Detecting the peak-to-peak value

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
Attachments:
labview calculation.xls ‏377 KB

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.
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To measure and hold the peak value of voltage while measuriong using an accelerometer

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Attachments:
leads.vi ‏271 KB
New Folder (2).zip ‏51 KB

The peak detector graphs the amplitudes vs locations in an xy graph. You only graph the amplitudes in a waveform graph. Whatever you are doing is completely different.
Graph the data AND the detected peaks in an xy graph, for example.
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Using LabVIEW 8.0, you will need to place the data from the 9215 into a dmaFIFO buffer, such that you do not need to poll the 9215. It is the polled or the interrupt process that reduces the sample rate.
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[email protected]
www.ni.com/mcm
www.ni.com/soundandvibration
www.ni.com/biganalogdata
512-683-5444

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Dear All,
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hello,
here is one way
detecting all pics index to build parts of array with each min/max value then assembling them
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hold_val.vi ‏20 KB

What does the location of the peak detector mean

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Greetings!
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Eric P. Nichols
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How can I get peak value? Thanx

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Hi,
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Wiebe Walstra.
"t
ao" wrote in message
news:[email protected]..
> I have a labview program which can get signals from my system and draw
> some waveform. The waveform has two peaks with some distance. Then how
> can I let labview give me the peaks' values? thanx a lot!

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Global Programs   64 MB / 3 %   (Used/Allocated 24.356.400 / 67.108.864 Bytes, 36 %)
Global Data   1.300 MB / 62 %   (Used/Allocated 755.387.792 / 1.362.748.332 Bytes, 55 %)
Global Copy-Only Data   507 MB / 24 %   (Used/Allocated 109.891.968 / 532.101.872 Bytes, 21 %)
Global Admin Data   3 MB / 0 %   (Used/Allocated 85.008 / 3.608.576 Bytes, 2 %)
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Hello.
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Attachments:
extract values.vi ‏33 KB

First, I wanted to thank you, Kumar for the quick answer: 5
stars for the answer, this is exactly what I was looking for. I would not have
found it by myself.
I have an other problem to plot now Col( B)=f (Col( C))
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Does anyone know why the waveform peak detect function provides accurately the position of the peaks but not the value?

Does anyone know why the waveform peak detect function provides accurately the position of the peaks but not the value?
I have been looking at my data at the position indicated by the function as a peak, and it is correct at that place the wave has its peak, but the value provided by the function is higher than the actual value at that point.
Attachments:
Test.jpg ‏53 KB

The help makes it clear that the VI will make a quadratic fit to the data, so the locations are not integers (i.e. not aligned with you exact data). From that analysis, the peak is between two of your points, and slightly above the neighboring data.
See the coercion dot. Make the "locations" array DBL (Why did you change it to I64, that makes no sense at all!)
Quote from the help:
"Locations contains the index locations of all peaks or valleys detected in the current block of data. Because the peak detection algorithm uses a quadratic fit to find the peaks, it actually interpolates between the data points. Therefore, the indexes are not integers. In other words, the peaks found are not necessarily actual points in the input data but may be at fractions of an index and at amplitudes not found in the input array."
All clear?
LabVIEW Champion . Do more with less code and in less time .

Find out the peaks and check them against a value

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It would have worked, if you had converted the dynamic-data to a double before you pass it to the > / < operators.
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Don't be afraid to rate a good answer...
Attachments:
CompareMaxMin.vi ‏169 KB

Deleting peak values detected by peak detector vi

Hi,
I m using the peak detector vi to detect peaks every 100 samples, if the difference between two consecutive peaks is greater than 15 i want to delete the peak with the higher amplitude only. This data set, should be plotted again on another waveform. I m able to detect peaks that have amplitudes greater than 15, but I dont kn ow how to delete only these peaks.
Attached is the waveform, with a single peak with high amplitude which I want to delete.
Any help would be appreciated.
Thank you.
Regards.
Attachments:
peak_detection.doc ‏88 KB

Hi Prakruthi,
please have a look at this forum thread:
http://forums.ni.com/ni/board/message?board.id=170&message.id=69416&requireLogin=False
It contains a complete VI for deleting peaks. You only have to insert one more condition to deal with the "only peaks with difference > 15" requirement.
Regards,
Johannes Bauer

Detecting the peak-to-peak value

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