Past NDL. And then this???

[admikar]

This is complicated by the fact that people are throwing tech diving into the discussion. For recreational diving, I agree with this 100%. For technical diving, if my computer says I am done with a decompression stop and should ascend to the next stop, and my buddy's computer says to stay at that stop longer, then I am going to stay with my buddy.

Of course, you and your buddy would plan your dive first, and if one of you use GF 10/95, the other one would be uncomfortable with that, and you would agree on common plan, set your computers to that plan, or write it on slates, and than you would dive that plan.

 

[boulderjohn]

In light of this thread, it is important to understand the difference between working as a buddy team with computers BEFORE a diver goes into deco and AFTER a diver strays into deco unintentionally. This thread points out the problems of a diver not understanding what his computer told him, and I have a very similar story with a diver not understanding a different computer that was using the same RGBM algorithm. My story illusrates the issue pretty clearly.

I was completing a training dive with some students, and there were other divers on the trip with me diving at the same time but not as a part of my training group. We surfaced at the same time, and immediately one of the other divers said his computer was acting really strange on the dive. It gave him a signal he did not understand, then it started counting minutes UP rather than DOWN as he was used to. Now the computer was just saying "Er." What was up with that?

I asked him what that final number was, and he didn't remember. I immediately took him back down, checking to make sure he had plenty of gas as I did. We hung out at safety stop depth for 20 minutes. Being in error mode, his computer was no help to me in knowing how far he had gone into deco. He seemed fine, so we surfaced, and I had him breathe oxygen for a while.

BEFORE you go into deco, your computer counts DOWN the number of minutes before you have a decompression obligation. When it gets to a reasonable point, you should start your ascent, and your buddy should ascend with you, even if his opr her computer is indicating more time. AFTER you have gone into deco, your computer will start counting UP the number of minutes of decompression you owe. At first it will be nothing more than an extended safety stop, but eventually it will tell you to stop deeper than that standard safety stop, and in that case you are now in the opposite situation--now you must stay down rather than go up. If your buddy is allowed by the computer to ascend before you do, then your buddy should stay down with you at the deeper depths, knowing his or her computer will adjust to that situation. If you instead ascend with your buddy when your computer wants you to stay deeper, and if your computer has the RGBM algorithm, it will not only not adjust to that changing situation, it will go into error mode and no longer be of use for you for 48 hours, other than giving you basic information like depth and time.

 

[Slamfire]

Even if you read all the supplied documentation it is still not easy to figure out how some computers will behave under varying conditions like repetitive dives or going beyond ndl on a second dive. This affects their reliability. Even if its brand new and in perfect condition an unpredictable computer is unreliable.

 

[elmo]

Even if you read all the supplied documentation it is still not easy to figure out how some computers will behave under varying conditions like repetitive dives or going beyond ndl on a second dive. This affects their reliability. Even if its brand new and in perfect condition an unpredictable computer is unreliable.

This is especially true of dive computers that use unpublished models, such as RGBM rather than Buhlmann and VPM-B.

 

[kafkaland]

Even if you read all the supplied documentation it is still not easy to figure out how some computers will behave under varying conditions like repetitive dives or going beyond ndl on a second dive. This affects their reliability. Even if its brand new and in perfect condition an unpredictable computer is unreliable.

Here's is what I did to figure out what my computer does when it goes into deco, before I was deco trained: I used a second, backup computer, as primary for the dive, on Nitrox. And set my usual primary computer to air. It went into deco fairly quickly, and on ascent I did whatever I took make it happy, knowing fully well from the othe computer that was properly set to Nitrox that I was still well within my actual NDL. But this way I learned what my computer would tell me in an actual accidental deco situation.

 

[Dan]

Here's is what I did to figure out what my computer does when it goes into deco, before I was deco trained: I used a second, backup computer, as primary for the dive, on Nitrox. And set my usual primary computer to air. It went into deco fairly quickly, and on ascent I did whatever I took make it happy, knowing fully well from the othe computer that was properly set to Nitrox that I was still well within my actual NDL. But this way I learned what my computer would tell me in an actual accidental deco situation.

Let get this straight. You were comparing a computer on air with another on Nitrox? Did you have Nitrox or air in your tank at the time?

 

[kafkaland]

Let get this straight. You were comparing a computer on air with another on Nitrox? Did you have Nitrox or air in your tank at the time?

Nitrox. And diving well above the MOD for the mix. But following the deco profile the "air" computer gave me, while staying well within the NDL of the accurately set Nitrox computer.

 

[KeithG]

This is especially true of dive computers that use unpublished models, such as RGBM rather than Buhlmann and VPM-B.

Regardless of the algorithm, I have found that every dive computer manual I have read does a very good job of clearly explaining exactly what the information on the various computer screens means.

This thread is not about "i do not know what this weird computer is doing", it is more about "i did not read the manual, hence i do not understand what it is telling me to do".

 

[Centrals]

This thread is not about "i do not know what this weird computer is doing", it is more about "i did not read the manual, hence i do not understand what it is telling me to do".

He did read the manual but did not fully understand or execute the instruction.
His computer told him to go to 4m and stay for 7mins. But he "claimed" he did not understand why the penalty added up with every sec he had stayed below 4m.
Who to blame, computer of user?
My ageing Uwatec Aladin Pro nitrox is using ZH-L8 ADT algorithm. And if I delay my ascend the deco obligation will also increase. No difference for RGBM.