Info More info on algorithm lock

[Cheizz]

This is a topic inspired by discussions about algorithm lock in dive computers. This thread started it: New diver, looking at Suunto D5

I have gone through a selection of dive computer manuals and looked for the infamous 'algorithm lock' (the dive computer locks the algorithm if you violate mandatory decompression stops for too long).

I had two basic questions:
1. Is the way the algorithm lock is described consistent over dive computers that run the same algorithms, but are manufactured by different brands (in other words: is it algorithm-related)?
2. If not, how do different manufacturers view and use this lock mechanism?

Exhibit A: Suunto EON Core (Fused RGBM2)
In short: algorithm lock engages mid-dive, rendering the computer useless for safe diving, stays locked for 48 hours after the dive

Exhibit B: Mares Puck Pro (RGBM)
In short: the dive computer will continue to be used to end the dive, but will only be able to be used in gauge mode for repetitive dives

Exhibit C: Cressi Leonardo (RGBM)
In short: the algorithm locks for 48 hours. Not sure if this already happens mid-dive (like the Suunto), or after the dive

Exhibit D: Seac Action (Bühlmann ZHL-16C Sport Version)
In short: during the dive, a violation message is shown, alternating with decompression information to complete the dive safely. Afterward, the scuba mode cannot be used for 18 hours. Note: Seac uses penalty points instead of a set violation duration.

Exhibit E: Aqualung i300C (Z+)
In short: after a violation, the algorithm keeps working during the dive, but will not count off-gassing time while violating. After the dive, the computer will be in gauge mode for 24 hours

Conclusion
Every brand has its own take on things, despite running the same algorithm in some cases. Suunto is the strictest, Cressi is a bit vague about the moment of actual locking. All other brands in this small sample opt to punish you mostly after the dive itself. Shearwater and Ratio say nothing at all about locking the algorithm.

PS: The Seac Action is a very nice entry-level dive computer, I must say! Being one of the cheapest as well, I would definitely recommend that model over some others in the same category.

 

[scubadada]

...The Seac Action is a very nice entry-level dive computer, I must say! Being one of the cheapest as well, I would definitely recommend that model over some others in the same category.

I agree. One drawback is the range of the 6 presets with a GF high of 85 down to 60. A GF high of 85 is roughly equivalent to diving PZ+. This moderate/middle of the road setting might prove to be too conservative for some divers.

At $300 in the US, the Seac Screen is a bargain and I would prefer it over one of the budget computers running an RGBM algorithm.

 

[Cheizz]

I agree. One drawback is the range of the 6 presets with a GF high of 85 down to 60. A GF high of 85 is roughly equivalent to diving PZ+. This moderate/middle of the road setting might prove to be too conservative for some divers.

'Some' divers that you talk about most likely are not the kind that would opt for a recreational, non-AI, LCD screen computer - just guessing. For the majority of recreational divers, I think that level of conservatism is perfectly acceptable. My opinion, of course...

 

[scubadada]

Hi @Cheizz

You may be right, however, I have been diving DSAT since 2002, a few over 2200 dives. I now dive that along with a GF high of 95. Of course, I control my surfacing with SurfGF these days.

Divers purchasing a new computer should simply be aware that decompression algorithms and settings vary significantly in the spectrum from conservative to liberal.

 

[Belzelbub]

Conclusion
Every brand has its own take on things, despite running the same algorithm in some cases. Suunto is the strictest, Cressi is a bit vague about the moment of actual locking. All other brands in this small sample opt to punish you mostly after the dive itself. Shearwater and Ratio say nothing at all about locking the algorithm.

Thanks for sharing this. This is interesting.

Shearwater and Ratio don’t lock out. Not sure about the Ratio manual, but the Shearwater Perdix Rec manual says this.

Garmin has a lockout by default. I’m not positive what parameters would institute a lockout, but I recall reading somewhere that it was post dive. This lockout can also be disabled.

 

[dmaziuk]

Cressi is a bit vague about the moment of actual locking.

Two minutes after getting into omitted deco mode is my reading. I expect the part about going below the mandatory stop depth is the translation/ESL problem, but it generally sucks at deco: once it has a mandatory stop, it won't clear unless you complete it exactly as prescribed. If you come up to above 10 msw it will not recalculate your deco obligation no matter how long you stay there.