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divetheworld · 11th December 2006, 21:11

[quote=Tom Rose;82793]

Quote: (Originally Posted by jaap)

A NDIR system "counts" the molecules of CO2 in the gas path....the greater the number of CO2 molecules the less signal to the detector....the number of molecules in the path is due to a combination of proportion of CO2 and pressure. Regardless, you cannot tolerate but so high a percentage of CO2 molecules in the gas mix reported as if it was at the surface.

Therefore it does not care about pressure or concentration. It just tells you the absolute amount of CO2 in the IR path.

Just like oxygen....pure oxygen at the surface is not a real problem to breath....but take that pure oxygen to 100 feet and we have a problem...houston control

We certainly do not want to breath CO2 levels of 5% at the surface or at 130 feet breath 1% CO2. Fortunatly properly working scrubbers keep the CO2 at lower and lower percentage as depth increases.

Hope this helps,
Tom

Question, am I missing something?
If you are using an IR absorb sensor then it will be specific to a frequency, but that frequency will change with pressure.
So as the pressure increases so will the error. IR is usually only accurate over a specific range.

Brent

11th December 2006, 21:11	#14 (permalink)
divetheworld Dive porn pimp Current Rebreather/s: Inspiration Classic Other CCR Other Rebreather/s: Not Bought Yet Inspiration Classic Inspiration Vision Classic Kiss Other CCR Join Date: Mar 2005 Location: Leeds, England Posts: 1,560	Re: Co2 Sensor At Dema [quote=Tom Rose;82793] Quote: (Originally Posted by jaap) A NDIR system "counts" the molecules of CO2 in the gas path....the greater the number of CO2 molecules the less signal to the detector....the number of molecules in the path is due to a combination of proportion of CO2 and pressure. Regardless, you cannot tolerate but so high a percentage of CO2 molecules in the gas mix reported as if it was at the surface. Therefore it does not care about pressure or concentration. It just tells you the absolute amount of CO2 in the IR path. Just like oxygen....pure oxygen at the surface is not a real problem to breath....but take that pure oxygen to 100 feet and we have a problem...houston control We certainly do not want to breath CO2 levels of 5% at the surface or at 130 feet breath 1% CO2. Fortunatly properly working scrubbers keep the CO2 at lower and lower percentage as depth increases. Hope this helps, Tom Question, am I missing something? If you are using an IR absorb sensor then it will be specific to a frequency, but that frequency will change with pressure. So as the pressure increases so will the error. IR is usually only accurate over a specific range. Brent __________________ Attitude and self praise is no reccomendation. Dont try to be a great man, just be a man and let history be the judge of you. CHECK OUT OUR INTERWEBS FOR CUSTOM REBREATHER UPGRADES *WWW.NARKEDAT90.CO.UK* *http://www.grpservices.com/pursuit/* Supporting Shearwater Research Products in Europe Last edited by divetheworld : 11th December 2006 at 21:17.
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