backup computer

[Ronreg]

hey guys

so as i start to look into more tec and solo diving i got into the discusion on having a backup dive computer and got curious what peoples opinion were on it
in hopes of starting a helthy discusion why and why. not i wanted to ask what do you do dive

• no backup computer
• with a cheep (sunto zoop or anything like that)
• diving the same computer for primary and backup
• using you old computer after upgrading

is it a overrated thing or is it most important thing in your kit mby its only used for dives below 30 meter or when a deco dive is intended?
hope to here some of your guys thougt on the topic and learn some now things!

The tech divers I know have the same type of computer for primary and backup.

 

[Pressurehead]

I always dive with two computers: one primary and one backup.

Same.^^
Only once [since I have been using 2 computers, for years now] have I splashed with one computer.
So excited to do this dive I hit the water without my Perdix AI on my right wrist, bugger, but not a problem though.
The Shearwater Peregrine clipped off in my tech shorts is used, as is the SPG still attached.

Two Shearwater computers whether solo or not.

Ditto ^^.

 

[boulderjohn]

If I was rec diving with just one computer and it failed, I would use tables or planning software to know the time/depth limits for NDL and keep diving.

So let's say you are doing a multi-level dive (for the sake of argument, on air). Your maximum depth was 91 feet, but you were there only about 8 minutes before beginning a multi-level ascent. You are at 36 feet when your computer fails after 36 minutes of dive time.

Tell me what you do next, both on that dive and the dive coming up after a 60 minute surface interval.

 

[rhwestfall]

For the last 10 years, I've dove 2 computers. My current favorite "generic" diving setup is a Shearwater Perdix AI with a Deep6 Excursion as a backup (same algorithm, small size so no real estate issues). If it is a tech dive, two Shearwaters... I still have an SPG (mini) on a splitter block on a hose off the transmitter (idea from @rsingler ).

 

[rhwestfall]

So let's say you are doing a multi-level dive (for the sake of argument, on air). Your maximum depth was 91 feet, but you were there only about 8 minutes before beginning a multi-level ascent. You are at 36 feet when your computer fails after 36 minutes of dive time.

Tell me what you do next, both on that dive and the dive coming up after a 60 minute surface interval.

Hint - something about sitting the next 24 out....

 

[boulderjohn]

Hint - something about sitting the next 24 out....

but...but...but...he said he could "keep diving."

 

[rhwestfall]

as the saying goes, "Stupid should hurt."

 

[steinbil]

So let's say you are doing a multi-level dive (for the sake of argument, on air). Your maximum depth was 91 feet, but you were there only about 8 minutes before beginning a multi-level ascent. You are at 36 feet when your computer fails after 36 minutes of dive time.

Tell me what you do next, both on that dive and the dive coming up after a 60 minute surface interval.

If you keep track of average depth, this is actually quite simple. On any ascending multi-level profile (starting at max depth and gradually diving shallower) it's not problematic to use the average depth with tables.

Let's say the average depth was 65ft, round it up to 70ft. 36 minutes at 70ft gives you letter R on the PADI RDP. Continue diving tables this way. If you think this is not safe, I challenge you to simulate any similar profile, and you will see that it is MORE conservative than a square profile to 70ft for 36 minutes, in other words similar or lower risk.

 

[ofg-1]

Don't those backup computers make an annoying beeping noise?

 

[boulderjohn]

If you keep track of average depth, this is actually quite simple. On any ascending multi-level profile (starting at max depth and gradually diving shallower) it's not problematic to use the average depth with tables.

Let's say the average depth was 65ft, round it up to 70ft. 36 minutes at 70ft gives you letter R on the PADI RDP. Continue diving tables this way. If you think this is not safe, I challenge you to simulate any similar profile, and you will see that it is MORE conservative than a square profile to 70ft for 36 minutes, in other words similar or lower risk.

You are at depth when your computer fails. Where do you find your average depth?