Help on FFT or ReFFT

[superman2008]

when we use FFT or ReFFT in Labwindows/CVI, we always get a frequence of integer.

For example, acuqire a wave of 10Hz with 10kHz sampling, analysed by ReFFT, we get the frequence is 10, that is correct.

But if the frequence is 9.2Hz what can I do to get the frequence[9.2] correcttly?

thank you.

帖子被superman2008在03-04-2007 09:49 PM时编辑过了

[superman2008]

why none help me?

where are engineers?

[msaxon]

FFT is not necessarily the best way to accurately estimate the frequency of a signal (and it seems that that is what you are trying to do). Time domain methods, such as auto correlation or zero-crossing detection, are generally better.

If you insist on using an FFT method for this, you must be prepared to use some sort of interpolating estimator on the output of the FFT to identify the likely position of a signal peak 'between' the output frequency bins.

There are plenty of tutorials on the web that identify the uses and limitations of FFT. NI have an interactive tutorial here.

[superman2008]

thank you!