Glossary
©
National Instruments Corporation
G-11
PCI-4451/4452/4453/4454 User Manual
nonreferenced signal
sources
signal sources with voltage signals that are not connected to an absolute
reference or system ground. Also called floating signal sources. Some
common example of nonreferenced signal sources are batteries,
transformers, or thermocouples.
NRSE
nonreferenced single-ended mode—all measurements are made with
respect to a common (NRSE) measurement system reference, but the
voltage at this reference can vary with respect to the measurement system
ground
Nyquist frequency
a frequency that is one-half the sampling rate. See Nyquist Sampling
Theorem
Nyquist Sampling
Theorem
the theorem states that if a continuous bandwidth-limited analog signal
contains no frequency components higher than half the frequency at which
it is sampled, then the original signal can be recovered without distortion
O
offset-binary format
a method of digitally encoding sound that represents the range of amplitude
values as an unsigned number, with the midpoint of the range representing
silence. For example, an 8-bit sound stored in offset-binary format would
contain sample values ranging from 0 to 255, with a value of 128 specifying
silence (no amplitude). See two’s complement format.
onboard channels
channels provided by the plug-in data acquisition device
operating system
base-level software that controls a computer, runs programs, interacts with
users, and communicates with installed hardware or peripheral devices
optical isolation
the technique of using an optoelectric transmitter and receiver to transfer
data without electrical continuity, to eliminate high-potential differences
and transients
oversampling
sampling at a rate greater than the Nyquist frequency
