rjchandler
Contributor
maybe an ascent violation?
Deco dives and "normal" computers
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OP
Maybe you are confused as to what the computer was saying.
The Suuntos can also issue a mandatory safety stop. This looks a little bit different from a recommended safety stop. It flashes a ceiling and even a descend warning when violated. 3 training dives with an eager instructor could set it off.
If youve never seen either a mandatory safety stop or a deco on your vyper, they could be confused for one another.
The Suuntos can also issue a mandatory safety stop. This looks a little bit different from a recommended safety stop. It flashes a ceiling and even a descend warning when violated. 3 training dives with an eager instructor could set it off.
If youve never seen either a mandatory safety stop or a deco on your vyper, they could be confused for one another.
My spouse had her old reliable matrix master along for the ride on Sunday. She got a low battery warning at depth (not uncommon in very cold water) but then it got a little nuts and insisted on a 4 min stop at 20 ft and a 14 min stop at 10 ft. This was on a non deco dive where every other computer in the group was either in the bottom of the yellow or top of the green.
A fresh set of batteries and Monday's dives were entirely normal so I am wondering if low voltage caused some sort of error.
As far as planned deco, if you use a computer, you need a computer designed for intentional deco. Most are just designed to do deco to the extent needed to get you to the surface when you screw up on a recreational dive. Some will only allow stops down to 30 ft or so and if you exceed that, they will shut off and leave you on your own.
Ideally, a deco computer should be able to handle one or more gas switches to allow accellerated deco with one or more deco gases like Nitrox 50, Nitrox 80 or pure O2. Use of these gases for more efficient deco pretty much requires you get training in Advanced Nitrox and Deco Procedures.
Even if you use a computer it is a good idea to back it up with a bottom timer and contingency plans derived from a table or software as computers can and do fail and a deco dive is a very bad time for this to occur. This contingency planning again requires some level of training in deco procedures consisting of either formal training from a agency or informal training from a competent, very experienced and knowledgeable buddy.
Personally, my preference is to plan the dive and cut the tables on the spot with Palm VPM or DPlan and then use the computer as the backup in the event the dive deviates significantly from the plan. For example if someone calls the dive significantly early, its nice to be able to use the computer to follow a significantly shorter deco schedule than to have to stay with the much longer deco schedule originally planned with the tables or software.
A fresh set of batteries and Monday's dives were entirely normal so I am wondering if low voltage caused some sort of error.
As far as planned deco, if you use a computer, you need a computer designed for intentional deco. Most are just designed to do deco to the extent needed to get you to the surface when you screw up on a recreational dive. Some will only allow stops down to 30 ft or so and if you exceed that, they will shut off and leave you on your own.
Ideally, a deco computer should be able to handle one or more gas switches to allow accellerated deco with one or more deco gases like Nitrox 50, Nitrox 80 or pure O2. Use of these gases for more efficient deco pretty much requires you get training in Advanced Nitrox and Deco Procedures.
Even if you use a computer it is a good idea to back it up with a bottom timer and contingency plans derived from a table or software as computers can and do fail and a deco dive is a very bad time for this to occur. This contingency planning again requires some level of training in deco procedures consisting of either formal training from a agency or informal training from a competent, very experienced and knowledgeable buddy.
Personally, my preference is to plan the dive and cut the tables on the spot with Palm VPM or DPlan and then use the computer as the backup in the event the dive deviates significantly from the plan. For example if someone calls the dive significantly early, its nice to be able to use the computer to follow a significantly shorter deco schedule than to have to stay with the much longer deco schedule originally planned with the tables or software.
You can use a normal air computer for DECO dives under the following condiitons.
1) You use the air computer as a bottom timer only to track depth and time, using this information to follow you run tables.
OR
2) You use a dive computer that is designed for decompression diving on air, and use nitrox durring your deco stops for added safety. This of course requires you to PLAN YOUR DIVE prior to doing the dive, to ensure you have enough gas for the dive. AND!!! You have been trained to actually do a decompression dive.
To just jump in and let your computer control your dive with no training, is just asking to be added to the annual Darwin Awards honor role.
1) You use the air computer as a bottom timer only to track depth and time, using this information to follow you run tables.
OR
2) You use a dive computer that is designed for decompression diving on air, and use nitrox durring your deco stops for added safety. This of course requires you to PLAN YOUR DIVE prior to doing the dive, to ensure you have enough gas for the dive. AND!!! You have been trained to actually do a decompression dive.
To just jump in and let your computer control your dive with no training, is just asking to be added to the annual Darwin Awards honor role.
If you do number 1 and use a normal air computer as a bottom timer, make sure that getting out before the computer says you should will not cause it to go into a violation mode where it will shut off. If you are using a table or software based on a bubble model incorporating deep stops and/or accellerated deco with nitrox, this is a likely occurrence.
Most nitrox computers have a gauge mode, but I am not aware of any air computers that do. Some will default to gauge mode when you violate them however and this is preferable to having them just shut off.
Regardless of the computer used, you should have a backup depth gauge and timing device in the even the computer quits for any reason. And a proper degree of training and proper equipment configuration is required as the best deco schedule or computer in the world is useless unless you have the gas planning and redundancy to ensure you will have the gas to follow the required deco schedule. Jumping in with a computer and a single tank with no redundant air supply and doing intentional deco is synonomous with playing russian roulette - you will die if you play long enough.
Most nitrox computers have a gauge mode, but I am not aware of any air computers that do. Some will default to gauge mode when you violate them however and this is preferable to having them just shut off.
Regardless of the computer used, you should have a backup depth gauge and timing device in the even the computer quits for any reason. And a proper degree of training and proper equipment configuration is required as the best deco schedule or computer in the world is useless unless you have the gas planning and redundancy to ensure you will have the gas to follow the required deco schedule. Jumping in with a computer and a single tank with no redundant air supply and doing intentional deco is synonomous with playing russian roulette - you will die if you play long enough.
matt_unique
Guest
partridge:
I have a Suunto recreational computer (Fusion). I used to stretch my profile into deco thinking the software worked for proper deco purposes. It does not. During my first deco class the instructor plugged my last deco profile into a deco software package. My Suunto indicated my first stop was 20'. The deco software generated profile indicated several more stops at deeper depths. That was an eye opener for me.
I still use my Suunto computer as one of my depth, time, temp, etc. devices but I follow deco profiles cut from deco software. My computer always indicates "ERROR" beeping me to oblivion, skull and cross bones, etc. as I ascend to the surface. (I am kidding about the skull and crossbones graphics but that would be funny)!
To give you a loose example....all depends on back/deco gases, etc., etc., etc. but an extra 5 minutes of bottom time can represent 15 minutes and more of required deco obligations. You would not read this on your computer at depth. This can mean the difference between getting bent and not....getting cold....causing insufficient gas for you to complete your stops....biological needs if no p-valve....buddies on the surface wondering where the hell you are....etc., etc., etc.....
Recreational computers do not work for safe decompression diving.
--Matt
matt_unique:
Thats not really a fair comparison, all that says is some decompression models take into account deep stops and others dont - its nothing really to do with the computer itself. There is huge variation out there between all the commonly used decompression models and software that more than account for this.
Whats wrong with gauge mode ? Again this highlights the differences between 2 different models not the computer itself.
Thats a dive planning issue not a computer issue.
Like to see some statistics to back this up. For *properly* planned decompression dives at least.
I agree the difference in stops was most likely due to different models used in the dive computer and software applications. Personally I prefer the gradient or variable permeability models used in DPlan or VPM to the buhlman or haldane derived computer models used in most rec computers, but that is not to say the other models are not "safe" to an adequate degree.
I also agree that staying even a few minutes longer than planned at depth can double the deco required and that this is not always intuitively obvious on a computer that only shows the depth and time for the first stop. Some computers will show total ascent time, but leave you somewhat in the dark as to what time will be required at what stops. In either case thorough planning including contingency planning is critical to ensure you will have the gas to complete the required deco even if things go wrong. Those skills are hard to develop adequately without proper training in deco procedures.
I also agree that staying even a few minutes longer than planned at depth can double the deco required and that this is not always intuitively obvious on a computer that only shows the depth and time for the first stop. Some computers will show total ascent time, but leave you somewhat in the dark as to what time will be required at what stops. In either case thorough planning including contingency planning is critical to ensure you will have the gas to complete the required deco even if things go wrong. Those skills are hard to develop adequately without proper training in deco procedures.
String:
The whole premise of a recreational computer is that deco is ***NOT*** planned. A point you seem to be unable to fathom. You cannot plan a deco dive on one because they don't have the capability to do so, unlike those few computers that do. Not a very difficult concept to grasp.
TX101
Contributor
MechDiver:
Well every dive is a deco dive - which makes every planned dive a planned deco dive... but I understand your point.
I know someone will be along in a minute telling us computers will rot our brain and you should be doing deco in your head.. however I quite like my AI console computer (uwatec smart com).
It's got a 'bottom time remaining' indicator which takes into account gas required for deco. Of course, you shouldn't rely on it (and can't if you carry multiple gasses - although they have just released a new computer called the smart tek which tracks up to 3 gasses), but it's a really useful piece of info sometimes.
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