User`s manual

Signal Connections 37
ADLINK Technology Inc. PCI-9524
Copyright 2008 User’s Manual
Figure 3-7: Ground-referenced source and differential input
AI
n+
AI
n-
n = 4, ..., 7
Ground
Referenced
Signal
Source
To A / D
Converter
A
IGND
+
-
Instrumentation
A
mplifie
r
V
cm
Common-
mode noise &
Ground
potential
+
-
Input Multipexe
r
Figure 3-8 shows how to connect a floating signal source to PCI-
9524 in differential input mode. For floating signal sources, you
need to 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 100
Ω, you
can simply connect the negative side of the signal to AIGND as
well as the negative input of the Instrumentation Amplifier without
any resistors. In differential input mode, less noise couples into the
signal connections than in single-ended mode.
Figure 3-8: Floating source and differential input
AI
n+
AI
n-
n = 4, ..., 7
Ground
Referenced
Signal
Source
To A / D
Converter
A
IGND
+
-
Instrumentation
A
mplifier
+
-
Input Multipexer