First Dive Computer

[stuartv]

If you're after education, why do you consistently neglect to tell the whole story? E.g. mention that creators of DSAT stated it's not suitable for 6 tanks/day? -- Which you can do if you follow the numbers to the letter. Why do you omit the part where if something makes you overstay the NDL, you ought to have sufficient gas to complete your deco? -- So if you intend to go for "more bottom time", you should include gas planning, your RMV, and "better bent than drowned" into your risk analysis. This is aimed at people asking about their first computer, they are probably new at this and likely not aware of just how much difference there is between "more bottom time" for a single 3-tank day and "more bottom time" for 7 days straight. Do you ever mention that in your educational posts?

In my book education is when you try to give them the full picture. When you don't, that's more like brainwashing.

I have never gotten a hint of an impression that anyone I have ever conversed with about this was planning anywhere near 6 tanks/day.

The issues with overstaying your NDL are the same no matter what computer you are using. I don't recommend that anyone do that without getting deco training.

I do recommend that anyone shopping for a computer learn about dive computers - all aspects, including readability, battery types, watch vs console vs puck vs brick, wireless AI versus hoseful AI vs non AI, gauge mode, etc., including algorithms. And then learn even more about the algorithm in whatever computer they choose. And then I recommend that anyone with a new computer start off diving it conservatively. Work their way up to diving to the full NDL gradually. Don't just immediately start diving it and staying down until NDL=0. Build up experience incrementally and pay attention to their body after their dives to see how they feel.

As I am not aware of any data showing that a "conservative" recreational dive computer is actually any safer than a "liberal" recreational dive computer, I don't attempt to use snippets of data and factoids to scare people into buying a "conservative" computer.

Since you are so concerned that people are fully educated on why "more bottom time is bad", why don't you post some citations of the reports or data that supports the idea that dive computers that give longer NDLs (i.e. "liberal" computers) are less safe than computers that give shorter NDLs?

My own personal experience is that when I bought my first computer, I learned everything I could about dive computers before I bought one and I chose one that, among other criteria, had a "liberal" algorithm. I am still using that computer today and still glad that I bought it. I have done dives with a buddy that had a Cressi and had my dives cut shorter than they would have been if we were following my computer, because my buddy's computer ran out of NDL. Consistently.

You keep saying or implying that recreational computers that are more liberal are bad. Show us the data.

 

[dmaziuk]

You keep saying or implying that recreational computers that are more liberal are bad. Show us the data.

Show me one post where I said or implied that an algorithm is bad and I'll apologize (I may have posted sloppily worded stuff that might be interpreted that way, it is entirely possible). I would not normally call an algorithm "bad": it's just a tool, designed for a purpose. It would be like saying a screwdriver is less good than a hammer: of course it is, for hammering nails.

I keep saying that Suunto-bashing and "bigger NDL numbers" posts here range from, let's say "lopsided", to plain ridiculous, yes. I did and will continue laugh derisively at ScubaLab "computer studies" used as "supporting evidence". Like you and your "friend with a Cressi": all available evidence suggests that on the 1st dive with no additional conservatism, all algorithms should be within 2 minutes of each other at the most. So are you saying your dives have been "cut shorter" by entire hundred and twenty seconds? And he couldn't just go 2 metres up and be your buddy from there? Gimme a break.

 

[Jay]

FWIW I bought a Geo 2.0. It was cheap, does it core functions well and I'm happy with it. I don't bother hooking it up to my computer as I'm too cheap to buy the cable

geeez it gets bad mannered a little too quickly

Craig's insistence on "educated algorithm" and NDL numbers being the key to everyone's "future diving needs" gets a bit old.

It's not relevant what person XXXXX says. Bad manners just waste space on the forum and clutter threads, and more etc etc ....

yes. I did and will continue laugh derisively at ScubaLab "computer studies" used as "supporting evidence". Like you and your "friend with a Cressi": all available evidence suggests that on the 1st dive with no additional conservatism, all algorithms should be within 2 minutes of each other at the most. So are you saying your dives have been "cut shorter" by entire hundred and twenty seconds?

I was just going to haul out the ScubaLab 2016 and 2017 data (and the analysis I did on it here Place of dive tables in modern diving )

Could you let me know why you are dismissive of ScubaLabs study?

 

[scubadada]

Craig's insistence on "educated algorithm" and NDL numbers being the key to everyone's "future diving needs" gets a bit old.[/QUOTE
Your defense of an inordinately conservative decompression algorithm also grows old. My premise is to let educated divers decide, what is yours, let ignorant divers buy whatever they will?

 

[Jay]

Your message @scubadada is a little hidden ... it doesn't even seem to be white on white

 

[dmaziuk]

Could you let me know why you are dismissive of ScubaLabs study?

Did you read e.g. the DSAT paper? The discussion of underlying assumptions, design goals, the interpretation, parts about confidence intervals etc.? If so, read the ScoobyLoo rubbish and see if you spot the difference.

Pressurizing a bunch of computers and looking at their reading at a few random points proves only one thing: that they had those numbers at those points in the process. Nothing less, nothing more. And as I recall they couldn't even get the same numbers the second time around.

 

[stuartv]

I was reminded today of a post from Newbie Stu (thank you, @peterak) that seem relevant to this thread:

So you want to buy a new computer?

 

[scubadada]

Did you read e.g. the DSAT paper? The discussion of underlying assumptions, design goals, the interpretation, parts about confidence intervals etc.? If so, read the ScoobyLoo rubbish and see if you spot the difference.

Pressurizing a bunch of computers and looking at their reading at a few random points proves only one thing: that they had those numbers at those points in the process. Nothing less, nothing more. And as I recall they couldn't even get the same numbers the second time around.

Do you have better, or any other data, on repetitive diving and performance of dive computers?

There's nothing basically wrong with the standard profiles. I actually think they were chosen, in some part, to ensure that the conservative algorithms, like Cressi RGBM, did not go into deco. They could have been more aggressive for other algorithms. How would it have looked if several of the more conservative algorithms went into deco while the more liberal remained under NDL? Would that make a point?

Quite obviously, you and I are very different divers

I can't seem to find any published information regarding the derivation of the Cressi RGBM algorithim, could you please share with me?

 

[dmaziuk]

Quite obviously, you and I are very different divers

You and I have very different brains, so I don't expect you to get this: I don't have a problem with algorithms. What I find ridiculous is the idea that if you don't buy a most "liberal" computer now, all your future dives will be cut short.

 

[scubadada]

You and I have very different brains, so I don't expect you to get this: I don't have a problem with algorithms. What I find ridiculous is the idea that if you don't buy a most "liberal" computer now, all your future dives will be cut short.

No, not all your dives, just some of them, especially when your gas consumption improves

You didn't answer any of my other questions

I don't care what deco algorithms people dive. I do want them to make an informed decision on which computer to buy with reasonable knowledge of the variation in deco algorithms. You're happy with Cressi RGBM, good for you.