History behind Dive computer error mode

[KenGordon]

My Oceanic computers say that any dive with a first decompression stop much below 70 feet will lock you out. The computer simply doesn't have a viable solution.

Do you have a source for that? This is a genuine question, I am interested.

I don't think that sounds the same as the Zoop manual at all.

"The Error Mode results from omitted decompression, i.e. when you stay above the ceiling for more than three minutes."

Sounds to me that you are ALREADY off the curve, rather than DUE to be.

When doing 50 to 60m 20ish minute dives where the first stop might be at 27 or 30 my Zoop is pretty much tracking the Helo2 until the gas switch. I have never been too interested in what it thinks the ceiling is on a dive (the other computer knowing the actual gas etc) but typically (from memory) it is never much below 12 or 14m for these dives according to suunto's dive planning software.

I think it is also worth considering that in some models there is a very significant difference between ceiling and stop depth. The Zoop does not have 'deep stops' but the Suunto Helo2 does, but they are not 'go above this and die' stops, if you blow past them you will spend longer shallower rather than be left in an error mode.

Totally person opinion but I think vendors face some considerable testing issues with computers and their decompression models outside of the 'working' parameters. The need to be able to support (even if only to themselves) the case that the computer is doing the correct thing. Once the user starts to ignore the computer there opens up a wide range or (hopefully) rare and hard to predict scenarios. Testing both the algorithm and the implementation and then explaining the behaviour to an end user will be challenging. It may also confuse the user, as it stands apparently people get confused between remaining NDL and ascent time, is having and extra 'in error but limping back to the surface but all bets are off' mode actually a help on average?

The answer is to 1) get trained to not miss your stops 2) during the training ask the instructor your "what if" questions. 3) discuss with you buddy whether you will send them to the surface on a blob and wait out your deco or put yourself at risk getting them to the surface.

You might think 3) is a joke, but take a look at the BSAC incident report and some of the recent incidents discussed on here (SB) and you may think "**** me the second diver only got hurt rescuing a corpse".

Maybe I should add 4) do a rescue course of some sort - a good one will make you consider that sometimes you cannot help and that understanding that and having a think about it ahead of time might be an idea.


BTW, I think the original post is rather different to the air vs trimix conversation, surely there must be a whole sub forum for that

 

[Dr. Lecter]

It took me about 10 seconds of googling to come up with an Oceanic manual clearly describing the bizarre deco behavior he mentioned. The new Aeris has the same limitation.

During a Dive, if a ceiling greater than 70FT (21M) is required,an Immediate Violation Mode will be entered. This situation would be preceded by entering Delayed Violation Mode #2,previously described. The Veo 100 would then operate with limited functions in Violation Gauge Mode during the remainder of that dive and for 24 hours after surfacing.

 

[KenGordon]

It took me about 10 seconds of googling to come up with an Oceanic manual clearly describing the bizarre deco behavior he mentioned. The new Aeris has the same limitation.

Is it really bizarre?

I don't know if the oceanic ones are helium computers, but getting a 21m ceiling on air takes some doing. Using Suunto's PC software planning an air dive to 60m for 80m or 90 minutes gets you there, alternatively a 100m dive on 10/50. The Zoop claims its depth sensor is good to 80, the Oceanic manual I looked at said it would just say "Up!!!" beyond 100m. These seem like very unlikely profiles for a recreational or light technical diver who would use these computers.

I notice that the oceanic has a violation mode #1 which is like the Suunto error mode but with 5 minutes rather than 3. Maybe the oceanic would suit the OP better.

I suggest that these are reasonable parameters of behaviour beyond the intended usage of the devices.

 

[boulderjohn]

PLease show real world examples of ANY PDC simply quitting during a dive because of a violation.

Since you asked....

My buddy and I planned a dive that would use a V-Planner generated ascent profile. When we were about to do the dive, he said that he had just gotten the brand new Suunto HelO2 and wanted to see what it would do. He had set its parameters to be as close as possible to V-Planners. We followed the V-Planner schedule perfectly, and it wanted us to ascend sooner than the HelO2 did. It went into error mode during the 30 foot stop.

 

[Dr. Lecter]

Is it really bizarre?

I don't know if the oceanic ones are helium computers, but getting a 21m ceiling on air takes some doing. Using Suunto's PC software planning an air dive to 60m for 80m or 90 minutes gets you there, alternatively a 100m dive on 10/50. The Zoop claims its depth sensor is good to 80, the Oceanic manual I looked at said it would just say "Up!!!" beyond 100m. These seem like very unlikely profiles for a recreational or light technical diver who would use these computers.

I notice that the oceanic has a violation mode #1 which is like the Suunto error mode but with 5 minutes rather than 3. Maybe the oceanic would suit the OP better.

I suggest that these are reasonable parameters of behaviour beyond the intended usage of the devices.

If one only plans on never, ever, no matter what circumstances present themselves, going into deco…I suppose it's fine. Personally, I think it's like buying a car with a governor set at 55mph, or a mini-cannister of pepper spray instead of a .45. I like knowing my dive computer is capable of performing any dive on which I might find myself. There's also no good reason for this software behavior - better computers don't have this limitation, and I seriously doubt it's because they have more and more capable software engineers. The difference is manufacturer focus: Oceanic, Suunto, Aeris, and the like are clearly more concerned about their liability, while Shearwater, Liquivision, Atomic and the like are more concerned about making sure a diver using their tools has the best possible shot at performing an effective ascent.

 

[KenGordon]

Since you asked....

My buddy and I planned a dive that would use a V-Planner generated ascent profile. When we were about to do the dive, he said that he had just gotten the brand new Suunto HelO2 and wanted to see what it would do. He had set its parameters to be as close as possible to V-Planners. We followed the V-Planner schedule perfectly, and it wanted us to ascend sooner than the HelO2 did. It went into error mode during the 30 foot stop.

You left off where he said "It won't lock up during a dive, it will tell you what depth for how long." which I expect the HelO2 did and so he could still follow his slate.

This illustrates the importance of planning with the algorithm and settings you will actually dive. If you dive a plan that has you at 10m when the computer wants you at 14m it will get upset and become less useful.

---------- Post added July 27th, 2014 at 09:07 PM ----------

Dr Lector -"If one only plans on never, ever, no matter what circumstances present themselves, going into deco…"

for more than an hour or so in the case of the Oceanic or ignoring the stops in the case of it or a Suunto.

There are plenty of reasons to prefer a Petrel over a HelO2 but for me at least this isn't one.

 

[boulderjohn]

You left off where he said "It won't lock up during a dive, it will tell you what depth for how long." which I expect the HelO2 did and so he could still follow his slate.

This illustrates the importance of planning with the algorithm and settings you will actually dive. If you dive a plan that has you at 10m when the computer wants you at 14m it will get upset and become less useful.

In a parallel situation, I dived with a group that was planning a dive using V-Planner and using Liquivision computers using the same algorithm as backups. I agreed to follow the group's plan, but I had a Shearwater Predator on Buhlmann for a backup. I punched in the gases and bottom time to see what the Shearwater wanted to do, and I saw it was extremely different. We did the dive exactly as planned. My Shearwater kept objecting and recalculating. When we came to the end of the planned dive, the Liquivisions cleared within 30 seconds of the V-Planner schedule being completed, and my Shearwater cleared a few seconds later.

 

[KenGordon]

In a parallel situation, I dived with a group that was planning a dive using V-Planner and using Liquivision computers using the same algorithm as backups. I agreed to follow the group's plan, but I had a Shearwater Predator on Buhlmann for a backup. I punched in the gases and bottom time to see what the Shearwater wanted to do, and I saw it was extremely different. We did the dive exactly as planned. My Shearwater kept objecting and recalculating. When we came to the end of the planned dive, the Liquivisions cleared within 30 seconds of the V-Planner schedule being completed, and my Shearwater cleared a few seconds later.

That would be interesting to try the other way round, planning and diving Buhlmann and carrying a VPM computer. How often did the predator want to be deeper than the VPM plan?

When I am using a HelO2 and my buddy has a Shearwater we just wait out each other's deep stops and magically by the last stop we are within a couple of minutes. Meanwhile of course the Zoop is telling me I will be some time...

 

[flots am]

My buddy and I planned a dive that would use a V-Planner generated ascent profile. When we were about to do the dive, he said that he had just gotten the brand new Suunto HelO2 and wanted to see what it would do. He had set its parameters to be as close as possible to V-Planners. We followed the V-Planner schedule perfectly, and it wanted us to ascend sooner than the HelO2 did. It went into error mode during the 30 foot stop.

Did it still display depth and dive time, but not know how to calculate a safe ascent, or did it freeze or do whatever it's SOS thing is?

 

[fire_diver]

Since you asked....

My buddy and I planned a dive that would use a V-Planner generated ascent profile. When we were about to do the dive, he said that he had just gotten the brand new Suunto HelO2 and wanted to see what it would do. He had set its parameters to be as close as possible to V-Planners. We followed the V-Planner schedule perfectly, and it wanted us to ascend sooner than the HelO2 did. It went into error mode during the 30 foot stop.

Wow, that should be completely unacceptable. I'm shocked they would go into an error mode while in the water instead of trying to continue working something out, especially since you were following a deco schedule you couldn't have been wildly outside of parameters.