wjcroft
Joined: Jul 30, 2008
Posts: 15
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 Posted: Mar 24, 2012 5:43 PM Post subject: Fidlib filter response graphs |
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Try creating a Butterworth 4th order bandpass filter from 13 to 15 Hz. Then look at the resulting graph on the Properties. X-axis is all weird with numbers 13 13 14 15 15, etc. Get's even weirder if you expand the size of the dialog box. Filter delay shown is also unusual, 510 ms.
And the bandpass shown on the graph is not correct either, it rolls off way before it hits the upper Hz limit, which should be at the half-maximum requested (15 Hz in this case.)
Wondering if Fidlib was doing something odd, I downloaded the Fidlib / Fiview package from http://uazu.net/fidlib/ , and tried the same filter, \"fiview 256 -i BpBu4/13-15\". Looks completely fine on their graphs, with the half-maximum points where you would expect (13 and 15 Hz!)
I'm assuming this is just a display problem in BioEra, and I can use my normal min and max frequency values without having to adjust anything to get the graph to \"look right\". Using BioEra 2.3.193.
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Is there a way to search the Forum for previous topics, on Filters for example? I could not see how to do this. |
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