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Re: Digital filter question [message #3092 is a reply to message #3002]

Thu, 03 November 1994 09:38

soc
Messages: 12
Registered: October 1994

Junior Member

MEL (larkum@optolab.unibe.ch) wrote:
: I can't understand description of DIGITAL_FILTER in the PV-Wave
: manual. I have some data with an annoying 50Hz mains signal that
: I'd like to try to filter out. The manual talks about the Nyquist
: Frequency as 1/2T, where T is the time elapsed between data samples.

: Well, I have data sampled at 20 kHz, so as far as I can tell,
: the Nyquist frequency for this data is 10 000. Am I right?
: Now what? (besides read a book on digital signal processing).
: What should my low and high frequencies be to set a bandpass
: filter around 50 Hz, expressing them as "fractions of the
: Nyquist frequency" as "numbers between 0 and 1".

: Thanks anyone,

I havent used the routine but I expect your 50Hz is just 50/10000
so that the two numbers setting the low and high are 49.5/10000 and
50.5/10000 for a bandpass of 1Hz centered on 50Hz..ie 4.95e-3 and
5.05e-3

Hope this helps...
Rob

: Matthew.
: ____________________________________________________________ ______________
: Matthew Larkum
: Physiologisches Institut
: Buehlplatz 5, CH-3012 Bern Switzerland
: Ph. 41 31 658726 Fax. 41 31 654611
: Internet: larkum@optolab.unibe.ch
: matthewl@cortex.physiol.su.OZ.AU

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[Message index]

		Digital filter question By: larkum on Tue, 01 November 1994 03:45
		Re: Digital filter question By: sgs on Fri, 04 November 1994 12:49
		Re: Digital filter question By: alps on Fri, 04 November 1994 06:25
		Re: Digital filter question By: soc on Thu, 03 November 1994 09:38

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