Difference between MB levels and Gradient Factors

[Mobulai]

That isn't how that works: if your computer's fastest TC is 5 minutes, the meaningful recalculation frequency, from the algorithm's POV, is measured in minutes. Say you use Nyquist's law as a guide and set your recalculation rate to 2 minutes and 29 seconds: in that time you could ascend 20 m @ 9m/min, dropping your Pamb by 2 atm, or you could ascend 40 m @ 18m/min and drop your Pamb by 4 atm.

IRL your computer's fast enough to support pressure sampling frequency & recalc frequency on the order of seconds, so what you're saying is probably likely true, but I'd want to read the fine print to be sure.

My computer, OTOH, has its fastest TC at 2.5 minutes and is thus much more sensitive to ascent rate, which translates into annoying beeping every time I turn head-up and raise my arm to vent from the corrugated hose.

How did you get info on this TC value? And what does the acronym stand for?

 

[Mobulai]

What? What mental gymnastics? I'm not sure you understand GF and SurfGF as you seem to be equating them to the same thing. I'm trying to understand what could be so difficult to understand.

I'll start with GF. In essence, this is the conservatism setting for the DC. A little prior research into what GF Hi and GF Lo are and you can set to where you want it to be. Or, if not, you can just choose one of the defaults. They are usually labeled as High, Medium, Low Conservatism. That's pretty easy to figure out. Once it's set, those settings apply. The computer functions just as it would otherwise with the desired conservatism settings providing the boundaries for NDL or the Deco plan. I don't see how having GF set to one or the other has users "staring at their computer trying to figure it out."

SurfGF is an additional piece of information. I find it useful, so have added it to the main dive screen on both my computers. If a diver can't figure out what it means, then they don't need to use it. It's not that hard, so again I don't see how having SurfGF displayed leads to divers "staring at their computer trying to figure it out." It's simply additional information. The diver can decide what they want the max SurfGF number to be before they begin the final ascent. It's simply then an act of understanding if the number displayed is greater than or less than the number the diver decided on. If the diver can't identify if a number is larger or smaller than another number, they probably shouldn't be diving. They probably would also have difficulty with other tasks as well.

You like your G2. That's great. No need to make up nonsense about SurfGF and GF to validate your purchase.

No idea what SurfGF metric implies, but by extrapolation seems analog to how (super)saturated would you be at surface?
If so I’d say that’s sounds useful (to me) just like the PDIS

 

[Mobulai]

Or at least you would, if you knew the old risk.

Which IIRC is mentioned in the DSAT report and possibly may be mentioned in Tauchmedizin but I don't read German. If anyone knows what it is for various flavours of RGBM or PZ+, I never heard them tell teh rest of us. Ditto for various GF settings on top of ZH-L16.

As it is, IRL this is mostly the matter of trust. You trust ZH-L16+GF85: good on yah. He trusts ADT+MB: good for him.

I can read German… would you mind sending me the article? I can also share with the class

 

[Mobulai]

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A ScubaBoard Staff Message...

Moved from Basic

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Agreed cuz now I’m even more confused from a basic POV; but here’s to learning Advanced stuff

 

[Belzelbub]

No idea what SurfGF metric implies, but by extrapolation seems analog to how (super)saturated would you be at surface?
If so I’d say that’s sounds useful (to me) just like the PDIS

Correct. At any point in the dive it displays what your tissue loading would be if you were to be instantly transported to the surface. Uses whatever is the leading compartment and displays as a percentage with 100% representing the M value saturation.

 

[Mobulai]

Correct. At any point in the dive it displays what your tissue loading would be if you were to be instantly transported to the surface. Uses whatever is the leading compartment and displays as a percentage with 100% representing the M value saturation.

and that's a shearwater feature?
sounds like an even more important feature than PDIS considering the slower tissue ofgassing issues of deep stops from bubble models; as an analog to simplified version fo the tissue hitograms Dr. Mitchell et al presented as part of the NEDU study

I'd say brilliant, also seems intuitive enough that I knida guessed it (no mental workout needed really)

(referring to this)

 

[Belzelbub]

and that's a shearwater feature?

Yes. Among others. I think it was first offered in Shearwater DCs. It also showed up in Garmin after an update, and I think it’s available on a couple others. Only on DCs running Buhlmann, and not all of them.

There is a chart around here. Let me see if I can find it.

Found it. May not be complete as it’s only for wrist DCs with air integration, but it appears that Shearwater, Garmin, and Mares are the only ones with SurfGf at this point.

Air Integrated Wrist Computers in the US

*See last spreadsheet posted for update* There have been a number of new AI wrist computers in the last year. I have been keeping a spreadsheet for myself, thought others may be interested. All errors are my own, easy to correct if you let me know. Edit, I'll start with the errors, Suunto...

scubaboard.com

 

[Mobulai]

so I stumbled across this thread since I (a rec diver, starting to slowly step into tec) have used a G2 for the last 3 years, and just got myself a 2nd DC that can do Buhlmann GF.... plz don't roast me (at least be gentle)... a G2 HUD (just got it yesterday used for a firey deal)

I was bidding on it in parallel to hunting for a used Petrel2 4pin (no luck), but my main motive is a cost aspect, I already got a G2 with AI; I just started diving in SM; I got a redundant DC and an extra transmitter (that works on both in parallel) for less than the price of a Luna, also HUDs feel cool (will have to donn it to see if I can see)

in the words of @rsingler "I am not a SP fanboy" (said while wearing their T)

I wanted to figure out a way to match the G2 to the HUD and offline plan using GFs, so I just binged this thread in one sitting; kudos for everyone being motivated which has helped me better understand some things, but my eyes hurt.

But One day, one of the G2s will have to go.
Since I bought the G2 I always knew I wanna end up with a Perdix or Petrel; just not now, when I actually own (not train on) a CCR I would do that; and I will still keep one of the G2s (maybe the wrist version, the reason I chose that "compromise" is the pictures capability which I adore for dive maps, maybe the HUD for GF and GPS)

seems like there have been multiple factions here all with valid points (on one issue/level or the other)

I also like opensource sw and algos, so maybe the HUD would be the keeper and I'd have to let go of the pictures mode when I jump on the (probably) Petrel; but maybe also neither.

The way I chose to interrpet the MB algo is that it's a GF algo where the GF is blackboxxed from the user -- you input some "Human factors" and it kinda finds it's own GF to vibe with

But as @boulderjohn (if I am remebering correctly from this long AF thread I just chugged) complained (or was it @Wibble) about and called paying the sunnto tax -- that doesn't sound fun, and can given the right (or wrong) curcimstance be risky, and even harmeful; but I would still view it as a non absloute since it is a blackbox system.

My realistic view is, when the time comes for a "controller" DC, the HUD might not feel that natural to add to the setup (I like the idea of simple PPO2 LEDs, as logistics of other things require simplification on that eye side), and might endup with just the wrist G2 as the backup

the question now is, and I am hoping @tursiops would help me here since you provided some before; any more slides/info on translating MBs to GFs out there? that would be very helpful to enable untriggered utilization of 2 DCs of various algo.s side by side.
If not I guess I will have to run the experiment myself and (eventually) get back to y'all

also: damn that G3, I'd take a Garmin anyday over it -- at least the G2 (love/hate it or not) had some real estate to read off easily.

thanks everyone for keeping this very intresting and educational

 

[dmaziuk]

I can read German… would you mind sending me the article? I can also share with the class

It's not an article, it's Herr Doktor Buhlmann's pinnacle work: the book called Tauchmedizin. It was never translated to English and is not cheap either (but may be obtainable on interlibrary loan).

 

[dmaziuk]

How did you get info on this TC value? And what does the acronym stand for?

Which acronym? Tissue Compartment?