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Time-frequency analysis of vibrational signals

Hello to everyone,

first of all  I'm a beginner of the signal's analysis and I hope someone can help me.

I'm trying to perform the time-frequency analysis of some vibration signals, acquired on a internal combustion engine. In particular I must do the tfa of a vibrational signal corresponding to one thermodynamic cycle of the engine; my Lb version is 2012.

In order to do this I'm using the advanced signal processing toolkit, in particular the "tfa stft spectogram" and I have attached in this message the simple VI I created. My issue is that in the intensity chart I should see frequencies about kHz, instead in my VI i see at max 25Hz.

Can someone help me in telling me in what I'm wrong?

 

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Message 1 of 7
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Have you provided the correct sample rate to the spectrogram vi?

 

Load some meaningful data and then rigth click on the XY Graph -> Data operations-> Make current values default

Save the vi and post it again. Or post a datafile too 😉

 

 

Greetings from Germany
Henrik

LV since v3.1

“ground” is a convenient fantasy

'˙˙˙˙uıɐƃɐ lɐıp puɐ °06 ǝuoɥd ɹnoʎ uɹnʇ ǝsɐǝld 'ʎɹɐuıƃɐɯı sı pǝlɐıp ǝʌɐɥ noʎ ɹǝqɯnu ǝɥʇ'


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Message 2 of 7
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Hi Henrik,

thanks for the answer and the help.

Yes I did,  if you mean the sample rate on the little block "tfa stft spectogram". However I followed your suggest but nothing's changed.

I attached one example of the vibrational signal of one thermodynamic cycle as you requested. Have you any other ideas?

 

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Message 3 of 7
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Almost 😉

Just play with the parameter (and read some basics to understand what you are doing)

TF.png

Greetings from Germany
Henrik

LV since v3.1

“ground” is a convenient fantasy

'˙˙˙˙uıɐƃɐ lɐıp puɐ °06 ǝuoɥd ɹnoʎ uɹnʇ ǝsɐǝld 'ʎɹɐuıƃɐɯı sı pǝlɐıp ǝʌɐɥ noʎ ɹǝqɯnu ǝɥʇ'


Message 4 of 7
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and the vi

Greetings from Germany
Henrik

LV since v3.1

“ground” is a convenient fantasy

'˙˙˙˙uıɐƃɐ lɐıp puɐ °06 ǝuoɥd ɹnoʎ uɹnʇ ǝsɐǝld 'ʎɹɐuıƃɐɯı sı pǝlɐıp ǝʌɐɥ noʎ ɹǝqɯnu ǝɥʇ'


Message 5 of 7
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Yes, that's perfect!

Thanks very much Henrik, you've created a great event driven VI!

Actually I'm going to start read the "time frequency analysis tools- user manual" by NI; do you think is it a good guide?

 

.

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Message 6 of 7
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Hello to everyone,

is there anyone that could tell me why when i try to plot the TFA  2D rappresentation (time vs frequency) in a 3D surface the values on the  three axis do not match with those of the spectrogram?

 

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Message 7 of 7
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