenced
Signal
Source
Common-
Mode
Noise and
Ground
Potential
AI GND
AI SENSE
Input Multiplexers
V
m
Measured
Voltage
Instrumentation
Amplifier
AI+
AI–
I/O Connector