Another Tables vs. Computers Thread
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C'mon man, you don't expect people to read the directions that come with their computer do you?Jason B:
Well, they refuse to take a class! 
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Again, just to show that there's little new in the universe, here's something I just came across (I found an old hard drive) that I wrote back in 1990:
A major misconception, held by many divers who use dive computers, is that they monitor, or model, exactly what is going on in the body. A dive computer, like a set of decompression tables, is only a guide, based on a theoretical model. The ability of a model to produce safe profiles may or may not have anything to do with how accurately the model describes the mechanics of nitrogen on-gassing and off-gassing during those profiles.
In all decompression models the major (and usually the only) variables that are considered are depth and time. Dive computers calculate their decompression status based solely on these two variables, and their model. Thus, the decompression status displayed by a dive computer does not usually consider water temperature, physical exertion, ascent rate (though it may be monitored in some cases), the diver's physical condition, age, gender, hydration, etc. These are all variables that are considered to affect a diver's susceptibility to decompression sickness. A strenuous dive in a cold water environment will produce the same read-out on most dive computer as a low exertion dive to the same depth for the same time in the warm Caribbean. To counter these factors, the diver must assume the responsibility of adding safety factors to their dives while using dive computers, just as they have been added in the past while using tables. Dive computers are not talismans that will guarantee the diver will not develop decompression sickness. They are nothing more then animated tables and must be used with common sense. The diver must be aware of potential of developing DCS during any dive.
Another area where the dive computer may deviate from reality involves the accuracy of the pressure transducer. As depth gauges, dive computer's have proven to be much more reliable than mechanical depth gauges. Their accuracy, in the worst case during a dive, is 2 fsw shallower than the actual depth. If this occurs, then the nitrogen pressure that is calculated will be less than the actual pressures that should have been calculated. The dive computer is computing a lesser decompression status than is needed. Preliminary calculations suggest a reduction of the M0 values to 95% of their current values would adjust for potential transducer error. This would have the effect of reducing the no-decompression limits as much as 20% in the shallower depth ranges.
A major misconception, held by many divers who use dive computers, is that they monitor, or model, exactly what is going on in the body. A dive computer, like a set of decompression tables, is only a guide, based on a theoretical model. The ability of a model to produce safe profiles may or may not have anything to do with how accurately the model describes the mechanics of nitrogen on-gassing and off-gassing during those profiles.
In all decompression models the major (and usually the only) variables that are considered are depth and time. Dive computers calculate their decompression status based solely on these two variables, and their model. Thus, the decompression status displayed by a dive computer does not usually consider water temperature, physical exertion, ascent rate (though it may be monitored in some cases), the diver's physical condition, age, gender, hydration, etc. These are all variables that are considered to affect a diver's susceptibility to decompression sickness. A strenuous dive in a cold water environment will produce the same read-out on most dive computer as a low exertion dive to the same depth for the same time in the warm Caribbean. To counter these factors, the diver must assume the responsibility of adding safety factors to their dives while using dive computers, just as they have been added in the past while using tables. Dive computers are not talismans that will guarantee the diver will not develop decompression sickness. They are nothing more then animated tables and must be used with common sense. The diver must be aware of potential of developing DCS during any dive.
Another area where the dive computer may deviate from reality involves the accuracy of the pressure transducer. As depth gauges, dive computer's have proven to be much more reliable than mechanical depth gauges. Their accuracy, in the worst case during a dive, is 2 fsw shallower than the actual depth. If this occurs, then the nitrogen pressure that is calculated will be less than the actual pressures that should have been calculated. The dive computer is computing a lesser decompression status than is needed. Preliminary calculations suggest a reduction of the M0 values to 95% of their current values would adjust for potential transducer error. This would have the effect of reducing the no-decompression limits as much as 20% in the shallower depth ranges.
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Thalassamania:
Almost a point in favour of NetDoc's "take my course" pitch.
My computer allows me to adjust the "conservatism" of the model. Of course, I have to know how to do this by reading the book. The computer does allow for the additional variable. Is it perfect? Not at all, but then again the way you adjust diving using tables to account for the other variables is subjective too. The only bit of advice I remember being given when I started with tables had to do with making an adjustment for temperature.
Thanks Ted!
Yes, my class deals with the definition and limitations of the SWAG. Of course this applies not only to computers, but to tables as well.
Yes, my class deals with the definition and limitations of the SWAG. Of course this applies not only to computers, but to tables as well.
limeyx
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tedtim:
funny. my brain allows me to vary my conservatism too. it also magically takes into account how i am feeling, how the current is, how hard i am working etc.
the downside is that once the batteries for your brain die, then it's not really possible (yet) to replace them
Ah,
so we are back to condescension mode.
If you think that you turn off your brain to dive with a computer, you have a fallacious idea of what is involved. You are the type of person who thrives in using a hammer to put in screws because a screw gun is too technical and rots your brain.
If you think that somehow being chained to a table, watch and depth guage is ANY different than being chained to a computer you are completely deluded!
If you feel that an OW student should be able to pull a table out of their arse you are completely delusional.
so we are back to condescension mode.
If you think that you turn off your brain to dive with a computer, you have a fallacious idea of what is involved. You are the type of person who thrives in using a hammer to put in screws because a screw gun is too technical and rots your brain.
If you think that somehow being chained to a table, watch and depth guage is ANY different than being chained to a computer you are completely deluded!
If you feel that an OW student should be able to pull a table out of their arse you are completely delusional.
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It is a point in favor. The problem with computers is that they've been dicked with by the recreational diving community and now have who knows how many levels of protection for the corporate suits from the law suits. How can you know where the cliff is (as unstable as that might be) when the manufacturers and agencies are scurying about trying to camo it up.
Doc's class seems to me to be a good idea, its not his fault that the product, by and large, has failed.
Doc's class seems to me to be a good idea, its not his fault that the product, by and large, has failed.
limeyx
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NetDoc:
actually I was (attempting) to make a joke.
If you can point to any of my posts that are condescending, I'd honestly be surprised since none of them were written with that intent.
I also dont really appreciate your comments. You dont know me, have (as far as I know) have never met me and you mis-characterize my point of view.
EDIT: actually a "joke" is not the best way of saying it.
I was attempting to suggest another possibility in a somewhat humorous way w/out offending anybody.
I never did actually trust the "conservative" factor on my Suunto -- how do I really know if I am feeling "not so OK" or "even more not so OK" ?
Maybe I need a computer class, if only someone offered one
EDIT2: Nice to know I am not only deluded but delusional to boot.
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