Necessity of a back up computer/watch for NDL diving

[caruso]

It's not a needle. It's a bubble, and very accurate.

I thought it was broken because I didn't see a needle.

 

[dmaziuk]

If you’re four days into no stop diving at or near NDLs on a live aboard and then day five decide to use a new computer you could very violate your actual NDL because the computer will give you an NDL and ascent profile that isn’t based on your actual tissue loading.

Yes, yes... it’s all theoretical and everyone is different and they’re all just models.... Ughh

Nobody's going to stop you from getting to see Dr. Darwin if you put your mind to it. When it comes to rational beings though, I don't need DCS anymore than the liveaboard captain needs bent customers, so I'm sure we'd figure out something mutually acceptable.

And pedantic or not, there's still no computed "ascent profile" on a no-stop dive. There's only safe ascent rate that is pre-programmed into NDL calculation.

 

[Diver-Drex]

And pedantic or not, there's still no computed "ascent profile" on a no-stop dive. There's only safe ascent rate that is pre-programmed into NDL calculation.

Ok, I’ll play... how is 30’/min not an ascent profile? It’s linear but it is without doubt an ascent profile.

 

[Diver-Drex]

And @dmaziuk - you do understand that the whole point is that a deco stops (non-linear) profile may be neeeded but the computer won’t calculate it because it isn’t accounting for residual nitrogen loading. You do get this right?

 

[Saniflush]

Mrs Flush and I dive two computers. It really wasn't planned to do so from the point of redundancy but simply because we started out with some console Sherwood computers then realized that we wanted ones that were easier to read so we bought Shearwaters. The redundancy was an afterthought but it has come into play once for me when my console computer started acting screwy on the first boat dive of the day six months ago. I still had my primary computer so I could enjoy the rest of my dive and the following one a few hours later without missing a beat.

 

[dmaziuk]

And @dmaziuk - you do understand that the whole point is that a deco stops (non-linear) profile may be neeeded but the computer won’t calculate it because it isn’t accounting for residual nitrogen loading. You do get this right?

No. I don't get where deco stops came from on a no-stop dive. I'm thick like that.

 

[Diver-Drex]

If you do two dives and then switch to a new computer for the third dive, how do you know you don’t exceed NDL on the third dive? How do you know if stops are required or not? Certainly not from the new computer.

 

[markmud]

What I had forgotten about, is my main computer ( Oceanic Pro Glide Plus 3 integrated air ) will reset its self back to 21% air after 12 hours of non use. My secondary computer ( wrist style Mares Puck Pro ) stays set to whatever you set it to forever until you put in a different setting.

Hi Clayton,

With my Oceanics, there is default switch that can be turned off so the computer does not default to 21%. The 21% default is turned off on all of ours.

dive on,
mm

 

[dmaziuk]

If you do two dives and then switch to a new computer for the third dive, how do you know you don’t exceed NDL on the third dive?

I have this life-saving device between my ears and I'm not afraid to use it. That's how I know.

 

[Storker]

I have this life-saving device between my ears and I'm not afraid to use it. That's how I know.

So... you have all of the formulae in ZHL-16 between your ears? That's rather impressive. Kudos.