In a not too old issue of Electronic Design, there was a very interesting
design of a pulse meter, that used the LED-SENSOR pair principle, and had a
brief but good explanation of the theory behind it. One of the nice things
about this design was that it had an analog output, and a digital one.

If anyone is interested I can dig the mag, and let you know the exact issue
and page.

Calvin

-----Original Message-----
From: Alex Torres <altor@CHAT.RU>
To: PICLIST@MITVMA.MIT.EDU <PICLIST@MITVMA.MIT.EDU>
Date: Lunes 30 de Marzo de 1998 3:36 PM
Subject: Re: More Heart Monitors


>> From: Craig Webb <lucid@MAGNET.CA>
>>
>> What is interesting about the IR type is that they can measure both
>> oxygenated and non-oxygenated blood levels (using different IR
>wavelengths)
>
>No, not different IR wavelength. Pulseoximetrs use 2 LEDs - one RED and one
>IR.
>
>> and I've also even heard of some researchers doing studies with the shape
>of
>> the pulse curve which can tell information about heart valves and
>blockages,
>> etc. Very interesting.
>
>Yes, but it is an expecive device. You need 20-bit ADC to measure REDmax,
>REDmin, IRmax, IRmin
>value and then calculate SO2, but I never see the formula to calculate
>it.....
>
>
>Alex Torres, Kharkov, Ukraine (exUSSR)
>altor@chat.ru
>2:461/28@FidoNet
>http://www.geocities.com/SiliconValley/Lab/6311
>