National Instruments Data Acquisition Device NI USB-621x User Manual
Page 170
Glossary
G-12
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PFI
Programmable Function Interface.
PGIA
Programmable Gain Instrumentation Amplifier.
physical channel
posttriggering
The technique used on a DAQ device to acquire a programmed number of
samples after trigger conditions are met.
power source
An instrument that provides one or more sources of AC or DC power. Also
known as power supply.
ppm
Parts per million.
pretriggering
The technique used on a DAQ device to keep a continuous buffer filled with
data, so that when the trigger conditions are met, the sample includes the
data leading up to the trigger condition.
pulse
A signal whose amplitude deviates from zero for a short period of time.
pulse width
The time from the rising to the falling slope of a pulse (at 50% amplitude).
Q
quadrature encoder
An encoding technique for a rotating device where two tracks of
information are placed on the device, with the signals on the tracks offset
by 90° from each other. This makes it possible to detect the direction of the
motion.
R
range
The maximum and minimum parameters between which a sensor,
instrument, or device operates with a specified set of characteristics. This
may be a voltage range or a frequency range.
real time
1. Displays as it comes in; no delays.
2. A property of an event or system in which data is processed and acted
upon as it is acquired instead of being accumulated and processed at a
later time.
3. Pertaining to the performance of a computation during the actual
time that the related physical process transpires so results of the
computation can be used in guiding the physical process.