Table 2-4
FFT Window Feature Most Suitable Measurement Item
Rectangle
The best frequency recognition rate, the worst amplitude
recognition rate. Basically similar to a status without adding
window.y recognition rate, the worst amplitude recognition
rate. Basically similar to a status without adding window.
Temporary or fast pulse. Signal level is generally the
same before and after. Equal sine wave of very
similar frequency. There is broad-band random
noise with slow moving wave spectrum.
Sine, cyclical and narrow-band random noise.Frequency recognition rate is better than the rectangle
window, but amplitude recognition rate is poorer.
Hanning
Hamming
Frequency recognition rate is marginally better than Hanning
window.
Temporary or fast pulse. Signal level varies greatly
before and after.
Mainly for single-frequency signals to search for
higher-order harmonic wave.
The best amplitude recognition rate and the poorest
frequency recognition rate.
Blackman
Definition :
FTT recognition rate means the quotient of the sampling and math points. When math point value is fixed, the lower the sampling
rate the better FFT recognition rate you get.
Nyquist frequency : To rebuild the original waveform, at least 2f sampling rate should be used for waveform with a maximum
frequency of f. This is known as Nyquist stability criterion, where f is the Nyquist frequency and 2f is the Nyquist sampling rate.
32
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