Tables & computers

[fjpatrum]

actually .... most of them are not anymore.



3 simple concepts: compartments, overpressure gradients and half times.


Here you go

Alberto (aka eDiver)

I know the concepts, but I can't see the math and the progression of how it affects my dive was my point.
The training course I mentioned in my first post still implies most computers use the tables as a basis for their algorithms. If that's not the case I guess I'm not the only one who "Knows" something incorrect.

Thanks for the link. I suspect that will help clarify things a bit.

 

[boat sju]

Computers CLEARLY allow more bottom time and therefore, I think it's clear, more nitrogen loading.

I don't know that I agree with this exactly. If you use your computer to do a multilevel reef dive, starting out somewhat deep and ending up extending your bottom time in 25 ft of water or so, nitrogen load wise you end up better off. This is where I see the real safety advantage of computers over tables.

 

[rongoodman]

The training course I mentioned in my first post still implies most computers use the tables as a basis for their algorithms. If that's not the case I guess I'm not the only one who "Knows" something incorrect.

I took the classroom version of TDI Nitrox and the text mentions dive computers using a "complex mathematical algorithm", which "may be similar to those used in certain dive tables". I can't say for sure that the online version says the same, but I'm guessing you misunderstood.

When I took my trimix course last fall, we used neither computers or tables, but just a few simple rules that you can figure on the back on an envelope, or in your head at 190'(Ratio Deco). I did compare the plans to schedules generated by desktop software, but there was never any significant difference.

 

[Thalassamania]

I don't know that I agree with this exactly. If you use your computer to do a multilevel reef dive, starting out somewhat deep and ending up extending your bottom time in 25 ft of water or so, nitrogen load wise you end up better off. This is where I see the real safety advantage of computers over tables.

Lots of people think this, but I may not be true, it depends on your profile. If you take a computer to near the decom limit, then ascent a few feet and take to near the decom limit, then ascend a few feet, and so on till you are ready to come up and then make a normal ascent to the surface you are quite possibly in worse shape than if you go to a defined depth, stay there to the decom limit and them make a normal ascent to the surface.

 

[boat sju]

Lots of people think this, but I may not be true, it depends on your profile. If you take a computer to near the decom limit, then ascent a few feet and take to near the decom limit, then ascend a few feet, and so on till you are ready to come up and then make a normal ascent to the surface you are quite possibly in worse shape than if you go to a defined depth, stay there to the decom limit and them make a normal ascent to the surface.

Yeah, but to ride the NDL's up like that you'd need a lot of air. And that's kind of part of the point I'm trying to make anyway. Instead of teaching tables why not teach the proper way to get the most (safety) out of a computer. I think most people could grasp the concept of nitrogen loading, including on-gassing vs. off gassing, without ever having to learn tables. (I think I'm an ok engineer and I never used a slide rule.)

 

[Jax]

I know the concepts, but I can't see the math and the progression of how it affects my dive was my point.
The training course I mentioned in my first post still implies most computers use the tables as a basis for their algorithms. If that's not the case I guess I'm not the only one who "Knows" something incorrect.

Thanks for the link. I suspect that will help clarify things a bit.

FJ - if you really want to know, buy the book Amazon.com: Deco for Divers (9781905492077): Mark Powell: Books.

 

[DiveNav]

..... I think most people could grasp the concept of nitrogen loading, including on-gassing vs. off gassing, without ever having to learn tables. ....

We have an App for that

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Alberto (aka eDiver)

 

[boat sju]

We have an App for that

View attachment 116810
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Alberto (aka eDiver)

. . . of course you do :cool2:

After my last post I got thinking that we have some pretty good rules of thumb for rec diving. Max depth equals the capacity of your tank and rock bottom pressure is depth x 10 plus 300 (thanks Lamont). But are there any good guidelines for multi-level dives? After time at depth ascend a minimum of 20 ft, 1 atm or what?

I think Thal pretty well defined how not to do it.

 

[fjpatrum]

I took the classroom version of TDI Nitrox and the text mentions dive computers using a "complex mathematical algorithm", which "may be similar to those used in certain dive tables". I can't say for sure that the online version says the same, but I'm guessing you misunderstood.

When I took my trimix course last fall, we used neither computers or tables, but just a few simple rules that you can figure on the back on an envelope, or in your head at 190'(Ratio Deco). I did compare the plans to schedules generated by desktop software, but there was never any significant difference.

Thanks. I'll go through the course material again to make sure I'm not misremembering or not misunderstanding. It's certainly possible I misread that section or didn't quite grasp what was said.

 

[Thalassamania]

Computers and tables find their base in an often identical "complex mathematical algorithm." The difference is only in the display, think of a computer as an animated cartoon of the "complex mathematical algorithm" and tables as a series of snapshots of the "complex mathematical algorithm." The math is exactly the same, or at least very close.