National Instruments USB-621 Series - Page 192

Glossary
© National Instruments Corporation G-15 NI USB-621x User Manual
trigger 1. Any event that causes or starts some form of data capture.
2. An external stimulus that initiates one or more instrument functions.
Trigger stimuli include a front panel button, an external input voltage
pulse, or a bus trigger command. The trigger may also be derived from
attributes of the actual signal to be acquired, such as the level and slope
of the signal.
t
sc
Source clock period.
t
sp
Source pulse width.
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.
U
USB Universal Serial Bus—A 480 Mbit/s serial bus with up to 12-Mbps
bandwidth for connecting computers to keyboards, printers, and other
peripheral devices. USB 2.0 retains compatibility with the original USB
specification.
V
V Volts.
V
cm
Common-mode voltage.
V
g
Ground loop voltage.
V
IH
Volts, input high.
V
IL
Volts, input low.
V
in
Volts in.
V
m
Measured voltage.
V
OH
Vo l t s, o utput high.
V
OL
Vo l t s, o utput low.
V
out
Vo l t s o ut.