YOKOGAWA DL6000 Series User Manual

2-31
IM DLM6054-01EN
Features
3
2
1
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5
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7
8
9
10
11
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13
14
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Index
App
        section 10.5 for the procedure
You can execute a fast Fourier transform (FFT) and display a power spectrum.
You can enable and disable the traces of the real and imaginary parts. If the trace of the imaginary part
is not enabled, only the real part is used for calculation, and negative frequencies are not displayed.
You can use a rectangular, Hanning, or flattop time window.
The rectangular window is best suited to transient signals, such as impulse waves, which attenuate
completely within the time window. The Hanning and flattop windows allow continuity of the signal
by gradually attenuating the parts of the signal located near the ends of the time window down to the
0 level. Hence, they are best suited to continuous signals. The Hanning window provides a higher
frequency resolution compared to the flattop window. However, the flattop window has a higher level of
accuracy. When the waveform being analyzed is a continuous signal, choose the appropriate window
for the situation.
You can set the number of points in the FFT to 2.5 k, 6.25 k, 12.5 k, 25 k, 62.5 k, 125 k, or 250 k.
You can set the FFT range to one of the displayed windows (the main, Zoom1, or Zoom2 window).
If the record length of the selected window is greater than the number of FFT points, the data is
downsampled before computation.
You can perform marker measurements and measure the peak values on an FFT waveform.
T
T
T
T
t
Sine wave
Time Window Integral Power spectrum
Rectangular
window
Hanning window
Rectangular window
Hanning window
Flattop window
: W(t) = u(t) – u(t – T) u(t): Step function
: W(t) = 0.5 – 0.5cos(2π )
: W(t) = {0.54 – 0.46 cos(2π )}
T
T
Flattop window
t
T
t
T
sin{2π(1 – 2t/T)}
2π(1 – 2t/T)
FFT Function
Given that the complex function resulting after the FFT is G = R + jI, the power spectrum can be
expressed as follows.
( )
10 log
R
2
+ I
2
2
R: Real Part, I: Imaginary Part
Log magnitude reference (0 dB): 1 Vrms
2
AC component
( )
10 log
R
2
+ I
2
DC Component
2.8 Analysis and Searching

YOKOGAWA DL6000 Series Specifications

General

Brand	YOKOGAWA
Model	DL6000 Series
Category	Test Equipment
Language	English