4-4
FFT Mode
4.3 Record Settings
(1)(3)(4)(6) (2)(5)(7)
(11)
(10)
(9)
(8)
(13)
(12)
(1) Frequency................. This parameter sets the analysis frequency, in the range 0.08 Hz to 400 kHz
(depends on the amps installed).
(2) Counts ...................... This parameter specifies the number of analysis points captured during
measurement. It can be specified as either 1000 points or 2000 points.
(3) Window ..................... This parameter specifies the window, which can be specified as Hanning or
Rectangular.
TIP
•The Window Parameter
Under normal conditions, signal input that can be subjected to FFT analysis will continue
infinitely. Out of such infinitely continuous input signals, the Window parameter lets you
conduct FFT analysis of the signal input only during a limited time interval, which is
called a "window." In the WR300's FFT mode, the Window length and the Frequency
setting are related as follows.
Window length = x Counts setting [seconds]
0.4
Frequency setting [Hz]
(The Counts setting in the WR300's FFT mode can be either 1000 or 2000.)
• The Impact of the Window on Analyzed Results
It is common knowledge that the result of FFT analysis on signal input that has been
extracted by a window will match the result of a Fast Fourier Transformation operation
on infinitely repeated signal input of the window length. As a result, except in cases
when the window length is equal to an integral multiple of the signal input's cycle,
ordinary signal input may generate a non-continuous segment due to extraction by the
window. Since this non-continuous segment did not exist in the original signal input, if
FFT analysis is executed in this status, the non-continuous segment will affect the result
of FFT analysis. Due to the WR300's operating principles, it is not possible to eliminate
the error caused by the window, but you can minimize the error by using an appropriate
window.
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