How can i display the signal out of a FFT block to a graph?

[St Augustine]

What conversion is required in order to convert a the output of a FFT block to a waveform display? The signal input to the FFT block is a binary pattern signal!

[JFT']

Hi, For the Y-axis, it depends of the input data binaries. I mean, if these come from a voltage signal or a collection of data or a sound signal, etc. It's necessary to know the factor conversion the voltage values, for example...
And for the X-axis, that represents the axis of frequencies, and its posible to reconstruct until the nyquist order of the harmonic frequency (FS/2). Also it's important, the lenght of the input data, it's a power of 2, since algorithm FFT gives a fast and optimal result.
Then connect the output to a "Waveform Graph" Display, on the front panel.
I hope this help.
Bye..

[Jyoti F]

Hello St. Augustine,

You should not need to do any conversion from the output of the FFT VIs to the waveform graph. Make sure, however, that you are wiring into a Waveform Graph.vi and not the Waveform Chart.vi.

Regards,
Jyoti F.
National Instruments

[jujian]

In order to display the spectrum properly, you'd better use the Array
subset to get half of the output of FFT. Then cluster the (0, df, FFT)
to visualize the results.

On Fri, 13 Feb 2004 00:58:04 -0600 (CST), St Augustine
wrote:

>What conversion is required in order to convert a the output of a FFT
>block to a waveform display? The signal input to the FFT block is a
>binary pattern signal!

[St Augustine]

i have tried what you suggested, however when i try to connect the output of the cluster to the XY graph i get an error. I have attached the VI so you can have a look yourself. The vi promts to open some data stored before and does some signal analysis.please help me if u can i would also try to attach the data to be read.thanks

[Jyoti F]

Hello St Augustine,

Unfortunately, I cannot open these files that you have attached so I cannot tell you for certain where your problem lies. However, if you are using one of the FFT VIs from the Analzye>Waveform Measurements sub-palette, then you should be able to wire directly from the VI to a Waveform Graph. Make sure you are trying to wire to a Wavform Graph not a Waveform Chart. If you are using the FFT VIs on the Analyze>Signa Processing>Frequency Domain sub-palette, you should also be able to directly wire into a Waveform Graph, but please refer to the KnowledgeBase document linked below for more information about plotting complex numbers.

http://digital.ni.com/public.nsf/websearch/C010A823CEA80D5386256938005A066E?OpenDocument

Rega
rds,
Jyoti F
National Instruments