how to analyze this kind waveform ?

[ateproject2007]

I get a waveform which is a Piezo output. See the attached. i want to know how many tones in the waveform ,and i can see the waveform .The tone is about 3k hz frequency. But i donnot know how to write a vi to get the tone numbers ? how to analyze to get it ? pls help to modify my vi ! thanks so much !

[andre.buurman@carya]

Do a function search on "Extract" in the function palette.

It will give you two tone functions, follow the help to figure out how to use the VI's.

Regards,

André

[ateproject2007]

i tried and failed. could your kindly help to give me your labview code ?

[tbob]

On the block diagram, look in the functions palette for Signal Processing - Waveform Measure - Extract Tones.  Wire the waveform into the Extract Tones function.  Right click on the output Multi Tone Information and select Create Indicator.  Run the vi.  You will see that there are 4 frequencies that compose the waveform.

[ateproject2007]

only can find "    extract single tone " , cannot find  "extract  multiple tone information" ?? where is it ? need special toolset for this function vi ?? thanks so much.

[andre.buurman@carya]

Hello,

It could depend on the LV version you have 7.1, 8.0, 8.2 or 8.5 and the flavour of LV Basic, FDS or PDS.

I have it in 8.5 PDS without any addons.

Regards,

André

[DFGray]

Andre is correct.  It depends on the version and type of LabVIEW you have.

You can accomplish the same thing, with a bit more work, by taking a power spectrum of the waveform (FFT Power Spectrum.vi) and looking for peaks (Peak Detector.vi or Waveform Peak Detector.vi), but these VIs are not in the Base package.  If you have the base package and cannot afford to upgrade, find a copy of Numerical Recipes in C by Press et.al. (it is in most libraries) and implement the algorithms yourself.  They are not particularly difficult with the high level functionality available in LabVIEW.

Good luck.  Let us know if you run into problems.