[Dive computer] buying advice

[DiverDownD3]

Hi @Nodeist

As @uncfnp wrote, I would suggest learning a little about decompression algorithms prior to making your computer purchase. Most 1st dive computers will have very similar features, the decompression algorithm will be one difference you may want to take into account. This is a topic generally ignored in OW training

I'm currently reading Deep Into Deco by Asser Salama and I'm learning a lot. Not really the type of book that you sit down and read like a fiction novel, but I'm enjoying learning the history of how we got to where we are today.

As far as computers are concerned. I started out with a one button Mares puck. It was fine for awhile, but the whole one button scrolling got pretty dang annoying after awhile. Especially when you are going through the Logbook section.

Another thing that shouldn't be overlooked is the ability for the computer to be bungee mounted (if you are going with a wrist computer). Either look for one that already has it built in or one you can buy an adapter from DSS. Bungee mounts have a couple advantages. Easier to take on/off. 2 bungee cords give you some redundancy. And personally, I like the computer to be more on my forearm than my wrist, hard to do that with a traditional watch strap. Just a thought.

 

[stuartv]

I'm currently reading Deep Into Deco by Asser Salama and I'm learning a lot. Not really the type of book that you sit down and read like a fiction novel, but I'm enjoying learning the history of how we got to where we are today.

As far as computers are concerned. I started out with a one button Mares puck. It was fine for awhile, but the whole one button scrolling got pretty dang annoying after awhile. Especially when you are going through the Logbook section.

Another thing that shouldn't be overlooked is the ability for the computer to be bungee mounted (if you are going with a wrist computer). Either look for one that already has it built in or one you can buy an adapter from DSS. Bungee mounts have a couple advantages. Easier to take on/off. 2 bungee cords give you some redundancy. And personally, I like the computer to be more on my forearm than my wrist, hard to do that with a traditional watch strap. Just a thought.

I thought Deco For Divers, by Mark Powell, was easier to read and equally informative.

I use NATO G10 style watch bands for my computers. Like this one:

NITROX-17

Easily long enough to fit over a drysuit - even over my forearm area in my drysuit. Easily trimmed to a shorter length. It goes through both strap pins, so you won't lose your (watch-style) computer, even if 1 pin breaks. It's not stretchy, but I use it with my drysuits and wetsuits and I don't really have any trouble with putting it on tight and it doesn't move around at depth.

For a wristwatch-style computer, I would no hesitate to buy another band like this, if I got a new computer. For pucks or bricks, I like elastic straps, like what come with the Shearwater Perdix computers or the Hollis TX-1. The stetchy wrist strap on my TX-1 works very well.

 

[Tassi Devil Diver]

Avoid computers that use the RGBM decompression algorithm, look for a computer that uses one of the Buhlmann algorithms which has undergone a significant amount of animal and human testing and is open source. RGBM is proprietary model that is not available to be scrutinized by anyone who chooses to and has undergone very little human testing (if any), which is why the computers that use the RGBM model tend to be overly conservative.

 

[rongoodman]

RGBM is proprietary model that is not available to be scrutinized by anyone who chooses to and has undergone very little human testing (if any), which is why the computers that use the RGBM model tend to be overly conservative.

There was a full implementation of RGBM(not the Suunto proprietary version) available for some Liquivision computers, but they're currently out of the market, so the only bubble model currently available is VPM as a Shearwater add-on.

 

[JohnN]

Avoid computers that use the RGBM decompression algorithm, look for a computer that uses one of the Buhlmann algorithms which has undergone a significant amount of animal and human testing and is open source. RGBM is proprietary model that is not available to be scrutinized by anyone who chooses to and has undergone very little human testing (if any), which is why the computers that use the RGBM model tend to be overly conservative.

A common complaint about Suunto is their algorithm is too conservative. My SAC rate runs around .5 cu ft/min (not exceptional I know), almost always dive with big (120 cuft) tanks, I almost always dive EAN32, almost always multi-level dives and always have SI's > 60 minutes. Given these, even on 4 dive days and multiple days of diving, I do not find the algorithm limiting my bottom time.

As for safety, there are a ***** load of people out there diving Suunto computers, I haven't noticed any reports of them dropping like flies

 

[ScubaSteve858]

I really like my Hollis DG03 from Divegearexpress.com It has optional air integration and Nitrox compatibility. For $250 it has served me well.

 

[stuartv]

Avoid computers that use the RGBM decompression algorithm, look for a computer that uses one of the Buhlmann algorithms which has undergone a significant amount of animal and human testing and is open source. RGBM is proprietary model that is not available to be scrutinized by anyone who chooses to and has undergone very little human testing (if any), which is why the computers that use the RGBM model tend to be overly conservative.

None of the recreational computers use Buhlmann. They use algorithms that are BASED ON Buhlmann, which is quite different. They are all proprietary.

The only computers I know of that have Open Source implementations are the Heinrich Weikamp OSTC 3 and OSTC 4. The Shearwater, Ratio, and other computers that run Buhlmann with Gradient Factors are running their proprietary implementations of a public domain algorithm.

I would personally avoid an RGBM computer, but not exactly for the reasons you gave.

A common complaint about Suunto is their algorithm is too conservative. My SAC rate runs around .5 cu ft/min (not exceptional I know), almost always dive with big (120 cuft) tanks, I almost always dive EAN32, almost always multi-level dives and always have SI's > 60 minutes. Given these, even on 4 dive days and multiple days of diving, I do not find the algorithm limiting my bottom time.

As for safety, there are a ***** load of people out there diving Suunto computers, I haven't noticed any reports of them dropping like flies

You're not limited by your computer's NDL. Cool. With your SAC and using 120s, it sounds like you are probably doing mostly shallow diving where any computer will give a really long NDL. I dive 120s with Nitrox, but my SAC is not as low as yours, and I am still almost always limited by NDL. But, most of my fun diving is NC or NJ wrecks, where depths are often greater than 100' and almost always at least 70', NDLs are usually 25 minutes or less, and it's no problem for my tank to last way longer than my NDL.

For people who are limited by their computer's NDL, they will most likely find any Suunto except an Eon Steel (which runs a different algorithm than any other Suunto - RGBM Fusion versus other RGBM flavors in the other Suuntos) to be more limiting for them than a computer running the DSAT algorithm (e.g. Oceanic, Aeris, Sherwood, and maybe some others).

 

[KenGordon]

Avoid computers that use the RGBM decompression algorithm, look for a computer that uses one of the Buhlmann algorithms which has undergone a significant amount of animal and human testing and is open source. RGBM is proprietary model that is not available to be scrutinized by anyone who chooses to and has undergone very little human testing (if any), which is why the computers that use the RGBM model tend to be overly conservative.

Has there been animal or human testing of GF?
And "overly" compared to what golden standard?
Can I see the source code of my Petrel?

 

[DiverDownD3]

@stuartv yeah it's not the easiest reading book, but I'm still able to get a lot from it. I'll probably read Deco for Divers afterwards. Really enjoying getting into the theory. Partly because I would like to understand decompression theory in depth and partly because I'm a nerd

 

[dmaziuk]

A common complaint about Suunto is their algorithm is too conservative. My SAC rate runs around .5 cu ft/min (not exceptional I know), almost always dive with big (120 cuft) tanks, I almost always dive EAN32, almost always multi-level dives and always have SI's > 60 minutes. Given these, even on 4 dive days and multiple days of diving, I do not find the algorithm limiting my bottom time.

+1

I dive a computer that some tossers over at scubalab coerced to show 2 minutes of NDL once. (Or was it 4?) I've not seen anything like that after 7-8 days of actual diving on typical vacation schedules of 2-3-4 Al80/air tanks/day. (And I wouldn't get my knickers in a knot if I had, but that's a topic from a different thread.)