User's 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.

Table 5. Crest Factor+

CF+ Severity

1 to 5 Good

6 to 10 Satisfactory

11 to 15 Unsatisfactory

above 15 Unacceptable

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.