poor man's cell check

OceanOpportunity · 28th April 2008, 18:31

Hey all,

Been diving my Shearwater GF for awhile now, and am very much liking the mV output view...note this is the first set of electronics that I've had this option on.

Question...does anyone have a 'scale' indicating expected mV outputs over a range of PO2's? For those without a fancy linearity checker, this info would naturally be helpful during both calibration and spot checks during a dive.

Thanks for any direction and info
ML

4ster · 29th April 2008, 01:09

Is this what you had in mind?

OceanOpportunity · 29th April 2008, 01:37

Quote: (Originally Posted by 4ster)

Is this what you had in mind?

This is definitely helpful. Two Q's: What is the source of this document?, and what do the -3, -1.5, 1.5, +3 refer to?

THanks

Nailer99 · 29th April 2008, 01:38

Quote: (Originally Posted by 4ster)

Is this what you had in mind?

Neat. Green sent!

4ster · 29th April 2008, 02:53

The formula for a linear cell:
Air_mV / .209 = X / .98
where X is the mV in O2 and .98 is the O2 purity of the test gas.

(This is what is neat about this community, I asked Bruce at Shearwater essentially the same question about a year ago when I was fitting a GF to my Dolphin, he kindly wrote back with a few suggestions on how to check linearity and the above formula. You will find this formula in other posts about linearity testing here.)

The idea for the spreadsheet was from another post here (but I can't remember who to credit), I adapted the poster's idea for my use. I wanted a single laminated sheet to check linearity to 1 ata O2. If you want, pm me your email address and I can send my excel sheet if that would help.

Since cells are seldom perfectly linear I wanted a quick way to judge just how non-linear a reading was. The -3, -1.5, 1.5, +3 refer to percent divergence from perfection.

28th April 2008, 18:31	#1 (permalink)
OceanOpportunity for a world of water Current Rebreather/s: Other CCR Dolphin Home Build Other Rebreather/s: Not Bought Yet Inspiration Classic Other CCR Dolphin Home Build Join Date: Nov 2006 Location: Providence, RI USA Posts: 479	poor man's cell check Hey all, Been diving my Shearwater GF for awhile now, and am very much liking the mV output view...note this is the first set of electronics that I've had this option on. Question...does anyone have a 'scale' indicating expected mV outputs over a range of PO2's? For those without a fancy linearity checker, this info would naturally be helpful during both calibration and spot checks during a dive. Thanks for any direction and info ML __________________ Michael Lombardi Oceans of Opportunity www.oceanopportunity.com Elected Director, Society for Human Performance in Extreme Environments MN'07, The Explorers Club Project Manager, Diving a Dream
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29th April 2008, 01:37	#3 (permalink)
OceanOpportunity for a world of water Current Rebreather/s: Other CCR Dolphin Home Build Other Rebreather/s: Not Bought Yet Inspiration Classic Other CCR Dolphin Home Build Join Date: Nov 2006 Location: Providence, RI USA Posts: 479	Re: poor man's cell check Quote: (Originally Posted by 4ster) Is this what you had in mind? This is definitely helpful. Two Q's: What is the source of this document?, and what do the -3, -1.5, 1.5, +3 refer to? THanks __________________ Michael Lombardi Oceans of Opportunity www.oceanopportunity.com Elected Director, Society for Human Performance in Extreme Environments MN'07, The Explorers Club Project Manager, Diving a Dream
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29th April 2008, 01:38	#4 (permalink)
Nailer99 Custom Title Allowed! Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Jan 2007 Location: Seattle, WA, USA Posts: 170	Re: poor man's cell check Quote: (Originally Posted by 4ster) Is this what you had in mind? Neat. Green sent!
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29th April 2008, 02:53	#5 (permalink)
4ster Addicted to Oxygen Current Rebreather/s: rEvo Other Rebreather/s: rEvo Join Date: Mar 2006 Location: Arlington, Washington Posts: 268	Re: poor man's cell check The formula for a linear cell: Air_mV / .209 = X / .98 where X is the mV in O2 and .98 is the O2 purity of the test gas. (This is what is neat about this community, I asked Bruce at Shearwater essentially the same question about a year ago when I was fitting a GF to my Dolphin, he kindly wrote back with a few suggestions on how to check linearity and the above formula. You will find this formula in other posts about linearity testing here.) The idea for the spreadsheet was from another post here (but I can't remember who to credit), I adapted the poster's idea for my use. I wanted a single laminated sheet to check linearity to 1 ata O2. If you want, pm me your email address and I can send my excel sheet if that would help. Since cells are seldom perfectly linear I wanted a quick way to judge just how non-linear a reading was. The -3, -1.5, 1.5, +3 refer to percent divergence from perfection. __________________ Steve "My problem is that I have trouble reconciling my gross habits with my net income." Errol Flynn
(Online)

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