National Instruments NI PCI-8254R User Manual
Page 41
Glossary
© National Instruments Corporation
G-3
P
pixel
The fundamental picture element in a digital image. The smallest
resolvable rectangular area of an image, either on a screen or stored in
memory. Each pixel has its own brightness and color, usually represented
as red, green, and blue intensities.
PLC
Programmable Logic Controller. An industrial computer used for factory
automation, process control, and manufacturing systems.
proximity sensor
Optical sensor which toggles an electrical signal when an object passes
near it.
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 degrees from each other. This makes it possible to detect the direction
of the motion.
R
RIO
Reconfigurable inputs and outputs.
rising edge
An edge trigger occurs when the trigger signal passes through a specified
threshold. A slope that is positive to the trigger is specified as the rising
edge.
T
trigger
Any event that causes or starts some form of data capture.
TTL
Transistor-transistor logic. A digital circuit composed of bipolar transistors
wired in a certain manner. A typical medium-speed digital technology.
Nominal TTL logic levels are 0 and 5 V.
twisted pair cabling
A twisted pair cable has two insulated copper wires that are twisted around
each other, to reduce crosstalk or electromagnetic induction between the
pairs of wires. Each connection on twisted pair requires both wires.