Detecting the peak-to-peak value

[Amila]

Hi all,

I just start learning LabView for less than 3 months. With a help from a friend, I did some experiments to measure displacement of a polymer when voltage is applied. The output is given in the form of sine signal (peak-to-peak). When I got this output file (in .lvm format), I will use Microsoft Excel to generate the graph and manually I will calculate the peak to peak value, average them and get the displacement.

My question is, can I do the calculation in Labview? Can Labview detect the value of every peak (positive and negative peak)? I have dozens of data and it time consuming to finish calculating all of them manually. I attached here an example of my excel file so that you can see clearly what I'm saying. I can't attached the .lvm file because it is not a valid extension for attachment in this discussion board.

Many thanks for your help.

Thank you.

Amila

[falkpl]

Yes try using signal operation, peak detection, run it once for peaks and once for valeys.  There are several other techniques I have used in addition to this but this depends on your signal (signal to noise, sampling frequence to p-p period...)

[Amila]

Thanks Paul.

So, that's mean I have to create another Labview program to do this task, right? I will try to do it. I come back if I have any problem.

Thanks.

[DFGray]

You can do almost any calculation in LabVIEW.  It has a huge set of analysis functions and you can always write anything it does not have.  If you can not find what you need in LabVIEW, check these forums and the LAVA forums; chances are good someone has done it already.

What version of LabVIEW are you using?  There is a VI, Amplitude and Levels, which does exactly what you want.  However, it only exists in the Full and Pro versions.  It was introduced about 7.0 or 7.1, so if your version is 7.1 or newer, you should be good.  Make sure you understand how it works so you can set the inputs correctly for your application.

If you do not have the Full/Pro version, you can write this yourself more easily in LabVIEW than can be done in Excel (assuming you were equally skilled in both).  There are a variety of algorithms, from a simple max/min (use Array Max & Min) to Fourier analysis, peak/valley find, and non-linear fitting.  LabVIEW can do it all.  So can Excel, but Excel gets unwieldy when your data sets get larger than about 2000 points.

[falkpl]

You dont have to make a seperate program, you can integrate the peak to peak finction right inline with your collection/display loop.