AI question - dive time remaining

[jhelmuth]

@jhelmuth: Assuming reasonable operation and maintenance, choice of SPG should not affect safety at all. When an SPG fails, the dive is aborted...unless a backup gauge is in use. The issue that Netdoc and I have a difference of opinion on is whether the wireless system or an analog SPG fails more frequently.

I appreciate that you brought up the issue of economics. Perhaps if I were a dive instructor or DM with access to keyman discounts (60-70% off MSRP), I would be willing to splurge on a wireless AI system...out of sheer curiosity.

Right... I guess I was taking the stance the failure (between the 2) does happen - but not with significant frequency either way GIVEN that both have been properly maintained and are checked (as required by SOP) each time just prior to a dive.

You may feel differently - and that's OK from where I sit....


All the best,

Jim

 

[jhelmuth]

OK, I see what you mean - But in that case I wouldn't call it becoming "almost useless" as you originally said, just maybe "nothing special", or nothing worth paying extra money for.

"almost useless".... "nothing special" (ec.)

It's all the same - to me.

 

[fnfalman]

Sorry, I don't have the time/money to collect such data for you. I would like to point out that the "gold standard," proven technology here is the older technology (analog SPGs).

Where does this "gold standard" come from? Any regulatory agency that had done any study to show that SPGs are more reliable than AI computers?

As far as proven technology = older technology goes, I'd dare say that J-valves are more reliable than SPG. They don't break as easily. They don't flood. They don't have hoses that fall apart.

Hell, old timers told me that they'd even forgo the J-valves and just listen to the hollow twang in the tanks to indicate fullness. They know what their air consumption rates at any depth, so with a timer they can tell how long they've been down and listening to the echo was their backup alarm.

No failure points.

 

[fnfalman]

I'm also going to point out that there are far more analog SPGs than wireless AI computers in service. Please consider how this might change the way you reconcile your personal experience with the true percentage of failures (analog SPG vs. wireless AI system).

Using this logic, there are far more poodle jacket BCs than BPW running around...ergo BPWs are inferior?

 

[vladimir]

As I have stated in this thread and elsewhere, I have never caught my D9 in a transmission lapse. As I was going through my manual looking for an answer to Bubbletrouble's question on pairing, though, I ran across a couple of indications of where Suunto stands on the reliability of its technology (emphasis added):

USE BACK-UP INSTRUMENTS! Make sure that you use back-up instrumentation, including a depth gauge, submersible pressure gauge, timer or watch, and have access to decompression tables whenever diving with the dive computer.

If the optional wireless pressure transmitter is used ensure that:
•the pressure transmitter has been properly attached and the cylinder valve is open
•the transmitter and the wrist unit have been properly paired on a suitable code
•the pressure transmitter is working (lightning symbol blinks, cylinder pressure is
displayed), and that there is no low battery warning displayed
•you have enough air for your planned dive. You should also check the pressure
reading against your back-up pressure gauge

 

[Kern]

Using this logic, there are far more poodle jacket BCs than BPW running around...ergo BPWs are inferior?

I fail to see the logic in your analogy. Comparing the numbers of an item being used to the lower numbers of another item being used for the same purpose may have nothing to do with the inferiority of either. To compare failure rates in any meaningful way however, you need to know the number of each item in use, the number of failures, & the time that each has been available also needs to be factored into the equation.

 

[Bubbletrubble]

Air-integrated computers are still dependent on battery power. I'm surprised that you are asserting that an electronic gizmo is more reliable than an analog SPG. :shocked2:

I have never seen a wireless unit transmit pressure that isn't there. However, I have seen three SPGs that showed pressure (and LOTS of it) when there was none.

I'm also going to point out that there are far more analog SPGs than wireless AI computers in service. Please consider how this might change the way you reconcile your personal experience with the true percentage of failures (analog SPG vs. wireless AI system).

Using this logic, there are far more poodle jacket BCs than BPW running around...ergo BPWs are inferior?

@fnfalman: Please allow me to clarify my previous statement:

In response to my comment on reliability, NetDoc asserted that he had "never seen a wireless unit transmit pressure" that wasn't there...but had "seen three SPGs that showed pressure (and LOTS of it) when there was none." I interpreted his statement to imply that (a) the failure rate for analog SPGs is higher than wireless AI systems and (b) the failure mode of analog SPGs presents a safety risk.

In response to (a), I pointed out that there are far more analog SPGs in service than wireless AI computers. Implicit in this statement is that more analog SPGs out in the wild = more opportunities for Netdoc to witness a failure. I asked him to think about how his personal experience (multiple analog SPG failures and presumably a higher number than wireless AI system failures) might be misleading.
I'm going to assume that a reasonable definition of failure rate is: # failures / # uses

Here's an example of how anecdotal evidence can be misleading:
Let's say that, over the course of his scuba career, Netdoc has personally observed 10 analog SPG failures and only 4 wireless AI system failures. His gut might tell him that analog SPGs fail more frequently than wireless AI systems. However, he may have actually encountered the use of analog SPGs 10X more often than wireless AI systems. Assuming that his sampling size is representative, wireless AI systems would actually have a higher failure rate (in this example, 4X higher).

I won't even go into the many ways in which a test population might not be representative of the overall population. The term for that is sampling bias.

Let me know if you'd prefer that I convert my explanation into a car analogy. I'd be happy to do so.

P.S. I don't think that BP/W are better than "poodle jacket" BCDs...or vice versa. They are just different. Each design has its advantages and disadvantages.

P.P.S. In the "standard, proven technology" discussion, you asserted that J-valves are more reliable than analog SPGs. I've never used a J-valve before, but it's my understanding that a diver really didn't know how much gas he had between full and approx. 300 psi (or whatever the reserve pressure was). The diver would breathe his tank down until the reserve was reached and then activate the lever to access his reserve gas. I think it's easy to see why divers found analog SPGs more convenient and safer in terms of gas management. I have read multiple accounts of J-valve users who had to do a CESA since the reserve switch had unknowingly been left open from the beginning. They were counting on the reserve gas...and when it wasn't available to them, they had to make for the big tank in the sky.

 

[vladimir]

Let me know if you'd prefer that I convert my explanation into a car analogy. I'd be happy to do so.

In the "standard, proven technology" discussion, you asserted that J-valves are more reliable than analog SPGs. I've never used a J-valve before, but it's my understanding that a diver really didn't know how much gas he had between full and approx. 300 psi (or whatever the reserve pressure was). The diver would breathe his tank down until the reserve was reached and then activate the lever to access his reserve gas. I think it's easy to see why divers found analog SPGs more convenient and safer in terms of gas management. I have read multiple accounts of J-valve users who had to do a CESA since the reserve switch had unknowingly been left open from the beginning. They were counting on the reserve gas...and when it wasn't available to them, they had to make for the big tank in the sky.

I have dived J-valves. They may have been more reliable, though I doubt it, but they are not really comparable to an SPG, [-]any more than a minivan is to a Porsche[/-] because an SPG is providing more capability than just reserving a fixed amount of gas.

 

[jhelmuth]

You all are beating dead horses in an attempt to prove something that doesn't need proving.

If you'd stop... step back and do some research (and keep it honest and unbiased), you'd find that EVERY NEW technology has been lambasted as being "unsafe" only to find that years later it has become widely accepted. If you talk to any sociologist, they'll tell you all about the nature of humanity and the reluctance to accept the new for the "tried-n-true".

Let's all just agree that we ought to go do some maintenance on our gear and check it out throughly for faults AND LETS GO DIVING! :mooner:

 

[fnfalman]

P.P.S. In the "standard, proven technology" discussion, you asserted that J-valves are more reliable than analog SPGs. I've never used a J-valve before, but it's my understanding that a diver really didn't know how much gas he had between full and approx. 300 psi (or whatever the reserve pressure was). The diver would breathe his tank down until the reserve was reached and then activate the lever to access his reserve gas. I think it's easy to see why divers found analog SPGs more convenient and safer in terms of gas management. I have read multiple accounts of J-valve users who had to do a CESA since the reserve switch had unknowingly been left open from the beginning. They were counting on the reserve gas...and when it wasn't available to them, they had to make for the big tank in the sky.

There are plenty of current accounts (visit the Accident/Incident subforum) about divers who are equipped with modern equipment (SPG, AI computer) that also run out of air. What does that tell you?