Glossary
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National Instruments Corporation
G-9
noise
an undesirable electrical signal—Noise comes from external sources such
as the AC power line, motors, generators, transformers, fluorescent lights,
soldering irons, CRT displays, computers, electrical storms, welders, radio
transmitters, and internal sources such as semiconductors, resistors, and
capacitors. Noise corrupts signals you are trying to send or receive.
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.
Nyquist frequency a frequency that is one-half the sampling rate.
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
.
operating system
base-level software that controls a computer, runs programs, interacts with
users, and communicates with installed hardware or peripheral devices
oversampling
sampling at a rate greater than the Nyquist frequency
P
passband
the range of frequencies which a device can properly propagate or measure
PCI
Peripheral Component Interconnect—a high-performance expansion bus
architecture originally developed by Intel to replace ISA and EISA. It is
achieving widespread acceptance as a standard for PCs and work-stations;
it offers a theoretical maximum transfer rate of 132 Mbytes/s.
PFI
programmable function input
