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11
3.2.3 Frequency detection and weighting
Certain standards have a second channel of interval data containing
the
frequency of the maximal vibration level
during the interval time.
Which standards having this second channel are written in the table of
International standards in section 4.2. These standards may also
include a number of frequency weighting models, which re-calculates
interval data according to the weighting algorithm:
1.
Detect all zero crossings in the vibration level signal
2.
For each zero crossing, calculate the frequency based on the
number of samples since last zero crossing
3.
Depending of weighting model, recalculate the maximum
vibration level value within the half period
4.
Check if the new weighted value is larger than last saved
maximum in the interval
Each weighting model recalculates the vibration level signal as stated
in its standard.
More facts about standards with weighting model:
Transient files are not affected by the weighting.
The trigger system uses weighted data, see a descriptive
example in Appendix D.
Note! The trigger event is delayed to the zero crossing after
the signal maximum.
Direct SMS messages from the Datalogger send weighted
vibration level values.
X85 Alarm Beacon uses weighted vibration level values for
the decision when to trigger an alarm.
LIVE, LAST and EVENT data
2
in the Datalogger display
shows weighted vibration level values.
Live mode in INFRA Net shows weighted vibration level
values.
The log file still contains the unweighted vibration level, and
considers only post-trig data.
2
LIVE (=current value), LAST (= last interval data) and EVENT (= transient data)
