Measurement in a singe period of a sampled signal

[a_brolin]

Hello!

I need some help i my LabView programming (quite new in this area).

I have a couple of sampled signals logged with NI VI LOGGER and now imports these into LabView for analyze and processing.

The first step I do is to import the signals with "Read From Measurement File" and then it's possible to graph, filter and make FFT and it works OK, but what I need to do is to measure the peak value of single periods of the signal and this in intervals of example (1000-2000samp, 4000-5000samp and so on).

This data should then be saved and processed further.

I've tried to split the signal with "Find All Zeros" and a couple of other ideas but I don´t get it working.

Also, the frequency of the signal is not steady, it is varying over time. 

I hope you understand my problem and maybe can give me some help. (I can attach picture or signalsample if thats necessary)

Thank you!

[a_brolin]

No one with any ideas?

[F._Schubert]

Yes, would be good to attach a picture.

There are some vis called PeakDetect and/or similar in the analysis package.
What was the problem with splitting the signal with the Find all Zeros? If noise was the problem, you could use advanced triggering with a windowed threashold.

Felix

[a_brolin]

OK, I attach some files to explain what I want to do:

First an example of a sampled signal to process (example.txt).

Then what I've done in LabView so far (sofar.jpg)

And a picture explaining what I want to do with the signal (peak.jpg).

As you see I want to save the peak-peak value of every cycle in a new array, is this possible? How?

[a_brolin]

Hm, the files don't seems to be attached...?

[johnsold]

If you Preview your post after attaching the file, the attachment gets disconnected. Attach last.

Lynn

[F._Schubert]

You can use the 'Trigger and Gate' Express vi. make a start trigger a bit above 0 and a stop trigger below 0. Define some Hysteresis. Place the Express in a loop. With autoindexing you recive the Portions of interest. then it is simple min/max. Here is a fast draft, not yet checking the number of cycles.

Felix

[a_brolin]

Thank you!

This way works quite as I want.

But I still got a problem, it seems that the output from max-min function don´t have the right values if you compare to the waveform? I dont know if the problem is in the "Trigger and Gate"?

I attach what I've done...and hope you can help me...