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| Applications >> Line voltage analysis >> Turbo engines testing >> Machines balancing >> Bearing fault diagnosis |
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| High accuracy spectral analysis |
The most frequently used technique for transforming data between time and frequency domains is the Fast Fourier Transformer.
FFT is based on the concept that the real world signals can be decomposed into a sum of sinusoids of different amplitude, frequency and phase.
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Signal composed of two sinusoids with amplitudes of 100 V and 40 V.
Waveform and frequency spectrum shown. |
| The above frequency spectrum corresponds to the situation when the time window has an integer number of signal periods. The two spectral lines have the hight and position corresponding to the actual amplitude and frequency of the sinusoidal components. |
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Signal composed by two sinusoids with amplitude of 100 V and 40 V.
Waveform and frequency spectrum in FFT leakage conditions. |
| In practice, because the time window doesn't have an integer number of signal periods, there is an energy transfer from the real components to the side components. This is the FFT leakage phenomenon.
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Signal composed by two sinusoids with amplitude of 100 V and 40 V.
Waveform and frequency spectrum in FFT leakage conditions.
Hanning window processing. |
Usually, the FFT leakage is
reduced
with FFT window functions.
Although windowing improves the spectral analysis results, the errors still exist and limit the quality and applicability of FFT analysis. |
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Signal composed by two sinusoids with amplitude of 100 V and 40 V.
Waveform and frequency spectrum in FFT leakage conditions.
Processing with digital resampling functions. |
With digital resampling functions, Fastview eliminates the leakage errors for the whole family of harmonics.
In the above picture, the high quality spectrum is seen, with components of amplitude at exactly 100.0 V and 40.0 V. |
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Signal composed by two sinusoids with amplitude of 100 V and 40 V.
Waveform and frequency spectrum in FFT leakage and variable frequency conditions. |
| The analysis of variable frequency signals is a major problem for FFT.
The obtained spectrum is continuous and doesn't offer much useful information. |
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Signal composed by two sinusoids with amplitude of 100 V and 40 V.
Waveform and frequency spectrum in FFT leakage and variable frequency conditions.
Processing with run-up/down functions. |
| Fastview processes the signal with complex run-up/down functions, which gives high accuracy results for amplitude, order and phase for different conditions of frequency variation. |
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| Applications >> Line voltage analysis >> Turbo engines testing >> Machines balancing >> Bearing fault diagnosis |
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| Home Products Services Applications Contact Versiunea romana |
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