SPG or Not? (Dive computer w/ air int)

[happy-diver]

Ha ha ha ha ha haven't been diving with people for three or four years thought I'd check it out last Sunday, and it was great to see so many of them getting great value from their computers

Constantly fiddling withn the ************* things instead of diving ha ha ha ha ha ha ha ha ha!

Now it's just not diving if you do not learn to use your SAC and SPG and Depth, as a computer

 

[lizardland]

Maybe I'll add to the offense, but this right here is spot on. I love having the extra info and convenience of the AI, but it's not failsafe. I had my perdix AI lose coms last dive. It eventually came back, but I was happy to have my SPG in the meantime.

I know I'm being a bit pedantic but it is failsafe, it failed safely in this case. For me, the issue is coming back online. If something fails and then comes back to life there is always an element of doubt around what you are looking at. Which leads into needing a reliable back up system. Which begs the question that if your back-up system is so reliable and has a lower failure rate than the primary, why is that not your primary system?

I'm involved in designing a rebreather controller system at the minute and the architecture of how the system fails is probably the single biggest suck of time in the project. Control and monitoring is the easy part. Trying to figure out the best way for it to die or recover in the event of a failure is probably 60-70% of where the effort has gone.

 

[Khoujo1]

If one reads all the responses, there are anecdotes of AI failures and anecdotes of SPG failures. The only reasonable conclusion is that a diver should have both during a dive. If you can afford a computer with AI, you can afford an SPG. It does not add much to your weight or kit, but does add redundancy and safety to a dive.

 

[Divin'Papaw]

If one reads all the responses, there are anecdotes of AI failures and anecdotes of SPG failures. The only reasonable conclusion is that a diver should have both during a dive. If you can afford a computer with AI, you can afford an SPG. It does not add much to your weight or kit, but does add redundancy and safety to a dive.

By that logic, if you do not have an AI computer, you should have two SPGs. Which is nuts. No one does that. Having one pressure monitoring device is adequate.

People need to remember that losing the ability to know your gas pressure is not a crisis. It doesn't mean the gas is gone. It doesn't mean you are about to run out. It just means you've lost the ability to see, in real-time, how much gas you have. If you are reasonably experienced, you know how long a tank will last you for a given profile. Losing gas monitoring, even for the entirety of the dive, should not be a huge deal.

 

[growcurlyhair]

Yeah i think this is a really good point that you brought up, now at least i have this consideration in case of a SPG failure. Bottom time is somewhat consistent and for us rec divers, we have to stick to our buddies in case of a serious issue. Asian rental spgs aren't the most reliable man..

I would personally signal to end the dive though, rather than go through the whole dive

 

[Blues Runner]

I have been diving a Perdix AI for many years. Convenient to have all information on one screen on my wrist. I have continued to use an spg with a smaller head. One extra hose clipped off. Cheap insurance......

 

[tursiops]

If something fails and then comes back to life there is always an element of doubt around what you are looking at

?? Not every thing. Maybe some things. Not the MH8A system; if it comes back after a signal loss, it is not possible for it to display an incorrect value. If the pressure is showing, it is good. Not like an SPG: just because the needle shows something does not mean that is the right answer....it might be stuck, or have gone off calibration.

 

[Divin'Papaw]

I have been diving a Perdix AI for many years. Convenient to have all information on one screen on my wrist. I have continued to use an spg with a smaller head. One extra hose clipped off. Cheap insurance......

Yup. Absolutely a viable, acceptable, common option. Lots of people keep the SPG. I did initially as well.

Dropping the SPG to get rid of the extra hose along with the leak-prone SPG spool is another viable, acceptable option. I did that several years ago and have not regretted it once.

As many of us have stated, it really is personal preference.