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03-22-2008, 07:11 PM
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#1 (permalink) |
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Grouper
  
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AI computer or gauges for safety?
From a safety stand point what is safer?
1. Redundant AI computers(2 computers using 2 transmitters) 2. SPG w/ depth gauge and an AI computer 3. Redundant SPG w/depth gauge (2 consoles) and timers Please no opinions without supporting facts! This is a price is no object question with standard commercial devices but consider only regular maintenance on the devices. My thinking is I've listed them in order of the safest first due to the accuracy of modern transducers and solid state devices when compared to mechanical gauges during their service and life cycle. I'd like to hear from people that service computers and gauges. Many people fear failure of electronic devices but I know in actuality that is rare. When is does happen it is more often a total failure that should cause an aborted dive. Redundancy would seem to cover the situation better in this case. Mechanical gauges however lose accuracy from use and that can create a different hazzard such as unexpected out of air conditions from gauges reading higher than actual pressure. This may even happen to redundant gauges that see the same environment and use cycles. What do the service centers see? |
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03-22-2008, 07:22 PM
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#2 (permalink) |
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Guppy
Founding Member
"Forum Admin" 
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Well I dive;
Spg as backup Aeris T3 as my main and the Oceanic Datamask (HUD) as a 2ndary main (Reason I still use the T3 is that the HUD mask does not do gas switching) (Both reading the same transmitter) 90% of the time I'm in doubles in some cave, or sink messing around at about 100' range 2 Transmitters, 1 on the back gas, 1 on my deco bottle. 
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if ( $answer == 0 ){ post->question } Last edited by ntburchf : 03-22-2008 at 07:34 PM. |
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03-22-2008, 11:14 PM
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#3 (permalink) |
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Barracuda
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I would have to say the most reliable would be an AI, attached to the hose computer, with a backup mechanical gauge set.
When you talk about wireless transmitters and such, the possibility of failure increases at least two-fold over a AI hose computer... As far as accuracy, same thing, electrical devices rarely fail, but when they do, they can fail completely, or just read inaccurately as well. I recall a Suunto problem not too long ago with a batch of their computers reading incorrect depths intermittently... So, the most reliable would be two hose consoles, one with an AI computer, one with mechanical gauges... Next, IMO, would be hoseless/wireless AI computer with a mechanical gauge backup...
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-cody / tusa bcj6900/rs460 w/ miflex hoses/oceanic geo/xpert zooms/princeton tec miniwave |
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03-22-2008, 11:46 PM
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#4 (permalink) | |
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Grouper
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Quote:
Many people seem to think that if a wireless computer misses data during a dive that is a failure but that is not the case missing an intermittent polling of the transmitter is acceptable as long as the computer is designed to reestablish it's sync within a few seconds and update it's calculations accordingly and it does so. Also from a safety stand point it should be considered that extra hoses add the posibility of extra stuff to get caught on. It would seem from your analysis that 2 different models of AI computers would avoid a batch or intermittent failure as with the Suunto problem you mention. Just a few more points to add to the discussion. I'd like to think of this thread as a brainstorming discussion. Still I would like to see documentation of failures instead of just opinions. Thanks for adding to the discussion.
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Opinions are like gas... We are all entitled to have some but most people appreciate it if you keep it to yourself when it stinks! 
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03-22-2008, 11:57 PM
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#5 (permalink) | ||
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Barracuda
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Quote:
for instance, I work on cars all day every day... every once in a while, a link is lost between a wireless tire pressure sensor and the control module for it for seemingly no reason, and although they are designed to reestablish links, they don't sometimes... reasons - no clue... but it does happen...
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-cody / tusa bcj6900/rs460 w/ miflex hoses/oceanic geo/xpert zooms/princeton tec miniwave |
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03-23-2008, 07:30 AM
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#6 (permalink) | |
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Guppy
Founding Member
"Forum Admin"
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The computer missing a sync time is not a failure.
I have mine set on 15 second polls/sync. Here's an example from a dive on Wed's where it loses sync, and it regains sync a few tics later. Simple fact of diving, that depending on where your arm is, where the transmitter(s) are located you are going to lose sync every now and then. I don't think that losing sync for 15 or 30 secs is really a failure or should it be considered one. Comp still going to pick up the PSI / depth etc on next sync. And even if it did do a complete failure, I have a SPG as a backup  Code:
DC Model:ELITE T3 DC Serial:1372 DC Dive No.:5 Dive Date: 03/19/2008 Dive Time: 13:49 Dive Mode: Gauge Surface Interval: 02:14 Max. Depth: 120 FT Elapsed Dive Time: 31 Minutes Min Temp: 68 F Tank 1 information ------------------- Transmitter ID: 76685 Start Pressure: 1690 PSI End Pressure: 890 PSI Cylinder Size: 200 FT³ Working Pressure: 3442 PSI SAC: 0.624 FT³/Min FO2: 22% Quote:
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if ( $answer == 0 ){ post->question } |
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03-23-2008, 08:18 AM
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#7 (permalink) |
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Barracuda
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I personally dive with a SPG and Suunto Transmitter. The Transmitter connects to my Suunto D9 and my Suunto Vytec when they are paired. Pairing is basically having the dive computer next to the transmitter for a few seconds when your cylinder is turned on. The dive computers pick up the wireless link and they then display your cylinder pressure.
I always trust my glass/brass SPG everytime. They are bullet proof. You might get issues with SPG creeping over the years (especially if they have been dunked in water without the dustcap). Normally you can see that the needle has creeped a little when its off the cylinder. I personally dont trust anything with electrical parts/batteries when it comes to dive gear and especially reading cylinder pressure. Sometime i havnt paired my computers to the transmitter which I ended up with no cylinder pressure readings on my computers. It didnt worry me as I knew that the SPG was there and I trust it more. I have personally seen transmitters fail either due an accident (cylinder dropped onto one) or batteries fail on a liveaboard. Its alwasy easy to replace a SPG but try replacing a transmitter in a remote place. Cost. A good Glass/Brass SPG is say $100 when compared to some transmitters which are $400+. When I am guiding I always use my SPG when asking for consumption from my customers. Its easy for them to understand what your asking them. If I just pointed to my dive computer I would get all different answers (its lunch time, Beer o'clock etc). Thats something else to think about. keeping it simple and easy for everyone to understand. Aussie |
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03-23-2008, 09:46 AM
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#8 (permalink) |
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Barracuda
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One other thing you have to consider with a wireless transmitter device - there are more things to potentially fail. Any time you have more components in a system, you increase the chance for failure.
With a wireless transmitter, you now have a second power source to potentially fail, you have a second set of electronics to potentially fail, you have a transmitter and receiver to potentially fail... As far as adding a hose and being more of a safety issue - a wireless transmitter does the same thing - its one more thing sticking off of the valve that could get something wrapped around it, or, if you were to run into something with it, potentially break it... Wireless AI's are great, but when talking about reliability, they are close to the bottom of the barrel, with a hose AI being better, as well as a standard SPG...
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-cody / tusa bcj6900/rs460 w/ miflex hoses/oceanic geo/xpert zooms/princeton tec miniwave |
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03-23-2008, 10:02 AM
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#9 (permalink) | |
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Shark
Founding Member
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Quote:
You're wrong on #1 based on personal experience of lost locks with no pressure readings on my computer, or the bottles which had transmitters on them. #2 must be more reliable, it has 2 DIFFERENT methods of verifying pressure. Of course which do you trust if they differ and you don't know your SAC rate? IME, AI computers are pretty reliable when it comes to Oceanic but not other brands, and I don't have the documentation because how could I come by that? All I do is dive with my buddies and I know what's failed because they're next to me. If you want proof, I can post pages of lost links but what does that prove that my word which says it happens can't? A computer is more likely to not tell you pressure than a mechanical gage, and I know this because of my diving and my buddies diving. Again, how could I prove the mechanic gage never failed? There's no photographic evidence? No logs from it, you have my word. I am sorry, proof is not possible for your question. You have to accept the fact that computers are more likely to lose lock than the SPG. Here's my config, VT3 with transmitters on all cylinders, and the good old fashioned SPG. Why? Because I've lost lock on dives that I needed to know the pressure on. One failure is too many.
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Matthew P. Cummings Moberly MO |
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03-23-2008, 06:29 PM
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#10 (permalink) |
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Grouper
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As I stated regular maintenance was to be considered.
Accidental damage can happen to any piece of equipment and is not a consideration. This is a question for state of the art regularly available products for the diving public. If you feel Oceanic is the best AI wireless then we should be judging by that as state of the art. Or if you feel the Sherwood Wisdom hosed AI computer is a better representative of state of the art I'd like to see supporting documents on it's failure rate. Failures are not to be considered battery gone dead as this would be a maintenance issue unless caused by a battery compartment flood. This is to be a comparison of properly maintained devices without failures caused by user error! Loosing sync for individual polling segments is not a failure and does not decrease dive safety! Also when I say redundant wireless AI I mean 2 transmitters on the same bottle used for separate computers. (really redundant) I know this is not the way these computers are used today but they could be and it would increase the safety margin. I do accept that sync can be lost but also that mechanical gauges (SPG) are more prone to inaccurate readings creating other safety concerns.
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Opinions are like gas... We are all entitled to have some but most people appreciate it if you keep it to yourself when it stinks!
Last edited by rawalker : 03-23-2008 at 06:32 PM. |
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00 45 FT N/A N/A 0-10 FPM N/A N/A N/A N/A N/A 68 1 1160 Linked 
00 40 FT N/A N/A 0-10 FPM N/A N/A N/A N/A N/A 68 1 1014 Linked