No. The worst you know you had ever mixed was... Bit of a difference.
Nope.. Incorrent.. So far I had been analysing all my mixes also for Helium content for the reason given by Baron..
For ease of mind. The argument I am represting here is not mine as well. I was sceptical in the beginning as well so I wanted to make sure.. The further I move ahead in time and experience in mixing and validating I come to the conclusion that the statement is in fact correct:
As long as your measured oxygen fraction is within the expected levels your Helium content is as well within a very tolerable variation (remember that is always a fill from scratch !)
Your argument comes down to "A trimix analyser is uneconomical because 1) I can empty first, and 2) I can borrow one". Did I get this right?
Not quite my argument comes down that it is uneconomical for most users and you'd have to compare the cost of it towards the cost of lost remaining fills (emptying instead of topping up)
Number second would only come into play for the remaining doubt (as it had been for me) for a lack of experience in mixing results, ease of mind etc..
1) how's that for uneconomical, and what happens when you're in the middle of nowhere and you need to top up your 12/50 with somebody's 10/70?
Well being in the middle of nowhere and having the need to top up with a different mix is a bit of a extreme edge argument innit?
You will always find a case to make an analyser sensible when you aim for that. It is a fair question if your majority of your diving is in an environment that you need to do this frequently.. well then the answer is simple.. you have the need for on, but I doubt that this is the case for a majority of the people buying a helium analyser..
Most buys are done for convenience more then an actual need, that is what I perceive..
As I said it was also just food for thought. If one comes to the conclusion to need one anyway, I am not threatening anyone with a gun saying don't buy it !
BTW I do not see your argument countering the economical side, but on the practical side to be able to do such dives or not..
Nevertheless it comes down to the qualitiy of the initial mixes to be topped up and to top up from.. If for instance these had been tested for He content before going into the middle of nowhere.. Analysing for Oxy level would be sufficient..
In an example 70 bars 12/50 topped up with another 70 bars of someones 10/70 to 140 bars.. the result should be a 11/60.. so if you measure oxygen level of around 11% oxygen.. then you are confident enough of your mix..
even when they not had been analysed for Helium (but the Oxy levels were alright) the the mixes should be somwhere between 12/47-12/53 and 10/67 and 10/73 so your worst resulting mixes (again when your oxy is ok) 11/57-11/63.. so please compare these gases in your planning tool and you will see that the impact on your schedule is negelctable..
2) so actually you do need one, you just don't want to spend the money, and all this "it doesn't matter" is just a posteriori justification
Nope I do not need one that is the whole point! All usage of it is just for convenience and ease of mind !