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Technical data are subject to change without notice.
ISO 9001 certified. © Copyright SPM 1996-9. 71411.B
SPM Instrument AB • Box 4 • S-645 21 Strängnäs • Sweden
Tel +46 152 22500 • Fax +46 152 15075 • info@spminstrument.se • www.spminstrument.se
Shock Pulse Analyzer A2010 is based on two quite
different methods for condition monitoring:
• bearing condition monitoring according to the
shock pulse method (SPM)
• vibration severity measurement according to ISO
recommendation 2372.
Each method is tailored to supply the most accurate
and useful information on the aspect of machine con-
dition it is used to monitor.
The difference between the two methods is best illus-
trated by showing what happens when a falling metal
ball strikes a metal bar.
At the moment of impact, the colliding molecules will
cause a pressure wave to spread through both bodies
(fig. 8A). The magnitude of this wave is a function of
the speed of the colliding bodies. It is independent of
their masses and shapes. The SPM method analyses
the first stage event, the ”shock pulse” travelling
through the material of the bar.
The impact will then cause the bar to vibrate (fig. 8B).
This vibration is a function of the speed, mass, and
shape of the bodies. Vibration measurement is used
to measure the movement of the bar.
When hit by a shock wave, a shock pulse transducer
responds at its own resonance frequency of 32 kHz. It
magnifies the high frequency shock signal, while all
machine vibration is filtered out.
The output of the shock pulse transducer is a rapid
sequence of electric pulses, proportional to the amp-
litudes of the shock waves. Shock pulses are measu-
red on a decibel scale (dBsv = decibel shock value).
For a general assessment of machine condition, ISO
recommends wide frequency band measurements of
vibration velocity, over the range 10 to 1000 Hz. The
transducer output is converted into a reading of vi-
bration severity, defined as the root mean square
(RMS) value of the vibration velocity, measured in
mm/s.
Wide frequency band measurement registers the com-
bined vibration of the different machine parts. The
velocity reading is directly related to the energy level
of machine vibration, and thus a good indicator of the
destructive forces acting on the machine.
Two Different Measuring Methods
Fig. 8
Fig. 9
Shock pulse
measurement
Vibration
measurement
Fig. 10
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