HOW TO DO STFT

[Drizvi]

HI

I AM WORKING ON THE NOISE LEVELS AND PERFORMANCE OF A 50HZ MOTOR. CAN U TELL ME HOW TO PERFORM AN STFT AND SHOW ITS RESULTS ON A 3 DIMENSIONAL GRAPH DISPLAY?

I HAVE TO ACQUIRE RESULTS SIMILAR TO THIS ONE:-

I CURRENTLY AM WORKING ON FFT....

I FOUND MANY STFT FUNCTIONS AND COULDN'T DECIDE WHICH ONE TO USE AND WITH WHICH DISPLAY..

PLZ HELP ME OUT

I'M ATTACHING MY VI

DANISH

[Chris V]

Hi Drizvi,

Have you taken a look at the TFA STFT Spectrogram.vi?  (Signal Processing > Time Frequency Analysis > Spectrogram > )

There's a good example of its implementation in the Example Finder. (Help > Find Examples > Toolkits and Modules > Time Frequency Analysis > Getting Started > Time-Frequency Resolution.vi )

Have a great day,

Chris V

[Drizvi]

HI Chris!

thank you for assisting me. i read it but that is not one graph with a 3 dimensional view. infact they are two graph of the related axis!.. isnt there a way that i can get the actual 3 dimensional view of my 50hz sinusoidal signal??. i think the picture i've included is from matlab!. can i have a similar 3 dimensional graph in lab view also??... although the colour scheme tells me about the signal strength. but i wanted to have a better looking 3 dimensional graph same as i have included only if its possible in LABVIEW???

do you know of any way?

regards

Drizvi

[Chris V]

Hi Drizvi,

If you go into the Example Finder and search for "3D" you will find several examples that can create 3D plots of your data.  You can simply wire the output of the Configure Spectrogram function into the Z Matrix input of the Plot Helper.

Have a great day,

Chris V

[Drizvi]

Hi Chris V

I searched for 3D graphed and found a number of examples as u told me i would. But the main prob with all of them is that the all have seperated x,y,z inputs. what i have is a 50 hz sine wave which has magnitude vs time information in it merged. then i have an fft power spectrum in which i have magnitude vs. frequency information of the same signal.

i dont have any way to extract the independant information(time, frequency and magnitude) out of the two graphs i have and then input it into the 3d graph plotter!. i hope i explained my self clearer to you now!

i'm attaching the VI with here. I'm an amateur in using LABVIEW right now. so please if u can help me plot my magnitude vs time vs frequency graph by modifying my VI. i'll indeed be very gratefull!.

once again.. i have to take the 3 dimensional fft of a 50hz sine wave 

Thanks

Danish Rizvi

[Chris V]

Hi Drizvi,

I'm a little confused.  Your VI is not using the Signal Analysis VI that we talked about.  The TFA STFT Spectrogram.vi outputs the correct data type to be wired into the z-array input of the plot helper.

Have a great day,

Chris

[Olive3003]

Hi Chris,

I use the STFT.VI but I can not visualize the  3D spectrogram time/frequency, would you have an example?Have a good day

[alexderjuengere]

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@Olive3003 wrote:

Hi Chris,

I use the STFT.VI but I can not visualize the  3D spectrogram time/frequency, would you have an example?Have a good day

---

Olive, Chris is talking about this particular vi:

http://zone.ni.com/reference/en-XX/help/371419D-01/lvtimefreqtk/tfa_stft_spectrogram/

Requires: Advanced Signal Processing Toolkit

In your danish.vi ‏31 KB

you do not use the "tfa_stft_spectrogram.vi" - it looks like you wan to create a program which is like the above "tfa_stft_spectrogram.vi"

you use the "fft_power_spec_psd.vi", which does not require the advanced signal processing toolkit

http://zone.ni.com/reference/en-XX/help/371361H-01/lvwave/fft_power_spec_psd/

[Olive3003]

Alex,

Sorry for not answering before, I had not seen your answer.

I'm not Drizvi and danish.vi is not mine.

I have "Advanced Signal Processing Toolkit" and "STFT.VI" but I can't visualize 3D spectrogram time/frequency.

I just try to find an vi's exemple to create a graph like "Figure4.20 : STFT spectrogram for healthy motor".

Have a good afternoon

[oscarfonseca]

Olive3003,

I suggest you try using the "3D Surface Graph.vi" example that ships with the 3D graphs solutions in LabVIEW. It uses the Plot Helper.vi and should make easier the development. Let us know which specific questions you have about this implementation, so we can provide better answers for you.

Warm regards,