
reduce the overall common mode voltage, or add isolated signal conditioning between
the source and your board.
4.2.6 Isolated Grounds / Single-Ended Inputs
Single-ended inputs can be used to monitor isolated inputs, though the use of the dif-
ferential mode will increase you system’s noise immunity. The diagram below shows
the recommended connections is this configuration.
System with a Large Common Mode Voltage,
Connected to a Differential Input
+
-
L
r
g
e
c
o
m
m
o
n
m
o
d
e
v
o
l
t
a
g
e
b
e
t
w
e
e
n
s
i
g
n
a
l
s
o
u
r
c
e
&
A
/
D
b
o
a
r
d
GND
Barrier
When the voltage difference
between signal source and
A/D board ground is large
enough so the A/D board’s
common mode range is
exceeded, isolated signal
conditioning must be added.
Amp
LL GND
CH High
CH Low
10 K
10K is a recommended value. You may short LL GND to CH Low
instead, but this will reduce your system’s noise immunity.
Isolated Signal Source
Connected to a Single-Ended Input
Amp
LL GND
CH IN
+
-
s
o
l
a
t
e
d
s
i
g
n
a
l
s
o
u
r
c
e
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