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James Appel · 29th April 2006, 15:40

Quote: (Originally Posted by GuyW)

James, you are correct.

there are two things to consider:
1. The O2% in the cylinder
2. The completeness of mixing in the head during calibration.

Neither are 100%. So to correct for this you put in your best guess / measurement of what O2% is being used as the basis for calibration.

In order to establish this you need to know what O2% is in the cylinder. If you can determine this then calibrate the unit normally with this O2% and then give the unit a really-really good flush and let it stabilize for a while so you are sure that the head contains 100% what is in the cylinder. See what the unit reads. If it is different to what you calibrated for then adjust the calibration number accordingly.

This "magic number" then corresponds to your typical gas quality and mixing completeness on calibration.

Or just use 98% like I do. ;-)

Guy

My point is that IF I were to do a complete 100% effective flush, then the % of o2 in the head would be exactly the same as that in the cylinder. So why am I not supposed to enter the % of O2 that is in the cylinder if a complete flush gives me a head that has 100% of whats in the O2 cylinder (which has never been 100% O2, but has varied between 97% - 99% depending on O2 supplier as I always analyze my cylinder contents).

29th April 2006, 15:40	#4 (permalink)
James Appel New Member Current Rebreather/s: Inspiration Classic Other Rebreather/s: Join Date: Jan 2006 Location: Springfield, Oregon Posts: 60	Re: % asked for Oxygen Quote: (Originally Posted by GuyW) James, you are correct. there are two things to consider: 1. The O2% in the cylinder 2. The completeness of mixing in the head during calibration. Neither are 100%. So to correct for this you put in your best guess / measurement of what O2% is being used as the basis for calibration. In order to establish this you need to know what O2% is in the cylinder. If you can determine this then calibrate the unit normally with this O2% and then give the unit a really-really good flush and let it stabilize for a while so you are sure that the head contains 100% what is in the cylinder. See what the unit reads. If it is different to what you calibrated for then adjust the calibration number accordingly. This "magic number" then corresponds to your typical gas quality and mixing completeness on calibration. Or just use 98% like I do. ;-) Guy My point is that IF I were to do a complete 100% effective flush, then the % of o2 in the head would be exactly the same as that in the cylinder. So why am I not supposed to enter the % of O2 that is in the cylinder if a complete flush gives me a head that has 100% of whats in the O2 cylinder (which has never been 100% O2, but has varied between 97% - 99% depending on O2 supplier as I always analyze my cylinder contents).
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