# Different FFT Windowing types / How to use / Example Screenshots

Quote from AdminTC on 12. October 2020, 15:15Depending 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

HannorFlat TopWindowing 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

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

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