Dive Computer Error

[eelnoraa]

If your computer malfunctions, there's only one (approved/trained) recourse - immediately ascend and end your dive. You don't need gauge redundancy for that.

I can't agree more with Andy's statement. Too often folks on SB will argue procedures in the case of what appears to be a relatively minor failure of gear. We should all remember, if you have equipment failure, end the dive. Once safely on the surface, try to effect repair or call it a day. Doesn't matter how much the trip cost you, it's not worth your life.

I totally agree too, but unless you know something about how the computer should behave, how do you know it is doing something un-reasonable.

Sometime, it is not all about a computer malfunction, user error play a part too. Say you forget to reset the EAN percentage from your last dive, your computer give you an unusual long NDL time for diving air, things like this.

 

[GrumpyOldGuy]

I like the term Ronald Reagan used often, Trust but Verify

In my little corner of the world, we calibrate instruments (compare to a known standard) at periodic intervals because even properly working instrumentation drifts a bit over time and exposure to the elements.

Most dive computers never get calibrated after they leave the factory. So you have no idea if its even registering the depth correctly unless you compare to a known standard or a sampling of other computers (I.E. buddies). After this compare you dive computer to your tables on some simple dive plans, it not hard to verify its working so you confidence will not be misplaced.

 

[TomZ]

There are many posters here with much more diving experience than I have. I ask this purely because I want to know...........................................................................................................................................................

The concept of ascending due to a computer malfunction: ..............................................................................................................................................................
I carry both air and Nitrox tables in my BC. I have an SPG and depth gauge in my console. I set the timer on my watch just prior to descending. I started diving prior to computers and learned on tables, so I trust and know how to use them. I dive with a buddy and can compare my equipment to his/hers to identify the malfunctioning computer. Under these conditions would it be considered unsafe to switch from a computer to calculating tables on the fly? I'm sure we could confuse the question with what if's, so for the sake of simplicity let's assume this is the first dive of the day and the RDTs are not a concern.

As an aside, I recently got a new computer and have been diving two computers during the last several dives, until I'm totally proficient with the new one. How does the SB braintrust feel about an SPG/depth gauge/timer and one computer in agreement? Still thumb the dive?

 

[Lorenzoid]

When I have my battery changed, the service center apparently takes the computer for a pressurized test ride, as it shows one dive to something like 200 feet. I wonder if they look at that number to see if it's calibrated properly?

 

[windapp]

There are many posters here with much more diving experience than I have. I ask this purely because I want to know...........................................................................................................................................................

The concept of ascending due to a computer malfunction: ..............................................................................................................................................................
I carry both air and Nitrox tables in my BC. I have an SPG in my console. I set the timer on my watch just prior to descending. I started diving prior to computers and learned on tables, so I trust and know how to use them. I dive with a buddy and can compare my equipment to his/hers to identify the malfunctioning computer. Under these conditions would it be considered unsafe to switch from a computer to calculating tables on the fly? I'm sure we could confuse the question with what if's, so for the sake of simplicity let's assume this is the first dive of the day and the RDTs are not a concern.

As an aside, I recently got a new computer and have been diving two computers during the last several dives, until I'm totally proficient with the new one. How does the SB braintrust feel about an SPG/timer and one computer in agreement? Still thumb the dive?

Plan your dive and dive your plan. You can safely continue your dive if you meet the following conditions:

You have a backup dive computer OR

You planned your dives using tables on the surface AND
You tracked all of your dives using tables, and are still on the table (haven't exceed any table NDL's) AND
Your current dive is within your planned depth AND
You know this for a fact AND
Your current dive is within your planned NDL based on tables AND
You know this for a fact as well (You need a backup time piece to do this).

I personally think the idea of doing calculations on the fly, under the water, in no decompression diving is insane. It is way to easy to make a mistake. If you didn't plan for it, abort your dive, and plan for the next dive on the surface.

---------- Post Merged at 05:55 PM ---------- Previous Post was at 05:51 PM ----------

When I have my battery changed, the service center apparently takes the computer for a pressurized test ride, as it shows one dive to something like 200 feet. I wonder if they look at that number to see if it's calibrated properly?

That would be the point behind the test. If you ask, they will probably show you the test results.

 

[highdesert]

This is why I have multiple instruments.
I have a depth gauge on my console and a dive timer

I also vote for redundancy, but in my case it's an AI computer on a hose, plus a separate wrist computer (same algorithm) and separate SPG.

 

[supergaijin]

You get that a lot of these algorithms that computers run are artificially conservative, right? And if you want to use your noggin and stay longer (well within the range of most dive tables, as well as some other computers), they lock you out so you can't even use it.

And yet I know more than a few instructors who have had chamber rides even after diving within the 'artificially conservative' limits imposed by Suunto's RGBM algorithm. It is strange to call one model "artificial"; they all are artificial- just someone's best guess as to what is likely to happen.

I would be interested in

the range of most dive tables

that allow longer dive times than any modern computer- care to name one?

RGBM can be considered 'better' for most recreational divers who tend to do multiple dives following a reef slowly upwards from a max depth of around 25m.

If it's longer time at depth- eg. deep wrecks that are your main reason for diving, then go Buhlmann but this model isn't called 'Bend and Mend' for nothing.

 

[windapp]

I don't think it is accurate to call decompression models a "best guess". The models we used are all corelated with data taken from real human trials, and they are based on substantial investigation into decompression theory. While none are perfect, they are far from a "best guess".

 

[ajduplessis]

You get that a lot of these algorithms that computers run are artificially conservative, right? And if you want to use your noggin and stay longer (well within the range of most dive tables, as well as some other computers), they lock you out so you can't even use it.

I don't know of any DC that is more conservative than tables and I have a couple of Suunto's.

 

[Searcaigh]

Since I have two computers (well three actually but one does not do Nitrox) I carry both on all dives, but I also have an idea of time and depth limits in my head from using tables for many years.