VIBTOOL 02.2009
27
Ideal measurement position
When taking vibration measurements using VIBTOOL, care
must be taken to position it correctly. If VIBTOOL is not
held correctly against the machine, unreliable measure-
ment values and damage can occur. So be sure to observe
the following:
• The measurement surface must be metallic, flat and
clean (or, preferably, prepared with the VIB 8.610 coun-
tersink, see page 56 for details). Otherwise, the frequen-
cy range may be reduced due to poor mounting tech-
nique.
Where to measure
Several measurements should be taken to obtain complete
information for vibration analysis: four radial readings
(offset from each other by 90°) and one axial reading.
In practice, non-critical machines may only require e.g. two
radial measurements to be taken on a regular basis. If
vibration increases, measure the other locations as well.
Most machine manufacturers' vibration limits are based
upon readings taken directly at the bearing housing.
Practical limitations, however, often prevent access to this
ideal location so that points some distance away must be
chosen. Generally, though, measurements should still be
taken as close as possible to the bearings on the stiffest
possible section of available machine casing. Of course,
cantilevered or poorly-supported housing sections are par-
ticularly resonance-prone
and therefore unsuitable as
measurement locations.
Once the exact measure-
ment locations have been
determined, be sure to
mark them clearly so that
all subsequent measure-
ments can be taken at the
same points. This is espe-
cially important as vibra-
tion readings can vary
greatly if the probe location
is moved even slightly.
E
NT
E
N
T
M
Vibration measurements
Radial (vertically)
Axial
Radial
(horizontally)
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