VMI VIBER X5 MKIII, Instrument Manual, Page: 91 / 121

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Bump Test
In this menu you can change the Measurement Type , Shown Units and the
Detection Type , how the “Bump” is detected.
When conducting a Bump Test we strike the machine to cause an amplification of the
resonant vibrations, by measuring these oscillations we can gain an understanding of the
machines resonance.
Use a “hammer” proportional to the weight of the analyzed object. A timber log can be
used for heavy objects while a rubber hammer can be used for smaller objects.
Let the “hammer” bounce on to the object and never let it rest on the object. The intension
is the same as hitting a guitar string. The string will resonate a while after the “bump” and
the same will the mechanical structure even if it is unnoticeable to the naked eye. Do not
use a hard hammer it will only produce high frequencies with low “bump” energy at low
frequencies (below 100Hz).
Mount the vibration transducer in the same, horizontal, vertical or axial direction, as the
bump direction.
1. Select
Measure in the main menu.
2. Select Advanced in the Measurement menu.
3. Select Bump test in the Advanced
Measurement menu.
4
. Adjust your settings
5. Press the ENTER button.
The message Start Bumping will appear, press the
ENTER button to begin.
Bump several times within the next 8 seconds,
while the instrument is auto scaling.
Bump again several times while the instrument is collecting the time signal. Try to use
approximately the same bump force and position for both the auto scaling and collection.
You only require one bump for the test but by bumping several times you have the choice
to select the best bump.
Move the cursors to the beginning of the bump or to one of the bumps with the left or right
buttons.
Increase or decrease the time (distance) between the cursors with the
Ctrl+up or Ctrl+down
buttons. You are now actually selecting the number of samples within the cursors.
The larger the time distance, the larger the number of samples and the higher the resolution you
will get in the spectra.