I am in the market for a wristwatch style computer to use as a backup. An Oceanic Atom is the logical choice because it is a Pelagic style like my primary computer. But I like Suunto instruments and wonder how a Mosquito would work. Is the difference in the algorithms so drastic that NDL on the Pelagic would cause the Mosquito to hit decompression?
Backup computer w/ different algorithm
- Thread starter ckm
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ckm:
Perhaps I am missing it, but where is the problem?
Two different computers (actually, the same computer model with two different firmware versions) may offer to you different scenarios in terms of "safe" ascent speed, remaining bottom time, deco stop(s) and so on...
If you have two computers you have to trust either one or the other
DareDevil
Ontario Diver
Guest
Are you doing decompression dives?
If you are not, the rule is simple - if you computer fails - ascend and call the dive - resume diving after 24 hours (to clear the RNT) . If you are doing NDL diving, you don't really need a backup. If you are doing staged deco - then you should have tables calculated anyway and not rely on a computer - and if you use a backup computer it must be identical to the primary.
If you are not, the rule is simple - if you computer fails - ascend and call the dive - resume diving after 24 hours (to clear the RNT) . If you are doing NDL diving, you don't really need a backup. If you are doing staged deco - then you should have tables calculated anyway and not rely on a computer - and if you use a backup computer it must be identical to the primary.
Ontario Diver
Guest
First of all, if you are doing recreational diving and staying well within your NDLs - I do not believe that there is much benefit to a backup computer. There may be a reason for a larger number of repetitive dives with a severe time schedule - but for most divers on a trip I can't see the reason.
If you were to dive with two different computers - the only safe way to do it would be to dive the more conservative algorithm as your primary. Which in this case is probably the Suunto.
If you were to dive with two different computers - the only safe way to do it would be to dive the more conservative algorithm as your primary. Which in this case is probably the Suunto.
Damselfish
Contributor
It's simple, if they're not the same algorithm you follow the more conservative one. (I don't think you should even push the more conservative one to it's NDL.)
I get tired of reading statements that there's no benefit to a backup computer. I mostly dove tables when I was doing local diving, and it was perfectly adequate for what I was doing. 2 computers is appropriate for the type of diving I do now. Everyones diving is not the same. It's been covered on other threads, but - if I've paid a lot of money to get to an distant place and plan to dive 4-5 a day, and one computer craps out, I don't have to call a dive or sit out anything. Especially when the next dive up is that world famous site you've been waiting to see for 10 years. There's a LOT of value to that. Sure I could keep track and see what the tables say, but given the typical profiles in this type of diving the tables will generally declare me to be dead so that's of rather limited use.
Other people will have other reasons for wanting a backup. Maybe they're doing a couple dives locally on the weekends and it's not as big a deal to bag and sit out, or falling back to the tables is more viable - but maybe they still don't want to do that. If they can afford the second computer why the heck not?
I get tired of reading statements that there's no benefit to a backup computer. I mostly dove tables when I was doing local diving, and it was perfectly adequate for what I was doing. 2 computers is appropriate for the type of diving I do now. Everyones diving is not the same. It's been covered on other threads, but - if I've paid a lot of money to get to an distant place and plan to dive 4-5 a day, and one computer craps out, I don't have to call a dive or sit out anything. Especially when the next dive up is that world famous site you've been waiting to see for 10 years. There's a LOT of value to that. Sure I could keep track and see what the tables say, but given the typical profiles in this type of diving the tables will generally declare me to be dead so that's of rather limited use.
Other people will have other reasons for wanting a backup. Maybe they're doing a couple dives locally on the weekends and it's not as big a deal to bag and sit out, or falling back to the tables is more viable - but maybe they still don't want to do that. If they can afford the second computer why the heck not?
ckm:
A good solution for your scenario could be to get a bottom timer (uwatec makes one) and pack your tables.
Then, if your computer blows up, you will still have reliable info on that dive, ability to plan and execute the next dive (using tables and the BT) and save your self the over kill expenditure and potential confusion of multiple full-function dive computers.
I dive a Vyper and a Uwatec bottom timer, and have found this to be an adequate setup for in-water redundancy and fail-safe trip preservation.
pdoege
Contributor
For non-deco dives the algorithms are all pretty much the same. The question is conservatism.
Just buy another version of what you are using now.
As regards to the Suunto, they are very conservative and the Suunto RGBM is not a particularly good implementation of a bubble model.
I dive a Mares M1 (ZHL-12) and a Cressi Archimedes (ZHL-16); they are within a minute on NDL dives.
Why 2 computers? If 1 craps out on a live aboard, boat, trip, whatever you don't lose a day's worth of dives.
Peter
Just buy another version of what you are using now.
As regards to the Suunto, they are very conservative and the Suunto RGBM is not a particularly good implementation of a bubble model.
I dive a Mares M1 (ZHL-12) and a Cressi Archimedes (ZHL-16); they are within a minute on NDL dives.
Why 2 computers? If 1 craps out on a live aboard, boat, trip, whatever you don't lose a day's worth of dives.
Peter
rjchandler
Contributor
Ok since I actually do what ckm is asking.
Yes, your suunto will go into deco before your pelagic. Carrying them both on the same series of dives can result in some dramatic differences in available NDL time. Whether those differnces matter depends on the diving you are doing - you may not be getting close to deco on either computer anyways.
My suunto went into deco once when my oceanic showed 15 min NDL left. That has only happened once in the 300+ dives that I have paired the two computers. YMMV
Yes, your suunto will go into deco before your pelagic. Carrying them both on the same series of dives can result in some dramatic differences in available NDL time. Whether those differnces matter depends on the diving you are doing - you may not be getting close to deco on either computer anyways.
My suunto went into deco once when my oceanic showed 15 min NDL left. That has only happened once in the 300+ dives that I have paired the two computers. YMMV
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