HERE IS A LINK TO A uK SITE THAT IS TALKING ABOUT COMPUTERS AND NDL LIMITS AND OR SAFETY SETTINGS
Safety Factor settings on dive computers
Safety Factor settings on dive computers
Matching Dive Computer Algorithms
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Jay
Need to dive more!
I am saying you need two unlikely events to have a problem, and the second of those is an acceptable risk 100% of the time to some people (eg Scubadada)
Imagine a RB diver with a computer and a backup. The first is set to 50/80 and the second to 49/99. The plan is to dive 50/80 unless there is a co2 hit requiring a swift exit or an electronics failure on the primary.
I think every one will agree the probability of getting hurt with. GF of 99 is higher than with a GF of 80.
If we call lots of dives at 80 good odds, and lots at 99 poor odds then I am suggesting that the shift from good to poor which occurs on one dive, in the case of an unlikely failure (co2 hit or hardware failure) is very small. The chances are you will get away with the one 99 ascent, whereas the chances are you will not get away with 1000 GF 99 ascents, 999 at 80 and 1 at 99 is essentially the same as 1000 at 80.
Google Erik Baker.
Really they just ignore a first stop as being too short to matter and then the limiting GF and so tolerated ppN2 leaps in a single bound from GF lo to nearly GF hi.
You need to take a ruler to the proper ‘how GF works’ diagrams and have a think, but be careful because most of those diagrams are wrong, projecting the GF low line linearly below the first stop.
I'm the bloody migrant here, I'm the one supposed to not get "horse's mouth". Read a book mate.
Jay
Need to dive more!
Thanks for that.
I 're-found' this other thread for those interested about the two ways GFLo can be implemented: Gradient Factors and recreational diving
Comparing the algorithms between the Cressi SF0 and Petrel 50/80 has been interesting. Work has been crazy so not a lot of free time but impressions thus far on Nitrox and non-square profiles...
On first dive, the Cressi is more liberal.
Repetitive dives vary. On second dives the Cressi still tends to be more liberal, especially early or deepish in the dive. On 3rd dives after a long lunch break, the Cressi regains some ground and tends to liberal over the Petrel again but 4th dives go to the Petrel.
Overall observations...
The Cressi loves my Bonaire style of diving even with repetitive diving, deepish early and often abbreviated SI’s. I assume it is because the last half of the dive is 30 to 15 feet. The Cressi was less conservative for the majority of the 26 dives over 7 days.
The Cressi was less enthused with my Cozumel trips. Dives tended no deeper but average depth is slightly deeper since I don’t have those long shallow endings. The Petrel often became the most liberal on the second dive, but not by much. At least not until I do ascend more shallow. Then the difference becomes noticeable.
One of the most notable differences was the way they handled ascents after approaching NDL’s. Both the Cressi and Petrel would regain NDL time as I ascended but typically the Petrel started it deeper and was more generous. I would often hit “99” on the Petrel at 40 feet or so but not on the Cressi until about 20.
On first dive, the Cressi is more liberal.
Repetitive dives vary. On second dives the Cressi still tends to be more liberal, especially early or deepish in the dive. On 3rd dives after a long lunch break, the Cressi regains some ground and tends to liberal over the Petrel again but 4th dives go to the Petrel.
Overall observations...
The Cressi loves my Bonaire style of diving even with repetitive diving, deepish early and often abbreviated SI’s. I assume it is because the last half of the dive is 30 to 15 feet. The Cressi was less conservative for the majority of the 26 dives over 7 days.
The Cressi was less enthused with my Cozumel trips. Dives tended no deeper but average depth is slightly deeper since I don’t have those long shallow endings. The Petrel often became the most liberal on the second dive, but not by much. At least not until I do ascend more shallow. Then the difference becomes noticeable.
One of the most notable differences was the way they handled ascents after approaching NDL’s. Both the Cressi and Petrel would regain NDL time as I ascended but typically the Petrel started it deeper and was more generous. I would often hit “99” on the Petrel at 40 feet or so but not on the Cressi until about 20.
Might be an artifact of the recalculation frequency: if e.g. petrel does it every 20 seconds and giotto: every 40 seconds, then it'll take the latter twice as long to compute 99. You'd typically expect it from a beefier computer, simply because its CPU is faster. Whether any interval shorter than the fastest tissue's halftime is actually meaningful as far as the model is concerned, is a completely different question.
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