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Fast Fourier Transforms
Reference
3Ć38
Figure 3Ć21:ăDefine FFT Waveform Menu
5. If the selected math waveform is not FFT, press Change Math DefiniĆ
tion (side) ➞ FFT (main). See Figure 3Ć21.
6. Press Set FFT Source to (side) repeatedly until the channel source
selected in step 1 appears in the menu label.
7. Press Set FFT Vert Scale to (side) repeatedly to choose from the followĆ
ing vertical scale types:
H dBV RMS Ċ Magnitude is displayed using log scale, expressed in
dB relative to 1 V
RMS
where 0 dB =1 V
RMS
.
H Linear RMS Ċ Magnitude is displayed using voltage as the scale.
H Phase (deg) Ċ Phase is displayed using degrees as the scale,
where degrees wrap from -180_ to +180_.
H Phase (rad) Ċ Phase is displayed using radians as the scale,
where radians wrap from -p to +p.
The topic Considerations for Phase Displays, on page 3Ć47, provides in
depth information on setup for phase displays.
8. Press Set FFT Window to (side) repeatedly to choose from the following
window types:
H Rectangular Ċ Best type for resolving frequencies that are very
close to the same value but worst for accurately measuring the
amplitude of those frequencies. Best type for measuring the freĆ
quency spectrum of nonĆrepetitive signals and measuring frequency
components near DC.