Now it's time to choose a wrist computer.

[SaltyCracker]

This is a 1st clean dive on air to 60 ft. NDLs come from my Shearwater Teric running Buhlmann ZH-L16C, and my Oceanic Geo 2, running both DSAT and PZ+. The NDLs vary widely, from 32 to 57 min. If you were to dive GF 35/75, 40/85, 45/95, or PZ+ to the DSAT NDL of 57 min, you would accrue deco time, somewhere between 17 and 3 min

View attachment 697745

Mine runs the Buhlmann ZH-L16C unmodified. Are you able to indicate how mine would act in the dive profile you show here assuming mine is set to whatever conservatism level yours is set to? Is this even a realistic question? I don't know what I don't know.

 

[dmaziuk]

That was an informative post, thank you.
I was wondering if a conservative setting of 4 might be a little too aggressive, even for a cautious beginner with his trusting child in tow. You don't think so? I have to assume even a setting of 1 is still "safe" but more likely to include stops correct?

I would expect the child to be "safer" as in better tolerating decompression stress. Somebody (@scubadada?) posted the gradient factors for seac "conservatism levels" once, IIRC the most liberal of them was the closest to DSAT: the only model actually designed and tested for recreational diving. So I wouldn't worry about any of them being too aggressive -- but see how you feel after the dive: too tired may be a sign of sub-clinical decompression stress, try one step down if that happens.

 

[SaltyCracker]

I would expect the child to be "safer" as in better tolerating decompression stress. Somebody (@scubadada?) posted the gradient factors for seac "conservatism levels" once, IIRC the most liberal of them was the closest to DSAT: the only model actually designed and tested for recreational diving. So I wouldn't worry about any of them being too aggressive -- but see how you feel after the dive: too tired may be a sign of sub-clinical decompression stress, try one step down if that happens.

Okay... I just want to be sure I'm using the language that I should be. When considering a conservatism level between 0-5, I'm assuming 5 would be the most 'conservative' therefore the most restrictive. And 0 would allow for the most liberal dive plan while still remaining within calculated NDL.

 

[Dan]

That's fine. I'm not looking to debate it at all. I don't know enough to do so anyway. I'm just curious what the basic opinion is. Is the RGBM algorithm out of date and inaccurate?
So it's the ZHL-16C algorithm that is recommended then? It looks like two on my list would satisfy that wish if it was important. I wonder how much it is though for people that do conservative non-decompression diving.

I started with RGBM (SUUNTO D4) and found it's too conservative. Then I moved to ZHL-16C (Shearwater Teric). I dove with both D4 and Teric and compared them (RGBM vs ZHL-16C with Medium Conservative 40/85). I had to turn down the D4 RGBM conservatism from 100 to 50 to match ZHL-16C Med Conservative 40/85.

Other good things about Shearwater computer are much user friendly than SUUNTO, brightly lit display and Teric is wireless charging. I can use my iPhone wireless pad to charge my Teric.

 

[dmaziuk]

Okay... I just want to be sure I'm using the language that I should be. When considering a conservatism level between 0-5, I'm assuming 5 would be the most 'conservative' therefore the most restrictive. And 0 would allow for the most liberal dive plan while still remaining within calculated NDL.

Yes, however, nothing's ever simple:
- the core value is "maximum allowed supersaturation": that's the bit that's statistically derived to produce a known incidence of clinical DCS.
- These values are believed to be "too liberal" for "bare" ZH-L16.
- The conservatism adjustment commonly used for ZH-L is known as "gradient factors" or GF (not to be confused with "Surfacing GF" nor "GF 99"). It is given as a pair of numbers: "High" and "Low", of which only GF High matters for no-stop diving.
- ZH-L16C GF High that roughly corresponds to DSAT is about 97 (?), at least for the first few dives -- Craig knows better, he dives a Teric and an Oceanic together.

Now, what we want to know is the GF numbers that correspond to Seac's conservatism levels. My guess is it's GF High 95 or less for the "least conservative" level -- 95 being marginally more conservative than DSAT, -- but Seac Sub is "helpfully" not spelling it out in their f...ine manual. I'm pretty sure they're not doing bare ZH-L16C though.

 

[Dan]

I would think about how much night diving you do to. An LED display is much nicer for that than a backlit LCD (having just switched, I really noticed it). Alas, I don't know of many economical choices with LED (colour) screens. Maybe the Atmos mission one, if the firmware issues are sorted out.

Indeed. Here’s what my Teric display look like at night or day. Also, I had the info setup such away to show all the info I need during the dive so I don’t need to press any button, just glance at it.

 

[Dan]

(Or any other proprietary algorithm, let alone one which will lock itself up if you make it unhappy.)

I locked my SUUNTO D4 once for surfacing before clearing deco obligation (diving Nitrox but forgot to set the EAN32 on the computer). The Teric won't do that. It'd just tell you that you have been a bad boy.

 

[rongoodman]

Which is a perfectly reasonable thing for it to do. I had a backup Shearwater to the same thing to me on a rebreather dive once, probably because I hadn't entered the proper set point. It didn't just quit working, though.

 

[SaltyCracker]

Somebody posted the gradient factors for seac "conservatism levels" once, IIRC the most liberal of them was the closest to DSAT: the only model actually designed and tested for recreational diving.

So would "the most liberal of them" be 0 or 5 on my SEAC Screen (or for that matter, any other computer that uses that scale)?
And you're comparing the most liberal of the scale to DSAT?
And DSAT is considered "the only model actually designed and tested for recreational diving"?
It seems to me that an algorithm designed primarily for the rec diver community would be more on the conservative liberal side. I'm trying not to be dense or split hairs. But something seems backward to me.

Here's what I'm understanding so tell me what I have wrong okay:
0 = the most liberal setting.
5 = the most conservative setting.
DSAT could be seen as a more conservative dive algorithm better suited for rec divers.
ZH-L16C could be seen as a more liberal dive algorithm better suited for the experienced and tech divers.

And when you say "bare" ZH-L16C, does that mean what my manual is calling ZH-L16C "unmodified"?

 

[inquis]

DSAT could be seen as a more conservative dive algorithm better suited for rec divers.
ZH-L16C could be seen as a more liberal dive algorithm better suited for the experienced and tech divers.

DSAT is on the LOW conservatism end of the scale. Most other algorithms give shorter NDL times.

ZHL16-C uses gradient factors to control conservatism: x/95 to x/97 is fairly equivalent to DSAT. Medium conservatism is x/85, and high is x/75. These are the "built-in" values on the latest Shearwater computers, but somewhat arbitrary. Think of the second gradient factor as relating to risk when reaching the surface. Dial in lower if you like, as it's very flexible. (The first factor, which I denoted by an "x", only applies during decompression diving.)

Many technical divers like ZHL16 because the algorithm is widely known (non-proprietary).