What's the point of these 3 gas computers?

[fnfalman]

There is no requirement for redundancy of an SPG.

Heaven forbids SPG had never failed before.

 

[FishOutUvH2O]

FYI - in practical application that's nonsense.

Thank you for your opinion. But, I'm probably going to have to stick with my own information, based on my own real world experience on this one.

 

[DevonDiver]

heaven forbids spg had never failed before.

there is no requirement for redundancy of an spg.

 

[gumbo717]

Some possible issues: Do you just put a transmitter on your backgas or on deco bottles as well? how does the computer react when doing a valve drill and the pressure it is reading goes to zero?
What about diving sidemount? A transmitter on each tank? Again,what does the computer do when one tanks pressure does not change for many minutes? How about scooters? Will the motor interfere with the wireless signal?
Lots of potential problems with no upside.

I will put some of this to the test on my Wed. evening dive. For now - I only have a transmitter on my back gas right post, left post has the standard SPG, I do not have additional transmitters on deco bottles they have their own REG/SPG setup.
When the pressure reads zero after shutting down and isolating that tank is flashes 0000 but continues the dive profile. Will double check this but I tested it once just to see what would happen.
Have not tried sidemount, I'm not into caves or tried diving that way, but never say never.
I have lost signal for 15-30 sec while using a scooter, twice, but it only effects the pressure reading and not the dive profile of the computer.

I would also like to say that I have never used the AI transmitter feature by itself, I have always made my dives with a SPG and will continue in the future. I do however like having a pressure readout on the computer because all of that information is in one place on my wrist.

Thanks again!

 

[Puffer Fish]

Huh? How can there be a failure point "issue" if the computer is being used in Gauge Mode? It's a puck worn on your wrist. How is that a hindrance as far as streamlining and stowability goes? It's not any bigger than a bottom timer.

The guy already has the VT3 computer AND it can be used as a bottom timer. Why should he go out and spend another hundred/two hundred dollars on another bottom timer?

I've seen "tech" divers use all sorts of different bottom timers...a VT3 would work just fine (not seen anyone use it, but I have seen lots of Galileo's used).

I think the issue of having a multigas deco computer, and the issue of technical diving are actually two different subjects, that from time to time cross paths.

Regarding "failure points"... the actual issue with wireless is reliability, not failure points. The question is, "is wireless more reliable, equal to or less reliable than a spg". To date, the answer has been less, so it would be a mistake to use in a cave.

However, as the computer works without the wireless... the question is, is AI (with a backup) safer than just an spg. That has the opposite answer. And because it has a huge number of safety checks built into the system if AI is used (remember it works without the AI)...the only real concern would be an overall computer failure.

 

[Puffer Fish]

I will put some of this to the test on my Wed. evening dive. For now - I only have a transmitter on my back gas right post, left post has the standard SPG, I do not have additional transmitters on deco bottles they have their own REG/SPG setup.
When the pressure reads zero after shutting down and isolating that tank is flashes 0000 but continues the dive profile. Will double check this but I tested it once just to see what would happen.
Have not tried sidemount, I'm not into caves or tried diving that way, but never say never.
I have lost signal for 15-30 sec while using a scooter, twice, but it only effects the pressure reading and not the dive profile of the computer.

I would also like to say that I have never used the AI transmitter feature by itself, I have always made my dives with a SPG and will continue in the future. I do however like having a pressure readout on the computer because all of that information is in one place on my wrist.

Thanks again!

You have it correct, and the multi gas feature works with or without the AI. Only advantage of having the sensors is that it checks that you are using the right gas. ou still get the change gas indicators..

 

[fnfalman]

there is no requirement for redundancy of an spg.

There's no REQUIREMENT for anything. There are no governmental rules and regulations that say you must have this or must have that. Industry practice recommends a certain configuration for doing certain things, but it's ridiculuous to do a cave dive, deep dive and think that ONE SPG setup is good enough without having another SPG setup for redundancy.

You SPG people always claim that computers fail. Well, SPGs fail too, so why shouldn't you want to carry another SPG backup unit?

 

[fnfalman]

I think the issue of having a multigas deco computer, and the issue of technical diving are actually two different subjects, that from time to time cross paths.

Regarding "failure points"... the actual issue with wireless is reliability, not failure points. The question is, "is wireless more reliable, equal to or less reliable than a spg". To date, the answer has been less, so it would be a mistake to use in a cave.

However, as the computer works without the wireless... the question is, is AI (with a backup) safer than just an spg. That has the opposite answer. And because it has a huge number of safety checks built into the system if AI is used (remember it works without the AI)...the only real concern would be an overall computer failure.

I would not use a rec AI computer to do tech diving (not that I know anything about tech diving). The algorithms are different. But I would use a rec AI computer switched to Gauge Mode to act as a bottom timer.

As far as reliability of SPG goes, it's probably as reliable as a hosed AI computer. But then we're talking about using rec computers with rec-oriented algorithms for deco diving. Rec computers have very limited deco diving algorithms programmed into them and I sure as heck wouldn't want to use them for true deco dives or 5-6 gases/trimix dives. That's why God makes deco dive tables and tech computers for.

 

[Puffer Fish]

I would not use a rec AI computer to do tech diving (not that I know anything about tech diving). The algorithms are different. But I would use a rec AI computer switched to Gauge Mode to act as a bottom timer.

As far as reliability of SPG goes, it's probably as reliable as a hosed AI computer. But then we're talking about using rec computers with rec-oriented algorithms for deco diving. Rec computers have very limited deco diving algorithms programmed into them and I sure as heck wouldn't want to use them for true deco dives or 5-6 gases/trimix dives. That's why God makes deco dive tables and tech computers for.

Using a three gas "what if" dive with Decocheck2 versus my Galileo, there is less than one minute difference after more than an hour.. (decocheck2 is ever so slightly more conservative, but if I use the first of five steps for more conservative diving, the Galalileo is several minutes difference. Having gone thru 20 or 30 (should count the files I saved)...I would trust the calculations.

 

[Scared Silly]

I do a little tech diving and I have a AI transmitter. Here are some random thoughts (much of which a has been discussed ad nauseum):

My transmitter is on a 9" hose on my right post and gets tucked down between the wing and manifold. I did this configuration for two reason - to gets it out of the way in case it gets bumped while under or out of the water. And to remove the possibility of someone using it as a handle.

This configuration has no more physical failure points than a std B&G SPG (at both ends of the hose). It does have an electronic failure point - in fact two of them (transmitter/receiver). My SPG has a mechanical failure point. I am not worried about the physical failure points of either in the least bit.

Have I had the computer not be able to sync? yes 2-3 times over 150 dives. In each case I just used my SPG. In fact, I use both during a dive. During gas switches, it does nothing. I just switch my computer to the other mix and continue my stop. Of course I am using my computer in conjunction with cut tables and another depth gauge/bottom timer (Both my tables and computer have similar profiles with different algorithms).

fnfalman - the reason you do not need a back up SPG is simple. If it fails the dive is over. You can make it back to the surface with a dead SPG. However, if a reg fails you need another to breath from otherwise you are apt to be dead. Similar with other redundant gear like buoyancy.

As for the rec/tec algorithms many are the same. Just that different parts may not be exposed.