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 How can I bandpass and notch filter waveforms with Origin?		  New Topic  Reply to Topic
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a_user

USA
0 Posts
Posted - 08/12/1998 :  5:22:00 PM  Show Profile  Edit Topic  Reply with Quote  View user's IP address  Delete Topic
I have seen some software packages that allow you to digitally filter
waveforms. The basic idea is to do a discrete or fast fourier transform
on the waveform (typically displayed as volts X time) and then display
the transformed data graphically in the frequency domain
(volts (or power) X frequency)). You can then specify those components of
the waveform to remove (e.g. > 1 kHz for a low pass filter, or < 100 Hz
for a high pass filter) and then do a reverse fourier to reconstruct the
now filtered waveform with the specified0 frequencies removed. Using this
general scheme one should be able to digitally construct high, low,
bandpass and notch filters on any waveform.

My question is: Has anyone out there worked out the scripts to do this
stuff? Any help would be appreciated.

Thanks,

Frank Gordon
Dept. of Pharmacology
Emory University
Atlanta, GA 30322

E-mail: fgordon@emory.edu

a_user

USA
0 Posts
Posted - 08/12/1998 :  5:23:00 PM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
Re:How can I bandpass and notch filter waveforms with Origin?

It would seem to me that scripts are not needed for this. Try this and let us
know whether it worked

1. Do the FFT on your data with Normalize Amplitude off.
2. Inspect it for the frequency components that you want to remove.
3. Single Click the lower layer to select the amplitude plot.
4. Use the data marker to select the frequency region of interest.
5. Do Backward FFT with Nomalize Amplitude off.
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Gary Lane

USA
150 Posts
Posted - 04/25/2000 :  8:02:00 PM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
Hi...

The release version of Origin 6.0 added a new Digital Filtering analysis feature. Origin 6.0 supports Low and High Pass Filters, a Band Pass Filter, a Band Block Filter, and a Threshold Filter.

With a Graph window active, select Analysis:FFT Filter:DesiredFilter from the Origin menu. See Section 15.9.5 Digital Filtering in the Origin 6.0 User's Manual or search on Analysis and scroll to Filtering in the index of the Origin 6.0 Help file.

-Gary
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greg

USA
1380 Posts
Posted - 04/25/2000 :  8:54:00 PM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
For an outline of the basic steps involved in Frequency Domain Filtering search our Knowledge Database for "Using the FFT tool and getting back the data you started with".
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