User`s guide

24
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Signal Connections
3.2.2.2 Differential input mode
The differential input mode provides two inputs that respond to signal
voltage difference between them. If the signal source is ground-referenced,
the differential mode can be used for the common-mode noise rejection.
Figure 9 shows the connection of ground-referenced signal sources under
differential input mode.
Figure 9: Ground-referenced source and differential input
Figure 10 shows how to connect a floating signal source to the
DAQ-2213/2214 in differential input mode. For floating signal sources, add
a resistor at each channel to provide a bias return path. The resistor value
should be about 100 times the equivalent source impedance. If the source
impedance is less than 100Ω, simply connect the negative side of the
signal to AIGND as well as the negative input of the Instrumentation Am-
plifier without any resistors. In differential input mode, less noise couples
into the signal connections than in single-ended mode.
A
IxH
A
IxL
x
= 0, ..., 7
Ground
Referenced
Signal
Source
To A /D
Converter
A
IGND
+
-
Instrumentation
A
mplifier
+
-
Input Multiplexer
Figure 10: Floating source and differential input
A
IxH
A
IxL
x
= 0, ..., 7
Ground
Referenced
Signal
Source
To A /D
Converter
A
IGND
+
-
Instrumentation
A
mplifier
V
cm
Common-
mode noise &
Ground
potential
+
-
Input Multiplexer