Advantech PCI-1713 User Manual page 19

The differential input configuration has two signal wires for each
channel, and the differential input responds only to voltage differenc-
es between High and Low inputs. On the PCI-1713 card, when all
channels are configured to differential input, up to 16 analog
channels are available.
If one side of the signal source is connected to a local ground, the
signal source is ground-referenced. The ground of the signal source
and the ground of the PCI-1713 will not be at exactly the same
voltage, as they are connected through the ground return of the
equipment and building wiring. The difference between the ground
voltages forms a common-mode voltage (V
To avoid the ground loop noise effect caused by common-mode
voltages, you can connect the signal ground to the Low input. Figure
3-3 shows a differential channel connection between a ground-
referenced signal source and an input channel on the PCI-1713 card.
With this connection, the PGIA rejects a common-mode voltage V
between the signal source and the PCI-1713 ground, shown as V
Figure 3-3.
P G IA
M easured
V olta ge
Figure 3-3: Differential input channel connection with grounded referenced
Internal
M ultiplexer
+
_
M ultiplexer
signal source
).
cm
A I0
A I2
A I30
A I1
A I3
A I31
G N D
I/O C o n ne ctor
Chapter 3 Signal Connections
cm
in
cm
External
G round-
R eferenced
S ignal
S ource
15