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Low pass filter
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Low pass filter

vgy posted on 26 Sep 2012 2:18 AM PST
Top Contributor
133 Forum Posts

 hi to all,

              what should be design criteria for low pass filter with cutoff frequency of 4 hz which is used for pulse oximeter




Re: Low pass filter

Bob Marlowe posted on 26 Sep 2012 04:16 AM PST
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1768 Forum Posts

What's about this?

 

Bob



Re: Low pass filter

danaaknight posted on 26 Sep 2012 04:55 AM PST
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1773 Forum Posts

Filter selection normally has one chosing type, eg. maximaly flat, linear phase, equi-

ripple, pulse response, cheby, bessel, ......but in this case it seems main purpose of

filter to reject body movement  and high ambient light levels.

 

http://incenter.medical.philips.com/doclib/enc/fetch/586262/586924/Pulse_Oximetry_Study_(ENG).pdf?nodeid=586928&vernum=1

 

http://personal.ph.surrey.ac.uk/~phs3ps/surj/v2/li.pdf

 

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3268017/

 

http://www.robots.ox.ac.uk/~neil/teaching/lectures/med_elec/notes6.pdf

 

http://www.ti.com/lsds/ti/apps/medical/end_equipment.page?DCMP=A_Medical_Medical_Medical&CMP=KNC-GoogleTI&247SEM

 

http://www.crcnetbase.com/doi/pdfplus/10.1201/9781420050790.fmatt

 

Regards, Dana.

 

 

 



Re: Low pass filter

PSoC Rocks posted on 13 Oct 2012 04:11 AM PST
Top Contributor
128 Forum Posts

 One suggestion to the image posted by Bob. Try reducing the filter gain from 0dB to some -ve value. If the filter gain is set to 0dB, you can see that there are ringing above 1. So this could saturate your filter if you do not handle your input & outputs properly. In order to avoid this, you can reduce the filter gain to a value so that step function peak is well within '1'.

 

Regards,

Kishore.






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