Low pass filter

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Anonymous
Not applicable

 hi to all,

   

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

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ETRO_SSN583
Level 9
Level 9
250 likes received 100 sign-ins 5 likes given

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?no...

   

 

   

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-Goo...

   

 

   

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

   

 

   

Regards, Dana.

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Bob_Marlowe
Level 10
Level 10
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What's about this?

   

 

   

Bob

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ETRO_SSN583
Level 9
Level 9
250 likes received 100 sign-ins 5 likes given

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?no...

   

 

   

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-Goo...

   

 

   

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

   

 

   

Regards, Dana.

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Anonymous
Not applicable

 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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