Glossary
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Chadwick-Helmuth Company, Inc.
FFT Describes a fast Fourier transform, that is, a
method used to record vibration spectra digitally.
An FFT consists of individual bins (also called
lines). Each bin contains a percentage of the RPM
range. The user may determine the actual RPM
range contained in each bin by dividing the
spectrum range (RPM) by the number of bins.
Fundamental A vibration source.
g A unit of measure of the rate at which a body
accelerates while changes direction.
Harmonic A vibration relative to some primary (fundamental)
disturbance.
Hertz One Hertz (Hz) equals one cycle per second.
IPS Inches per second; a unit of measure for vibration
velocity. In the context of the Vibrex 2000 and
Vibrex 2000 Plus, IPS represents a velocity peak.
Mil A unit of physical measure; one mil equals
0.001 in.
Move line A line connecting two balance points. These two
points may be two consecutive balance readings
with an adjustment in between or two balance
points on the same run with a change in power
setting (for fixed-wing applications).
Phase A term used to describe angular measure or time.
Phase lag The angular distance an object or assembly moves
before its movement is measured.
Reflective The optical quality of a surface to deflect light.
Retro-reflective The optical quality of a surface to return light to its
source.
RPM Revolutions per minute.
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