Tektronix 4000 Series, Руководство пользователя

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Analyze Waveform Data
If desired, use the zoom feature along with the horizontal Position and Scale controls to magnify and position the FFT
waveform.
Use the default dBV RMS scale to see a detailed view of multiple frequencies, even if they have very different amplitudes. Use
the linear RMS scale to see an overall view of how all frequencies compare to each other.
The FFT feature provides four windows. Each is a trade-off between frequency resolution and magnitude accuracy. What you
want to measure and your source signal characteristics help determine which window to use. Use the following guidelines
to select the best window.
Description Window
Rectangular
This is the best type of window for resolving frequencies that are very close to the same value but
worst for accurately measuring the amplitude of those frequencies. It is the best type for measuring
the frequency spectrum of nonrepetitive signals and measuring frequency components near DC.
Use Rectangular for measuring transients or bursts where the signal level before and after the
event are nearly equal. Also, use this window for equal-amplitude sine waves with frequencies that
are very close and for broadband random noise with a relatively slow varying spectrum.
Hamming
This is a very good window for resolving frequencies that are very close to the same value with
somewhat improved amplitude accuracy over the rectangular window. It has a slightly better
frequency resolution than the Hanning.
Use Hamming for measuring sine, periodic, and narrow band random noise. This window works
on transients or bursts where the signal levels before and after the event are signi
fi cantly different.
Tektronix 4000 Series Oscilloscopes User Manual 197