Calibration Back-Pressure and the Megalodon CCR

CombatDiver

bubnotbub

Hi Kevi,
thanks for your great work.

Regards

Aldo

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RonMicjan

kevin did a very well done, realitivly scientific test, hopefully now every one (especially Joe) can admit they are happy (or wrong) and admit that the early threads on this subject were in error.

If any analyser is providing errors in gas analysis when hooked up to a meg, then it is causing those exact same errors to EVERY mixed gas diver out there, CCR, OC or even commercial. You cant even tell me, or any of us, that we have been analysing gas, using OMS, or any other analyser, wrong, all these years.

My .02, and I will gladly have the last word here.

I still liked the way I phrased it the first time, leave it to stuart to forment a happy place, doubleplusgoodspeak for all!!

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scubagrunt

This is a fun thread!!!
ps. i enjoyed the article Kevin

correction this was a fun thread

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jradomski

Due to a disagreement between Leon and myself , I have pulled all my posts..

Anyone who as spoken to me know I think highly of his product and my only concern was of a POSSIBLE issue in some cases by methodology, all my responses, with the exception of one, specified testing was done on other units.


When I have time I will document the cal procedure using various meters, to either back up kevin's testing or highlight possible irregularities.. I will do the testing initially with a simplified model to show what may happen, and will keep out any references to any particular unit.. If it warants I would proceed with an actual head of whatever RBs people ask me to test and that I can get a hold of..

The only Thing that I will leave in this thread is this following statement:

Calibrating gases of various ean mixtures and/or oxygen, any added pressure is irrelevant as long as the calibration method used, is also used to measure the unknown mixture.. In effect you are "nulling" any added pressure.

Calibrating for PO2, the presure in the sensor chamber is important.

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michael

Great articie thanks kevin

michael bering

schford

I have now tidied up this thread a little. Hopefully every one will be fairly happy (well as happy as any one ever is!)

Joe, as any user can has deleted his own posts due to an off board discussion. I have perma deleted them so we don't end up with blank posts and so it does not detract from the superb job that Kevin did.

I have also tweaked the others ever so slightly so it flows right and we are all one big loving happy community and again we dont detract from the great job that Kevin did.

So you my call me Mr nice big brother today (thats a joke )

Stuart

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Steve

Sounds like you may be full of hot air or possibly suffering from calibration back pressure.

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schford

What are you saying about my asse ohhh back pressure hehehe

__________________
Bailout and Kit Management account for Murphy's Law

The only bad question is one you did not ask and later wish you had.

Use of RBW is subject to the Rebreather World Terms & Conditions of Use

AD_ward9

Kevin has done a very nice piece of work, and produced a good article.

Surprising in the discussion that so much heat can be generated from just a few millibar of resistance!

Kevin's results surface here, but they apply to almost all EAN mixes: after all, the little O2 measuring devices for measuring EAN mixes rely on backpressure to be within a certain range. The flow restrictors on portable monitors are nowhere near as good as Joe's method which he describes in another excellent article on this subject. It would be good if Kevin posted his article on a number of the other O.C. SCUBA boards.

For me, Joe's cal method was one of the better ones. Though I cal on air, I respect the camp that cal on O2. I check on O2, and the other camp probably check using air. The check mechanism would pick up anything that is wrong with using too much flow, for a rebreather, but for O.C. with an EAN mix, there is no equivalent check done usually. This means Kevin's paper is much more important to O.C. divers than for rebreathers - though it is still instructive.

These two articles go hand in hand: Joe's on O2 cal, and Kevin's on the error band.

I do not know if Kevin and Joe met in a pub, agreed to each describe half of the same issue, and then be vehement in arguing it out to make sure we all understood. However your Machevelian scheme was planned out, by serendipity or a pint of 90 shillings, it worked well! Everyone will remember the need to do cal, then check.

Thanks to both for doing a nice job.

Cheers,

Alex

NB: In Scotland, we grade beer by Shillings. 90 Shillings is nice strong beer, shared amongst friends because it is not so easy to come by. So, you go into a Scottish pub and say, "A pint of 80 Shillings please", or 60, 70 or 90 as the evening takes you.