Glossary
PCI-4451/4452/4453/4454 User Manual
G-14
www.ni.com
SMB
a type of coaxial connector
SNR
signal-to-noise ratio—the ratio of the overall rms signal level to the rms
noise level, expressed in decibels
software trigger
a programmed event that triggers an event such as data acquisition
software triggering
a method of triggering in which you simulate an analog trigger using
software. Also called conditional retrieval.
source impedance
a parameter of signal sources that reflects current-driving ability of voltage
sources (lower is better) and the voltage-driving ability of current sources
(higher is better)
S/s
samples per second—used to express the rate at which a DAQ device
samples an analog signal
STC
system timing controller
switchless device
devices that do not require dip switches or jumpers to configure resources
on the devices—also called Plug and Play devices
synchronous
(1) hardware—a property of an event that is synchronized to a reference
clock; (2) software—a property of a function that begins an operation and
returns only when the operation is complete
system noise
a measure of the amount of noise seen by an analog circuit or an ADC when
the analog inputs are grounded
T
TC
terminal count—the highest value of a counter
THD
total harmonic distortion—the ratio of the total rms signal due to harmonic
distortion to the overall rms signal, in decibel or a percentage
THD+N
signal-to-THD plus noise—the ratio in decibels of the overall rms signal to
the rms signal of harmonic distortion plus noise introduced
transducer
See sensor.
transfer rate
the rate, measured in bytes/s, at which data is moved from source to
destination after software initialization and set up operations; the maximum
rate at which the hardware can operate
