Feedback on recent two-tank and dive limits

[rongoodman]

I f you read the original statement made by the inquiring gentleman:

1. On the first dive there appears to be no reference to a stop by the dive computer.

2. On the second dive a 5 min stop appears on the computer, which the divers interprets as a safety stop however his perception is that it is mandatory and consequently is anxious about being forced to directly surface omitting the 5 min stop.

There would have been a 3 min safety stop on the first dive, whether or not he mentions it. He refers to the second one as a safety stop too. He expressed concern about his short NDL on the second dive but makes no mention of GF or anything else about the algorithm involved, other than he had heard that Shearwaters "skewed conservative". Where do you see that he was confused by the idea of gradient factors? It appears that he had never heard of them until posters here brought them up.

 

[Blackcrusader]

There would have been a 3 min safety stop on the first dive, whether or not the he mentions it. He refers to the second one as a safety stop too. He expressed concern about his short NDL on the second dive but makes no mention of GF or anything else about the algorithm involved, other than he had heard that Shearwaters "skewed conservative". Where do you see that he was confused by the idea of gradient factors? It appears that he had never heard of them until posters here brought them up.

Yup he had to go and check his settings to know what GF was being used. This would imply he had never checked the settings. He also did not know about adaptive stops which can give longer safety stops.
However I am sure he does now.

 

[David Carron]

If you don't know if the computer displays safety or a deco stop, that's a UI issue. Looking at the user manual I gave a screenshot above, I've trouble to find this aspect confusing for the Peregrine display.

If you don't know what are safety and deco stops and how to act when the computer shows one, that's a training issue.

Reading the first message, I think we are in the second case, but the thread has drifted away from that aspect a long time ago.

Without going into all sorts of UI design things which would be little more than bike-shedding anyway, honestly, this:

doesn't seem all that simple to me and certainly way more complicated than I'd expect a typical rec diver to be using or needing.

 

[JMarc]

Without going into all sorts of UI design things which would be little more than bike-shedding anyway, honestly, this:

View attachment 913622​

doesn't seem all that simple to me and certainly way more complicated than I'd expect a typical rec diver to be using.

And this is tech layout of the Perdix. There is a simpler rec layout, and AFAIK the Peregrine used by the OP only has the rec layout which look like

Here I gave a capture of how the upper right corner change for a deco stop.

 

[Belzelbub]

I f you read the original statement made by the inquiring gentleman:

1. On the first dive there appears to be no reference to a stop by the dive computer.

2. On the second dive a 5 min stop appears on the computer, which the divers interprets as a safety stop however his perception is that it is mandatory and consequently is anxious about being forced to directly surface omitting the 5 min stop.

From this statement, it is quite clear to me that the that the distinction between the safety stop and a stage decompression stop are not being differentiated by the dive computer to the diver. Consequently the diver is confused and anxious. This is not a good outcome. Despite the fact that both dives may have been well within the no decompression limit (NDL) confusion and subsequent anxiety has occurred.

In other words, what is clear to you is actually a misunderstanding of what the OP wrote. On the first dive, the OP did not make a mention of a stop. That does not mean that the DC did not prompt a Safety Stop. I’m certain that it did.

The 5 minute stop reported by the computer is not a deco stop. As has been stated before in this thread, the OP had Adaptive Safety Stop turned on. This will change the Safety Stop recommendation from 3 minutes to 5 minutes if the dive is deep enough or the NDL drops under 5 minutes. It’s not a Deco stop, and is clearly identified by the computer as a Safety Stop.

My point is, if the diver had been using a computer by OCEANIC with DSAT or straight Buhlmann (dual algorithms). When simply set on DSAT it would have given him a longer NDL bottom time for the first dive and automatically provided a predictable 3min safety stop at 15 ft. The NDL bottom time for the second dive would probably be shorter and again automatically provided a 3 min safety stop at 15 ft. It works for NDL recreational diving why convolute it with GFs.

That is exactly how it worked for the OP on the dives. The NDL was shorter on the second dive. The OP stayed under the NDL, but as Adaptive Safety Stop was turned on, the Safety stop was 5 minutes instead of the usual 3. This is an additional safety feature. It’s clearly explained in the manual, and when it happens, is also clearly displayed as a Safety Stop. The manual also explains how to turn this feature off or on.

This is the basic scuba section. My guess is that over 95% of recreational divers have no interest in technical diving or convoluted pseudo technical diving equipment. When it comes to dive computers, they just want to slap it on the wrist and jump into the water. They want a no fuss computer that gets them in, gets the job done and get out.

Which is exactly what the OP’s computer did. The Peregrine is not convoluted pseudo tech diving equipment. It’s a recreational computer that is quite easy to use. It’s got a well written user manual and a user interface that is easy to use. Significantly easier to use than the DSAT and dual algorithm computers I have at home.

 

[Blackcrusader]

Without going into all sorts of UI design things which would be little more than bike-shedding anyway, honestly, this:
doesn't seem all that simple to me and certainly way more complicated than I'd expect a typical rec diver to be using or needing.

As I have written my Perdix is setup for Tec Mode so I can have what I need where I want it for my recreational diving and that includes recreational deco diving. I spent many hours studing my settings, learning what I could do re screen setup and colours, what GF settings I wanted to run, and studying gradient factors and using the Perdix dive planner. A lot to learn after my Suunto RGBM DC.

When people buy a DC it is on them to learn its settings and its functions. Many divers never even read the user manuals. When you never bother the read the user manuals or learn about your DC then eveything about it is complicated.

 

[inquis]

Conclusion, Erik Baker did not have recreational diving in mind when he developed gradient factors

Your speculation is rather immaterial, as lots of inventions have been applied in ways not conceived of by their inventors. The only question is whether it achieves a desired goal. The entire point of one of those factors (GFHigh) is conservatism when surfacing, which absolutely applies to recreational diving.

 

[boulderjohn]

As people have already noted in the last couple of pages, the fact that the OP was confused about safety stops does not say anything about the concept of GFs as the Buhlmann system for setting a level conservativism on the computer.

The fact that how to use GFs appears in articles about tech diving does not in any way indicate that they were not also intended for NDL dives as well. That claim is a total non sequitur.

 

[grantmac]

Without going into all sorts of UI design things which would be little more than bike-shedding anyway, honestly, this:

View attachment 913622​

doesn't seem all that simple to me and certainly way more complicated than I'd expect a typical rec diver to be using or needing.

That computer is in Tec mode. Rec mode offers much less information, I've never dove with it set-up in anything other than Tec mode because information is a good thing.

 

[Blackcrusader]

That computer is in Tec mode. Rec mode offers much less information, I've never dove with it set-up in anything other than Tec mode because information is a good thing.

Told him several pages back I only use Tec Mode. Wrote that on page 2 of this thread.
I've never used REC mode on my Perdix.