Measurement Computing CIO-DAS16 - Manual (Page 19)

3.3.3 Common Mode Voltage < +/-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.
Figure 3-6. Common Mode Voltage < +/-10V/Single-Ended Inputs
3.3.4 Common Mode Voltage < +/-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-DAS16/F). Figure 3-7 shows recommended connections in
this configuration.
Figure 3-7. Common Mode Voltage < +/-10V/Differential Inputs
15
+
-
In p ut
A m p
To A /D
A /D B o a rd I/O
C o n n ec to r
L L G N D
C H H ig h
C H L o w
S ig n
al S o
u rce
w i
th C o
m m o
n
M o d
e Vo
ltage
S ig n a l s o u rc e a n d A /D b o a rd
w ith c o m m o n m o d e v o lta g e
c o n n e c te d to a d iffe re n tia l in p u t.
G N D
T he vo ltag e d ifferen tia l
b etw ee n the s e groun d s,
a dde d to the m a x im u m
in p ut s ig na l m ust s ta y
w ithin +/-10 V
S ys tem w ith a Large C om m on M ode Voltage ,
C onne cte d to a S ingle-E nded Input
I/O
C o n n e c to r
+
-
In p u t
A m p
To A /D
LL G N D
C H IN
A /D B o a rd
L arge com
m on
m
od e v
oltag
e
bet
w ee n
signal
sou rce
& A
/D boar
d
G N D
Is o la tio n
B a rrie r
W h en the voltage difference
betw e en sign al source a nd
A /D boa rd gro un d is large
eno ugh so the A /D bo ard ’s
com m o n m od e ra n ge is
excee de d, isolate d sig nal
cond ition ing m ust be add ed.