PAGE 6
SENSO
RS AN
D INS
TRUME
N
TATIO
N F
OR MAC
HINE
CON
DITIO
N M
ONIT
ORIN
G
Crest Factor Plus
Details: This is similar to Crest Factor, but the output has been adjusted such that the value always
increases as the bearing condition gets worse. This uses a sum of Crest Factor, RMS Acceleration, and
True Peak Acceleration. These are weighted differently such that the sum of the three always increases
as bearing condition gets worse, even if 1 value decreases. This primarily corrects for the fact that Crest
Factor decreases when the fault is very severe. By adding RMS Acceleration into the equation, the
decreasing Crest Factor is counteracted by the increasing RMS Acceleration as bearing condition is very
poor. The output is a unit-less severity scale from 1 to 16.
The acceleration signals used for this output are high pass filtered at 250 Hz.
Best Uses: Crest Factor Plus is best suited for variable speed machinery when trending is not possible or
not desired. The value will always increase over the entire life cycle of the bearing as its condition
worsens. This allows the user to simply set an alarm value for the severity scale and not worry about
keeping historical data for trend monitoring.
Scaled Output (1-16)
Bearing Condition
1 to 5
Good
6 to 11
Satisfactory
12 to 15
Unsatisfactory
Above 15
Unacceptable
Figure 2
– Bearing Condition Guide for
Compensated Peak Acceleration, Crest Factor and Crest Factor Plus
