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Old 21st December 2005, 10:35   #4 (permalink)
nigelh
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Re: Ir detection limit

Quote: (Originally Posted by joshhan2000)
I was not talking about the deviation of the Pressure. There really is not much difference in that at all.
Sorry. That's how I took VdW.
Quote:
But when you increase the pressure by 10 bars you have also decreased the space the gas occupies by 10 times. This decrease in space leads to formation of CO2 crystal structures. Although these crystal a quick forming and quick to fall apart the still are there.
This is new to me. I clearly need to read up.
Quote:
So when you use the 4500 nm wave length of light to activate the CO2 you will get a falsely high reading form the crystals and will not achieve the 97% accurate that we all want. I not saying that IR can not be adjusted using things like Fourier Transform or by doing a calibration scale but in the lab we just simply cut the gas pressure down. I know that last year when using IR to measure CO emission of cars it took 25 know samples to calibrate the IR to read acutely. IR is not a linear scale that we are all use to on the O2 sensors. It is polymeric and will take a lot of work to calibrate the scale properly.
I make a lot of my living doing measurement systems but mostly these days lumps of metal trailing nasty shock waves so I find this area interesting. Do I assume that the problem here is the CO2 is a sublimating solid? Does it even have a gaseous state at 10 bar? Sheesh. I think I'll go and sit in a darkened room and hold my head.


Thanks for the reply
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