Computers that don't lock out tangent.

[rongoodman]

Now, I'm sure there are holes in my understanding of decompression theory but I thought that once bubbles form, even micro bubbles, they don't dissolve and off gas the way normally dissolved gas in tissue does, hence the long chamber rides for bendy people. Also, can't the micro bubbles act as sort of a nucleus for larger bubbles to form up on?

I thought the current thinking was that bubbles form on all dives and are routinely filtered out in the lungs. Too many, or too large, and the process breaks down. The issue with PFOs is that those bubbles can gain access to the arterial circulation before being removed and be pushed into places where they don't belong.

the tech stuff is another world and it's voodoo gets spooky down there.

There is no difference in the physics between tech and rec dives. Rec dives simply limit the inert gas load to that which can be handled safely with a normal ascent to the surface. Increase it beyond those limits and stops along the way become required to allow for safe off gassing.

 

[tbone1004]

@Diving Dubai the way I understand the Suunto is it will give you mandatory deco when you don't need it because of all of the things that it deems are "bad". We had an AI get locked out once when doing CESA's. We were on day 5 I think of OWT and because teaching often gives you sawtooth profiles and rapid ascents, both of which cause penalties to be assigned, it decided after the second batch of CESA's that day that he had mandatory deco and locked him out for 48 hours. Absolutely ridiculous.
Mares computers will lock you out for rapid ascents unless you disable something in their menus, even more ridiculous.

 

[loosenit2]

Suunto EON Steel - Features - Algorithm lock

Got curious what the Suunto literature said about lock outs. Link is above but their literature for eon steel says if you miss a deco stop by more than 2 feet for more than 3 minutes the computer algorithm shows locked as will not display any further decompression data. It does give you visual and audio alarms before it locks.

This seems to me to be an unreasonable approach. In my mind the right approach is to say, yes diver you screwed up, but here is the best path forward that I can provide to minimize the damage, even if some Is not totally avoidable.

The lock out approach to me is akin to someone being shot and taken to the hospital and the hospital refusing treatment because this person should have known better than getting shot.

An additional challenge with the bubble models in most computers is that they are propriety and thus users done truly know the logic of what the computer is telling them, at least with the Bühlmann models they open source is easy to determine why the computer is telling you something.

 

[Diving Dubai]

@Diving Dubai the way I understand the Suunto is it will give you mandatory deco when you don't need it because of all of the things that it deems are "bad". We had an AI get locked out once when doing CESA's. We were on day 5 I think of OWT and because teaching often gives you sawtooth profiles and rapid ascents, both of which cause penalties to be assigned, it decided after the second batch of CESA's that day that he had mandatory deco and locked him out for 48 hours. Absolutely ridiculous.
Mares computers will lock you out for rapid ascents unless you disable something in their menus, even more ridiculous.

When I'm teaching I keep my Eon set to very conservative, and had lots of ups and downs that you get (as you know) with OWD students)

I've then gone off on another weekends dive and forgotten to reset my profile, and been on a DPV in current - pretty much doign everything a Suunto should hate. Now apart from NDL times there was no difference between the Eon and the Perdix on my other wrist

What I do see (depending on conservatism) is that the Suunto will "pad" the next dive to take these into account. Having a short SI will really decrease the NDL, but unless you actually hit Deco, it won't violate you

The Eon has a thing where it'll add time to the SS if you've been "naughty" often 30 seconds. this is coloured red as a mandatory (deco is orange) but if you break the Red stop it won't give you a lock out. I've had a few times where its been prudent to abandon the dive and stops because teh current has become too dangerous and never had a lock out

 

[rongoodman]

The various commercial versions of RGBM are proprietary. The only implementation of RGBM that I'm aware of which claimed to be the full iterative version was an aftermarket upgrade for the discontinued Liquivison Xeo. VPM is more widely available, although I don't know if it's actually open source. It's available as an add-on for various Shearwaters, but they don't offer it for the Teric due to recent changes in thinking about bubble models.

 

[Diving Dubai]

Link is above but their literature for eon steel says if you miss a deco stop by more than 2 feet for more than 3 minutes the computer algorithm shows locked as will not display any further decompression data

Correct.

If you are above the ceiling it will "scream" at you.

3 minutes is a huge amount of time. If you bust your ceiling .and get a lockout there are 2 reasons

1. You're too inept to be able to hold a stop - thus shouldn't be there. If the diver's buoyancy is so rubbish that they can't hold that stop ceiling then they should be slightly deeper.

If they don't realise for 3 mins they're above the ceiling - they shouldn't' be deco diving. Again in almost 1000 dives on the Eon, lots with deco, I've never bent it.

2. If a diver has a real emergency that can't be mitigated with their redundancy and plan and absolutely must go up, then 48 hrs lockout shouldn't bother them because they've probably got more serious things to worry about. If it's because their gear, plan and skills were insufficient for the dive they undertook, let it be a lesson to them

 

[Diving Dubai]

The various commercial versions of RGBM are proprietary. The only implementation of RGBM that I'm aware of which claimed to be the full iterative version was an aftermarket upgrade for the discontinued Liquivison Xeo. VPM is more widely available, although I don't know if it's actually open source. It's available as an add-on for various Shearwaters, but they don't offer it for the Teric due to recent changes in thinking about bubble models.

OSTC used to be open, don't think it is now.

But realistically with out actually examining the code on the computer you don't know how "pure" the manufacturers implementation is? Some (Cosmic I think) added a "fudge factor" to their Buhlmann

Also people either use a planner as a guide and follow their computer, or follow the plan precisely and use their comp as a guide.

I once put my Suunto in a pot and ran the "dive" exactly to the DM5 plan and they agreed. Underwater however there would be some disparity because of the nature of not diving as precisely as a computer.

For the dives I've done, I know I can plan either RGMB or Bulhmann and know what factors to apply to the other computer to get it very close - and in real life this happens. I have faith in both algorithms for the type of diving I do

 

[loosenit2]

Correct.

If you are above the ceiling it will "scream" at you.

3 minutes is a huge amount of time. If you bust your ceiling .and get a lockout there are 2 reasons

1. You're too inept to be able to hold a stop - thus shouldn't be there. If the diver's buoyancy is so rubbish that they can't hold that stop ceiling then they should be slightly deeper.

If they don't realise for 3 mins they're above the ceiling - they shouldn't' be deco diving. Again in almost 1000 dives on the Eon, lots with deco, I've never bent it.

2. If a diver has a real emergency that can't be mitigated with their redundancy and plan and absolutely must go up, then 48 hrs lockout shouldn't bother them because they've probably got more serious things to worry about. If it's because their gear, plan and skills were insufficient for the dive they undertook, let it be a lesson to them

You appear to be very pro lock out, I've never seen someone argue so vehemently for a lock out screen, you must work for Suunto.

You did not however address my point, that the purpose of a computer is to assist you. Even if a diver makes a mistake the computer should not take its ball and go home, it should continue to assist you in minimizing worst possible effects u til you surface.

 

[Lorenzoid]

I thought the lock-out feature, at least on my old Suunto, would continue to indicate the proper ceiling until you surfaced, and only AFTER surfacing would it lock itself up for the next 48 hours. Do I remember incorrectly?

 

[AJ]

I thought the lock-out feature, at least on my old Suunto, would continue to indicate the proper ceiling until you surfaced, and only AFTER surfacing would it lock itself up for the next 48 hours. Do I remember incorrectly?

Yes, unless you screw really bad. Then, as far as I know, Suunto will lock during the dive because it does not know anymore what to do. But you have to really screw up to achieve that.