YOKOGAWA ScopeCorder DL850E - Page 245

App-11
IM DL850E-01EN
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.
0
1
Time
Time
Setting
(%)
Setting (%)
1 frame = 100%
100%
Exponential window
Force window
Weight
Weight
0
1
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.
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 20 40 60 80 100
Record length (%)
Damping rate: 1%
Damping rate: 20%
Damping rate: 50%
Damping rate: 90%
When the Force Window Area Is Set to 80% and the Data Outside the Area Is
Taken into Account
Weight
The damping rate does not change for the the
outer area (80% to 100% of the record length).
• Application Example on the DL850E/DL850EV
0 20 40 60 80 100
0
0.5
1
1.5
2
Record length (%)
When the Damping Rate Is Set to 20% and Force 1 Is Set to 80%
Weight
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.
Original data
Computed result
from the
exponential
window
Computed result
from the
exponential and
force windows
Appendix