When To Use Non-Referenced Single-Ended (Nrse) Connections With Floating Signal Sources - National Instruments Data Acquisition Device NI USB-621x User Manual

Chapter 4 Analog Input
NI USB-621x User Manual
DIFF input connections are recommended for greater signal integrity for
any input signal that does not meet the preceding conditions.
In the single-ended modes, more electrostatic and magnetic noise couples
into the signal connections than in DIFF 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 Referenced Single-Ended (RSE) Connections for
Floating Signal Sources
connections.
When to Use Non-Referenced Single-Ended (NRSE)
Connections with Floating Signal Sources
Only use NRSE input connections if the input signal meets the following
conditions:
• The input signal is high-level (greater than 1 V).
• The leads connecting the signal to the device are less than 3 m (10 ft).
DIFF input connections are recommended for greater signal integrity for
any input signal that does not meet the preceding conditions.
In the single-ended modes, more electrostatic and magnetic noise couples
into the signal connections than in DIFF 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 (NRSE) Connections for
Floating Signal Sources
connections.
section for more information about RSE
section for more information about NRSE
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