How to obtain the fft and display it from an array input.

[akjryarcamo]

The output of the sum of frequencies doesn't connect to the spectral measurement function. I need to display the frequency response to verify the frequencies added from the mathscript.  Any help? please. it says that the output is an arraywhich cant be directly connected to the spectral measurement function. attached is the VI

[altenbach]

Why are yo randomly bolding words in your post? Just to irritate us?

Looking at your code:

What is the purpose of the FOR loop? If just calculates 5000x the same thing. Once is probably enough.... delete the FOR loop and you get a 1D array instead.

Use "build waveform" to add timing information to the 1D array (such as dt) so df can ce calculated correctly by the analysis function. (If you wire the 1D array directly, it will be coerced to a waveform with dt=1.)

[akjryarcamo]

How do i obtain the waveform for the frequency response? amplitude vs the frequency.. using the spectral measurement function, it displayd the amplitude versus time.. but the one needed is the ampitude vs frequency. thanks

[altenbach]

The output of the spectral measurement is amplitude vs frequency. You simply need to manually change the name of the x-axis to "frequency". (the data does not contain the axis name!).

The output is a cluster of f0, df, and [magnitude], see picture. This will correctly set the units for the x-axis.

Of course the frequency axis will only be correct if dt of the waveform is correct. I don't know what it is, so I haven't set it yet.

[akjryarcamo]

How do i modify the x axis to be correct? I am a newbee with labview. 😞 i obtained the correct graph from the spectrum analyzer yet the the values in the x-axis are not the same.

[akjryarcamo]

Oh i got. Thanks for the info about the dt! Thanks sir.