peak detector vi issue

[dg_lbe]

Hi,

  Am using the example vi advanced peak detector and find it does not save the highest peak value.  Its close but not the value thats the highest.  I've tried adjusting the width.. without success.

Has anyone solves the issue?

Thanks........

[0utlaw]

Hello dg_lbe,

It sounds like you're experiencing an offset in the detected waveform peak, do you have any examples of the behavior you've seen?  Screen captures, expected vs. actual results, information on the steps or settings you've tried, or even a sample data set that shows the incorrect result would be extremely helpful.

Thanks,

[dg_lbe]

At the moment can't provide data.. I've also tried saving the data to array from the random number generator part of the vi and then scrolling through to prove this happens.

[0utlaw]

Hello Dg_lbe

This shipping example performs a least squares fit to extrapolate the most likely peak amid noisy data. Depending on the number of points taken into account (the width) and the general trend of the data, this will not always report the actual highest or lowest data point - rather, it will return the peak implied by the curve at a given location. Using this function on random data (noise) will not typically return meaningful results, although if an extremely narrow width is used you will probably find most of the highest or lowest points. I would recommend looking at the context help for the various controls and indicators for more in-depth descriptions of how they impact the results. 

If all you are looking for is a point-to-point peak, you may be better served by the standard Peak Detection VI found in the Signal Detection Palette- this is the basis for the Advanced VI.

Regards,

[NarayananK]

Hi All,

By definition of the Size of "Width" in peak detection VI it says "The value should be no more than about 1/2 of the half-width of the peak/valley".

I would like to understand how the Width is to be calculated from this definition.

It would be great if someone to could an example in which the maximum and minimum possible width is demonstrated.

With Regards,

Narayanan

[NarayananK]

Hi All,

Did a thorough search and found this example explaining exactly what i needed.

http://digital.ni.com/public.nsf/allkb/2B685D5B2A919E2A8625654C006AF03C

The definition of half of half width of maximum peak/valley is clearly explained in this url.

Thanks.