Some words about the meaning of Real-time
FFT (as for fft software):
The Fast Fourier Transform (FFT) gives a direct representation
of the signal in the frequency domain. This technique computes
frequency spectrum and derived results like FRF from time
domain data acquired by blocks.
While using an fft analysis software, real-time can have two
meanings: one, quite obvious, is that you can see the frequency
spectrum in live mode, continuously. This is an equivalent
to the oscilloscope in the frequency domain.
The second meaning, which is the real meaning, is that the
computation takes into account all the time domain data to
compute the frequency spectrum. A consequence is that the
computation rate has to be faster than the acquisition rate.
This is a hard constraint for some analyzers on the market,
but a must condition to have an exact representation of the
signal spectrum. Any loss of time domain data results in an
error in the frequency spectrum.
The real-time band is then a critical parameter if you want
some precision on your measurements with an fft analysis software.
Let’s take an example: vibration analysis on a rotating
machine. The vibration spectrum of a machine can be quite
rich and complex due to the number of phenomena producing
vibrations: in addition to the normal vibrations: unbalancing,
roll bearings, gear meshes, it is important to detect clearly
any abnormal vibrations like a shock at the bearing roll passing
frequency or at the teeth gear passing frequency. These phenomena
are non stationary and it is then essential that the analyzer
takes into account all the data during several tenths or hundreds
of revs of the machine to have a pertinent vibration spectrum.
Vibration diagnostic is a typical case where real-time analysis
is absolutely essential. It is the same for many other applications.
Industrial applications of Oros analyzers :
acoustic measurement
automotive vibration analysis
cabin noise
engine vibration
engine vibration analysis
Oros range of vibration analyzers :
dynamic signal analyzer
fft analyzer
fft analyzers
fft software
fft spectrum analyzer
multi channel analyzer
noise analyzers
sound analyzer
vibration analyzer
Noise and vibration measurements :
1/3 octave
fft analysis software
nvh measurements
operating deflection shapes
order tracking matlab
vibration order tracking
|
