National Instruments PCI-8254R User Manual page 41

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.
V
VDC Volts direct current.
voltage The electromotive force.
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Glossary
NI PCI-8254R User Manual