Different FFT Windowing types / How to use / Example Screenshots
Depending on the signal you wish to measure you should choose the right FFT windowing type otherwise you might get a wrong amplitude measurement or could even miss a signal.
In most cases the Hann or Flat Top Windowing works fine (default setting).
A comparrison of some FFT windows is shown in attached scrennshots using a single tune CW signal.
Some selection help is seen in below table but these are just a few of the possible window functions. There is no universal approach for selecting a window function. However, the table below can help you in your initial choice. Always compare the performance of different window functions to find the best one for the application.
Hann
- Unknown content
- Sin wave or combination of sin waves
- Narrowband random signal (e.g. vibration data)
Flat Top
- Sin wave (amplitude accuracy is important)
- Accurate single tone amplitude measurements
Uniform
- Broadband random (white noise)
- Closely spaced sin waves
- Two tones with frequencies close and almost equal amplitudes
Hamming
- Closely spaced sin waves
Kaiser
- Two tones with frequencies close but amplitude very different
Attached a comparison graph for all windowing functions using a simple CW tone:
But the reality is this graph (showing the bins):
