FFT Mode
4-5
Rectangular Window:
No operation is performed for the signal input extracted by the window. When using
ordinary continuous waveforms, use of a window to extract a specific range of signal
input will cause an error. With this Rectangular Window, however, you can obtain
results that are not adversely affected by the window in the case of transient
waveforms that attenuate inside the window or of signal input with a window length
that is an integral multiple of the signal input's cycle.
0
T
Signal input
T
After Window processing
T
Window Function
Rectangular window
Spectrum display
T = Measured waveform cycle x N T ≠ Measured waveform cycle x N Spectrum has a wide base
Approaches the linear spectrum Optimum measured waveform
(V)
(f)
(V)
(f)
For signal input that converges in
the time window like a transient
waveform
Rectangular
window
Hanning Window:
To prevent the generation of non-consecutive points due to the use of a window to
extract a specific range of signal input, the Hanning window gradually decreases the
signal input to become zero at the starting and end points of the window. Because the
signal input becomes zero at both ends of the window, you can minimize the adverse
impact of using a window to extract a specific range of signal input, even when you
have extracted a continuous waveform.
0
T
Signal input
T
After Window processing
T
Window Function
Hanning window
Spectrum display
T = Measured waveform cycle x N T ≠ Measured waveform cycle x N Spectrum has a wide base
The main lobe’s width increases, but
the spectrum’s base does not spread
The main lobe’s width increases, but
the spectrum’s base does not spread
(V)
(f)
(V)
(f)
For regular cyclical waveforms and
random waveforms
Hanning
window
(4) Average Mode........... This parameter sets the Average Mode processing, and can be set to one of four
settings: Off, Summation, Exponential, or Peak Hold.
CHECKPOINT
The green waveform represents the measured data, while the white waveform represents
the averaged results.
(5) Ave. Count ................ This parameter specifies the number of samples to be averaged, and can be
specified in the range of 2 to 9999.
CHECKPOINT
Averaging cannot be performed on data that was captured in Recorder mode and then
output and analyzed in FFT mode.
(6) Display Format ......... The Display Format parameter can be set to one of four settings: 1 Division, 2
Divisions, 4 Divisions, or Nyquist.
(7) Grid ........................... The Grid parameter for display and recording can be specified as either On or Off.
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