PADI not teaching dive tables anymore?

[lowviz]

While computers sometimes quit working, have you (or anyone else on this thread?) ever seen one actually give wrong data? Like for 18 minutes NDL at 130 ft on air?...//...

My VR3's are notorious for flaking out if the battery covering isn't removed before the battery is inserted. They can jam in the holder and momentarily lose contact if the DC is bumped sharply. A while ago someone reported a DC that read depth at the surface. Remember that real-world sensors feed the ever-reliable computer.

And there is this: http://www.scubaboard.com/forums/basic-scuba-discussions/432837-dive-computer-error.html

...//... Most divers don't 'understand' the tables that well; they simply know that the table says at this depth on that gas head up before this time passes. ...//...

As boulderjohn alluded to, you don't "understand" tables. They are just the chunky tabular output from a mathematical simulation. Worse yet, the simulation may have just been designed to give "expected" results (exploded goats) rather than mimic tissues. If so, the parameters have no direct correlation to human physiology. Your computer may be running the exact same simulation, just does it with much greater resolution and can track depth changes. I would prefer that the agencies better taught estimation and gas planning as a skill along with a clear intuitive explanation of how tables and computers came to be.

...//...That's a good point, but the kind of people who'd pass on computers to dive with tables don't seem to me to be the kind of people who'd not plan even if they used a computer, and the crutch-lovers will use computers. ...//...

Agree with both cases, but I was speaking to the crowd in the center that may attempt to obtain a deeper understanding if only the material was served up more clearly.

 

[DiveNav]

..... A single malfunctioning micro-transisitor will introduce a false 1 or 0 into the equation and, therefore, cause a false readout. It might be minor or significant, but it is there, nonetheless.....

Do you own a car? Do you drive it?
Do you have any idea on how many "micro-transistors" (btw, these days most likely they are "nano-transistors" ..... as the semiconductor manufacturing processes broke the sub-micron level quite some time ago) are there in a car?

Alberto (aka eDiver)

 

[dfx]

For me, I simply do not trust a computer to always give me valid information. Any number of small, but significant, errors can be introduced due to malfunctions in the circuitry or programming. A single malfunctioning micro-transisitor will introduce a false 1 or 0 into the equation and, therefore, cause a false readout. It might be minor or significant, but it is there, nonetheless.

Ahm, but that's not how computers work. If there's a malfunction, even the tiniest one, then you'll have the whole thing acting up on you. I'm sure you've seen plenty of computers (not necessarily dive computers, but all kinds of them) crash. Usually people blame the software, but that's only half the truth. Many times, especially on those weird, random, unexplainable crashes, there's an underlying hardware problem that's causing the crashes, but people will never know because they don't bother to analyze things.

 

[boulderjohn]

Although I know computers fail, it has never happened to me in the water.

On the other hand, I own several dive watches, and I use them while teaching pool sessions. The cheapest one is more expensive than two very basic computers combined. One day I glanced at the watch during the pool session to see how I was doing in terms of the class schedule. Pretty well! I had more time than I expected! Then I got out of the water, looked at the wall clock, and was shocked at how late it was. I guess that at some point during the session, the watch had stopped for a while and then started again.

No big deal in a pool session, but what if I were diving tables and thought I had that much more time before I reached my limits? There is a good chance I would have been on my way to the chamber afterward.

Dive watches are as apt to fail as computers, and bottom timers are nothing more than computers with very limited functions.

 

[lowviz]

So now it is not so hard to see why I feel that anything can fail and nobody really "has your back". I value the ability to recover from where I am at any point in my dive or to be able to say that "this or that" sounds just plain wrong. "Tables types" tend toward this approach also, I respect them.

Others are just fine with blindly following their DC's. Personal choice. Chances are, on the average, we will all be OK...

 

[Pullmyfinger]

Just do exactly as your OW instructor taught you, and you will be OK.

 

[lowviz]

Now you are batiting me. But it was quite nicely done.

 

[iamjblevine]

All it takes is the failure of a single micro-transistor to cause a computer to produce false data.

a critical sensor in a flight system would use quadruple redundancy, if any one sensor is out of tolerance it is omitted from the algorithm. No idea if dive computers use multiple sensors or not.

 

[drrich2]

Since dive watches & SPGs can malfunction, is a tables diver really less likely to suffer a gear malfunction than a dive computer user is?

Is the failure rate of a human brain in generating bad info. or, via inattention, multi-tasking, etc..., acquiring bad data (e.g.: got deeper than expected & didn't check SPG, or misread the gauge), not greater than the odds of a dive computer giving you false information due to glitch of some kind.

We know computers fail; freeze up, won't come on, had a bad battery, etc..., as any gear can fail. The concern seems to be that a computer might give badly wrong info.; wrong NDL's being key. I suspect table divers would, on average as a trend across a large group, make more such errors.

Some people dive with both a computer & a backup computer (I do; love my Cobalt, but use my old VT3 unit as a wrist depth gauge). Seems that would address the fear of wildly off NDLs.

Richard.

 

[Diver0001]

a critical sensor in a flight system would use quadruple redundancy, if any one sensor is out of tolerance it is omitted from the algorithm. No idea if dive computers use multiple sensors or not.

They don't. And in fact they're a lot more prone to failure than many people might think.

A good habit to get into is to compare your computer to your buddy's computer during the dive and/or to take a redundant gauge, like a bottom timer, so you can get an early warning if the computer is showing incorrect depth.

R..