YOKOGAWA ScopeCorder DL850E User Manual page 245

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Force Window
Set the area over which computation is performed in terms of a percentage from the first FFT point, taking the
set number of FFT points to be 100%. The areas (force 1 and force 2) can be set in the range of 1 to 100%
(1% resolution) of the input/output signal. When an area is set to 100%, the window functions like a rectangular
window. On the DL850E/DL850EV, the outer area is the average of the results of the window function for the
data outside the area.
Force1: This setting applies to the input signals of one-waveform and two-waveform FFTs.
Force2: This setting applies to the output (response) signal (second parameter) of a two-waveform FFT.
Exponential window
1
0
Combined Form of the Exponential and Force Windows
The DL850E/DL850EV uses a window function that combines the exponential window and force window to
perform computations. The outer area of the force window is the average of the results of the window function
for the data outside the area.
When the Force Window Area Is Set to 80% and the Data Outside the Area Is
Taken into Account
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0
Application Example on the DL850E/DL850EV
When the Damping Rate Is Set to 20% and Force 1 Is Set to 80%
2
1.5
1
0.5
0
0
IM DL850E-01EN
100%
Setting
(%)
Time
20
40
60
Record length (%)
The damping rate does not change for the the
outer area (80% to 100% of the record length).
20
40
60
Record length (%)
The outer area (80% to 100% of the record length) is the average
of the results of the window function for the data outside the
area with no change to the damping rate.
Force window
1
0
Setting (%)
1 frame = 100%
Damping rate: 1%
Damping rate: 20%
Damping rate: 50%
Damping rate: 90%
80
100
Original data
Computed result
from the
exponential
window
Computed result
from the
exponential and
force windows
80
100
Time
Appendix
App-11

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