Safety of some popular dive computer algorithms???

[eponym]

But I've heard it on the boats: My computer beeped down there? I wonder why?

I was going to say something about fool-proof interfaces versus the ingenuity of fools, but it would sound flippant.

Given the title of this thread, it's important to remember that no dive computer is safe if you don't pay attention to it while diving. Or if you don't know how to interpret its display.

I heard a sobering anecdote (I've forgotten the source) about someone who incurred a deco obligation while diving with a Suunto computer. He interpreted the "STOP" display (which means you're going to have a mandatory stop higher up, later on) to mean "stop here, now." And patiently, foolishly waited for the display to change while using up air and going further into deco.

Bryan

 

[DepartureDiver]

I heard a sobering anecdote (I've forgotten the source) about someone who incurred a deco obligation while diving with a Suunto computer. He interpreted the "STOP" display (which means you're going to have a mandatory stop higher up, later on) to mean "stop here, now." And patiently, foolishly waited for the display to change while using up air and going further into deco.

That sounds foolish at first, but stress and other factors always come into play ... which is why the display needs to be kept uncluttered and very, very simple.

 

[ChrisA]

I'm very intrested in the AERIS Atmos Elite and The OCEANIC VT PRO wrist mounted, hoseless dive computers, my concern is that they borth use the Haldanean Algorithm, which at some points on the last dive, gave 74 minutes of no-deco time when ascending, while the RGBM gave 30minutes of no-deco time.

In conclusion, i want a safe computer, but not a paranoid one. Based on these different algorithms, is it okay to add that much no-deco time when ascending? Which algorithm or theory is correct? I don't intend to pretend that i know a whole lot about this subject, i've just read the Scuba Lab's results and some other material. Thanks for your responses, i know this is kinda long...

Oceanic owns Pelogic which is the company that build the computers for Aeris, Oceanic, Sherwood and many others. They all use the same Haldanean algorithm. I have a Serwood version ad yes it give a LOT of NDL time on multilevel dives. I went down to about 90 feet then came up and swamm at the 35 foot level back to the exit point. By the time we got back my computer giving me over an hour of NDL and after a zero minute surface interval would let me go do a dive to 60 feet for abbout 40 minutes. Yikes. After comming up from 90 feet most sane divers might want a surface interval a bit longer than zero minutes. OK my computer is older, but you can find profiles that go against common sense. The Suunto seems more reasonable.

But for most dives if yu keep a one hour or more ssurface interval your air supply will limit you. For example at 40 feet my computer gives my over two hours. My tank is not that big so the computer's algorithm is moot. Even at 100 feet I'm more limited by air than NDL It is only on repetitive dives that the algrithm maters but if you keep a one hour SI the algorithm matters less. That said, my next computer will be one of the Suunto models. Because it recommends about what I think is reasonable

It likely only really matters on a liveaboard where you will be doing a zillion dives back to back for a few days and nights

 

[CuriousMe]

That sounds foolish at first, but stress and other factors always come into play ... which is why the display needs to be kept uncluttered and very, very simple.

Well, yeah but....that's kind of like saying the reason a diver couldn't use their compass is that with stress and other factors, it was to complicated to read.

I'm sorry but, there's no reason in the world why you shouldn't know what your computer display means before you get into the water with it. If it's to complicated for you to understand, you shouldn't be diving with it until you figure it out.

Peace,
Cathie

 

[rjchandler]

I went down to about 90 feet then came up and swamm at the 35 foot level back to the exit point. By the time we got back my computer giving me over an hour of NDL and after a zero minute surface interval would let me go do a dive to 60 feet for abbout 40 minutes. Yikes. After comming up from 90 feet most sane divers might want a surface interval a bit longer than zero minutes. nights

why yikes? What was the computer really telling you? Does it recognize "zero minute" surface intervals ifyou actualy go back in the water right away?

 

[DepartureDiver]

Well, yeah but....that's kind of like saying the reason a diver couldn't use their compass is that with stress and other factors, it was to complicated to read.

I'm sorry but, there's no reason in the world why you shouldn't know what your computer display means before you get into the water with it. If it's to complicated for you to understand, you shouldn't be diving with it until you figure it out.

Peace,
Cathie

Except a compass won't kill you. You should see some of the original air integrated computer displays when they first came out. It was all about being fancy. Check out Tekna's old one as well as the original Oceanic/U.S. Diver one. Displays have changed a lot, but some are still complicated. When you are overloaded with information, it can get confused. For example, are you looking at your bottom time, your no-stop time, the amount of time left based on your gas consumption, or the time left based on your oxygen CNS level. If all of this is on there (and some come close) it is information overload. Fortunately, some hard lessons have been learned and they are made easier to read. All divers have made at least one dumb mistake and thought about how dumb it was. So mistakes will happen. Layouts must take into consideration how we process information instead of just putting all possible information out there and this should be taken into consideration when deciding what computer to purchase. More gadgets and display information isn't necessarily better.

 

[CuriousMe]

Except a compass won't kill you. You should see some of the original air integrated computer displays when they first came out. It was all about being fancy. Check out Tekna's old one as well as the original Oceanic/U.S. Diver one. Displays have changed a lot, but some are still complicated. When you are overloaded with information, it can get confused. For example, are you looking at your bottom time, your no-stop time, the amount of time left based on your gas consumption, or the time left based on your oxygen CNS level. If all of this is on there (and some come close) it is information overload. Fortunately, some hard lessons have been learned and they are made easier to read. All divers have made at least one dumb mistake and thought about how dumb it was. So mistakes will happen. Layouts must take into consideration how we process information instead of just putting all possible information out there and this should be taken into consideration when deciding what computer to purchase. More gadgets and display information isn't necessarily better.

I see your point.....but still think it's a cop out to say that it's the comp designer's fault.

I have two different computers and I know what every graphic indicator/number that might show up on the screen means. 60ft just isn't the place to ponder what something that shows up on your comp should mean.....that's why they come with a manual.

I've seen so many folks get on a dive boat and then try and figure out how to use their computer.....some don't even have the manual with them! It just doesn't make any sense to me.

Peace,
Cathie

 

[DandyDon]

I've seen so many folks get on a dive boat and then try and figure out how to use their computer.....some don't even have the manual with them! It just doesn't make any sense to me.

Exactly right! Study the manual and key the buttons until you know the machine. Then run the simulations; I get emotionally caught up on those when the sim-dive goes bad! Do a sim-dive into the red, then do slow ascents, deep & shallow stops, and see how long it takes to get back to the Green. Plan the dive, dive the plan, and make the puter part of it all.

 

[DepartureDiver]

I've seen so many folks get on a dive boat and then try and figure out how to use their computer.....some don't even have the manual with them! It just doesn't make any sense to me.

I was on a live aboard once many years ago and a diver ahd a Skinny Dipper and he had been turning it off after every dive and starting fresh on the next dive. This was discovered when he started not feeing good ... but fortunately he was fine. A simple read of the manual would have prevented this. But dive stores also love to sell equipment to novices as they are heading out the door to a dive boat and not all explain how to use a computer or even fully understand themselves how they work. Too many believe that if they stay within the limits of the computer they will be fine. As seen in this thread, smart divers want more information and to understand computers. But the staff of many dive stores simply don't understand differences in computers (other than how they look and the display information) to fully inform the differences to the customer I think your point about the manual is well taken and hopefully dive stores will stress how important it is to read the manual. This of course is no excuse for the diver to not be responsible for their own safety on the simple operation of a computer.

 

[eponym]

But dive stores also love to sell equipment [. . .] and not all explain how to use a computer [. . .]. I think your point about the manual is well taken and hopefully dive stores will stress how important it is to read the manual. This of course is no excuse for the diver to not be responsible for their own safety on the simple operation of a computer.

Certainly applies in my case, at my LDS. As a new diver, I bought a Suunto Vyper and the extent of the staff involvement in my learning how to use it consisted of pointing out the handy menu structure flowchart inside the back cover of the manual.

It required a good deal of study on my part to master all the features and all the displays--and I've designed computer interfaces, so I'm not unskilled at learning them.

Based on what Suunto puts out I'd say they could do a much better job of creating a readable discursive introduction to their products' operation, not just a reference book with concise and disconnected presentations of each feature. Something on CD or DVD would be nice . . .

I also agree that the owner is responsible for doing the work of learning. But the shops don't help matters when they sell dive computers without stressing the need to master them before diving with them.

Bryan