Question Do we have viable alternatives to Shearwater?

[David Carron]

Not intending to be inflammatory or contentious (I’m a hugger not a hater) but that’s a strange question that seems to shift responsibility for prudent judgment and control from the diver to the DC.

I'm not wondering what the correct behaviour for the diver is when the computer's model has been pushed outside its operating limits, but what the correct behaviour for the computer itself is: what might be the best display option if the computer judges that it cannot display a valid ascent profile?

I gave two examples of out-of-limits dive behaviour above, the first of which results in an extended NDL, the second in reduction of total decompression time and I really wonder if in these cases displaying those profiles was the best option.

 

[z0rk0l]

Had one and sent it back. It bricked (red screen, no recovery) in the middle of a dive. They authorized a replacement unit but after two months of waiting (backorder), I returned it and bought a Shearwater Peregrine TX (which works with the two Apeks transmitters I bought). Haven't had a single issue with the Shearwater and the screens easier to see.

Ah the old error 10. I also had this and switched for a perdix2 ti. So its a common issue then

 

[pdwh]

Ah the old error 10. I also had this and switched for a perdix2 ti. So its a common issue then

Part of why I returned it. Did some research, found it a was a common problem. Too bad - I loved the features and the two dives on got on it before it happened.

I sort of took the logic that everything I've read everywhere says Shearwater in general can be trusted so that's what I got instead. My backup is a Garmin fenix 8 that I wear all the time as a smartwatch (and really love). So I've always got two on now.

 

[ChrisMBC]

My next idiotic idea is to run a non-profit open source collaborative for making a simple ZHL-16 GF computer. No navigation. no AI. Minimal logbook. "Next dive plan only. Never locks(looking at you Suunto). 150 meter depth. full trimix.
Like a cellphone in a case taking the Subsurface or multideco algorithm and adding a depth guage. A cheap android phone is now your wrist console. No idea if this would even be possible, but I chew crayons and still can't do 1+1.

Have you looked at the Heinrichs Weikamp computers? I have the 'Bottomtimer' from there, and it's an exceptional piece of hardware. Really bright display as well. Their 'real' computers (OSTC 2, OSTC Sport, OSTC 5) are all open-source, you can view the code here. OSTC+ is rated to 120m, OSTC 5 is 200m.

 

[scubadada]

Have you looked at the Heinrichs Weikamp computers? I have the 'Bottomtimer' from there, and it's an exceptional piece of hardware. Really bright display as well. Their 'real' computers (OSTC 2, OSTC Sport, OSTC 5) are all open-source, you can view the code here. OSTC+ is rated to 120m, OSTC 5 is 200m.

Heinrichs Weikamp computers are generally not available in the US (sales and service).

 

[SelfDiver]

Gotta ask, do you see yourself doing open circuit trimix dives to 150 meters?

OC to 100-120m about 10 times and twice to 150m every year

 

[Whitrzac]

I have a friend that dives the ostc4 computers.

By his own calculations, he's had 2 working computers on approx 70% of his dives.

The last time we dove together the screen fell off of one of them...

 

[dmaziuk]

A model like ZHL16 can predict a safe ceiling, but ascents which violate that ceiling are outside of its domain.

Yesno: you're over the M-value and are no longer "safe" but it can still track your gas loading. I too wonder what good that'd do you if you're bent into a hundred nazi crosses, but there's no mathematical reason it couldn't. Whereas a more sophisticated model that has convoluted formulae for bubble magic, or is built on statistics that don't go where you are, may possibly be pushed into division by zero or some other impossible math and therefore be genuinely "out of bounds".

 

[broncobowsher]

Too bad Liquivision is no longer in business. They were another Canadian technical computer manufacturer.

Back when I was getting my first real computer to replace my 1-button puck, there were 2 games in town. Shearwater and Liquivision. It was when Shearwater only sold the Petrel, even before the Petrel 2. It was the HD-DVD vs. BlueRay, of VHS vs Beta. I had a dealer for both in town.

The Liquivision would not boot in the store. The dealer said something about it got left on and the battery went dead. Didn't want to take a charge. Didn't find that encouraging. Went into the other store and bought the Shearwater. Dropped a AA battery into it. Still a viable computer to this day.

Now shearwater has a whole line of products. Mostly form factors of how you want it packaged.

 

[David Carron]

Yesno: you're over the M-value and are no longer "safe" but it can still track your gas loading. I too wonder what good that'd do you if you're bent into a hundred nazi crosses, but there's no mathematical reason it couldn't. Whereas a more sophisticated model that has convoluted formulae for bubble magic, or is built on statistics that don't go where you are, may possibly be pushed into division by zero or some other impossible math and therefore be genuinely "out of bounds".

It seems likely that the situation is worse than that. If you exceed your "m value" ZHL16 will certainly point that out, but as soon as you redescend ZHL16 will not only forget the whole thing but will reward you by reducing your decompression time. As far as I know, nobody knows what the best thing to do is in that case, but it seems vastly unlikely that ZHL16's purely dissolved gas calculations, purely designed to calculate the safe ceiling, are going to handle it.

My only real question though is "what would be a good thing for the computer to display when the model is (as a very reasonable supposition) wrong" not "what is the right thing for the diver to do"