User`s manual

4.2.5 Common Mode Voltage > +/-10V
The PCI-DAS1602/12 will not directly monitor signals with common mode voltages greater than +/-10V.
You will need to either alter the system ground configuration to reduce the overall common mode voltage,
or add isolated signal conditioning between the source and your board.
14
+
-
Input
Amp
To A /D
A/D Board
I/O
Connector
LL GND
CH High
CH Low
Signal Source
with Common
Mode Voltage
Signal source and A/D board
with common mode voltage
connected to a differential input.
GND
The voltage differential
between these grounds,
added to the maximum
input signal must stay
within +/-10V
System with a Large Common Mode Voltage,
Connected to a Single-Ended Input
I/O
Connector
+
-
Input
Amp
To A /D
LL GND
CH IN
A/D Board
L
arge common
mode voltage
between signal
source & A/D board
GND
Isolation
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.
System with a Large Common Mode Voltage,
Connected to a Differential Input
L
arge common
mode voltage
between signal
source & A/D board
GND
Isolation
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.
+
-
Input
Amp
To A /D
A/D Board
I/O
Connector
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.