Wrong FFT graph

[Matipa]

Hi,

When I run my signal I can see a spectrum but it is correct only for one number of samples, when I change it the frequency doesn't match, amplitude isn't correct too. What is wrong with this FFT 😞 ?

Thank You,

Mateusz

[altenbach]

Can you reduce it to a simple example that does not contain drivers and missing subVIs.

Most of us don't understand Polish. Which graph is the FFT?

What number of samples is correct and what happens when you change it to something else? What amplitude do you get and and what do you expect to get instead? Are you correctly setting df based on dt and N?

[GerdW]

Hi Mateusz,

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@Matipa wrote:

What is wrong with this FFT 😞 ?

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Are you talking about that "Auto Power Spectrum" function before the "Widmo Sygna" graph?

Did you notice that coercion dot at its input? Do you know the meaning of coercion dots?

Did you read the help for that function? Did you wire ALL its inputs (as already asked by Christian)?

[Matipa]

Hi,

Yes, i am talking about that "Auto Power Spectrum" function before the "Widmo Sygnału" graph.

I noticed that coercion dot, I know that it mean that program is making conversion there (I know it should be made by me not by program too).

I used help of course and I didn't wired all of inputs just because i have waveform not dbl 😕 I don't know how to do this to be correct for sure.

I used now other block to make a spectrum without any conversion (possible to see it in uploaded program), but now I can't do the measure of frequency on which is the peak and amplitude of it.

[GerdW]

Hi Mateusz,

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@Matipa wrote:

I used now other block to make a spectrum without any conversion (possible to see it in uploaded program), but now I can't do the measure of frequency on which is the peak and amplitude of it.

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Why don't you use Waveform functions, when you are working with waveforms?

See this:

(This is just an example of how to connect functions to your wires WITHOUT any syntax errors, coercion dots or DDT wires/ExpressVIs. It is not meant to exactly do what you are looking for in a mathematical/physical/technical sense.)