Fluke 810 User Manual page 145

Misalignment. In machines, perfect alignment occurs
when the centerline of two coupled shafts coincide. When
they do not coincide, misalignment exists. Angular
misalignment is when the centerline of the two shafts
intersect but are not parallel. Parallel misalignment is
when the centerline of the two shafts are parallel but not
concentric.
Mounting Pad. Mounting pads (bronze or stainless steel)
can be placed at appropriate measurement locations on
machines using an industrial adhesive. The triaxial
accelerometer is attached to these pads for data
collection. The pad ensures a good transfer of vibration
data to the transducer by providing a strong and
consistent mounting location.
Orders. With regards to rotating equipment, orders are
multiples or harmonics of the running speed (or
associated reference component). For example, 1X
means "one times running speed."
Piezoelectric Element. Any transducer (sensor) that
uses a piezoelectric substance as an active element.
Examples are force transducers, accelerometers,
pressure transducers, and phonograph pickup cartridges.
Radial. One of the three vibration axes (Radial,
Tangential and Axial), the radial plane represents the
direction from the transducer to the center of the shaft on
rotating equipment. For typical horizontal machines, radial
equals the vertical axis. For horizontal machines radial
refers the horizontal axis upon which the accelerometer is
attached.
Range (Frequency). Frequency range of data collection.
Hi indicates the High or wide range of frequency within a
spectrum (i.e. 0-100X). Lo indicates the Low or narrow
range of frequency within a spectrum (i.e. 0-10X).
Running Speed. The speed, usually expressed in
revolutions per minute (RPM), at which a rotating
machine runs. It may also be expressed in Hz by dividing
RPM by 60.
Sensor. Transducer, or accelerometer, whose output is
directly proportional to acceleration. Piezoelectric
elements are most commonly used to produce the
Sensor's output.
Signature. The signature, usually called the vibration
signature, is the overall vibration pattern of a machine. It
is said that the vibration signature contains more
information about the machine than any other
nondestructive test can discover.
Spectrum. Plural Spectra. The plot of the vibration
signal's amplitude (y –axis) against frequency (x-axis),
also referred to as the "vibration signature," an "FFT" or
"spectral plot". Vibration signals can be transformed from
the time domain (amplitude against time) to the frequency
domain (amplitude against frequency) by using the Fast
Fourier Transform (FFT) method. A spectra simplifies
vibration data interpretation as certain vibration
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Glossary
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