Dive Computer No Deco Computations Question

[GreggS]

To follow up on what @runsongas said, yes, when diving 2 computers running different algorithms, you must run the more conservative as your primary. The reason for this is with most brands of computers if you run it as your back-up and it puts you into deco before your primary does, it will lock you out of using it for 24-48 hours depending on the brand. Once it is locked out, the only way you can use it is as a bottom timer. But if you use it as a bottom timer before the lockout ends, it will add another 24 hours to the dive mode lockout.

So be careful with that.

 

[tursiops]

42 minute surface interval

There is your problem, with Suunto. It penalizes you with a shorter NDL on the following dive.

 

[boulderjohn]

First dive was 81 feet for 43 minutes, 42 minute surface interval and the second dive was 64 feet for 46 minutes. The split was on the second dive.

I assume you mean that the split happened at some point in the second dive, you saw the split, not at the end.

Others have pointed things out before I got to post. I do not quibble with their posts.

GreggS made an important point. If you violate the limits of the Suunto, it will go into gauge mode for 48 hours and be close to useless for you.

You said the conservancy of your Suunto was set to zero. The Suunto has several conservancy choices, including altitude. Suuntos are one of the rare computers that do not calculate altitude on their own and have to be set. Are all your settings at zero? Years ago I was diving with a Shearwater (Buhlmann algorithm) in Florida, after having thrown together a regulator set in Colorado. I decided to use my old Suunto Cobra air integrated computer (on a high pressure hose) as a pressure gauge. On the second dive of the day, my mind wandered to the last time I had used that Suunto, and realized it was for some dives I did in the Denver area years before. I realized it was set to the highest altitude setting. I checked and, sure enough, I was already well into deco. Since I only wanted it for a pressure gauge, it wasn't a problem, but if I had been wanting it as a computer, I would have been sunk.

 

[butterwm]

Thank you all for your responses. From what I gather collectively the Sunnto software and algorithm seems to have some limitations and flaws. However, you have to honor the most conservative of the two.

With that being said, a dive computer is an expensive and major purchase. Some of your nicer and higher recommended models (Shearwater Teric for example) run over $1,100. How many divers out there are really spending the money to buy another expensive second computer to use as a backup? I feel like if you buy a “cheap” computer as a backup then you pay the price like I am with my Suunto.

 

[DiveLikeAMuppet]

Thank you all for your responses. From what I gather collectively the Sunnto software and algorithm seems to have some limitations and flaws. However, you have to honor the most conservative of the two.

RGBM (or the approximation of RGBM) in Suunto simply works based on a different model and theory. It tends to “punish” you for certain things like short surface interval, yo-yo profile or a second dive deeper than the first - because at the time, the prevailing theory supported such approach. But later we returned back to Buhlmann… In 10 years, someone might come up with something completely else.

Apple Watch has its own flaws - for example, I believe that it will stop working if you violate the depth limit and stop calculating any stops. That’s not really acceptable for a real dive computer because it should always bring you to safety, not stop working because of some legal liability limitation. Suunto might lock you out but it will still properly calculate any stops that you might need to make to get safely out of the water.

 

[inquis]

There are some cheaper computers that run the Buhlmann LZH-16+GF algorithm: Shearwater Peregrine ($550), Deep 6 Excursion ($350), and Mares Puck 4 ($390), for example. Used is another option.

A backup computer is effectively insurance against missing the remainder of the dive day or sitting out 24 hours of what may have been an expensive dive vacation.

 

[boulderjohn]

Some of your nicer and higher recommended models (Shearwater Teric for example) run over $1,100.

You are looking at computers that are integrated using a radio transmitter. You don't need that. I do just fine without it on my Shearwaters myself.

 

[mrtechbench]

I have been diving 2 computers whenever I go for the last 20 years either as computers or gauge mode, currently using a pair of Perdix. I've had 2 different computers fail mid dive years ago (different dives), including watching one reboot at 90 ft, so I don't fully trust them. I don't get to go diving as often as I like, so it's insurance against missing dive(s) if computer fails, plus gives me a warm fuzzy feeling about redundancy.

 

[butterwm]

RGBM (or the approximation of RGBM) in Suunto simply works based on a different model and theory. It tends to “punish” you for certain things like short surface interval, yo-yo profile or a second dive deeper than the first - because at the time, the prevailing theory supported such approach. But later we returned back to Buhlmann… In 10 years, someone might come up with something completely else.

Apple Watch has its own flaws - for example, I believe that it will stop working if you violate the depth limit and stop calculating any stops. That’s not really acceptable for a real dive computer because it should always bring you to safety, not stop working because of some legal liability limitation. Suunto might lock you out but it will still properly calculate any stops that you might need to make to get safely out of the water.

I am aware of the Apple Watch issue and what happens if you exceed the maximum depth. I also agree with you that no matter what it should still provide info to safely get you to the surface in the event that happens. I rarely dive beyond 100 feet so fortunately this is not an issue.

From what I gather all computers seem to have shortcomings of some sort then. Is there a particular brand or model that is known to not have any shortcomings?

 

[gordonscuba]

Thank you all for your responses. From what I gather collectively the Sunnto software and algorithm seems to have some limitations and flaws. However, you have to honor the most conservative of the two.

With that being said, a dive computer is an expensive and major purchase. Some of your nicer and higher recommended models (Shearwater Teric for example) run over $1,100. How many divers out there are really spending the money to buy another expensive second computer to use as a backup? I feel like if you buy a “cheap” computer as a backup then you pay the price like I am with my Suunto.

On OC: dual Perdix 2.

On CC: Petrel 3 and NERD 2. In any case it's always two trimix-capable Shearwaters.

Sometimes I use a Teric for backup if I want a smaller object on the wrist, but the Perdix is preferable because I can just carry a spare battery and switch on the boat if needed. The Teric, one must remember to keep charged.