FFT Analyzer Basic FAQ
Question number FAQ-0748
What is the relationship between the time window length and the number of sampling points?
The finite number of points in the time window of the FFT (i.e., the number of points in the FFT) is referred to here as the sampling points.
The time window length of the FFT is determined by the number of sampling points and the sampling period (sampling interval).
Now, if we let N be the number of sampling points, Δt be the sampling interval (s), and fs be the sampling frequency (Hz), then the time window length T (s) is:
 | （1） |
This is the relationship.
For example, if the frequency range is 20 kHz, the sampling frequency is 51.2 kHz. Also, 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: 2009-11-16