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Chapter 4 Analog Input
NI 6232/6233 User Manual 4-14 ni.com
Use DIFF input connections for any channel that meets any of the following
conditions:
• The input signal is low level (less than 1 V).
• The leads connecting the signal to the device are greater than 3 m
(10 ft).
• The input signal requires a separate ground-reference point or return
signal.
• The signal leads travel through noisy environments.
DIFF signal connections reduce noise pickup and increase common-mode
noise rejection. DIFF signal connections also allow input signals to float
within the common-mode limits of the PGIA.
Differential Connections for Ground-Referenced Signal Sources
Figure 4-4 shows how to connect a ground-referenced signal source to a
channel on the device configured in DIFF mode.
Figure 4-4. Differential Connections for Ground-Referenced Signal Sources
PGIA
–
+
–
+
–
+
V
s
AI GND
V
m
AI +
–
+
V
cm
Ground-
Referenced
Signal
Source
Common-
Mode
Noise and
Ground
Potential
Input Multiplexers
AI –
Instrumentation
Amplifier
Measured
Voltage
Digital
Isolators
Isolation
Barrier
M Series Isolated Device Configured in DIFF Mode
I/O Connector