Are you really wanting to notch out all of the 50 Hz harmonics, or go with a low pass filter? The LP filter is the simple solution and can be implemented in analog form or DSP. A notch filter to remove only the 50 Hz harmonics would best be done with DSP. Stanford Research makes a amplifier/filter box that might be suitable if all you need is a LP filter. I don't know if it is differential or only single ended.
A DSP can be designed to have a shorter settling time than the analog filter. Dave Cuthbert Micron Technology From: John Woodgate [mailto:j...@jmwa.demon.co.uk] Sent: Monday, August 25, 2003 2:47 PM To: emc-p...@majordomo.ieee.org Subject: Re: Comb Filter I read in !emc-pstc that ITL-EMC User Group <itl-...@itl.co.il> wrote (in <2D1037012914D4118DB8204C4F4F5020275AD4@ITLLTD01>) about 'Comb Filter' on Sun, 24 Aug 2003: > I am looking for a manufacturer of an active "comb filter" to notch > out 50Hz+harmonics noise from bio-medical signals. I can't tell you of any suppliers, but since this is a common problem, it would be surprising if nothing is available commercially. There are two ways to do this: either split the signal into two, delay one by 20 ms and re-combine them, and use a DSP chip to achieve the same effect. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk Interested in professional sound reinforcement and distribution? Then go to http://www.isce.org.uk PLEASE do NOT copy news posts to me by E-MAIL! This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
