PeakTech 1210 Operation Manual page 101

Selecting an FFT Window
The FFT feature provides four windows. Each one is a trade-off between frequency resolution and magnitude
accuracy. What you want to measure and your source signal characteristics help determine which window to
use. Use the following guidelines to select the best window.
Type Description
This is the best type of window for resolving frequencies
that are very close to the same value but worst for
accurately
frequencies. It is the best type for measuring the
frequency spectrum
measuring frequency components near DC.
Rectangle
Use rectangle for measuring transients or bursts where
the signal level before and after the event are nearly
equal. Also, use this window for equal-amplitude sine
waves with frequencies that are very close and for
broadband random noise with a relatively slow varying
spectrum.
This is a very good window for resolving frequencies that
are very close to the same value with somewhat
improved amplitude accuracy over the rectangle window.
It has a slightly better frequency resolution than the
Hamming Hanning.
Use Hamming for measuring sine, periodic, and narrow
band random noise. This window works on transients or
bursts where the signal levels before and after the event
are significantly different.
This is a very good window for measuring amplitude
accuracy but less so for resolving frequencies.
Use Hanning for measuring sine, periodic and narrow
Hanning
band random noise. This window works on transients or
bursts where the signal levels before and after the event
are significantly different.
This is the best window for measuring the amplitude of
frequencies but worst at resolving frequencies.
Blackman Use Blackman-Harris for measuring predominantly
single frequency waveforms to look for higher order
harmonics.
Fig.20,21,22,23 show four kinds of window function referring to sine wave of 1KHz.
measuring the amplitude
of nonrepetitive signals
100
Window
of those
and