FFT
Clicking on FFT button is possible to see the rapresentation of the signal in the Frequency Domain only for the first Channel. The range of visible frequencies on screen can be selecting zooming-in or out with the fingers on the screen.
Activating the STATS button is possible to see the top 3 frequencies in the selected frequencies range. These values are corresponding to the computed FFT values and not to the real values that can be checked better with the ruler.
FFT Windows
It is possible to select between standard windows and Flat Top windows for the FFT. Flat Top windows (HFT90D and HFT248D) are used when is required to determine the exact amplitude of a sinusoidal component in the input signal. They have bandwidths W3dB of about 3 . . . 5 bins, roughly twice as wide as non-flat-top windows with comparable sidelobe suppression, but very low maximum amplitude error emax.
WINDOWS SUMMARY
| Bartlett | W3dB = 1.2736 bins emax = −1.8242 dB = −18.9430 % |
| Hanning | W3dB = 1.4382 bins emax = −1.4236 dB = −15.1174 % |
| HFT90D | W3dB = 3.8320 bins emax = −0.0039 dB = 0.0450 % |
| HFT248D | W3dB = 5.5567 bins emax = 0.0009 dB = 0.0104 % |
Harmonic Cursor
When you use one single Vertical Cursor in the FFT module, it will show also the Harmonics of the selected frequency, up to the 10th harmonic.
