Fiddling with your handsets at 110msw

abowie

At the risk of performing "re-illitiratio", can someone explain to a non Inspo trained diver why the unit would have done this?

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Andrew Bowie

Rebreather-friendly Buddy

Mark Chase

How long have you got?

Dodgy battery
Dodgy contacts in the battery box
Dodgy contacts under the battery box
Water in the hand sets due to cracks


I suspect one of the above with a possablt flaky cell thrown in for good measure.

ATB

Mark Chase

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Is it supposed to make that noise ?

I took my unit to the dive shop and demanded they bolt on every thing that would fit.

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sven

I had a low battery warning and a cell warning almost simultaneously. For some reason, the master would not let the slave come up and get data, after I accidentally re-started the slave (attempting to force the slave to become master but switching off the wrong controller). To be really honest, I do believe that the master did get stuck, otherwise the slave should have come up normally once switched back on again.

For cases like this, I would love to have a DETAILED log of events for download ... Once the brown stuff hits the proverbial fan, it becomes very hard to re-construct the chain of events. And, believe me, I would not want to try and repeat this experience :-)

Is there any research about the effect of pressure on brain function? I mean besides "normal" physiology, are there any other side effects known??? Or, do you think I simply stressed out because of fear?

__________________
Regards,
Sven

[SIZE=1]The Sydney Project website: [URL]http://www.sydneyproject.com[/URL]
My Blog: [URL]http://sven.rebreatherworld.com[/URL]

"Whenever you find yourself on the side of the majority, it's time to pause and reflect." Mark Twain[/SIZE]

abowie

What I was getting at was that all of the (presumed Inspo trained) replies didn't seem fussed that the unit chose to shut down at 110m.

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Andrew Bowie

Rebreather-friendly Buddy

abowie

Ahh. Something I do know about.

Essentially, your brain (or anyone's for that matter) is never going to function as well at 12 bar as it does on the surface.

Unless you're using heliox as your dil (and you don't believe in O2 narcosis) there's always a component of inert gas narcosis.

HPNS is said to cut in at over 15atm and is descent rate dependant and predominately motor. That doesn't mean that there isn't some cognitive impairment independent of nitrogen due exclusively to pressure. HPNS is thought to be due to neuronal membrane distortion due to pressure.

Finally good old task loading, when combined with a bit of cognitive impairment, is going to further hinder you.

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Andrew Bowie

Rebreather-friendly Buddy

sven

Andrew,

The controller did not switch off, but I believe it ended up in an undefined state, due to some chain of events which I cannot re-construct from memory. A simple sequence of steps would/should have resolved this issue:
1) switch off master
2) slave takes over
3) switch on ex master, which now becomes the slave

But there is another niggling question ... If my hunch is right, and the master ended up in an undefined state, WHY/HOW?

In the meantime, I completely stripped down my unit and checked batteries, cables, sensors, handsets. All looks OK, apart from one sensor that needs replacement. Both batteries deliver 6.07V under load (maybe a bit low if they get cold?). But the key question is, can the electronics get "stuck"??? So your question is indeed a very! valid one.

__________________
Regards,
Sven

[SIZE=1]The Sydney Project website: [URL]http://www.sydneyproject.com[/URL]
My Blog: [URL]http://sven.rebreatherworld.com[/URL]

"Whenever you find yourself on the side of the majority, it's time to pause and reflect." Mark Twain[/SIZE]

sven

Glad you did not mention old age :-)

__________________
Regards,
Sven

[SIZE=1]The Sydney Project website: [URL]http://www.sydneyproject.com[/URL]
My Blog: [URL]http://sven.rebreatherworld.com[/URL]

"Whenever you find yourself on the side of the majority, it's time to pause and reflect." Mark Twain[/SIZE]

Mark Chase

Thats because we shouldn't be.

Training experience and the design of the unit should deal adequately with the situation. You lose the master the slave takes over. Personally id have dropped the slave to 0.7 and ran the dive manually from there on in.

ECCRs go wrong. Its how they fail and the systems for handling it that make it a good/bad ECCR The classic has some good safety features like two independent hand sets (I don't like the Vision single hand set design) and it has a Hard off switch (I dont like the HH that you cant turn off)

The classic sufferers from being a 10 year old design with some minor inherent faults but its still a good unit thats done more sucesfull deep dives than all the other units put together.

As a result the point of this thread is the errors made by the diver which he had the guts to post on here. The unit did a pretty good job of keeping him alive despite the screw up and he did a good job of not loosing it completely.

So a nice happy ending.

ATB

Mark Chase

__________________
Is it supposed to make that noise ?

I took my unit to the dive shop and demanded they bolt on every thing that would fit.

Join my elite diving teem and get a Tshirt

"Doing It Chasey"Hammerhead Eccr Advanced Diving System

RonMicjan

geeze you guys, I leave you alone for a month and you try to thin the herd! Glad you made it out OK Sven, G'donya M8. Say hi to the rest of the gang for me.

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Ron
"Life is pain princess, anyone who tells you different, is selling something", The Dread Pirate Wesley.


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AD_ward9

This answer applies to all the controllers out there. Megs can do this too, as can Shearwaters.

Processors depend on lots of different things all working right. Power supplies being within 5% of what they should be, clocks working, resets staying low, memory working perfectly, low jitter on bus transfers (an open bus eye). All these have both hard failures, and jitter type failures. That is, in a bus transfer for example, from the memory to the processor data is clocked half way between the clock edges, but the data itself has a jitter on it (random timing variance), and the strobe has jitter, so once in a blue moon, the wrong data will be captured. This is true of all processors. The processor then hangs. Now apply the same thing throughout all the logic, because the logic is made up of registers with certain set up and hold times. Now go to the memory, which contains the program, this too is liable to have soft errors, particularly Flash memory.

So what is the solution? A life critical system should not be controlled from a single clock, a single processor or a single anything. Which all eCCR controllers are when you dig down deep enough. There are architectures such as the TTA safety architectures than companies use for things like this, but most rebreather controllers are not designed by people versed in safety systems.
Result is, your handset can do anything it wants, any time it wants to. One simply has to have a strategy to deal with that, as you did ultimately, until SIL rated controllers are available that do not do this sort of thing.

Alex

NB: TTA is "Time-Triggered Architecture". Almost all flight controllers use it, railway signalling uses it, even cars use it in ABS and in active braking. No-one worth their salt would design a safety control system any other way nowadays, unless they work in a garage for a rebreather company At least using the kit is not boring: it keeps all of us Mr Bean wannabies on our toes ..