using a differential input to measure a common ground signal source. However the reverse is not true. Figure 5-4 is a connection
diagram for a common ground / single-ended input system.
Figure 5-4. Single-Ended, Common Ground
5.3.2
Common Ground / Differential Inputs
The use of differential inputs to monitor a signal source with a common ground is a acceptable configuration though it requires more
wiring and offers fewer channels than selecting a single-ended configuration. Figure 5-5 shows the recommended connections in this
configuration.
Figure 5-5. Differential Input, Sharing Common Ground
5.3.3
Common Mode Voltage Less Than +/-10V / Single-Ended Inputs
This is not a recommended configuration. In fact, the phrase common mode has no meaning in a single-ended system and this case
would be better described as a system with offset grounds. Anyway, you are welcome to try this configuration, no system damage
should occur and depending on the overall accuracy you require, you may receive acceptable results.
5.3.4
Common Mode Voltage, Less than +/-10V / Differential Inputs
Systems with varying ground potentials should always be monitored in the differential mode. Care is required to assure that the sum of
the input signal and the ground differential (referred to as the common mode voltage) does not exceed the common mode range of the
A/D board (+/-10V on the CIO-DAS1400). Figure 5-6 shows recommended connections in this configuration
-9-
+
-
In p ut
A m p
To A /D
A /D B o a rd
I/O
C o nn e cto r
LL G N D
C H IN
S ign
a l
S
o urc e
w ith
C o
m m o n
G n d
O p tio n al w ire
since signa l sou rce
and A/D bo ard sh are
com m on g round
S ig n a l so u rc e a n d A /D bo a rd
s ha ring c o m m o n g ro u n d c o n n e cte d
to sin g le -e n d ed in p u t.
+
-
In p u t
A m p
To A /D
A /D B o a rd
I/O
C o n n e c to r
LL G N D
C H H igh
C H L ow
S ig n
a l
S
o urc e
w ith
C o
m m o
n G n
d
O p tio n al w ire
sinc e signa l so u rce
an d A /D bo ard sh a re
co m m o n g rou nd
R eq u ired co nn ection
of L L G N D to C H Lo w
S ig n a l s o u rc e a n d A /D b o a rd
s h a rin g c o m m o n g ro u n d c o n n e c te d
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