Difference between MB levels and Gradient Factors

[tursiops]

I would never consider using a computer that goes into gauge mode in the middle of a dive.

Exactly.

 

[Sevenrider860]

Here is a story about lockout features.

As I said above, when I started tech diving, we just used written plans, with no computers. One one dive in Florida with a maximum depth of 270 feet, my buddy and I were following a plan (with contingencies) derived from V-Planner. My buddy had just bought a dive shop (Fill Express), and Suunto was trying to get him to carry their products. They gave him their hot, new tech computer, the HelO2, to try out. He brought it on the dive to see how it would work. Its RGBM algorithm was close to our VPM to begin with, and he tweaked it to get it as close as possible.

Well, we followed out written plan about as well as we possibly could, but it did not match what the HelO2 wanted us to do. During one of our deco stops, my buddy informed me that the HelO2 had gotten pissed off enough to go into gauge mode. "Well, that's just plain worthless," I decided.

I would never consider using a computer that goes into gauge mode in the middle of a dive.

While I don't think the G2 is some miracle device as has been described, I don't think it is a bad computer for a very large majority of divers....even with the SOS mode.

The standard G2 is fine for the majority of divers that do not know VPM from ZHL-16 to RGBM. There are not a large number of divers getting bent on the G2. If the diver's only plan is to follow the computer, then who really cares about the proprietary algorithm that makes unknown and undocumented changes to the NDL based on heart rate or skin temperature? Who cares about the MB settings which are really no different than adding conservatism and shortening the NDL? The divers have no concept of decompression algorithms and they have no other plan than to follow their computer. The G2 work just fine in these instances.

While I also like computers that don't go into "lockout" or "SOS" mode (Shearwater and Garmin), it is not an easy task to accomplish with the G2. On the G2 Tek, to go into SOS mode, you are diving ZHL-16 with gradient factors at 100/100 and missing a mandatory deco stop for more than 3 minutes. I dive 50/70. If I miss a stop my Shearwater will not go into gauge mode...but neither will the G2. The Shearwater will calculate the next stop at 50/70 even though you are past the GF line and into the safety margin, the G2 will adjust to the next set of gradient factors that places you back under the calculated GF line. Only when you have so badly messed up your plan that you are diving a pure Buhlman profile, does the SOS mode even kick-in.

I do not know the underlying mathematics in the ZHL-16 algorithm. I understand it is nice to have a computer that still runs calculations when you are on the wrong side of the Buhlman M-value line on your stops. But if you are already on the wrong side of that line...what information are those calculations really providing you? What studies exist that making depth and stop decisions on the wrong side of the M-value line will keep you from getting bent? It seems everybody wants a computer that is still calculating depth and stops when you are in the pink shaded area below, but is that going to reduce the chances of them getting bent compared to just following the missed deco procedures we learned in our technical diving classes or what is taught in basic open water? I do see where it would be nice to know if I surfaced at 110% versus 170%, but would the precautions taken once on the boat still be the same?

I also use the computer as the controlling factor for a planned decompression dive where I have a written dive plan with the standard too long, too deep and lost deco schedules. The rule I follow is that my written plan should use the same algorithm that my computer will use. I don't plan dives on VPM and then expect to follow my computers that are using Buhlman. If you planned your dive using VPM and assumed that the Suunto HELO2 would match it with its RGBM algorithm...well that is on you. Suunto actually had (maybe still has) an offline planner (Suunto DM??) that matched the Suunto RGBM algorithms used by the different computers (Technical, Fused, etc.). Suunto Technical RGBM did not even match a standard RGBM offline planner like GAP. A "bricked" HELO2 is still a bottom timer which could be used against your written plan. The primary issue started before you ever splashed...plan VPM and try to follow a computer using Technical RGBM.

 

[L13]

This is best one: Feel free all those that blindly promote GF as best because you can select "level of conservatisim, this is why GF better than G2 and whatever it does." Ok so now we have level of conservatisim and which is best? Feel free to show exact settings and why? Best you going to get from any manufacturer is L, M, H or levels 0 - 9. But somhow this always gets turned on head, in fafor of marketing retoric or outright misinformation. O'h and please also show reserch showing which GF best for many factors including age?


You really should limit your comments on the Subject of the Scubapro G2.

"In technical diving a dive computer is not
the primary instrument to follow during the
dive. Before the dive you must make a plan
and during the dive follow it. If your plan and
the computer show different schedules,
follow the more conservative one."

The above is a primary factor of why so many "adult" divers take advantage of what the G2 has to offer.

But again, when half of the posters commenting here are more involved GF99 and SurGF, ON THE FLY as compared with diving the decompression plan, what would you expect? Calculating and reccomending deep deco diving on the fly is just wrong. This is turned round by the retoric and praise of live GF monitoring. (Feel free to stare and attempt to dcipher what your dive coumputer is telling you on the fly. The mental gymnasitics are huge. I set my G2 to the plan, it instanly alerts me when I have exceeded the parameters I set it for when I made my dive plan, I value this feature. ) So says the sales literature. Perhaps when we have people that have actually used the G2 AND have used other brands, we can all have an adult discussion instead of this ill and uninformed constant bantering. I suspect the vast majority here do not own multiple units, much less understand fully.

The constant attacks regarding the G2 SOS mode is just one example of the intentional ignorance and misdirection that continues to surface here. Do yo know why SOS mode is important in light of repetitive diving? And the fact that most of those GF types fall very, very short on this subject? When you enter SOS mode, neither the computer AND YOU can use the decompression features, which is basicially why many purchase a dive computer in the first place. Why then does other brands, other than Scubapro continue to bash a safety feature when circumstances which create the safety feature are caused by ignoring the units in the first place. And then these other manufaturers try to turn a deficit into a markiting positive. You can always reset the thing, or use it to monitor depth and time, but alas so many try to use propaganda and lie and say the unit shuts off or whatever. Personally if the conditions exsist that cause a copmputer to go into SOS mode, you really shouldnt be diving again, period. And the fact that the unit is telling you something about the dive you just did, well I am glad it locks (SOS mode NOT lockout) out, because you are asking it to guess or remember something you ignored in first place. I use the G2 to track multi day dives, it is the best at that. PDIS takes care of Deep stop issues, G2 best at "efficency" if anyone would bother to learn and actually study manual.

"When the G2 is set to Gauge mode, it will
only monitor depth, time, and temperature,
and will not carry out any decompression
calculations."


"WARNING
Dives in Gauge mode are performed at your
own risk. After a dive in Gauge mode you must
wait at least 48 hours before diving using a
decompression computer."

"When on the surface in Gauge mode,
the G2 will show neither the remaining
desaturation time nor the CNS O2 % value.
It will, however, display a surface interval up
to 24 hours and a 48-hour no-fly time. This
no-fly time is also the time during which you
cannot switch back to computer mode."

Here is the official rational regarding SOS / Gauge mode: If you are stupid enough or perhaps had some kind of emergency and incure a massive deco debt, I am not going to let you back into the water. You are going to have to do things like reset the device or do the right thing and have a big surface interval, cause you have done something so that I can no longer keep track of your deco. Now here is the thing, other manufacturers leave your mistakes and ignorace up to you then get you to belive that this is a benifite.

Real facts from real users of the device are in short supply here. You have previously admitted basicailly you have "never even seen" one of these units.

PDIS in the G2 is not and has never been a promotion for Deep Stops way of thinking. Scubapro MB is not be confused with promoting deep stops either, but so many of you try!!! WHY?
"Along the same lines,
PDIS will account for the accumulated
nitrogen from previous dives; hence,
PDIS is also repetitive-dive dependent." >>>So many other manufaturers can not make the same stement.

Here is other favorite lie: "Workload , no scientific proof, just gimmick." <<<< But there is research, and lots of it that support the other factors are very, very impoortant. You could also state the reverse of this lie as well, there is no research contradicting workload isn't a benifite. Use brain, temperature, respiration, heart rate, temperature very important. Anyone who say otherwise is just attempting to manipulate and lie to those who want their hands held and can't be botherd invest in learning.


I would guess that you base your "Opinions" upon a quick read of the online manual? It takes long time to fully learn something. Perhaps putting in effort beyond what you willing to do? No free lunch with G2, designed for efficency and actual real use, as compared with faux hand holding and features that have sever demands upon thinking. And biggist irony of all, G2 has more features, first, and same features just described differently. Any experinced G2 user can spot the retoric and misdirection, but then why bother coreecting them, they seem to have agenda and would listen anyways.

I would offer that would be a mistake. The G2 does not hold your hand with markiting retoric, which in fact increases risk taking by the fact that to use a G2 as compared with other dive computers, you really do need to know your stuff. There is no hand holding here as clearly evedent in other units.

So why not real owners of G2 speak up here, cause they know better than to deal with people who not fully versed and informed, Keep your marketing materials and incomplete understanding, who can't be bothered. You especially, you do not own a G2, you have never used a G2, you have never seen one, you post misinformation about G2, and yet your mouth keeps moving.

Short version.

Where is the short version?

This is such an unreadable word salad of rantings and misspellings that I can barely make out anything except that you believe the G2 is magically better than all others.

The fundamental flaw with the G2 is that everything about how it might work better is proprietary, along with all the research that shows it. Nothing can be verified. I could even accept the proprietary algorithm if there was at least meaningful public research showing the G2 outperforming other computers in preventing the bends. As it is, it is a giant "Trust Me Bro."

 

[BoltSnap]

While I don't think the G2 is some miracle device as has been described, I don't think it is a bad computer for a very large majority of divers....even with the SOS mode.

The standard G2 is fine for the majority of divers that do not know VPM from ZHL-16 to RGBM. There are not a large number of divers getting bent on the G2. If the diver's only plan is to follow the computer, then who really cares about the proprietary algorithm that makes unknown and undocumented changes to the NDL based on heart rate or skin temperature? Who cares about the MB settings which are really no different than adding conservatism and shortening the NDL? The divers have no concept of decompression algorithms and they have no other plan than to follow their computer. The G2 work just fine in these instances.

While I also like computers that don't go into "lockout" or "SOS" mode (Shearwater and Garmin), it is not an easy task to accomplish with the G2. On the G2 Tek, to go into SOS mode, you are diving ZHL-16 with gradient factors at 100/100 and missing a mandatory deco stop for more than 3 minutes. I dive 50/70. If I miss a stop my Shearwater will not go into gauge mode...but neither will the G2. The Shearwater will calculate the next stop at 50/70 even though you are past the GF line and into the safety margin, the G2 will adjust to the next set of gradient factors that places you back under the calculated GF line. Only when you have so badly messed up your plan that you are diving a pure Buhlman profile, does the SOS mode even kick-in.

I do not know the underlying mathematics in the ZHL-16 algorithm. I understand it is nice to have a computer that still runs calculations when you are on the wrong side of the Buhlman M-value line on your stops. But if you are already on the wrong side of that line...what information are those calculations really providing you? What studies exist that making depth and stop decisions on the wrong side of the M-value line will keep you from getting bent? It seems everybody wants a computer that is still calculating depth and stops when you are in the pink shaded area below, but is that going to reduce the chances of them getting bent compared to just following the missed deco procedures we learned in our technical diving classes or what is taught in basic open water? I do see where it would be nice to know if I surfaced at 110% versus 170%, but would the precautions taken once on the boat still be the same?


View attachment 788856
I also use the computer as the controlling factor for a planned decompression dive where I have a written dive plan with the standard too long, too deep and lost deco schedules. The rule I follow is that my written plan should use the same algorithm that my computer will use. I don't plan dives on VPM and then expect to follow my computers that are using Buhlman. If you planned your dive using VPM and assumed that the Suunto HELO2 would match it with its RGBM algorithm...well that is on you. Suunto actually had (maybe still has) an offline planner (Suunto DM??) that matched the Suunto RGBM algorithms used by the different computers (Technical, Fused, etc.). Suunto Technical RGBM did not even match a standard RGBM offline planner like GAP. A "bricked" HELO2 is still a bottom timer which could be used against your written plan. The primary issue started before you ever splashed...plan VPM and try to follow a computer using Technical RGBM.

Thank you!!

 

[tursiops]

There are not a large number of divers getting bent on the G2.

Nor with any modern computer.

 

[Sevenrider860]

Nor with any modern computer.

100% agree, and a large number of these recreational computers have SOS, Lockout, Gauge modes. The Shearwater line, Garmin (as a user option), and the TDC-3 are the only ones I am aware of that do not have some sort of violation lockout that ranges from 24 to 48 hours.

 

[L13]

The G2 does purport to take into account additional factors(pulse, temp, etc.) that everyone knows are important and that other computers don't. I think that is a valuable step in the right direction. However, without more transparency, that step is rendered almost meaningless.

 

[Sevenrider860]

I no longer dive the standard G2, I am using the G2 Tek and PDIS is not available on this version. However I have seen a lot of comments about PDIS, Deep Stops, NEDU Study, etc. Having used the computer, the G2 did have some nice informational options. PDIS was one of them. PDIS is off on a G2 by default, I liked to turn it on.

While Scubapro markets PDIS as a 2 minute intermediate "stop", it did not have to be used that way. Many computers with a Deep Stop option simply divide the maximum depth by 2 and suggest a stop at that depth. PDIS is different in that it determines the depth where the leading compartments (minus the two fastest compartments) used for the decompression calculation switch from on-gassing to off-gassing. Think of it as a binary Shearwater GF99 type function. Below the PDIS depth you are on gassing, above it you are off-gassing and that value changes based on your repetitive dives and your current dive profile. You never had to make the stop and you were never penalized for not taking the stop, but it allowed a quick view of what your on-gassing/off-gassing depth was.

I never used the standard G2 for planned decompression dives specifically because it had an algorithm that I could not use an offline planner for. The default options on a G2 will not adjust the algorithm based on anything but depth and time...however you can enable a number of options that will have the algorithm changing throughout the dive based on conditions other than depth and time. I just left them off.

 

[Wibble]

100% agree, and a large number of these recreational computers have SOS, Lockout, Gauge modes. The Shearwater line, Garmin (as a user option), and the TDC-3 are the only ones I am aware of that do not have some sort of violation lockout that ranges from 24 to 48 hours.

Which you're saying is a good thing?

Or to put it another way, why do you need to tie an expensive brick to your wrist?

There's a good reason why Shearwater computers are popular with most rebreather manufacturers and technical divers. And it's not because they become part time bricks (or have some made-up proprietary algorithm).

Well, we followed out written plan about as well as we possibly could, but it did not match what the HelO2 wanted us to do. During one of our deco stops, my buddy informed me that the HelO2 had gotten pissed off enough to go into gauge mode.

Because it was running a different deco curve than the plan called for. So it goes into a massive sulk like some sullen teenager.

I would never consider using a computer that goes into gauge mode in the middle of a dive.

Nor a computer that bricks itself on the surface for a 2 day arse covering sulk.

 

[boulderjohn]

While Scubapro markets PDIS as a 2 minute intermediate "stop", it did not have to be used that way. Many computers with a Deep Stop option simply divide the maximum depth by 2 and suggest a stop at that depth. PDIS is different in that it determines the depth where the leading compartments (minus the two fastest compartments) used for the decompression calculation switch from on-gassing to off-gassing. Think of it as a binary Shearwater GF99 type function. Below the PDIS depth you are on gassing, above it you are off-gassing and that value changes based on your repetitive dives and your current dive profile. You never had to make the stop and you were never penalized for not taking the stop, but it allowed a quick view of what your on-gassing/off-gassing depth was.

Could you post the studies that show this is beneficial? I have done a lot of research on this topic, and I seem to have missed them.