Sliding window over wavetrain in waveform graph?

[CoastalMaineBird]

If your X-axis is scaled properly (in uSec, the way you want it), then picking out the CURSOR1 - CURSOR LOCATION - XVALUE property will give you a value in uSec.

[DonRoth]

...Which means you would have to divide the cursor values (say two cursors are defining your window) by delta t (the x-axis multiplier) to get the proper indices (should be whole numbers) to feed to the array subset....Don

[Alvaro_Ortiz]

Thanks for the ideas ...

My problem is going now into this way ...

I have a signal that goes from 0 to 204.6 uSec ... the data that i have comes from an excel file .. but the time is in sec .. so it goes from 0 to 204.6 sec .. that implies that we know that we have to multiply by 10^-6 ...

So when I pass this data to labview the time goes from 0 to 204.6 sec (but the problem is not here, I just can say that x10^-6) then I apply a FFT and there comes the problem .. because here is where the exact values must to get in to give a exact value in frequency of the FFT ..

The second problem is when I use the sliding window .. because this one takes the values indexed from the array and not the time in seconds so then I apply a FFT to the window and again the frequency is wrong because is not taking the time (is taking the index of the array).

I really dont know how to work with property nodes .. I am looking for a good tutorial on that .. but I still dont get it ..

For that reason I have been trying to change all from the arrays that I have ..

If you could help me with this problem or you have any suggestion .. please let me know .. i really appreciatte your help ..

Thanks ..

[DonRoth]

I think you just need to learn LabVIEW a little more.  Take your data array itself and multiply it by 1e-6 after import.  I think that would clear up your issue. The FFT should display proper frequency range.

Sincerely,

Don

[Alvaro_Ortiz]

Thanks for the comment Roth,

But the problem is different .. I just can not multiply the array by the constant because I don't have an array by itself. Let me explain you ... I have a text file that contains 17 columns for 1024 values each. I read that excel file and from that point my analysis begin .. If I multiply this array for the constant the data values are going to be multiplied (and not the time).

Im trying to figure out how to pass that file into labview like a complete array .. Each value and from that point I can choose one of the columns and multiply it by any constant.

Any ideas will be helpful ...

Thanks ..

Im going to attach a portion of the program that could show how it is working .. in this portion I am working with the peak detector .. but the peak detector needs an array .. in this case .. is like the waveform is only taking the first value.

[DonRoth]

Well I would save the .csv file to .txt file in Excel if possible and do something like the attached.  This way you have complete access to the actual values including time array within the LabVIEW program....Don

Message Edited by DonRoth on 06-15-2009 11:27 AM

[Alvaro_Ortiz]

Don .. thanks for your answer .. I also figure out two different ways ..

I have another thrade with this question if you want .. post this answer there and I could give you the kudos .. and also Im going to post my other two solutions ...

The other post is ... (array waveform peak detector) search in tags by Alvaro_Ortiz.

Thanks ..