GE SCOUT100-Ex, Reference Manual

Page: 131 / 282

Section 5 — Set Measurement Options
120
Windowing
Measured data is NOT usually used directly to generate a spectrum. It is
first modified using a
Window
function. The purpose of windowing is to
compensate for certain FFT algorithm limitations that cause signal
leakage. Windowing involves multiplying blocks of data values by a
suitable mathematical function (window type). This ensures the data
block begins and ends with zero amplitude and makes the data block
display as a complete wave.
NOTE: Windowing is NOT available with waveforms.
Choose Window Type
You can choose a
Hanning
or
Rectangular
(no window) window type.
Each type of window has characteristics that make it better suited for
some applications and less well suited for others. The following table is a
general guide only. You should match the window type to the nature of
the signal you are trying to capture (e.g. random or transient signals).
Window Type Purpose
Hanning
window
Provides the best frequency resolution. The
Hanning
window is a good general purpose window.
Rectangular The FFT is NOT adjusted (i.e. this is equivalent to NOT
using a window).
Waveform Parameters
This section provides more information on the available waveform
parameters:
•
Equivalent Fmax
•
Number of Samples
•
Duration