Question Perdix Shearwater AI

[rongoodman]

Basically for rec diving the only downside is it's not a Perdix.

Proprietary algorithm and will lock you out if you make it sad. I'd call those downsides.

 

[Divin'Papaw]

Proprietary algorithm and will lock you out if you make it sad. I'd call those downsides.

Indeed. Locking you out if you piss it off is a very major downside.

 

[grassybreakfast]

Proprietary algorithm and will lock you out if you make it sad. I'd call those downsides.

Is that something people do with any regularity in the type of diving you consider recreational?

I don't think the vast majority of recreational divers even do any deco dives, let alone busting the deco stops enough to make the computer lock up.

According to the manual, the i770R, the only times it will lock up is on exceeding 100m (function restored upon ascend above 100m), or if it calculates a deco stop required deeper than 21m. With an ignored deco stop it will only lock up for 24h after surfacing. If that happens something has gone seriously wrong and not being able to dive again in 24h is probably the least of my worries.

I guess if your definition of rec diving including pushing and violating deco obligation regularly, I guess that would be a very major downside.

 

[tursiops]

I don't think the vast majority of recreational divers even do any deco dives, let alone busting the deco stops enough to make the computer lock up.

The problem is, in fact, people who do not do deco diving, but exceed their NDL for whatever reason. They have no idea what their computer is telling them and blow off the deco stops. Then their computer locks out for 24 or 48h....and they blame the computer, of course. Saw exactly this happen two dive trips ago.

It need not be done regularly to be a problem; once is a problem, especially if you are on a dive trip and you lose a day or two of expensive diving.

 

[rongoodman]

Most of the lock-outs I’ve seen have been due to user error, not actual missed deco. Bricking the computer in response seems extreme when an error message could get the point across. I had that happen once when my back-up Perdix thought I had skipped some deco because it was’t on the same page as my rebreather. I acknowledged the error, felt mildly foolish, and went about my business.

 

[grassybreakfast]

The problem is, in fact, people who do not do deco diving, but exceed their NDL for whatever reason. They have no idea what their computer is telling them and blow off the deco stops. Then their computer locks out for 24 or 48h....and they blame the computer, of course. Saw exactly this happen two dive trips ago.

It need not be done regularly to be a problem; once is a problem, especially if you are on a dive trip and you lose a day or two of expensive diving.

That sounds like a huge knowledge gap in training. A diver who doesn't even know that probably shouldn't be diving.

I only have BSAC SD (that's something like 10 open water dives from brand new), and my training already included simulated emergency deco, and obviously we all know what NDL meant and what to do if it's exceeded (follow computer's instruction for deco... it's not that hard considering most computers use the same interface for safety stops).

I would hope anyone even considering buying a computer as expensive as a Perdix (or the Aqualung) would know that?

It seems to me like better education is a safer solution than a more lenient computer here.

 

[Divin'Papaw]

The problem is, in fact, people who do not do deco diving, but exceed their NDL for whatever reason. They have no idea what their computer is telling them and blow off the deco stops. Then their computer locks out for 24 or 48h....and they blame the computer, of course. Saw exactly this happen two dive trips ago.

It need not be done regularly to be a problem; once is a problem, especially if you are on a dive trip and you lose a day or two of expensive diving.

Or worse ... the offending diver borrows someone's backup or someone's spare and continues diving without their computer having the necessary residual nitrogen loading data. If you're going to be stupid enough to exceed NDL and blow off a deco stop because you have no idea what the computer is telling you, you're also going to be stupid enough to keep diving with a different computer.

I'm of the opinion that computers that "brick" and lock out future diving are in fact less safe because it leads to the foolish practice I listed above.

 

[Divin'Papaw]

That sounds like a huge knowledge gap in training. A diver who doesn't even know that probably shouldn't be diving.

I only have BSAC SD (that's something like 10 open water dives from brand new), and my training already included simulated emergency deco, and obviously we all know what NDL meant and what to do if it's exceeded (follow computer's instruction for deco... it's not that hard considering most computers use the same interface for safety stops).

I would hope anyone even considering buying a computer as expensive as a Perdix (or the Aqualung) would know that?

It seems to me like better education is a safer solution than a more lenient computer here.

You'd think but those of us who have been diving awhile have seen it, most likely many times.

 

[tursiops]

Or worse ... the offending diver borrows someone's backup or someone's spare and continues diving without their computer having the necessary residual nitrogen loading data. If you're going to be stupid enough to exceed NDL and blow off a deco stop because you have no idea what the computer is telling you, you're also going to be stupid enough to keep diving with a different computer.

I'm of the opinion that computers that "brick" and lock out future diving are in fact less safe because it leads to the foolish practice I listed above.

Also, it leads to the helpful dive guide hanging your computer on a string down to 10-15 ft to let it complete its deco stop, and thus avoid the lockout.

 

[Belzelbub]

Is that something people do with any regularity in the type of diving you consider recreational?

I don't think the vast majority of recreational divers even do any deco dives, let alone busting the deco stops enough to make the computer lock up.

Maybe not intentionally, but it happens. The problem, in my mind anyway, is not so much that there is a lockout, but rather that the length of the lockout is rather arbitrary and punitive. There are sometimes reasons where it may be prudent to cut a deco stop short. Does that warrant a 24 hour lock? I don’t know. I’d need more information.

Using Subsurface, I’ve played with the GFs just to see what would happen. Doing that, I can turn several NDL dives into deco dives. So, with a conservative algorithm, you may find that a missed deco obligation is really not that big of a problem. And now what? The computer still functions in gauge mode, so you could still technically use it, it just won’t guide you anymore.

I’d rather have a computer that gives me the information decide how severe the infraction was. Information like SurfGF, GF99, or the tissue compartment graph all provide the diver with resources to make an informed decision. Maybe it was a minor transgression, maybe it was more severe. A computer that locks you out seems to treat all violations with the same severity.