HP do one for their pulse oximeter and the clip on part is essentially a throw away part. HP did a writeup in a relatively recent HP journal which gave EXTENSIVE detail on what they did and why and how. They clearly think that (Don Lancaster's opinion au contrare) patents will protect the important protectable parts and that its too hard for you-and-me (pulse oximetry that is, not pulses per se). HP journal is available online I believe from HP. Here's the reference HP journal February 1997 Pages 39 - 53 (3 articles) 39 A new family of sensors for pulse oximetry 48 Volunteer study for sensor calibration 52 Neonatal sensor clinical validation Fascinating stuff. The clip part from HP gear should be readily available, not too dear and well engineered. Pulse oximetry uses the 2 LEDs as a reference - the visible is not affected by varying haemoglobin but IS affected by gross blood flow while the IR led has an absorption band affected by Oxyhaemoglobin. For pulse either and or both could be used. -----Original Message----- From: Scott Dattalo To: PICLIST@MITVMA.MIT.EDU Date: Thursday, February 11, 1999 10:59 AM Subject: Re: heartbeats >On Wed, 10 Feb 1999, Mark Willis wrote: >> Stan Ockers wrote: >> > Does anyone know an easy way to convert heartbeats to pulses that a PIC >> > could read? I'm not interested in the amplitude but just the time between >> > beats. I would like to have a PIC log the times between beats to tell >> > when they become irregular, especially when I'm asleep. >> >> The oxygen saturation and pulse rate sensors I've seen all TOO much of >> when Robin's in hospital, have a red LED and a photosensor, perhaps an >> IR pair as well, in something rather like a large plastic clothespin (I >> know what they look like but didn't feel like disassembling them while >> there ) >> >> You clamp it onto a finger and watch the light conductance wavef orm >> for pulse rate, I know I've read before how they determine O2 saturation >> but don't remember just now. Basically, the blood pressure changes >> change the light transmission through the skin I imagine you could >> use this on a wristband or whatever as well, sort of a "back-scattering" >> mode of the same thing. >Check out patent #5,243,992. A sensor SRI developed and patented is >described there. >Scott