Maximum frequency using power spectrum

[benndamann33]

HI all,
so I'm having a little trouble using the power spectrum vi .I have a signal that I'm generating, its a 10 kHz sine wave, and I also have some random white noise in it. I know that the power spectrum will return with a maximum peak at 10 kHz but I'm doing this exercise simply to learn to use labview better. Anyway, so I have this sine wave and I can take the power spectrum and plot it, and I see my nice peak at .1, which I'm sampling at 100 kHz, so .1 corresponds to 10 kHz and all is well. However, I want to not determine this by visual inpsection but rather I want to output from the power spectrum the time corresponding to the peak(in this case .1), automatically. Is there a way to do this? Thank you
Ben  

[Van_L]

Hi Ben,

If you must use the power spectrum vi, you can do so by unbundling (refer to the diagram below)
But then you would have to cycle through and find the largest element in the magnitude array and using x0 and dx to find the frequency.

You should use Tone Measurements vi, this way you can extract the frequency directly




Hope this helps


Message Edited by Van_L on 04-08-2008 06:28 PM

[benndamann33]

definitely didn't know about the existence of this function - I went through the other method and was able to get the desired result but it was much messier than this - thanks for the clean solution
Ben  

[dominik198]

I know that this post is very old, but anyway: where did you find that Power spectrum VI, because I can't find it in Labview 2016 (I have installed signal processing and sound and vibrations modules)

[GovBob]

Signal Express>>Analysis>>Frequency-Domain Measurments

[dominik198]

Firstly, I would like to thank you for your answer, however it has arisen two new questions.

I use Labview 2016 and by now, I haven't been successfull finding that particular Power Spectrum VI from few posts above.
So, is that VI so old, that it is not present in newer versions of Labview (I have installed Spectral Measurements, Advanced Signal Processing Toolkit, Sound and vibration toolkit, Analog Modulation and Sound and Vibration Measurement Suite )? or it is necessary to have TestStand Environment installed? which I momently don't have.

Thank you!

[crossrulz]

It is not the express VI, but the one I use is Signal Processing->Waveform Measurements->FFT Power Spectrum And PSD.vi

[GovBob]

TestStand is a test architecture and you do not need it. It was just part of my tag line and I'm sorry about the confusion. I would follow crossrulz advice. You have all the tools you need judging from the toolkits you listed. I personally don't really use express vi's which is the one you are looking for. 

[RavensFan]

Bob,

It is probably a good idea to put a break line or two in your signature to help separate the actual message from the signature.

[dominik198]

Thank you guys for your advice, I think that I have already found suitable vi