Hypothetical - 2 AI transmitters instead of backup SPG?

[dmaziuk]

In the case IMO in pressure sensors there is a primary need and that is to provide tank pressure top know if youare going to run out of air. any purpose beyond that is not a life necessary need.

Personally I know by now that on my regular average dive an Al80 lasts about an hour to 500-800 psi, that I can comfortably swim some 90 feet on a single breath, and that my wife's SAC is about the same as mine when I chase critters to frame shots etc. So under normal circumstances all I need is a watch for tank sensor and for emergency backup: turn off the camera and get closer to my perma-buddy... but I'm sure people sporting a Teric on every wrist and ankle believe I'M GONE DIE!!!

([invisible sarcasm tag] and they're probably not wrong [/invisible sarcasm tag])

 

[Joneill]

I dont think you have any concept of what constitutes failure points or behaviors at all. You premis of diffferent time of purchase making the argument moot is also moot. If you have 2 reg sets irregardless of age, do you get one rebuilt in jan at SHOP A and and the other in aug at SHOP B. Or do you eventually get them done together during off season at the same shop to simplify things. Same goes with computers if you and your wife send in your gear for annuals you quite often send the puters in also for fresh batteries to dive the year on. The only way to avoid the effects of people habits is to have a backup that is not subject to peoples habits or subject to a different set of habits. that is what valildates a reliable backup system. The very nature of the backup being different than the primary system with minumum reliance on common factors is what makes it work.

In this thread there have been m any comments such as MY COMPUTER WARNS ME OF A LOW BATTERY. Yes it does because that was instituted because of the failure point a battery going dead. Our processes have become simpler not because they are perhaps but possibly because they are not being taught which starts a domino effect of not having backups for failures. I think computers are probably the greatest advancement to diving i know of. but for it to be a an asset you have to know how to use them. Majority do not know crap about their puter beyond the main screen. They dont know the concepts of a dive table or how to use one so you buy a puter to do it for you, and you still have no clue if the info is right or not. The solution is to buy a backup puter for that???? Now you have 2 puters that you dont know how to use. you cant remember how to get to the menus to shut off the audio alarms on one let alone 2 puters. Many cant tell if they are set for nitrox or air and compound the problem even more. My point being that some forms of backup is more a complication than a fix for a problem. And then you add to the mix the unknown of if the seal leaks or not when you tried to change your own battery on both our computers. What i just describes is a bad behavior that leads to possible failure with the potential ( not guarantee) of loss of all info you are accustomed to using and with out the logic or hardware to shift to something basic to get you home. Im not saying that there is no 100% solution to any problem but their are answers to problems that are better than others. Of course BETTER is a relative word and is often driven by opinion more than facts.

Wow - lots of silly assumptions there... I know my Perdix AI and Teric inside and out. I also fully understand dive tables and how to use them.

I do 3-4 week long+ dive trips a year and don't ever want to have to cut a dive short or affect subsequent dives because I had a computer or transmitter failure (as unlikely as that actually is) - so I have full redundancy. Batteries are also cheap and easy to swap out, so I typically replace the batteries in my transmitters every other dive trip (and always carry spares). My Perdix AI has a battery level indicator as does the Teric - so easy to see when the Perdix needs replacement or the Teric recharged (Teric lasts several days but normally drop it on a QI pad every night on a trip anyhow). I'm not sure why you seem to have such an issue with this approach - it works perfectly for me!

To the OP - it's not a dumb idea and, if you have the means and deisire to do so, there is nothing wrong with a 2 transmitter (or even 2 computer) set up. Ignore the naysayers and equip yourself as you see fit in this area!

 

[loosenit2]

I dont think you have any concept of what constitutes failure points or behaviors at all.

1. you are getting overly personal rather than keeping the discussion reasoned and respectful.

You premis of diffferent time of purchase making the argument moot is also moot. If you have 2 reg sets irregardless of age, do you get one rebuilt in jan at SHOP A and and the other in aug at SHOP B. Or do you eventually get them done together during off season at the same shop to simplify things. Same goes with computers if you and your wife send in your gear for annuals you quite often send the puters in also for fresh batteries to dive the year on. The only way to avoid the effects of people habits is to have a backup that is not subject to peoples habits or subject to a different set of habits. that is what valildates a reliable backup system. The very nature of the backup being different than the primary system with minumum reliance on common factors is what makes it work.

2. That is not how failure probabilities work. If you have two 18 wheelers get transmissions rebuilt at the same time and then subsequently exhibit similar driving profiles the two transmissions will likely not both fail at the same time or near the same time, in fact the probability of that occurring is rather remote. There are far too many other variables at play in when a failure will occur. Manufacture quality of individual parts, quality of workmanship, random effects that cannot be predicted (bug in the grease) etc etc etc. Most mechanical failure is modeled as an inverted bell curve with a higher probability of initial failure with the probability rapidly declining over the lifespan of the device and than rapidly increasing later in its lifespan. I would really recommend reading a book or article on Reliability Centered Maintenance, it is a concept that the Air Force developed for aircraft maintenance and has subsequently been adopted by much of the automobile industry and other industries as well. It may be superseded in the future by the development of onboard sensors but not yet.

 

[dmaziuk]

If you have two 18 wheelers get transmissions rebuilt at the same time and then subsequently exhibit similar driving profiles the two transmissions will likely not both fail at the same time or near the same time, in fact the probability of that occurring is rather remote.

And if you bolt an 18-wheeler I'm stupid to your 1st stage, it'll always show your tank pressure at 6L. But you'll save a ton of money on trim weights.

HTH, HAND

 

[loosenit2]

And if you bolt an 18-wheeler I'm stupid to your 1st stage, it'll always show your tank pressure at 6L. But you'll save a ton of money on trim weights.

HTH, HAND

I assume sarcasm again? What does HTH, HAND mean?

 

[dmaziuk]

Kids these days... Hope This Helps, Have A Nice Day

 

[loosenit2]

I wish I was a kid again, rather than the folically challenge 46 year old man I am, the kid in the picture is not me, it is my daughter, i am the balding man opposite her. There is much slang that I am not familiar with and often have to look up or ask what it means.

 

[dmaziuk]

Urban Dictionary: kids these days

(Note "often applied ironically")

 

[NAM001]

1. you are getting overly personal rather than keeping the discussion reasoned and respectful.



2. That is not how failure probabilities work. If you have two 18 wheelers get transmissions rebuilt at the same time and then subsequently exhibit similar driving profiles the two transmissions will likely not both fail at the same time or near the same time, in fact the probability of that occurring is rather remote. There are far too many other variables at play in when a failure will occur. Manufacture quality of individual parts, quality of workmanship, random effects that cannot be predicted (bug in the grease) etc etc etc. Most mechanical failure is modeled as an inverted bell curve with a higher probability of initial failure with the probability rapidly declining over the lifespan of the device and than rapidly increasing later in its lifespan. I would really recommend reading a book or article on Reliability Centered Maintenance, it is a concept that the Air Force developed for aircraft maintenance and has subsequently been adopted by much of the automobile industry and other industries as well. It may be superseded in the future by the development of onboard sensors but not yet.

My position is not over personal. It is an opinion based on premis that the more complicated something is the more chances of failure to happen are. It does not make sense to provide a complicated device to be a backup for another complicated device. I can say personally the i have had many xmitter failures and computer failures and I no longer use xmitter's becasue of those failures. I can not recall a SPG ever going bad. My position is as simple as that. I have no problem with those that use them and likewise have no sympathy for those that break them by hitting or snagging things on the xmitter that protrudes from the 1st stage.

 

[Joneill]

My position is not over personal. It is an opinion based on the more complicated something is the more chances of failure to happen are. It does not make sense to provide a comlicated device to be a backup for another backup device. I can say personally the i have had many xmitter failures and computer failures and I no longer use xmitter's becasue of those failures. I can not recall a SPG ever going bad.

I can say personally that I have had an spg develop a bad leak in the spool during a dive that made me surface a bit earlier than I'd like to - tech said gasket had gone bad (and only had about 50 dives on it). I also had an spg glass crack when it's face "tapped" against the ladder while reboarding in rough seas. However, I've never had a single issue with any of my Shearwater DC's or transmitters so far. I also would not consider them complicated devices - but that's just me. Dive as you see fit