Common Mode Voltage < +/-10V / Single-Ended Inputs; Common Mode Voltage < +/-10V / Differential Inputs; Common Mode Voltage > +/-10V - Measurement Computing CIO-DAS1601/12 Manual

5.2.3 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. You can try
this configuration, no system damage should occur and you may receive acceptable results.
5.2.4 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-DAS1600).
Figure 5-6 below show recommended connections in this configuration.
T he vo lta g e differen tia l
b etw een the se g ro un d s,
a dde d to the m ax im u m
in pu t sig na l m ust sta y
w ith in + /-10 V
S igna l source a nd A /D board
w ith com m on m ode volta ge
conn ected to a differential input.
Figure 5-6. Common Mode Voltage < +/-10V / Differential Inputs
5.2.5 Common Mode Voltage > +/-10V
The CIO-DAS1600 will not directly monitor signals with common mode voltages greater than +/-10V.
You will either need to alter the system ground configuration to reduce the overall common mode
voltage, or add isolated signal conditioning between the source and your board. See Figure 5-7 and 5-8
below.
Figure 5-7. Common Mode Voltage > +/-10V. Single-Ended Input


G N D
C o nn ec tor
Iso lation
B arrie r


G N D
W h en the voltage difference
betw een sign al source and
A /D boa rd gro und is large
enough so the A /D board's
com m on m ode ran ge is
exceede d, isolated sig nal
conditioning m ust be added.
S ystem w ith a Large C om m on M ode Voltage,
C onne cte d to a Single-Ended Input
C H H igh
+
Inp ut
A m p
C H L ow -
LL G N D
I/O
A /D B o a rd
C H IN
+
Inp ut
A m p
LL G N D
-
I/O
C o nn ector
15
To A /D
To A /D
A /D B o a rd