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Hume316
3 Posts |
 Posted - 02/16/2009 : 07:38:37 AM
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Origin Ver. and Service Release (Select Help-->About Origin):
Operating System: OriginPro 8.0 SR2
Dear Sir-
I have been running FFT on datasets in OriginPro 7.5 (SR6) for some time with no problems. However, now that I have upgraded to OriginPro 8.0, the FFT results have changed. It is probably a settings issue, but perhaps not?
I've added the following figures to walk you through the steps. The dataset (an 14 min 16 Hz time series) is exactly the same for both. I used the default FFT settings, but the results are different:
When running the FFT in 7.5, I used the following settings:
[url=http://img511.imageshack.us/img511/7554/fftv75lp7.png] [/url]
Results:
[url=http://img401.imageshack.us/img401/637/fftv75resultsgk0.png] [/url]
When running the FFT in 7.5, I used the following settings:
[URL=http://img17.imageshack.us/my.php?image=fftv80bn8.png] [/URL]
Results:
[URL=http://img9.imageshack.us/my.php?image=fftv80resultslh5.png] [/URL]
Do you have any idea what the problem might be? Thanks!
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Hume316
3 Posts |
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easwar
USA
1964 Posts |
Posted - 02/16/2009 : 10:09:14 AM
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Hi,
It would be much easier if you send an OPJ with the data, 7.5 results, and 8.0 results to tech support...
A few things to note:
Origin 8.0 uses FFTW library (www.fftw.org) which does not pad or truncate the data. So if your data size is not a power of 2, 7.5 pads or truncates whereas 8.0 does not.
In 7.5 there was amplitude output which can be optionally normalized. In 8.0 there is magnitude and separately amplitude. These, and manuy other output quantities, can be turned on/off using check boxes under the Plot branch in the dialog.
Again, please send the opj to tech whcih would then be easier for us to see what the differences are and help you.
Easwar
OriginLab
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FFT differences with OriginPro 7.5 and 8.0