17
An example of misalignment
：
The shaft rotational frequency (20.25Hz), the third harmonics (60.75Hz) and the
6
th
harmonics (121.5Hz) can be observed.
5.2 Diagnosis of rolling element bearings
Since the acceleration increases if a bearing defect becomes large, vibration acceleration is measured to diagnose
bearings. Attach the accelerometer to the bearing as near as possible. The measurement direction is available in
any directions among horizontal, vertical, and axial direction.
In survey diagnosis, the root mean square values and the crest factor of the vibration acceleration are measured
by Vibration Meter Mode. If the vibration acceleration exceeds the criterion and the judgment is abnormal, the
precise diagnosis is carried out. In precise diagnosis, the defected part can be predicted by FFT analysis of
acceleration envelope, if the information about the bearing to diagnosis is known, for examples, rotating speed,
diameter of ball, number of balls, pitch diameter, and contact angle.
Fundamental settings
High-pass filter
：
1 kHz
Low-pass filter
：
20 kHz
◆
Survey diagnosis
Analysis function
：
Vibration Meter Mode
Measurement data type
：
Acceleration rms value and Acceleration crest factor
◆
Precise diagnosis by time waveform
Analysis function
：
Time Waveform Mode
Measurement data type
：
Acceleration and Envelope
Frequency span, Number of analysis lines
：
Set up so that the time waveform can be observed
◆
Precise diagnosis by FFT analysis
Analysis function
：
FFT Analyzer Mode
Measurement data type
：
Acceleration and Envelope
Time waveform (velocity)
FFT (velocity)