SPM leonova emerald - Page 139

E
Vibration measurement E:17
Enveloping filter
Enveloping is a technique used to detect low energy
vibration typically caused by gear and bearing
damage. This type of damage tends to modulate the
amplitude of high frequency vibration, e. g. at the
natural frequency of the transducer.
To suppress all vibration in the lower frequency
ranges,ahighpass(HP)filterissetat1000or2000
Hz(1).Tosuppressvibrationsinboththelowerand
the higher frequency ranges, select one of the band
passfilters(Filter1- 4).
Quick mode
‘Quickmode’(2)isusedtospeedupthemeasure-
ment. The measurement calculations will be based on
the FFT instead of the time signal, resulting in faster
data acquisition time.
Quick mode can not be combined with enveloping,
timesignalorconditionparameters(Crest,Kurt,
Skew,NL1toNL4).
Average type
To achieve greater accuracy, one can order the
averageresult(3)fromastatednumbermeasure-
ments(averagecount,setonthenumberpad).Toget
a time synchronous average, a tachometer must be
connected which supplies a trigger pulse. This starts
each measurement with the shaft in the same posi-
tion. ‘FFT linear’ gives the mean value of the measure-
ments, while FFT peak hold gives the maximum value.
Average overlap
To achieve faster collection of measuring values,
onecanset‘Avergeoverlap’(4)to25%or50%.This
function reduces the measuring time by using less
time waveform data to produce the spectrum.
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