Tables & computers

[rhwestfall]

:nailbiter:

 

[Thalassamania]

Why is it that wherever you go on the internet there is always some wag that will chime in with an unverifiable, unproveable story about some non-repeatable occurrence that is necessarily spewed on a thread to try and disprove something that is obviously true?

First, you just verified me by 4 out 5 instances. None of you got the bent, thus 5 out of 5 of you experienced safe dives based on well known model limits. Thousands of dives were conducted today in perfect safety relying on those well known model limits. Read Weinkes books if you don't believe me, and then go argue with him about the close correlation and the figures he presents there.

Second, the outlier was obviously operator error or involved a computer no longer in production. The first error that is most commonly observed is that the diver in question had a hockey-puck/ Pelagic/other Nitrox reset and failed to set his nitrox mix, and then wouldn't admit that to you. If it wasn't that, then the operator set his computer to absurd levels of conservatism which is possible in some (even recent) computers. Uwatec Smarts have Micro bubble level settings that will create level-stop demands that are indistinguishable from deco stops during the running dive, yet are in no way mandatory in as much as the computers will not lock up when skipped. Other examples of operator error are too numerous to detail here. RTFM.

Third, you could not reproduce that outcome using any recent computers and you know it. It doesn't happen without operator error on comparably set computers. So what was your point. I know exactly what it was. Wish granted.

Fourth, there was no point to the whole concoction unless to say that in your opinion all computers are radically different, there is no correlation between models and that you daily expect any and all models to run flagrantly out of control. Is that your point? Better tell Dr. Wienke, correlation among the models is the underpinning of the design of his Thermodynamic EOS. He's wrong. You're right. Got it. Check.

Seems you sure got up on the wrong side of the bed this morning. Sorry about that, I sincerely hope it passes quickly. I did not read anything that Lynne wrote that I think Bruce would disagree with, so I fail to understand what you're so hot and bothered about.

I said no such thing. Why is it that the guy who jumps in to correct everyone (Mister Corrector guy who never originates anything) all the time continually misreads and misunderstands what he corrects. Read what I said again.

"reliable simulations of human physiological no-decompression limits in a recreational setting and well beyond."

Please respond with your explanation of where I indicated or used the word "human body". I even began the sentence in question with the warning, IN BOLD, declaring the theoretical posture of the models, yet in your zeal to spank someone (a decidedly non-moderator activity) you failed to comprehend the words.

How is it that you can ignore all this, stuff words in my mouth that I didn't say, reinterpret what I did say, and then correct it, without adding any plausible value to the proposition:
The models work. The models are reliable. Thousands of hours today, thousand of times today, yesterday, tomorrow and for years and eons yet to come.

You did not read the words. Shame on you.

Here are the words:

"Uwatec/Suunto/Pelagic/whatever computers will all recommend the same time limits to within a surprisingly small variance, because the limits and application of the fundamental model are that well known. While everyone in the world will jump on the decompression-models-are-theoretical bandwagon, they[models] have proven themselves millions, perhaps even billions of times to be reliable simulations of human physiological no-decompression limits in a recreational setting and well beyond."

Here are the facts:

The models do vary quite a bit, yes, they often yield rather similar no-D limits, but a lot of other functionality is often a bit passing strange. You pointed out several possible problems that would account for it, and there are a slew of others, not all of which require an incompetent operator or a damages/obsolete piece of gear.

Decompression models are not, in fact, physiological models, they are simply empirical models. That is a very different thing and that is what Lynne was pointing to. She is correct there the equations that are used in decompression computers do not, and are not intended to actually model inert gas as it diffuses in and out of the body. Rather they use a number of different mathematical techniques to arrive at an approximate answer to the question of how much risk of decompression problems is a person at given a particular past pressure exposure and an immediate potential controlled ascent. A simulation of, "human physiological no-decompression limits" would be entirely different kettle of fish and is well beyond even our best current theories.

 

[Pullmyfinger]

Bullshark is serious about deco discussions.

-Mitch

 

[Thalassamania]

Bullshark is serious about deco discussions.

-Mitch

Seriously?

 

[Pullmyfinger]

No...I meant that he was starting to get "too serious"...as in hostile.

-Mitch

 

[lowviz]

I read that as Thalassamania doing his best "Jax" impersonation. Double entendre? Who knows, -but yes, much too serious.


According to the TOS:

Please note: This forum has special rules. This forum is intended to be a very friendly, "flame free zone" where divers of any skill level may ask questions about basic scuba topics without fear of being accosted. Please show respect and courtesy at all times. Remember that the inquirer is looking for answers that they can understand. This is a learning zone and consequently, any off-topic or overly harsh responses will be removed.

 

[Thalassamania]

Sirius, no I'd rather be Betelgeuse.

 

[fjpatrum]

Almost makes me want to read the edited comment... almost. Anyway, thank you all for your input. I appreciate the reading recommendations and the information about whether or not you use tables and computers. As I've said several times now, this is about my education and goodness knows this has been an educational thread. Thank you all.

 

[Peter Guy]

For what it is worth, I was the diver with the "outlier" computer--Suunto Mosquito. The computer didn't "like" my profile, especially taking a long time from 40 to 20 feet. The Suunto algorythm penalized me for that time but the other computers gave deco credit. I am quite sure I could duplicate the issue if I had any reason to.

 

[Mr Carcharodon]

RGBM computers like the Mosquito make adjustments for repetitive dives, reverse profiles and rapid ascents. I’ve seen this myself where I found myself with 10 minutes of mandatory deco and my dive buddies were almost 20 minutes on the other side of NDL. Since my buddies omitted substantial amounts of mandatory deco according to my computer, if not theirs, it makes you wonder how mandatory that was. RGBM certainly can be different than computers running M value based models and very different than tables. That is a problem if you are trying to dive with a team.