Are dive computers making bad divers?

[tridacna]

In the past 10 years, I have yet to see any rec diver use tables. PDCs have simply taken over. This entire discussion is an exercise in SB mental masturbation producing zero value.

 

[fjpatrum]

In the past 10 years, I have yet to see any rec diver use tables. PDCs have simply taken over. This entire discussion is an exercise in SB mental masturbation producing zero value.

A lot like your comment.

Plenty of people use them. Hell, plenty of people responding to this thread have indicated they use them, and many are rec divers. I use tables every dive to give myself an idea what to expect. In most cases I run out of gas long before reaching NDL (because I'm a newb who doesn't get to dive often and I don't generally dive deeper than about 20-25 meters) but I want to know BEFORE my dive what I should be able to expect.

Is it the "norm" for most rec divers these days? Probably not, but that doesn't reduce the value of the conversation.

 

[doctormike]

In the past 10 years, I have yet to see any rec diver use tables. PDCs have simply taken over. This entire discussion is an exercise in SB mental masturbation producing zero value.

A lot like your comment.

Plenty of people use them. Hell, plenty of people responding to this thread have indicated they use them, and many are rec divers. I use tables every dive to give myself an idea what to expect. In most cases I run out of gas long before reaching NDL (because I'm a newb who doesn't get to dive often and I don't generally dive deeper than about 20-25 meters) but I want to know BEFORE my dive what I should be able to expect.

Is it the "norm" for most rec divers these days? Probably not, but that doesn't reduce the value of the conversation.

Sorry, I'm with tridacna on this one. People responding to SB threads are definitely not a representative sample of rec divers. If they were, everyone would be diving a BP/W.

This thread has gone on for quite a long time going over the same old tables vs PDC issues, as most of these do. I simply don't see the value of this discussion - I doubt that a lot of computer divers are going to start using tables based on anything brought up here.

From a practical, real world, rec diving point of view, PDCs are simply standard gear. Maybe not in newbie Caribbean trust-me cattle boat dives, but I guess that those operators keep people out of deco by relying on a hard, shallow bottom and high SAC rates. I don't think that those divers without computers are using tables either.

As had been said before, a table and a computer clearly BOTH give you your non-deco limit BEFORE your dive. The only difference is that the computer gives you an ACCURATE one DURING the dive.

 

[EFX]

Bottom line: fsw/msw isn't a physical depth. It's a pressure.

fsw/msw is a pressure but its value depends on the density and depth of the water. For example, at 30 m depth the equivalent pressure will be 30 m x 10.1 msw / 10 m or 30.1 msw. A dive in fresh water will exert the same pressure at 30 m x 10.4 mfw / 10 m or 31.2 mfw. Without knowing the type of water the pressure in these units cannot be determined. My computer has a setting for fresh or salt water. Therefore, it's using a fixed constant for salt water that does not take into account the density (salinity) of the water. If the algorithm uses msw/mfw for pressures and your DC's pressure sensor is calibrated in bar, then that pressure must be converted to a depth which is dependent on the density to come up with an equivalent pressure in msw/mfw. If the algorithm uses bar then the density (type) of water is not needed except to display depth. So, which is it? Does the algorithm use the value directly from the sensor or does it depend on an intermediate calculation to get msw/mfw?

Agreed. The only difference it makes is in the depth calculation.

 

[NAM001]

I was snot trying to go into to far into grammer , god knows im no expert, however on can say the the word " I " generates the action and the word " me " receives the action. I gave to you . You gave to me. Not you gave to I. all that aside. My saying it does not sound right was just avoiding further un-needed explanation. The purpose of my comment was that anyone can speek right or wrong and get a message across, but without some background of how to speak you will never do it right. Those that speak we-be are perfect example of this. WE-be, ebonics, samo samo. Thats what i be sa-in. Instructors just cant teach the variety of computers on the market to students. Most use computers as glorified depth gages and an alarm clock to tell them when to head up and that is about all. Those whose knowledge in dive computers are limited to that extent are set up for failure, whether it be use of audible alarms or realizing wrong information.

I think your analogy is apt, but not for the reason you think. The reason you give for "Me and Bob went to the store" being incorrect has nothing to do with learning to diagram sentences. Research has indicated that being able to diagram sentences makes a person able to diagram sentences, but not much more than that. What it teaches is soon forgotten and rarely used, as it was in this case.

With sentence diagramming (or other methods of teaching those formal rules of grammar), you would have come to your conclusion differently from the way you describe. You would have recognized that the combination of "me and Bob" is a phrase functioning as the subject of a clause. It could have been the main clause of compound sentence or a compound complex sentence, or it could have been a sentence in itself. You recognize its function is the subject of the clause by the fact that it is performing the action of the verb "went," with the remaining words forming an adverbial prepositional phrase modifying the verb and answering the question ""where." You would have recognized that while "Bob" is a proper noun, "me" is a pronoun, and pronouns must be in the proper case. Since the pronoun is part of a phrase functioning as the subject of a clause, then it needs to be in the nominative case rather than the objective case. Since "I" is the nominative case and "we" is the objective case, "Me and Bob" is incorrect.

You had instruction that taught you that, but it is not what you remember, and it is not the method you described using. You also had a teacher who taught you a very simple shortcut in lieu of that system: when you have a combination like Me and Bob, if you take them individually and listen to the result, you can tell if one is wrong. How can you tell? Well, by the fact that "Me went to the store" sounds wrong. You know this because your brain internalized that fact over years of listening to the way people speak. Linguists believe that children internalize 90% of the rules of grammar by age 5, long before they have had any formal instruction, although they could not put those rules into words. In fact, people learned to speak, read, and write English before the rules of grammar were invented. Shakespeare never had a single lesson in formal English grammar, because it had not been invented yet.

So that is one of the reasons that sentence diagramming is almost never taught these days. It is hard, in fact, to find a textbook that includes it. (I used to purchase such textbooks.) It teaches very little that you really need, and almost everyone forgets it.People need to use need some other way to decide what is correct.

I took my very first dive trip to Cozumel back in the last millenium, and I pulled out my newly-learned tables to track my dives. Everyone who saw me burst out laughing. The multi-level dives we were doing made the tables useless there. If you wanted to dive in Cozumel, you had to follow a DM by law, and even back then those DMs were using computers to track their multi-level dives. I had three choices. 1) I could just follow the DM and trust him to keep me safe. 2) I could hire a private DM to lead me on square profile dives. 3) I could get a computer.

That time that I pulled out my tables in Cozumel was the last time I ever saw any recreational diver use recreational dive tables anywhere in the world. They work for square profile dives, but like sentence diagramming, most people have forgotten how it is done and have chosen a different system for tracking and planning their dives.

---------- Post added December 11th, 2015 at 01:52 PM ----------

It is a problem if it was set up for nitrox and you did not know it. And then how many computers revert back to air after xx minutes of SI and you are still diving nitrox. I cant tell you howmany times i have been hit with the latter. finding the numberw out of whack at depth and having to re assign nitrox for the rest off the dive. The key there is "recognizing". As we said in the military, garbage in garbage out.

How likely is that failure mode? You have established that it is sensing depth and the display is operable, in other words it operating and not detecting an internal fault. After that it's algorithm execution. Are you saying it might make a mistake?

---------- Post added December 11th, 2015 at 01:59 PM ----------

No it is not the same. a data programmer and a key punch entry person do not do the same job. learning how to use your computer and understanding what it does are 2 different things. Based on your post alone you are the example of what computers turn people into. dependant non questioning users.

If you learn your computer, or any program that's available or any simulator u learn the SAME thing that the tables have

Enter simulator enter depth enter time...

You can learn them if you want... You don't need a table... It's archaic to think that that information exists in table alone.


Sent from my iPhone using Tapatalk

 

[tridacna]

A lot like your comment.

Plenty of people use them. Hell, plenty of people responding to this thread have indicated they use them, and many are rec divers. I use tables every dive to give myself an idea what to expect. In most cases I run out of gas long before reaching NDL (because I'm a newb who doesn't get to dive often and I don't generally dive deeper than about 20-25 meters) but I want to know BEFORE my dive what I should be able to expect.

Is it the "norm" for most rec divers these days? Probably not, but that doesn't reduce the value of the conversation.

Sure. 10 people on SB make up a quorum. In their own minds perhaps. I work in a dive shop and see what the other 99.999% of divers do. Hint: It aint tables and they're not getting bent either. Like the good doctor said above, if you believe everything that you read here, most divers would be diving BP/Ws, 7 foot primary hoses, octos on 70 degree swivels, steel tanks, Shearwater Petrels on all available limbs AND carefully planning their 30 feet dives with tables. Good luck finding those when you're not diving caves. Worthless conversation indeed.

 

[phoenix31tt]

I was snot trying to go into to far into grammer , god knows im no expert, however on can say the the word " I " generates the action and the word " me " receives the action. I gave to you . You gave to me. Not you gave to I. all that aside. My saying it does not sound right was just avoiding further un-needed explanation. The purpose of my comment was that anyone can speek right or wrong and get a message across, but without some background of how to speak you will never do it right. Those that speak we-be are perfect example of this. WE-be, ebonics, samo samo. Thats what i be sa-in. Instructors just cant teach the variety of computers on the market to students. Most use computers as glorified depth gages and an alarm clock to tell them when to head up and that is about all. Those whose knowledge in dive computers are limited to that extent are set up for failure, whether it be use of audible alarms or realizing wrong information.





---------- Post added December 11th, 2015 at 01:52 PM ----------

It is a problem if it was set up for nitrox and you did not know it. And then how many computers revert back to air after xx minutes of SI and you are still diving nitrox. I cant tell you howmany times i have been hit with the latter. finding the numberw out of whack at depth and having to re assign nitrox for the rest off the dive. The key there is "recognizing". As we said in the military, garbage in garbage out.



---------- Post added December 11th, 2015 at 01:59 PM ----------

No it is not the same. a data programmer and a key punch entry person do not do the same job. learning how to use your computer and understanding what it does are 2 different things. Based on your post alone you are the example of what computers turn people into. dependant non questioning users.

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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[Steve_C]

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

And why does it matter anyways?

I think that it is useful to understand where they come from, not all the details. Once you know that it is all data-model based with fudge factors thrown in you understand that being within NDL does not guarantee safety and going over NDL does not mean instant disaster. And what it means changes from day to day. You keep that in mind when riding NDL and you stay calm if life forces you to exceed things a bit. So I will ride NDL on my Zoop but not my Aeris although both are pretty safe. I dive 1.3 or less rather than 1.4 or higher. It is all probability and those are my choice of odds.

 

[CAPTAIN SINBAD]

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.

 

[drrich2]

Summing up what I glean from a number of posts, the main purpose of teaching tables per some is to instill an intuitive sense of roughly what NDL's for a given depth should be, so if the computer glitches & provides a much higher NDL on a repeat dive at depth where gas supply over more than one tank at substantial depths might throw someone into unknowing deco.

The question then becomes, historically, did teaching tables, which most divers don't continue to use substantially, successfully instill that 'NDL common sense?'

If not, for some hypothetical majority of divers, perhaps there is something profitable to be done for OW training, but tables aren't the best way to do it?

Just some thoughts.

Richard.