Recording data for power spectral density

Hello
I need to record the power spectrum for a duration of 2 weeks for 2 hours per day. I can get the averaged power spectrum for the 2 hour duration per day as it is embedded in the Power Spectrum Function. Is there a possiblity of saving the data to some Excel file and later calculating the averaged power spectrum for the whole 2-week duration..
Please Help. Thank you.

I was save the data into a TDMS file.  The API is fairly simple and there is a free add on to view the data in Excel.
You can later also read the TDMS file and do whatever averaging, etc you want to do with the data.
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  • Power Spectral Density.vi

    Can someone tell me what the parameter "ENBW" stands for and what it really means in Window Parameters.vi (in Scaled Time Window.vi)  (used for Power Spectral Density.vi). See attached.
    Is it "envelope bandwidth?" I checked some of my signal processing books but came up with no definite answer.
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    Attachments:
    enbw.png ‏283 KB

    It's the equivalent noise bandwidth of the window.
    From the help file (LV8) on Scaled Time Domain Window:
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    plots are the result of applying scaled smoothing windows to the time-domain
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    1.10
    Flat Top
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    3.77
    <0.01
    Here's another discussion on it:
    http://forums.ni.com/ni/board/message?board.id=230&message.id=2637&requireLogin=False
    Message Edited by Jonnie 5 on 04-06-2006 10:55 AM
    2006 Ultimate LabVIEW G-eek.

  • Power spectral density

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    thanks for your help in this matter, I really do appreciate it. First and foremost let me mention that I am working with SVT version 3.1- maybe quite antiquated; i un- and reinstalled it just to make sure that no one here in my lab had fooled with it. On that note, my spectrum units.vi looks somewhat different to yours (see attachment). The relevant portion of the naming of the y-axis variables comes in the "svl_Modify Unit Label for Spectrum Type and Spectral Density.vi". If we look in this VI (also attached) we see that the larger outer conditional, which defines if the units are X^2 / Hz or X / sqrt(Hz), has itself a condition that only allows free movement when the input is linear. When the input is in dB, the conditional is always false, which amounts to forced labeling the Y-axis with X / sqrt(Hz). I actually see the same conditional in the VI you posted.
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    Regardless of the semantics of the data computation, the units reported on the y-axis are always wrong when dB is active. Following the computation of the data in sv_Linear to dB.vi, they should always be EU^2/Hz, and not the other way around.
    In order to fix this, I am compelled to convert the 20log(Vin/Vref) computation to 10log(Vin/Vref) and to remove the "linear" condition in the svl_Modify Unit Label for Spectrum Type and Spectral Density.vi.
    What do you think of this idea? Am I completely wrong in my thoughts? 
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    Attachments:
    spectrum units.JPG ‏67 KB
    unit label.JPG ‏77 KB
    Linear to dB.JPG ‏120 KB

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