National Instruments Data Acquisition Device NI USB-621x - Manual (Page 166)

Glossary
NI USB-621x User Manual G-8 ni.com
floating signal sources Signal sources with voltage signals that are not connected to an absolute
reference of system ground. Also called non-referenced signal sources.
Some common examples of floating signal sources are batteries,
transformers, and thermocouples.
FREQ OUT Frequency Output signal.
frequency The number of alternating signals that occur per unit time.
ft Feet.
function 1. A built-in execution element, comparable to an operator, function, or
statement in a conventional language.
2. A set of software instructions executed by a single line of code that may
have input and/or output parameters and returns a value when executed.
G
glitch An unwanted signal excursion of short duration that is usually unavoidable.
GND See ground.
ground 1. A pin.
2. An electrically neutral wire that has the same potential as the
surrounding earth. Normally, a noncurrent-carrying circuit intended for
safety.
3. A common reference point for an electrical system.
H
hardware The physical components of a computer system, such as the circuit boards,
plug-in devices, chassis, enclosures, peripherals, and cables.
hardware triggering A form of triggering where you set the start time of an acquisition and
gather data at a known position in time relative to a trigger signal.
Hz 1. Hertz—The SI unit for measurement of frequency. One hertz (Hz)
equals one cycle per second.
2. The number of scans read or updates written per second.