Air integrated Computers. Is the estimated time left reliable?

[mikeetee]

Is the estimated time left reliable?

Was the big question in our Divemaster course.
Has anyone got expierience with that.
Please let me know the computer you have and how do you like the
estimated time left feature?

I've got a sunnto cobra and i quite like that feature!

Thanks and may the air be with you!

mikee

 

[MikeS]

I also have a Sunnto Cobra. The remaining air time calculation is based on a running average (30-60 seconds) of air consumption, with a margin of 500 to 725 PSI. This is consistent with my observation that as you ascend the remaining air time increases.

The concern I have is that the remaining time estimate will be totally unreliable at the start of an emergency/stress situation. The estimate would be based on your relaxed air consumption and not initially take into consideration the increased air consumption due to stress and increased activity. For example if you’re serenely floating along, and you notice your buddy has become entangled, you go to help him, look at the estimated dive time and it indicates 10 minutes. But, because of the stress and increased activity your air consumption triples and you really only have three minutes left.

Also, the following issues, quoted from the Sunnto Manual decrease the accuracy:

“NOTE! Filling your BC will affect the air time
calculation, due to the temporary increase in air
consumption.”

“NOTE! A change of temperature will affect the
cylinder pressure and consequently the air time
calculation.”

So while it’s a great tool, it’s not a substitute for monitoring air pressure and making your own estimate.

Mike

 

[Jonathan]

Well it seems reliable to me, but then I have never bled it dry to test ut:

As to the stress question in an emergency - the same goes for a normal guage. There you are plodding along at a nice SAC of 15l/min looking at your guage and on past experience thinking no problem another 25 mins. Then wham, an emergency hits and your SAC goes up to 30,40 + - you gonna blame the guage for not telling you you have enough gas to cope?! I think not so why blame the computer - at least you can see your time going down, if you bother to look....

 

[Rick Murchison]

I find them interesting...
And useless.
Rick