FFT
FFT converts a time-domain (YT) signal into its frequency components
(spectrum). The oscilloscope can optionally display the source waveform at the
same time as the FFT waveform. Use FFT for the following types of analysis:
Analyze harmonics in power lines
Measure harmonic content and distortion in systems
Characterize noise in DC power supplies
Test impulse response of
fi
lters and systems
Analyze vibration
To use FFT, you need to perform the following tasks:
Set up the source (time-domain) waveform
Display the FFT spectrum
Select a type of FFT window
Adjust the sample rate to display the fundamental frequency and harmonics
without aliasing
Use cursors to measure the spectrum
Setting Up the Time-Domain Waveform
Before you use FFT, you need to set up the time-domain (YT) waveform. To do
so, follow these steps:
1.
Push
Autoset
to display a YT waveform.
2.
Turn the
Vertical Position
knob to move the YT waveform to the center
vertically (zero divisions).
This ensures that the FFT will show a true DC value.
3.
Turn the
Horizontal Position
knob to position the part of the YT waveform
that you want to analyze in the center eight divisions of the screen.
The oscilloscope calculates the FFT spectrum using the center 2048 points of
the time-domain waveform.
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