Measurement Computing PCM-DAS16x/16 - Manual (Page 29)

6.2.5 Common Mode Voltage > +/-10V
The PCM-DAS16x/16 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.
6.2.6 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.
25
System w ith a La rge C o m m on M ode Vo ltag e,
C o nne cte d to a D iffe rential Inp ut


L arge co
m m on
m
ode vo
ltage
be
tween
signa
l
sour
ce &
A/D b
oard
G N D
Iso la tio n
B a rrie r
W hen the voltage difference
between sig nal source and
A/D board g round is large
enough so the A/D boa rd’s
com m on m ode range is
exceeded, isolated sig nal
conditioning m ust be added.
+
-
Inp ut
A m p
To A /D
A /D B o a rd I/O
C o nn ecto r
LL GN D
CH H igh
CH Low
1 0 K
1 0K is a reco m m e nd ed va lu e. You m ay sh ort LL G N D to C H L ow
in s te ad , b u t this w ill re du c e yo ur s ystem ’s n o ise im m u nity.
Iso late d S ig n al S ou rce
C o n ne cte d to a Sin g le -En d ed In pu t
I/O
C o nn ector
+
-
Inp ut
A m p
To A /D
L L G N D
C H IN
A /D B o a rd


Is o la t
ed
s ig n a
l
s
ou rc e