Protection
Measurement Types
SKF Multilog On-Line System IMx-M
2 - 5
User Manual
Absolute Shaft Vibration
Absolute shaft vibration
is a technique for determining the total amount of shaft
displacement relative to some point in free space (such as the securing bulkhead). The
concept is shown in the figure below.
Figure 2 - 2.
Absolute Shaft Vibration.
However, what actually is observed here is that absolute displacement is the difference
between two different forms of displacement, namely:
Displacement of the machine relative to the securing bulkhead (µm #1), which can
be determined by means of a velocity sensor secured to a fixed point (such as a
bearing casing), the output of which is integrated to a displacement value in µm or
mil.
Figure 2 - 3.
Measuring the Vibration of the Machine.
Displacement of the shaft relative to the machine itself (µm #2), which can be
determined by means of a proximity probe, secured firmly to the machine casing.