Are dive computers making bad divers?

[Steve_C]

While I am a believer in computers, when people say that tables are only good for non-realistic linear profiles then I am a bit lost. When was the last time, you guys did your typical SAW-TOOTH bounce dive in which you went to 105 feet stayed for 10 minutes then went up to 20 feet for 15 minutes followed by 70 feet dip for 11 minutes and back up again for 30 feet for 21 minutes? Who dives that way? Yes there is a variation in depth when we swim across an uneven terrain but …

Lets be realistic. Keep in mind that SDI version of US Navy tables give you 60 minutes of bottom time for 60 feet depth. This means that as long as you are not diving deeper than 60 feet and not staying more than 60 minutes in the water, you are within the safety bracket that your 500 dollar UWatec computer will "calculate" and tell you. You can go up and down and still not need a computer or even a table as long as you remember two numbers in your life and those are 60:60. Stay above 60 feet and stay within 60 minutes and you are good without any computer or table.

What about the next dive of the day? Do I need a computer? In reality my typical surface intervals are never less than 60 minutes and rarely more than 1 hour and 44 minutes. So a typical, relaxed surface interval which goes over an hour does not change anything in the 60:60 rule for the next dive. If you wish to split hairs then a surface interval of an hour applied to the above dive only removes 2 minutes from the max bottom time at a depth of 60 feet so after an hour of surface interval you are doing 58:60 instead of 60:60. Big deal! In all practicality 60 minute dive to a depth no more than 60 feet followed by a surface interval of 60 feet is repeatable cycle that requires no computer or table.

I honestly do not see any point in having a computer for Open Water diving which is confined to 60 feet anyway. The only reason why Open Water divers believe that “tables only calculate square profiles and computers are essential” is because their instructor at the dive shop is also a sales person for UWatec or Alladin Pro etc. He gets commission when he sells OW students a dive computer. This is why we have divers who are so knowledgeable in high tech solutions while not knowledgeable in the problems those high tech solutions are really solving for them.

60 matters some places but not so much in others. Most of the dive sites I dive off NC the bottom is 80-100 ft. I see lots of OW divers on the 80ft dives and some on the 100 ft dives such as our ledges. A popular dive with NEW OW divers is the Hyde. Bottom at 80-85. Top deck at 60. A typical dive may spend some time at 60, some time at 80-85, some time back up at 60. I have instabuddied with new OW divers on the Hyde and they had maybe 4-6 quarry dives prior to our meeting up. And now a there are usually two dives a trip and the SI is about an hour. Second sometimes on the Markham where you are varying from 40 on top to 85 in the sand but everybody hits the sand to see the big props.

 

[drrich2]

When I visited NC to dive, I easily rented 120 cf Faber tanks, & the popular shop nitrox mix was 30%. On off-shore wrecks, NDL could easily be an issue before running out of gas, even on dive #1.

Richard.

 

[lowviz]

... For those senior divers who have been diving since before the computer revolution, do you feel that the new generation has been idiotized by computers, or no.

I tend to shy away from your trademark "post a provocative question and watch the feeding frenzy" posts, but this time I'll bite too.

I used to operate and maintain a Varian MAT 44 Mass Spectrometer. German. It was controlled by two large printed circuit boards chock full of primitive (by today's standards) IC's. The two board set was fronted by Seufert(?), funded by a consortium, and intended to be a high speed video controller. It failed to meed the ridiculous design specs. However, it was stupidly fast, logically complete, yet general (that is the kicker). Someone at Varian realized that it could also control hardware. Varian bought into that, yep, killer app.

I contend that this was among the very first real "microprocessors" or "personal computers". I remember sitting in a hotel lobby (Mass spec conference) in Chicago talking to Karlungen Hab... His "keepers" were most nervous. Engineers talking to engineers is always a serious threat to corporate secrets.

Anyway, There and then is where I came to appreciate the extension of logic into hardware. It did not exist in any real form before that.

And the true gem of the evening was when I complemented him on the insane welds. Things of beauty. He he smiled and said "Ooooh Boaht, low pressure inside, high pressure outside, no difference." He then got up and walked away with his entourage. Yep, repurposed the U-Boat welders to vacuum welding. They do nice work. I dive a lot of it off the NJ coast.

So speaking directly to your bait: "do you feel that the new generation has been idiotized by computers, or no."

No, I do not. Not in the least bit. As long as we can understand what has gone before, then we should feel encouraged to make best use of what is now available. Unless you enjoy being a Luddite.

Yes, I love tables and "rules of thumb". But only for whispering uncertainties into my ear if my DC is doing something stupid.

 

[NAM001]

Ill bite.

It should be never be expected to understand how the numbers on the tables are derived and the science behind it. Just an explanation to say these are the tables to show the findings of what happens , not why. You teach the why with the coke bottle and the effect over time with the results of table. You dont teach the creation as you are implying. You say this is the bible for your diving the rules and the safety it provides. You do a few examples to show the results of differences in bottom time on tissues and SI has on tissues and explain how the 2 work together. You explain what a half time is and how it fits in the function of the tables that reperesent your diving. You note the NDL's and explain the 120 rule. They can see how the rule came about and when it is applicable. This is very typical to driving and stopping distance tables to show the effects of higher speeds and the effect of braking on wet and dry surfaces. No where in that process is it covered the lab conditions that created the tables. That level of understanding is not relevant to recreational diving. This is where you are wrong in the assumptions regarding the motives of learning the tables. As for your ABS example it does not make a difference how they work, but it does make a difference in understanding what happens when you step on the brakes in a skid if you stop straight it is working if not there MAY be a problem with it. Just as it makes a difference in how you drive a front wheel vs rear wheel vehicle. And by the way I do understand your position and it is an all or nothing position. Once again computers don't make bad divers they pave the way for being a bad diver or diving badly when used as a substitute for understanding. Its a chain effect not a direct effect. Although I could say that booze does not make a bad driver, that it makes a driver, drive bad. The semantics is moot, Its the end result that is important. It either directly or indirectly contributes to good or bad driving. I agree that tables are not really valid for the types of dives rec divers do. The square profile is not what rec divers do. I agree that computers do a much better job when it comes to accuracy minute by minute. That has never been disputed probably by anyone. The largest benefit to computers in the rec world is that the diver does not have to keep track of the dive to know when it is time to head up (alarms !!!! so you don't have to pay attention). And that it is a single source for display of depth and time. Those benefits mean less and less over time as you learn to tell time by tank psi, depth changes by ear pressure till you really don't need one at all. New divers many times have eyes glued to he computer because they are bad divers and the computer is the compensation for that. I know there are many instructors that send out primo divers with skills that far exceed the OW standards. They can only be praised for they product. But there are those that sell the cards so to speak and say don't worry you have a computer to tell you what you need. One can only assume that by now YOU can tell when your computer is not saying what it should say. Red flags should go up and initiate some form of resolution for the unexpected data. You should probably be able to identify the problem and fix it rather easily. After all 1-200 dives is what 5 or more years of diving for the majority. Unfortunately the new diver with a dozen dives does not have the benefit that you perhaps enjoy from the knowledge you have gained in those years. Using a computer as a crutch for that lack of understanding till experience sets in is never a good plan. Most will never rid then selves of the crutch. I see it as using a down line so you don't have to learn to learn good buoyancy. The line is a good backup but not as a desirable primary method of maintaining depth. If this was a discussion about weighting, and you got an lp tank filled with a cave fill, what would you expect your buoyancy to be as result if no training was ever done on air weighing 8#/ 100 cuft. One final thought you post does not even address the issue of computer not being set for the proper gas being used. Again if you don't know what to expect you don't know when something may be going wrong on the dive. NOt having knowledge is one thing, having it and not using it is another, no matter how it was derived.

Clearly u don't understand what I mean... Which is learning a table does not mean learning how the table derived those numbers...

I guess u don't understand what it means when I say the only information a table gives you is how long you can stay under the water... You can learn how to use a table perfectly without knowing jack squat of how the actual values were derived...

What you also do not realise is your analogy about programmer and data entry couldn't be more wrong either...

A table, you "enter" value (s) and the table tells you what's your output (NDL)

The computer does the same thing automatically, inputs values and tells you what's your output (NDL)

Learning to use either does not mean you learn how they do what they do...

And why does it matter anyways? Does not knowing how/why ABS works make me a bad driver?

What about an automatic bread maker... Does not knowing how to manually make bread vs following a recipe and putting the ingredients in the bread maker make me a bad cook? If the rest of my food that I can't cast off on a machine taste awesome?

Silly... Give it up... Computers don't make bad divers period... Bad divers will be bad divers whether they learned to use tables or computers


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[phoenix31tt]

---------- Post added December 12th, 2015 at 02:32 AM ----------

Ill bite.

It should be never be expected to understand how the numbers on the tables are derived and the science behind it. Just an explanation to say these are the tables to show the findings of what happens , not why. You teach the why with the coke bottle and the effect over time with the results of table. You dont teach the creation as you are implying. You say this is the bible for your diving the rules and the safety it provides. You do a few examples to show the results of differences in bottom time on tissues and SI has on tissues and explain how the 2 work together. You explain what a half time is and how it fits in the function of the tables that reperesent your diving. You note the NDL's and explain the 120 rule. They can see how the rule came about and when it is applicable. This is very typical to driving and stopping distance tables to show the effects of higher speeds and the effect of braking on wet and dry surfaces. No where in that process is it covered the lab conditions that created the tables. That level of understanding is not relevant to recreational diving. This is where you are wrong in the assumptions regarding the motives of learning the tables. As for your ABS example it does not make a difference how they work, but it does make a difference in understanding what happens when you step on the brakes in a skid if you stop straight it is working if not there MAY be a problem with it. Just as it makes a difference in how you drive a front wheel vs rear wheel vehicle. And by the way I do understand your position and it is an all or nothing position. Once again computers don't make bad divers they pave the way for being a bad diver or diving badly when used as a substitute for understanding. Its a chain effect not a direct effect. Although I could say that booze does not make a bad driver, that it makes a driver, drive bad. The semantics is moot, Its the end result that is important. It either directly or indirectly contributes to good or bad driving. I agree that tables are not really valid for the types of dives rec divers do. The square profile is not what rec divers do. I agree that computers do a much better job when it comes to accuracy minute by minute. That has never been disputed probably by anyone. The largest benefit to computers in the rec world is that the diver does not have to keep track of the dive to know when it is time to head up (alarms !!!! so you don't have to pay attention). And that it is a single source for display of depth and time. Those benefits mean less and less over time as you learn to tell time by tank psi, depth changes by ear pressure till you really don't need one at all. New divers many times have eyes glued to he computer because they are bad divers and the computer is the compensation for that. I know there are many instructors that send out primo divers with skills that far exceed the OW standards. They can only be praised for they product. But there are those that sell the cards so to speak and say don't worry you have a computer to tell you what you need. One can only assume that by now YOU can tell when your computer is not saying what it should say. Red flags should go up and initiate some form of resolution for the unexpected data. You should probably be able to identify the problem and fix it rather easily. After all 1-200 dives is what 5 or more years of diving for the majority. Unfortunately the new diver with a dozen dives does not have the benefit that you perhaps enjoy from the knowledge you have gained in those years. Using a computer as a crutch for that lack of understanding till experience sets in is never a good plan. Most will never rid then selves of the crutch. I see it as using a down line so you don't have to learn to learn good buoyancy. The line is a good backup but not as a desirable primary method of maintaining depth. If this was a discussion about weighting, and you got an lp tank filled with a cave fill, what would you expect your buoyancy to be as result if no training was ever done on air weighing 8#/ 100 cuft. One final thought you post does not even address the issue of computer not being set for the proper gas being used. Again if you don't know what to expect you don't know when something may be going wrong on the dive. NOt having knowledge is one thing, having it and not using it is another, no matter how it was derived.

I'm glad you took the time to write all that because it proves you agree with what i'm saying all along... which is... training/understanding (using whichever tool, tables or computers) and diver attitude etc will determine a good/bad diver. You can train and understand everything you need to understand without using tables period. As i said many other times, there are many ways to illustrate what a table shows you.

It's true when you say a computer can be used as a crutch to provide a false sense of security for a diver who doesn't understand anything about it (at the very least they just follow when it's time to surface), and that still doesn't make them a bad diver. Table limits are usually way shorter than computer limits for the majority of divers, i remember the first time i used a computer i couldn't believe the difference it made, so even then having a table and knowing how to use it and cross check serves 0 purpose because there is nothing to sense check unless you are doing a square profile (rare for most divers) as even going up 10' gives you significant time credit.

So really and truly, if doing the typical dives, you can know your tables inside out and still not know that your computer is on the fritz... unless of course you cross check with your buddies, or a simulator, or some computer program. You certainly wont be able to use tables

 

[NAM001]

You clearly have no understanding of the tables or your computer. so i agree to disagree.

AFAIK this is not a limit but a recommendation... could be wrong but i believe that's what my certification said. Additionally, if it was a limit, it's not the computers that permit them to violate it as they would be able to do the same dives without a computer.

---------- Post added December 12th, 2015 at 02:32 AM ----------



I'm glad you took the time to write all that because it proves you agree with what i'm saying all along... which is... training/understanding (using whichever tool, tables or computers) and diver attitude etc will determine a good/bad diver. You can train and understand everything you need to understand without using tables period. As i said many other times, there are many ways to illustrate what a table shows you.

It's true when you say a computer can be used as a crutch to provide a false sense of security for a diver who doesn't understand anything about it (at the very least they just follow when it's time to surface), and that still doesn't make them a bad diver. Table limits are usually way shorter than computer limits for the majority of divers, i remember the first time i used a computer i couldn't believe the difference it made, so even then having a table and knowing how to use it and cross check serves 0 purpose because there is nothing to sense check unless you are doing a square profile (rare for most divers) as even going up 10' gives you significant time credit.

So really and truly, if doing the typical dives, you can know your tables inside out and still not know that your computer is on the fritz... unless of course you cross check with your buddies, or a simulator, or some computer program. You certainly wont be able to use tables

---------- Post added December 12th, 2015 at 01:06 AM ----------

Since you mentioned the 120's, I think you probably found them nice tanks to dive with and be able to get the max dive per NDL and still have enough to satisfy rock bottom psi.

When I visited NC to dive, I easily rented 120 cf Faber tanks, & the popular shop nitrox mix was 30%. On off-shore wrecks, NDL could easily be an issue before running out of gas, even on dive #1.

Richard.

 

[phoenix31tt]

You clearly have no understanding of the tables or your computer. so i agree to disagree.

Clearly... *yawns*


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[NAM001]

I agree with you on most points. Preticularly the 60:60. One would not know that if they had no clue about tables. Once you understand that you don't need the costly puter like you said. Rules of thumb came from somewhere and it wasn't the computer on your wrist. As fart as ow cpmouters that limit 60 ft. No need set the max depth alarm for 60 and dive. The cost of that... perpetuated sense of you dont have to watch your depth gage or watch.

While I am a believer in computers, when people say that tables are only good for non-realistic linear profiles then I am a bit lost. When was the last time, you guys did your typical SAW-TOOTH bounce dive in which you went to 105 feet stayed for 10 minutes then went up to 20 feet for 15 minutes followed by 70 feet dip for 11 minutes and back up again for 30 feet for 21 minutes? Who dives that way? Yes there is a variation in depth when we swim across an uneven terrain but …

Lets be realistic. Keep in mind that SDI version of US Navy tables give you 60 minutes of bottom time for 60 feet depth. This means that as long as you are not diving deeper than 60 feet and not staying more than 60 minutes in the water, you are within the safety bracket that your 500 dollar UWatec computer will "calculate" and tell you. You can go up and down and still not need a computer or even a table as long as you remember two numbers in your life and those are 60:60. Stay above 60 feet and stay within 60 minutes and you are good without any computer or table.

What about the next dive of the day? Do I need a computer? In reality my typical surface intervals are never less than 60 minutes and rarely more than 1 hour and 44 minutes. So a typical, relaxed surface interval which goes over an hour does not change anything in the 60:60 rule for the next dive. If you wish to split hairs then a surface interval of an hour applied to the above dive only removes 2 minutes from the max bottom time at a depth of 60 feet so after an hour of surface interval you are doing 58:60 instead of 60:60. Big deal! In all practicality 60 minute dive to a depth no more than 60 feet followed by a surface interval of 60 feet is repeatable cycle that requires no computer or table.

I honestly do not see any point in having a computer for Open Water diving which is confined to 60 feet anyway. The only reason why Open Water divers believe that “tables only calculate square profiles and computers are essential” is because their instructor at the dive shop is also a sales person for UWatec or Alladin Pro etc. He gets commission when he sells OW students a dive computer. This is why we have divers who are so knowledgeable in high tech solutions while not knowledgeable in the problems those high tech solutions are really solving for them.

---------- Post added December 12th, 2015 at 01:51 AM ----------

And all those decisions you mention is based on some level of undertanding of tables. Especially the LOOOOOONG safety stop comment. I also like the "problems with divers" paragraph.

I think it is incorrect to say that tables are a necessary tool to learn in diving or make bad divers who are dependent on computers. What do they teach us:

1 - Plan what max depth will be reached before dive.
2 - Reset Max depth indicator.
3 - Set Watch bezel or timer.
4 - Maybe recalculate if planned depth exceeded (definitely) or not reached.
5 - Time surface interval.
6 - Plan next dive based on residual nitrogen penalty - Go to step 1.

What have I learned: I learned how to follow information through shaded tables without a real understanding of what the number mean. With a max depth indicator and a watch, I was more aware of my dive times and depths and was a little more diligent in pre-dive checks. With modern bottom timers - other than a little more intimate understanding of my expected dive profile - nothing as my pre-dive checks do not have to be more involved than computers with the exception of step 1. In the end, you have no understanding of why specific times are used, what residual nitrogen really means to you, what algorithm is being used etc. If you have an issue while on tables and exceed limits on your repetitive dive, reach into your pocket and find they floated away even though you had tethered them (happened to be probably 5 times), what are you going to do?? In the end, you are going to do the same thing someone with a failed computer does, end the dive, maybe do a looong safety stop.

By using tables, I have learned no basics with regards to decompression theory. I have only added complexity to my predive (I cannot tell you how often everyone on the boat forgot to time the BT, SI or have the max depth). In the end, there is no added benefit to the diver to have an understanding of tables vs computer.

Problems with divers too dependent on the computer - this is a misnomer. It is really a problem with divers not being able to properly analyze, think through and resolve issues - Think situational awareness. It is not a dependence that causes a diver to have a problem when a computer fails. It is a problem with instruction, training and retention that the diver does not automatically know what to do! Your computer fails - No backup = End dive, Backup = maybe continue dive. When a second computer is beneficial, bring it. Multi day diving, highly desirable repetitive diving etc are dives a 2nd computer is worth it. When in doubt, blow the dive.

It would be far more beneficial to give even a rudimentary understanding of decompression theory to a recreational diver than teach an outdated, rarely used, prone to error method of maintaining NDL.

There are many tools we use now that we did not have 'back in the day'. Using computers with an understanding of their capabilities, failure modes and limits are what is needed.

---------- Post added December 12th, 2015 at 02:08 AM ----------

Well nothing will be solved here, Especially among the demographic of those posting. For most of us physical tables have no purpose ANYMORE. Perhaps some newer divers will explore the tables and find all sorts of holes in their training and answers to a lot of things they have been told but never really thought about. If new divers take away nothing more from this than a 120 rule, and validate it with tables, they have received some benefit from this thread, and I almost guarantee that they will not forget it and use it always whether they realize it or not. Then 5 years down the road a thread will be opened about the use of tables and each will say they don't use them. And again physically they don't but mentally they do. Or better yet. Who needs tables when you are diving 40 ft cause THE NDL IS LONGER THAN THE GAS SUPPLY. Where would they get that from??

 

[Storker]

Not unusual for this board, the excluded middle is about the size of a medium city.

What about, in the immortal words of Winnie-the-Pooh, "both, please"? Learning tables and getting a mental picture of NDLs at different depths doesn't mean you can't use a computer to get the benefit of multilevel diving and real-time tracking of your estimated N₂ loading. And using a PDC while diving doesn't mean you can't cook up a decent depth/run time estimate by glancing at a table instead of spending five minutes pushing buttons.

Just a thought...


--
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Typos are a feature, not a bug

 

[NAM001]

Thats what I do. I use a very basic level knowledge of tables to second check what the computer is saying, I consider the tables correct based on the reaserch that went into their creation. They are a standard to be measured against. if they are close i go with the computer if they are way off i end the dive and check to see if the correct gas is being used or some other configuration or sensor issue before i let it take me down the wrong road. Especially when diving with rental gear or with some one using rental gear. I am a dedicated computer user so I would not even try to promote not using one if given a choice. I believe they are just that good.. I trust but verify my tools, after all My petrel is jsut a computer with a program running. Those that go with trust with out verification are setting them selves up for failure. That process makes bad divers. As for those that mocked with "complex planning a 30 ft dive" I dont have to plan a 30 ft dive because I know the basic tables like so many do. I don't even pay attention to the NDL time left on a 30 ft dive because the spg is the controlling aspect of the dive's end time for shallow dives. How do i know that? Well.............

Not unusual for this board, the excluded middle is about the size of a medium city.

What about, in the immortal words of Winnie-the-Pooh, "both, please"? Learning tables and getting a mental picture of NDLs at different depths doesn't mean you can't use a computer to get the benefit of multilevel diving and real-time tracking of your estimated N₂ loading. And using a PDC while diving doesn't mean you can't cook up a decent depth/run time estimate by glancing at a table instead of spending five minutes pushing buttons.

Just a thought...


--
Sent from my Android phone
Typos are a feature, not a bug