Interesting, Dave - not that I would call the Marquette Solar 8000
old myself, of course.
I have had a dig around on line to see if I could find some examples of "how it's done". These days I suspect that the clever stuff is carried out inside custom chips* - using algorithms, Fourier analysis and such boffin-related wizardry.
I guess what we really need is a reference to the first monitor that ever included this feature, then take a look at the circuits it used!
Or failing that, one of the biomed text books (mine have all gone now).
Does anyone have any clues?
Lastly,
here's one that hopefully all can enjoy (I'll have a read of it myself later).
*
Such as AVR. See here ... and here. I am intrigued that this guy (Jim Lynch) was involved with the development of the Mennen Horizon 2000 - the first colour patient monitor (a hefty beast, if ever there was one) - and one that used Motorola 68000 processors (and sometimes spotted these days on eBay)!
