If you have a variable-frequency signal source, another way to observe aliasing is to adjust the frequency slowly while watching the
spectral display
. If some of the harmonics are aliased, you will see the harmonics decreasing in frequency when they should be increasing
or vice versa.
Blackman-Harris FFT window concepts
The frequency resolution when using the Blackman-Harris window is poor, the spectral leakage is very low and amplitude accuracy is
good.
The Blackman-Harris window has a low amount of energy leakage compared to the other windows. Its best use is for single frequency
signals to look for higher order harmonics. Use the Blackman-Harris window for measuring predominantly single frequency waveforms to
look for higher order harmonics, or several moderately or widely spaced sinusoidal signals.
Hanning FFT window
The frequency resolution when using the Hanning window is good, the spectral leakage is low and amplitude accuracy is fair.
The Hanning window has the narrowest resolution bandwidth, but higher side lobes. Hanning has slightly poorer frequency resolution than
Hamming. Hanning is best for measuring sine, periodic, and narrow-band random noise, and transients or bursts where the signal levels
before and after the event are significantly different.
Measurement concepts
3 Series Mixed Domain Oscilloscope Printable Help 268
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