Figure 3.3:Differential Input Ch. - Grounded - Advantech PCI-1713 User Manual

Differential Channel Connections
The differential input configuration has two signal wires for each chan-
nel, and the differential input responds only to voltage differences
between High and Low inputs. On the PCI-1713 card, when all channels
are configured to differential input, up to 16 analog channels are avail-
able.
Measured
Voltage
Figure 3.3: Differential Input Ch. - Grounded
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
and the PCI-1713 ground, shown as V
+
PGIA
_
).
cm
Internal
AI0
AI2
Multiplexer
AI30
AI1
AI3
Multiplexer
AI31
GND
I/O Connector
cm
in Figure 3-3.
cm
15
External
Ground-
Referenced
Signal
Source
between the signal source
Chapter 3