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2-9
If the signal source is grounded or ground-referenced, both the pseudodifferential and
differential input configurations are acceptable. However, the differential input configuration is
preferred, since using the pseudodifferential input configuration on a grounded signal source
creates more than one ground reference point. This condition may allow ground loop currents,
which can introduce errors or noise into the measurement. The 50 Ω resistor between the
negative input and ground is usually low enough to reduce these errors to negligible levels, but
results can vary depending on your system setup.
Configure the channels based on the signal source reference or DUT configuration. Refer to
Table 2-7 to determine how to configure the channel.
For maximum flexibility, the module’s input configuration is programmable on a per-channel
basis.
Note
The differential/pseudodifferential input selection is available for the voltage
measurement function. In the charge measurement function (PXIe-4480 only), the
negative input terminal is grounded.
Input Connections
Figure 2-5 shows the PXIe-4480/4481 voltage input connection with the terminals in differential
configuration.
Figure 2-5.
PXIe-4480/4481 Voltage Input Connection in Differential Configuration
Table 2-7.
Channel Configuration
Source Reference
Channel Configuration
Floating
Pseudodifferential
Grounded
Differential or pseudodifferential
1.62 M
˖
1.62 M
˖
+
–
Volt
a
ge
S
o
u
rce
+
–
PXIe-44
8
0/44
8
1
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