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Basic FAQ for FFT Analyzer

Question number FAQ-0748

What is the relationship between time window length and the number of sampling points?

The finite number of points in the FFT time window (that is, the number of FFT points) is referred to here as sampling points.

The time window length of the FFT is determined by the number of sampling points and the sampling period (sampling interval).

Now, let the number of sampling points be N, the sampling interval be Δ t (s), and the sampling frequency be fs (Hz), then the duration of the time window T (s) is;

（1）

will become a relationship.

For example, if the frequency range is set to 20 kHz, the sampling frequency is 51.2 kHz, and as explained in the FFT section, the number of sampling points N is usually a power of 2, so if N = 2048, then T = 2048/51.2 = 40 (ms).

Last updated: November 16, 2009