Nitrox Divers - in 'ere please

[Druid]

Originally Posted by Scubee

That's a bit harsh. 1% either way is supposed to be acceptable in recreational nitrox

Originally Posted by thehappychappy

I have to assume thats a joke, I've never seen an analyser thats sold to be 100% accurate, they are to my knowledge sold as + or - 1%.

It was meant to be a joke. Perhaps I should have put a after the first paragraph.

[drunkdiver]

go on, you know you want too

[Mr_Brown]

Originally Posted by Timbobaggins

Yes to marking

plus or minus 1% never killed or bent no-one!!!!!!!!!!!

i agree doesn't really matter, possibly to one DP now and again.

but in bold so i can see it , no DP.

[NotDeadYet]

I'm a tight git so I write my fill request on masking tape, electrical tape or anything else. The shop writes the analysis on with duct tape. If it's in duct tape then I know it's an analysis because I'm too f***ing tight to waste perfectly good duct tape myself

As for analysis, I use the analyser reading for noting it but I round it to use it. If it's within tolerance then I use it as the target gas with no alteration to the plan.

Cheers,

Stuart

[liamm]

i'd go for one decimal place. But i am a numbers obsessed geek. for the percentage i do one decimal place and the MOD rounded up to the shallower whole meter. For the computer / deco calcs id round down to the lower whole unit of oxygen.
I know it doesnt really matter unless you are running very high PPo2s, but i cant really see a reason not to.

[west coast diver]

Originally Posted by thehappychappy

I have to assume thats a joke, I've never seen an analyser thats sold to be 100% accurate, they are to my knowledge sold as + or - 1%.

Davie

Have a green for being the first to point out to that analysers are only accurate to plus or minus 1% (and only when they're new).
fractions of 1% therefore have little meaning.

To my mind there's practically no difference between plus or minus 5% if it's a deco gas.
you just swap over a couple of metres shallower/deeper to compensate.

Stick it in your suunto and fly accordingly.

Very rarely do I get bang on what I ordered in a dive shop anyway.

W.C.D.

[Frankie Price]

Originally Posted by spunkmire

Absolutely no point in marking to even 1 decimal point-
the oxygen cells just aren't that accurate,
gas mix may change if the tank is still cooling from the fill
makes effectively no difference to your decompression schedule, and if you stay exactly 0.1m above your MOD for an entire dive as a habit i will buy you a pint.

Putting too much detail on the stickers confuses things.

This is not the issue, I don't think anyone treats the O2 reading from a sensor as gospel.
The point is that regardless of the implied precise analysis of the gas, marking to one dp indicates to buddies that the gas has been re-tested prior to the dive.
We are getting mixed up here in the semantics of precision versus accuracy.
The O2 sensor is an accurate device fit for purpose (within it's operating tolerance bands) but is by no means a precision piece of equipment.

[Nick_lincoln]

Marked to one decimel point. Most recent was 86.5 %. Set computer to 86% as this assumes more nitrogen breathed than actual, therefore conservative in terms of tissue uptake of nitrogen. UPTD's & CNS max values always watched closely when rounding down O2 values, but really only becomes an issue if using nitrox for lots of dives in a day or a couple of dives with reasonable deco times and high % O2 mixes.

MOD written on it too and on my wrist slate with the mix % next to it

[NeilB]

When I fill club cylinders the analysis gets written to one dp...the mod they can work out themselves depending on the pp they want to play to.

[Rod Abbotson]

Nice one Garf!

At least we have a proper discussion!

As i blend all my own gas mine is always spot on

Good idea, my adage is "never dive with a gas you haven't personally blended"

Ok I can hear the groans! I do this as I train many blenders after the course they all leave me to blend everything!

Seriously though many times I have analysed after blending after getting a weird reading found the blending to be correct and the analyser wrong.

Many divers also do not calibrate the analyser properly or recalibrate before it has dropped back to 20.8 20.9 again! Very dodgy!