Decompression limits and long safety stops

[boulderjohn]

This thread should be a topic covered in basic open water. Instead its just use the computer and the dive tables are just barely mentioned, much less fully comprehended.

It is supposed to be covered in the basic open water class. The PADI computer version at least has extensive instruction on proper use of the computer.

 

[Blackcrusader]

Computers have come a long way, even for those of us that do mostly no-stop or light deco dives. My Teric gives me average depth, a dive profile, water temperature, starting and ending gas pressure, SAC, and starting and ending CNS O2 exposure, all off the onboard log. Downloading by Bluetooth to the Shearwater Cloud apps gives considerably more information. The Buhlmann ZH-L16C with GFs deco algorithm is infinity flexible to meet my personal requirements. The SurfGF function allows me to surface from my safety stop or deco stop with the safety margin I choose.


For recreational diving or light technical activity, with the major exception being air integration, the Shearwater Peregrine offers many of the same features of the Teric at less than half the price for the computer alone, not even considering the extra cost of a transmitter

Yes one of the good things for me after my Suunto died from the pressure sensor was buying a Perdix AI. There was also a lot of study for me for all the information the Shearwater has both onscreen and when uploading dive logs that I do review. Then the firmware upgrades with even more enhanced features. There is no point in buying a dive computer and not fully knowing how it works. Most recreational divers just buy a DC and dive, do not know their DC settings and maybe only learned how to switch from 21% to 32% nitrox. Perdix sure does have a lot of screen setups to choose from.

I have dived with many divers whose alarms are going off only for them to point at my Perdix. Firstly they don't know the Perdix does not have an audio alarm and secondly they don't know the alarm sounds of their own dive computer.

The OP should really upload his dive tables and study them as I do not think he knows really what happened on his dives.

 

[ginti]

There is no point in buying a dive computer and not fully knowing how it works.

I only partially agree with this statement. In fact, learning how to perfectly use a computer requires a lot of time and new divers might not want to do that, or even might be unable to do it since they can lack knowledge (e.g. bhulman Vs rgbm).

I use a Garmin descent MK1, I don't know all the features and I use just what I need plus just something else. I am trained to dive without computer, so what I strictly need to dive safely are just time and depth. What I also use (obviously, because there's no reason to play Rambo) is the bhulmann algorithm with appropriate GF, the selection of my mix, and the right gas mode (single- vs multi-gas).

Would it be better to learn everything about the computer? Yes.
Is it really necessary to dive safely? No.

 

[scubadada]

I only partially agree with this statement. In fact, learning how to perfectly use a computer requires a lot of time and new divers might not want to do that, or even might be unable to do it since they can lack knowledge (e.g. bhulman Vs rgbm).

I use a Garmin descent MK1, I don't know all the features and I use just what I need plus just something else. I am trained to dive without computer, so what I strictly need to dive safely are just time and depth. What I also use (obviously, because there's no reason to play Rambo) is the bhulmann algorithm with appropriate GF, the selection of my mix, and the right gas mode (single- vs multi-gas).

Would it be better to learn everything about the computer? Yes.
Is it really necessary to dive safely? No.

I'm with Ginti.

My diving is mostly no-stop and about 5% back gas deco. I run my Teric in rec mode in the standard layout with 3 pieces of information in the info row, including SurfGF, and the floating north pointer displayed. I use custom GF and air integration. I know essentially nothing about using the Teric with trimix or a CCR. These additional functions do not get in my way and are invisible to me.

If the Peregrine was AI, it would work fine for me for a fraction of the cost. I do like the watch form factor of my Teric.

 

[Esprise Me]

I'm with Ginti.

My diving is mostly no-stop and about 5% back gas deco. I run my Teric in rec mode in the standard layout with 3 pieces of information in the info row, including SurfGF, and the floating north pointer displayed. I use custom GF and air integration. I know essentially nothing about using the Teric with trimix or a CCR. These additional functions do not get in my way and are invisible to me.

If the Peregrine was AI, it would work fine for me for a fraction of the cost. I do like the watch form factor of my Teric.

I sometimes feel a bit sheepish about owning a Teric when I'm only doing rec dives (maybe not forever, but certainly for now). Even in rec mode, there's a function I've never used and never even bothered to figure out what it was until recently, after more than 300 dives with this computer. It's the "tag log" function, which allows you to put a digital sticky note on the graph of your dive for a number of pre-programmed events like "danger" or "waypoint." I wouldn't have had any use for that when I first got it, but now I sometimes find myself making a mental note of how many minutes it took me swimming straight out from shore before I hit the depth where I turn right, and then how many more minutes before I found the wreck, to help me refine my navigation in the future. I'll definitely use it if I ever spot a baby giant sea bass again; there's a local marine biologist who's interested in collecting data about where they were seen etc. (I'm definitely going to use the "danger" tag for the baby GSBs.) Anyway, I agree with you and ginti. It's essential to understand your computer's essential functions; the rest is optional, but potentially very cool.

 

[Marie13]

I sometimes feel a bit sheepish about owning a Teric when I'm only doing rec dives (maybe not forever, but certainly for now).

I don’t get this attitude. Cheapo rec computers seem to have crappy black on gray displays. No backlight unless you press a button. So a computer with a colorful easy to read display and nice user interface is only for tech divers?

 

[scubadada]

I don’t get this attitude. Cheapo rec computers seem to have crappy black on gray displays. No backlight unless you press a button. So a computer with a colorful easy to read display and nice user interface is only for tech divers?

I don't feel sheepish, I feel well equipped for my diving.

I used to extend my safety stop by a couple of minutes when I was close to deco and used to pad my deco stop by a few minutes also. With SurfGF there is no guesswork, I surface with the GF I choose. I'm not as young as I used to be and still dive fairly aggressively, it's reassuring to know that I am surfacing relatively conservatively. I don't end a dive with a surfacing GF of over 80 and my average is somewhere in the 50s.

 

[scubadada]

This dive had a surfacing GF of 73%. The GF on arrival at the safety stop was 21% and decreased to 9% at the end of the safety stop. It blossomed to 73% over the 1:20 final ascent. It's eye opening to see the increase of the GF during the final ascent. I try to make my final ascents over at least a minute.

 

[Blackcrusader]

I don’t get this attitude. Cheapo rec computers seem to have crappy black on gray displays. No backlight unless you press a button. So a computer with a colorful easy to read display and nice user interface is only for tech divers?

I know quite a few recreational divers using Teric's and Perdix DC's. I'm one of them as well. My point about divers knowing how their DC works really applies to the type of diving they do. A lot of people buy a DC and never even bother to read the user manual.
I do not use my Perdix for CCR and Trimix. But I have studied my manual and learned about the features it has that my Sunnto did not have.

So I studied and learned all the features I want for my diving. I dive my Perdix in setting in Tec mode not Rec Mode.
It would be good for the OP to upload his dive logs and review his dives so he can really understand what depths he was at and when he went past NDL into deco. Just my humble opinion.

 

[Blackcrusader]

It's eye opening to see the increase of the GF during the final ascent. I try to make my final ascents over at least a minute.

I do the same and people ask me why I am so slow in the last 5m to surface. When I want to explain about the Surf GF I get blank stares back as so many recreational divers do not understand this as their own DC perhaps does not have this feature. You can I study our own dive logs however I assume many people do not. Even on this quite shallow dive you can see my final couple of minutes to ascend from 5m depth to the surface.