User`s 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
PCIM-DAS1602/16). Figure 5-6 below show recommended connections in this configuration.
Figure 5-6. Common Mode Voltage < +/-10V / Differential Inputs
5.2.5 Common Mode Voltage > +/-10V
The PCIM-DAS1602/16 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. See Figure 5-7 and
5-8 below.
Figure 5-7. Common Mode Voltage > +/-10V. Single-Ended Input
16
+
-
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
m ode voltage
between signal
source & A/D board
GND
Isolation
Barrier
When the volta
g
e difference
between si
g
nal source and
A/D board
g
round is lar
g
e
enou
g
h so the A/D board’s
common mode ran
g
e is
exceeded, isolated si
g
nal
conditionin
g
must be added.