Dive computers: Conservative or liberal

[scubadada]

Save a little time and effort: www.missionscuba.com/other-scuba/dive-table-comparison.html

But the real telltale is subsequent dive NDLs. Cut and paste link - sorry

1st dive NDLs are interesting but knowing how your computer handles subsequent dive profiles is, perhaps, even more important. This kind of informaiton is more difficult to come by

 

[Aqua-Andy]

I won't say this often but I think the best data I have seen so far has been from Scuba Lab. They put the computers through three or four dives, the firs dives are usually not much different but the real difference comes in the third and fourth dives. Me I like a more liberal computer, I can always start ascending early but with a Conservative computer you are stuck with the shorter dive times weather you like it or not.

 

[ianr33]

What gas are we breathing for this test? Might want to define that!

 

[clownfishsydney]

On air:

Shearwater Predator on GF 30/85 is 92 mins total run time, so 47 minutes ascent time.

HW OSTC 2N on GF 30/85 is 100 mins total run time, so 55 minutes ascent time.

Interesting that someone else earlier had a different result for the Predator of 110 minutes total run time (I double checked mine).

Interesting for 30 metres, the no deco for both is about 14 minutes, but my very old 1991 Uwatec Aladin Pro shows 16 minutes.

Lots of computers do repetitive dives differently. My wife had a Tusa (actually a Suunto) till she got the Predator. It was more liberal on the first dive than my Uwatec Aladin Smart Com but far more conservative on second and third dives.

 

[tcoen]

On air:

Shearwater Predator on GF 30/85 is 92 mins total run time, so 47 minutes ascent time.
...
Interesting that someone else earlier had a different result for the Predator of 110 minutes total run time (I double checked mine).

The difference is probably due to your Predator being set to a last stop depth of 3m, and the other to a last stop depth of 6m. Using a last stop depth of 6m with air as the only deco gas results in inefficient decompression (due to the high nitrogen fraction of air).

Regards,
Tyler Coen
Shearwater Research

 

[NAM001]

Thank you for pointing that out. I did not like the numbers i got but could nt figure out why. Now i now. thank you. The guy that recommended the predator to me to ld me that when he had say 15 min deco the rec computers had 10-15 more.

Learned something and it didnt hurt. much

The difference is probably due to your Predator being set to a last stop depth of 3m, and the other to a last stop depth of 6m. Using a last stop depth of 6m with air as the only deco gas results in inefficient decompression (due to the high nitrogen fraction of air).

Regards,
Tyler Coen
Shearwater Research

---------- Post added January 28th, 2013 at 05:14 AM ----------

Thanks i made the min depth change to 10 ft and did the planner again with rmv of .53 and got 88 run time and tat of 43.

 

[miketsp]

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So, lets settle this once and for all.

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simple test for easy comparison.

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If you really think such a simple test will settle things "once and for all" then you're dreaming.
A lot of other factors will come into play. How much does your DC penalize you for a fast ascent (even if not all the way to the surface)? Sawtooth dive profile? Short SI? Exceeding O2 PP when diving Nitrox?

As other posters have indicated, a simple, single dive comparison won't give any idea of how the DC handles subsequent dives taking into account earlier profiles.