Crest Factor+ (High Frequency Measurement) - Fluke 805 FC User Manual

805/805 FC
Users Manual

Crest Factor+ (High Frequency Measurement)

Crest Factor is the ratio of the peak value / RMS value of a
time domain vibration signal. Vibration analysts use this
ratio to find bearing faults. However, the Crest Factor
method has a key limitation. The Crest Factor increases
during initial bearing degradation when the peak value
increases. It then decreases as the bearing damage
worsens and the RMS value increases. A low Crest Factor
value could show a healthy bearing or a significantly
degraded bearing. The problem is to know the difference
between the two.
The Meter operates with a proprietary algorithm,
Crest Factor+ (CF+), to overcome this limitation. To make
interpretation easy for the user, the CF+ value shows a
severity range. The higher the CF+ value is, the more the
bearing damage. Table 5 shows the relationship of the
values of CF+ to vibration severity.
18
Table 5. Crest Factor+
CF+
1 to 5
6 to 10
11 to 15
above 15
The CF+ value shows for each measurement in the
Bearing field on the Meter display. Push  and  to toggle
between the CF+ value and the high frequency vibration
level in units of acceleration.
Severity
Good
Satisfactory
Unsatisfactory
Unacceptable