Do you still use a SPG with a AI computer?

[MPW50]

Before you had your AI computer, did you utilize two SPG's? Just curious.

Cheers - M²

Hey Mike,

I did. Had a Pro Plus 3 and a small analog SPG. I wanted to drop a hose and have all my info in my wrist then switched to the perdix and removed the bulky PP3. I understand position of aborting your dive, etc. if you have failure and no back up however, with something as critical as my air supply, I would rather have the redundancy if there is a failure and to be able to continue my dive if I choose to. I also carry a backup computer to cover for that failure also so as not to have to abort my current dive and/or dive day if multi diving.

Cheers!

Matt

 

[dbnewton]

When I switched to AI I originally dropped the SPG. My intended policy was to abort on failure and of course hoped that would not happen. Well it did happen, I did abort. And as described I only lost one dive because I had the SPG in my save a dive kit.

The failure was not in the sending unit it was in the computer so I lost both cylinder pressure reading as well as computer. I did have a backup computer so I could have overcome the computer loss.

I decided to add back the SPG but clip it on my back to be used only as backup in the event of failure.

 

[mostlyirish]

How many of you still have a SPG as part of your everyday gear setup when using an air integrated computer?

Just entering AI realm. Purchased a Galileo Luna with transmitter. I still will utilize a spg and backup computer for redundancy.

 

[MargaritaMike]

I just had a thought (write this moment down). I have at least two AI computers that receive multiple transmitters. In order to eliminate the SPG hose, why wouldn't 2 transmitters with the two computers give the redundancy that an SPG on a hose would give? Also, I think rec diving is a different scenario than tech diving. IMO the NDL rec diver can abort and surface due to computer or transmitter failure much safer than a tech diver with planned deco or even a rec diver with planned deco. I may be wrong. Besides, it has been proven that when I "open my mouth" I dispel all doubt of my stupidity.

Cheers - M²

Edit - Corrected grammatical error

 

[t3chnobrat]

I just had a thought (write this moment down). I have at least two AI computers that receive multiple transmitters. In order to eliminate the SPG hose, why wouldn't 2 transmitters with the two computers give the redundancy that an SPG on a hose would give? Also, I think rec diving is a different scenario than tech diving. IMO the NDL rec diver can abort and surface due to computer or transmitter failure much safer than a tech diver with planned deco or even a rec diver with planned deco. I may be wrong. Besides, it has been proven that when I "open my mouth" I dispel all doubt of my stupidity.

Cheers - M²

Edit - Corrected grammatical error

Thats exactly what i switched two. Two transmitters and two DC's (i450t - Perdix ai) for rec diving. I couldn't be happier with the set up.

 

[scubadada]

Thats exactly what i switched two. Two transmitters and two DC's (i450t - Perdix ai) for rec diving. I couldn't be happier with the set up.

Hi @t3chnobrat

Do your computers match reasonably well or is your dive generally controlled by one of the computers? The Aqua Lung i450T's PZ+ is reasonably conservative, what GFs to you run on your Shearwater? As the computers use the same PPS transmitter, I assume you run 2 for the redundancy, kind of like an SPG and backup computer

 

[dbnewton]

I just had a thought (write this moment down). I have at least two AI computers that receive multiple transmitters. In order to eliminate the SPG hose, why wouldn't 2 transmitters with the two computers give the redundancy that an SPG on a hose would give? Also, I think rec diving is a different scenario than tech diving. IMO the NDL rec diver can abort and surface due to computer or transmitter failure much safer than a tech diver with planned deco or even a rec diver with planned deco. I may be wrong. Besides, it has been proven that when I "open my mouth" I dispel all doubt of my stupidity.

Cheers - M²

Edit - Corrected grammatical error

I think you would have "good enough" redundancy if both computers can monitor both transducers. You could suffer the loss of any one of the 4 units (2 Tx & 2 Rx) or even one of each (Tx & Rx) and still have pressure display. You would not suffer complete loss until you lose both Tx or both Rx and assuming they are of good quality and well maintained that sort of double failure is much less likely (for example if each has 99% reliability then probability that both fail is 0.0001 AKA 1 in 1000)

Hard to truly analyze without knowing the probability of failure of each component including the SPG.

 

[scubadada]

I think you would have "good enough" redundancy if both computers can monitor both transducers. You could suffer the loss of any one of the 4 units (2 Tx & 2 Rx) or even one of each (Tx & Rx) and still have pressure display. You would not suffer complete loss until you lose both Tx or both Rx and assuming they are of good quality and well maintained that sort of double failure is much less likely (for example if each has 99% reliability then probability that both fail is 0.0001 AKA 1 in 1000)

Hard to truly analyze without knowing the probability of failure of each component including the SPG.

Sure, each of the two computers primarily monitors one of the transmitters and is linked with Gas 1. You could link each of the computers with the opposite transmitter by linking with gas 2 and switch gases if necessary.

I'll stick with my backup SPG and computer, considerably less expensive than a 2nd AI computer and transmitter.

 

[t3chnobrat]

Hi @t3chnobrat

Do your computers match reasonably well or is your dive generally controlled by one of the computers? The Aqua Lung i450T's PZ+ is reasonably conservative, what GFs to you run on your Shearwater? As the computers use the same PPS transmitter, I assume you run 2 for the redundancy, kind of like an SPG and backup computer

I really haven't compared the two as far as how well they match on an actual dive because I control the dive from the Shearwater. Out of curiosity, I just set up a dive through the dive planner on both devices for 70 fsw on air, the i450 gives me a max bottom time of 35 minutes and the shearwater gives 36. GF is at 45/95. Each computer has it's own independent transmitter (actually both SW). Basically it is my SPG.

 

[scubadada]

I really haven't compared the two as far as how well they match on an actual dive because I control the dive from the Shearwater. Out of curiosity, I just set up a dive through the dive planner on both devices for 70 fsw on air, the i450 gives me a max bottom time of 35 minutes and the shearwater gives 36. GF is at 45/95. Each computer has it's own independent transmitter (actually both SW). Basically it is my SPG.

That is probably a close match, pay attention to the shallower NDLs, where the algorithms diverge