New dive computer for Divemaster internship

[SubAquatix]

A little research with DAN and other organizations that track incidents might sway you away from less expensive computers.

The reason is that less expensive computers lack the cpu power an memory to process multiple compartments in a timely manner. What they do instead is calculate 3 or 4 compartments, then extrapolate for the 12 or 16 they might be using as a part of the algorithm or model they are using. This could lead to a miscalculation in cases where extents are being pushed. Higher end computers have the capability to calculate for all compartments in a parallel manner in a timely manner.

If you choose to go with "On the Fly Deco" and eliminate using a computer, you may wish to consider UTD's course, found here:
http://www.utdscubadiving.com/en/events/detail/4371-54-ratio-deco

As an original developer of the process known as Ratio Deco, Andrew Georgitsis brings a perspective not found in other courses. More importantly, he allows you to participate in the class as internet based. At $125, it is money well spent regardless of what method you choose to employ to protect yourself!!!

 

[KenGordon]

SubAquatix, I would be interested in some examples of incidents which have been attributed to poor dive computer performance. I would also be interested in computers which are unable to provide a good profile whether or not that has resulted in an incident.

In recent years small processors have become very powerful. The limiting design concern in a small device like a dive computer is battery. Running for a reasonable time from the available battery is the challenge, but now there are very capable processors with average power draw in the micro amps, so the screen backlight dominates.

In the OP's case I would guess changing or charging a battery frequently would be a disadvantage. The colour LCD screens are the worst for battery. OLEDs are better but supply scale and long term availability make them unsuitable for dive computers (or any low volume, long lived product). That would suggest a Petrel might not be the best choice.

I suppose the OP might be diving morning and afternoon with different groups. This raises a point about how adjustable the algorithm is. Some models from the same manufacturer allow more aggressive settings than others.

Someone previously made good points about using whatever the shop sells, I don't know if that made it past the post culling.

Computers are a bit like cars, get one which matches what you want to do. What is best of a multi gas dive in dark water is not always best for 24 dives a week, month after month.

Do learn how to use it though. Also get used to the feel of the numbers.

 

[ScubaInChicago]

An issue you may want to research is what decompression algorithm is being used? Some computers use a proprietary algorithm that is under lock and key while others use an open source like Buhlmann or VPM. The advantage with the former is you can run profiles at home long before the dive to validate if the dive can be done safely. You can also run those models and chart M values of different compartments. With the proprietary stuff, it may involve trying to plan a dive on the dive computer itself which may prove to be very limiting. I personally don't like the idea of jumping in the water and hoping my dive computer will know my personal physiology to keep me safe.

Here is a link to that shows that computers don't always get it right:Corporate coverup exposed divers to grave risk / Company kept computer defect secret for 7 years, according to Oakland lawsuit - SFGate

 

[Oldbear]

I would select one that is easy to read, easy to program or set O2 levels, easy to find surface intervals, easy to plan a dive and easy to pull up the log book...especially on your last dive. Secondly preferably one that you can change the battery yourself. There are several on the market for less than $500 that you could buy.

P.S. If you go tech ms,e sure it switches to gauge mode.

 

[stuartv]

I'm surprised to see so much discussion of Deco and of algorithms in a thread about a new computer for a DM internship.

If he's looking at a DM internship, he's probably not going to be leading any deco dives, right?

It seems to me that the point of debate would, does he get the most liberal computer he can, so he doesn't end up taking clients up because he's at his NDL and then have clients who are unhappy because they still had a lot of NDL time left. Bearing in mind that his client might on their first dive of the day, where the DM might be on his 5th, just for example.

Or does he go for something middle of the road, in terms of being conservative, so that he doesn't end up leading clients where his computer says there's plenty of NDL left and his client ends up busting the NDL on their on computer because it's more conservative?

Client: "I was following you and I exceeded my NDL and now my computer is locked out for 24 hours. How could you be so irresponsible to keep me down for that long?!?!"

DM: "That is your own damn fault. You are responsible for watching your own NDL and ascending if you need to."

Yeah, I wouldn't relish the though of that latter conversation....

The DMs I have had have always used air, even when my buddy and I are using nitrox. They just said "I might run out of NDL before you and have to go up. If so, you can come up with me or hang out and come up when you're ready."

If that's pretty normal, then I'd say a DM ought to be prepared for the possibility of doing as many as 6 dives a day - 2 tanks in the morning, 2 in the afternoon, and 2 tanks of night diving - and having clients that cause them to bump up against the NDL at least some of the time. With all that, it seems to me like a DM would want the most liberal computer they can get, and then, depending on the circumstances, possibly crank up the Conservative Factor - like, maybe to match a client's computer more closely, if the client has a really conservative computer.

So, for the OP:

http://www.scubaboard.com/forums/co...zers/305374-so-you-want-buy-new-computer.html

and

http://www.scubaboard.com/forums/co...-you-want-buy-new-computer-4.html#post7378321

 

[Jim Lapenta]

Six dives a day is a lot of dives. If he's using nitrox he may run up against his limits on the cns clock pretty quickly. The computer is not something I would want to rely on for safety in those circumstances. Since the computer is not taking his individual limits or physiology into account.
I have no idea why my previous post was cut. I thought it was informative and realistic for a conscientious dive leader. Using the opportunity to educate his charges and help them to keep themselves safe. I stand by that. May have to start keeping my own copy of posts?
In any case a mid range computer like a dg03. Dg02, or one of the other AUP line from oceanic or AERIS would be my choice given the needs of the OP. AERIS comps can be gotten cheaply since they are being phased out /absorbed into oceanic. I would stay away from some of the more conservative lines. I'd also stay away from any operation that forced me to do 5 or 6 dives a day on a regular basis.

 

[SubAquatix]

SubAquatix, I would be interested in some examples of incidents which have been attributed to poor dive computer performance. I would also be interested in computers which are unable to provide a good profile whether or not that has resulted in an incident.

As stated, I would direct your questions and research through DAN or others that track accidents.

My own experience has found utilization and familiarity to be the greatest Failure. "B" an experienced Male Dive Pro here in NC, had an incident even though well within the parameters of his computer. In that case, it was originally blamed on the minimal conservatism of the computer, a default setting since changed by the manufacturer at the recommendation of DAN and others. Even so, there were other contributing factors determined after the face. "C" a female diver on her first Caribbean trip, had partied a little to hard before diving. She also blew through her safety stop and wondered "what that beeping" was.

All of that said, as stated much of that data is tracked, including what CPU and how much memory is used in many computers.

 

[stuartv]

Six dives a day is a lot of dives. If he's using nitrox he may run up against his limits on the cns clock pretty quickly.

As I said before, all my DMs so far have been diving with air. But, I have very limited experience, thus far. My last diving was 3 weeks ago off Oahu. I did a 2 tank night dive. I had the same DM that I'd had that morning for a 2 tank wreck/reef dive. And I know that he also did a 2 tank dive in the afternoon with other customers. I don't think anyone was FORCING him to do 6 dives a day. And they don't even offer night dives every day, so I know he doesn't do it every day. I think, that day, he was doing it because he wanted the work.

And I can also say that if my night dive (first one, to a wreck at just over 100') had been cut short because my DM was using a really conservative computer that required him to go up well before we were low on air or NDL, I definitely would have been, well, disappointed.

And if you look at the second link I posted earlier, it will take you to a post with links to some actual ScubaLabs testing showing that there is a HUGE range of NDLs that different computers give when you're talking about doing multi-level dives with multiple dives in a day. One example was one computer giving 2 minutes of NDL, on a 3rd dive, where another computer was giving 72 (I think) minutes, and several others were giving over 50 minutes.

This is why I would think that the computer choice for a DM would be all about how liberal/conservative the computer is for doing multiple dives (even if it's only 4) in a day.

 

[Jim Lapenta]

As a DM he is also supposed to be a role model. Flying the computer is not role model behavior. Role model behavior for a DM would be leading his charges using the most conservative profile.

His computer should not be dictating the dives. Nor should it be the computer of his guests. If he has not been leading the same group all day it is possible that his charges would have considerably more NDL time. In that case he should be using a computer that is conservative for himself and explain that the dives may be short if he runs into an issue with NDL's. The divers are then free to decide if they will do the dives, call them, or plan and dive their own profiles within the parameters set by the operation. As they should be doing anyway. The plans the divers are diving with their computers should not be dependent upon the DM's. Nor do they need to be the same. They should have their own plans.

I still stand by my recommendation that a working DM who is diving a lot and may need to do that for a living should look out for his best interest when it comes to safety. If he needs to surface early the divers are always left with the option to continue on their own. They may get yelled at on the surface. So what? You find another op that treats you like an adult.

It's the main reason I don't do DM led dives. I don't want them or their computers governing my dive profile.

 

[KenGordon]

As stated, I would direct your questions and research through DAN or others that track accidents.

My own experience has found utilization and familiarity to be the greatest Failure. "B" an experienced Male Dive Pro here in NC, had an incident even though well within the parameters of his computer. In that case, it was originally blamed on the minimal conservatism of the computer, a default setting since changed by the manufacturer at the recommendation of DAN and others. Even so, there were other contributing factors determined after the face. "C" a female diver on her first Caribbean trip, had partied a little to hard before diving. She also blew through her safety stop and wondered "what that beeping" was.

All of that said, as stated much of that data is tracked, including what CPU and how much memory is used in many computers.

It is your claim that there exist dive computers so useless and underpowered they hurt people as a result. Surely you should be prepared to back that up?

The Aladdin example is now almost 20 years old.

Re ScubaInChicago's planning point, Suunto have software you can download for free before buying their computers which allows planning. It has 3 or 5 levels of conservatism, it's descriptions. Using GF you have 10000. How to chose?

I dived with a person who was on VPM 0 once. He'd bought the computer and had no idea that the base was 3 ish. I certainly agree user error is a likely cause of issues.