Hi,
	I have developed a product that detects CO and I think the sensor
can also detect CO2. the sensor is like the ones at www.citytech.com, but a
lot cheaper. I cant disclose the brand nor any detail, sorry, but that link
might be of help.

	Regards,

Mauricio Jancic
Janso Desarrollos
www.janso.com.ar
info@janso.com.ar
(54) 11-4542-3519
 

> -----Original Message-----
> From: piclist-bounces@MIT.EDU 
> [mailto:piclist-bounces@MIT.EDU] On Behalf Of James Newtons Massmind
> Sent: Monday, July 03, 2006 6:07 PM
> To: 'Microcontroller discussion list - Public.'
> Subject: RE: [EE] Caphograph design
> 
> And may we ask WHY you want this? I'm trying to see the application.
> 
> ---
> James.
>  
>  
> 
> > -----Original Message-----
> > From: piclist-bounces@MIT.EDU
> > [mailto:piclist-bounces@MIT.EDU] On Behalf Of Russell McMahon
> > Sent: 2006 Jul 03, Mon 05:59
> > To: PIC List
> > Subject: [EE] Caphograph design
> > 
> > I wish to build a Capnograph.
> > Don't know what that is?
> > I didn't either until yesterday - even though I wanted one.
> > It's an instrument to measure exhaled CO2 content.
> > Exhaled CO2 content is typically in the range 2% - 10.% Y.CO2.M.V.
> > 
> > Real ones cost real money.
> > Most straight forwards method is measuring absorption at about 4.2 -
> > 4.3 nm where CO2 has an absorption peak.
> > This usually involves producing light which includes this 
> wavelength 
> > and then filtering it with a suitable filter.
> > These are commonly enough avail;able due to their use in Automotive 
> > gas analysers, and, not surprisingly, in Capnographs. Such 
> filters are 
> > nastily  expensive - typically hundreds of dollars. This is a 
> > 'discretionary'
> > project and while such a cost is bearable it would be much 
> better if a 
> > cheaper solution was available.
> > 
> > One possible solution is the use of a diffraction grating 
> or possibly 
> > a prism.
> > 
> > Other people may have alternative innovative suggestions for 
> > addressing the 4.2 nm line approach OR may have alternative 
> methods. I 
> > want a potentially "breath by breath" response and ideally 
> electronic 
> > logging so chemical means are unlikely to be useful.
> > 
> > I can imagine a "colour wheel" approach where CO2 is absorbed on a 
> > substrate causing eg colour change, read by a sensor and then 
> > regenerated by eg heating, all on a rotating wheel, might provide a 
> > viable real time solution. How one achieves such a colour or other 
> > change I don't yet know.
> > 
> > Pushing that a little further, exhaled air could be bubbled 
> through a 
> > solution causing transparency change and light occlusion and the 
> > solution subsequently regenerated. Much messier than I 
> would like, but 
> > such "idea starters" may lead to other things.
> > 
> > FWIW the End Tidal value (the CO2 level at the end of
> > exhalation)  is an amazingly sensitive and valuable 
> indicator for many 
> > medical situations. ET value gives far faster response than Pulse 
> > Oximiter blood oxygen readings to oxygenation changes (one breath 
> > versus a minute plus), is a sadly accurate indicator of 
> resuscitation 
> > prospects and a good indicator of whether resuscitation is working 
> > (reading at 20 minutes resus gives near certain indication of 
> > death/life prospects). It's invaluable as an intubation 
> indicator and 
> > monitor for patients during critical transfers.
> > 
> > 
> > 
> > 
> >         Russell McMahon
> > 
> > 
> > 
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