National Instruments E Series - Manual (Page 54)

Chapter 4 Signal Connections
DAQCard E Series User Manual 4-18  National Instruments Corporation
Single-Ended Connection Considerations
A single-ended connection is one in which the DAQCard E Series card
analog input signal is referenced to a ground that can be shared with
other input signals. The input signal is tied to the positive input of the
PGIA, and the ground is tied to the negative input of the PGIA.
When every channel is configured for single-ended input, up to 16
analog input channels are available.
Use single-ended input connections for any input signal that meets the
following conditions:
• The input signal is high level (greater than 1 V).
• The leads connecting the signal to the DAQCard are less than 10 ft
(3 m).
• The input signal can share a common reference point with other
signals.
DIFF input connections are recommended for greater signal integrity
for any input signal that does not meet the preceding conditions.
You can software-configure the DAQCard channels for two different
types of single-ended connections—RSE configuration and NRSE
configuration. Use the RSE configuration for floating signal sources;
in this case, the DAQCard provides the reference ground point for the
external signal. Use the NRSE input configuration for ground-
referenced signal sources; in this case, the external signal supplies its
own reference ground point and the DAQCard should not supply one.
In single-ended configurations, 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.