Specifications

IFFT
Time Envelope
0
1.0
Spectrum
Envelope
Coherence Function
Coherence function
The coherence function is for evaluating the
linearity and correlation of input and output
of a transmission system, obtained in the
frequency domain. The rate of contribution
of the input signal to the output signal is
represented as a digit from 0 to 1 for each
frequency, for evaluating the reliability of
the frequency response function, locating a
key factor from multiple noise and vibration
sources, and evaluating the correlation.
Inverse Fast Fourier Transform (IFFT)
Inverse Fast Fourier transform (IFFT)
After frequency analysis, a time-axis waveform
of a selected band can be obtained again by
performing Inverse Fast Fourier Transform
(IFFT) for the selected frequency band. For
example, by selecting a waveform portion
excluding an unnecessary frequency band
confirmed in the FFT result and then performing
Inverse Fast Fourier Transform (IFFT) for it, a
time-axis waveform can be obtained with the
selected high frequency band eliminated.
Hilbert Transform
Hilbert transform
A logarithmic damping factor can be
obtained by obtaining a time envelope of
a time-axis signal by means of Hilbert
transform.
Cepstrum
Cepstrum
Cepstrum is obtained by performing
Fourier transform of the power spectrum
again, allowing detection of the periodicity
contained in the spectrum. In addition,
reflected waveforms can be eliminated
and fundamental frequency extracted by
estimating a spectrum envelope from the
Cepstrum. Cepstrum can be applied to
make an analysis of the sound waves,
seismic waves, biowaves, etc.
8
Vibration measurement in a plant using the CF-7200 and
an NP Series Acceleration pickup
Rotational vibration measurement of a large blower using the CF-7200