Chapter 4 Analog Input
© National Instruments Corporation 4-33 NI USB-621x User Manual
In the single-ended modes, more electrostatic and magnetic noise couples
into the signal connections than in differential configurations. The coupling
is the result of differences in the signal path. Magnetic coupling is
proportional to the area between the two signal conductors. Electrical
coupling is a function of how much the electric field differs between the
two conductors.
With this type of connection, the NI-PGIA rejects both the common-mode
noise in the signal and the ground potential difference between the signal
source and the device ground.
Refer to the Using Non-Referenced Single-Ended Connections for
Ground-Referenced Signal Sources section for more information about
non-referenced single-ended connections.
When to Use Referenced Single-Ended Connections
with Ground-Referenced Signal Sources
Do not use referenced single-ended connections with ground-referenced
signal sources. Use non-referenced single-ended or differential
connections instead.
As shown in the bottom-rightmost cell of Table 4-2, there can be a potential
difference between AI GND and the ground of the sensor. In referenced
single-ended mode, this ground loop causes measurement errors.
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