WARNING: FFT src wfm (ils mode) extended.
In the Interleaved Sampling Mode, there are two time-base settings
(I ~sec/div and 0.5 ~sec/div) in which the record of 25000 points shown
on the screen is incomplete. Starting at the left hand edge of the
screen, 0.08 and 0.4 div respectively are blank. Before computing the
FFT, the leftmost valid point of such records is copied leftward,
through to the left edge of the screen. This will generate harmonic
components not present in the original record.
If possible, you should use the Single-shot mode before FFT at these
time-base settings.
WARNING: FFT src wfm (roll mode) incomplete.
In the Roll Mode (time/div < 0.5 sec), you can stop the acquisition of
trace before it fills the entire width of the screen. The remaining
portion of the record is blank on the display, but the memory contents
remain undefined. FFT is computed on this partially undefined record.
You should avoid stopping the acquisition in this manner if you wish to
obtain meaningful FFT results.
VARNING: FFT src vfm overlunderflov.
The source waveform has been clipped in amplitude, either in the
acquisition (too high gain or inappropriate offset) or in the previous
processing. The resulting FFT contains harmonic components which were
not present in the unclipped waveform.
You should repeat the acquisition or previous processing of the source
waveform, with changed settings.
11.8 Table of Nyquist Frequencies
FNyquist
Number of SS/RIS
Time/div
Points
25.000 mHz
50 SS
I00 sec
62.500 mHz
125 SS
I00 sec
0.125 Hz
50 SS
20 sec
0.125 Hz
125 SS
50 sec
0.125 Hz
250 SS
i00 sec
11-22
Fast Fourier Waveform Processing
Option (WP02, V 2.06FT)
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