Signal Analysis Question?

[fgowash]

Need assistance in determining if a LabView function or vi exists that can take data from the Peak Detect function and determine the 1/2 power points or sidebands.  This seems like a standard processing thing and is common in vibration data analysis. Any alternate approach would also be appreciated.

Thanks

[bspears]

Hi,

With the Sound and Vibration Toolkit we have a Power in Band VI that you can use to determine the power in the sidebands. Additionally, there is a good document online that uses very little programming and shows how to do a half power measurement:

http://www.engr.iupui.edu/me/courses/me340lab/labexp11.pdf

Hope this helps!

Brian Spears

[fgowash]

Brian,

Thanks. Unfortunately we do do have the sound and vibration toolkit and I'm not sure that it does the job. What is happening here is that I use the peak detection vi to extract peaks from a range of amplitude vs frequency data. The canned vi is performing a 3 pt poly fit to determine peaks but does not necessisarily return the actual peak . Instead the peak is determined from the curve. Since I do not have the curve coefficients I cannot work torward the .707 peaks which represent the 1/2 power points. If I could do that then calculation of Q would be straightforward. I am trying to avoid reinventing what somewhat else may have already done. Isn't that what LabView is all about?

Fran

[Jack_A.]

Hey Fran -

Here's a VI which will use the half power measurement technique to compute teh damping factor of a signal.  This VI is built with analysis from the Sound and Vibration Toolkit.

-Jack