BISOPE series 41 Octave and FFT analysis octave, spectrum noise and v...

BISOPE series 41- Octave and FFT analysis (octave, spectrum) - noise and vibration frequency analysis)

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When physical phenomena (vibration, noise, etc.) are measured using a sensor or an oscilloscope is used by an arbitrary signal generating device, the 'amplitude' of a wave can be checked according to the passage of 'time'. This amplitude is expressed as values of displacement, velocity, and acceleration, and such a graph is called a ‘time waveform’ or ‘waveform’. This time waveform always takes a complex and natural form unless it is an ideal sine wave in a real scene, and if you analyze this form, you can see that it includes many waveforms. So, mathematicians were able to decompose these complex periodic functions into several simple harmonic functions (FT), and among them, they devised FFT, which performed fast operations by omitting regular terms again. It should be understood that since this is an FFT, it is by no means synonymous with a spectrum. In other words, the harmonic waveforms separated through FFT are simply expressed as 'frequency-amplitude' in a graph called spectrum.

 

FFT, Octave, Spectrum, bands

Using a spectrum graph, various frequency components can be identified at a glance and abnormal behavior conditions can be easily identified, so it is widely used in facility diagnosis and other vibration analysis. This is called 'frequency analysis'.

The spectrum graph, which is the result of using the 'FFT vibration analyzer' with built-in S/W or DSP device that converts the analog signal measured by the acceleration sensor into a digital signal and processes FFT, is the neighbor of the sampling processing speed and the horizontal axis (frequency). It can be said that it expresses the performance of the measurement system because it depends on the interval between frequencies and the interval between the upper and lower widths of the vertical axis (amplitude). precise analysis is possible.

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Briefly, an 'octave' is a frequency-amplitude graph using a ' constant percentage bandwidth filter' after FFT processing. On the other hand, 'FFT analysis' can be said to mean all frequency analysis confirmed by the spectrum graph (both constant width type and fixed width type) after FFT processing.

 

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