Digital Storage Oscilloscope 17
2.7.2.2 Displaying FFT Spectrum
Push the MATH MENU button to display the Math menu. Use the options to select the
Source channel, the Window algorithm and the FFT Zoom factor. Only one FFT
spectrum can be displayed at a time.
Math FFT
Options
Settings
Comments
Source
CH1, CH2
Choose a channel to be the FFT source.
Window
Hanning, Flattop,
Rectangular,Bartle
tta and Blackman
Select a type of the FFT window. For more
information
FFT Zoom
X1, X2, X5, X10
Change the horizontal magnification of the
FFT display. For detailed information
Vertical Base
Vrms
dBrms
Set the Vertical Base in a mode.
2.7.2.3 Selecting FFT Window
Using windows can eliminate the spectral leakage in the FFT spectrum. The FFT
algorithm assumes that the YT waveform repeats all the time. When the number of
cycles is integral (1, 2, 3 ...), the YT waveform starts and ends at the same amplitude
and there are no discontinuities in the signal shape.
If the number of cycles is nonintegral, the YT waveform starts and ends at different
amplitudes and transitions between the start and end points will cause discontinuities
in the signal that introduces high-frequency transients.
