the large fft frequency

Hello

Before all sorry for my English, I'll try to do my best.

I'm analyzing a data acquired with a FFT, but I want to refine or reduce the frequency of each 'window' (I only want to analyze the 0-350 Hz region)

in order to see better where my maximum in the frequency domain is.

If you have an idea where I can edit this wide frequency in order to refine the plot, please tell me!

Thank you very much!

The sample rate determines the scope of the FFT calculation.

Using the Nyquist theorem, if you sample a 1000 samples per second, the FFT will calculate the range 1000/2 = 500 samples per second.

You NEED to taste at least twice the highest expected frequency in order to use the FFT module to find this frequency.

The resolution of the FFT module is determined by the size of the block. For the spectrum of amplitude by default, TFF will display a block which is also 1/2 on the incoming block. Size of block = 512, FFT block size is 256.

You can increase the resolution by increasing the size of the block and also by changing the size of the block to a number which can divide the sampling frequency. For example, if the

sampling frequency is 1000 and the block size is 500, the FFT output will have a resolution of 250 on a beach of 500.

You can use the data window module to change the block size - increase it to use more data and to increase the resolution of the calculation of TFF. Decrease that it resembles an interval of time smaller and lower resolution of FFT.

I hope this helps.

Tags: NI Products

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