is my computer trying to bend me ?

[Finless]

Originally Posted by al kennedy

I hate being left in suspense...

Sorry. I was going to say "................ giving you duff info as opposed to just being concerned because of the diff no stop times" but I went back and read the opening thread again and ................. it's my age.

[colinpjenkins2]

It doesn't take much in depth variations to give different reading. I dive with a Suunto Cobra with the hose clipped to my BCD and a back up Gecko on my wrist even they can give a 3 min variation between them on a dive so it shows you dont have much of a diffence in depth to have an effect on the none spot time.

[Bottle Maker]

[quote=liamm;860795

mal i get what you are saying, i'm just interested to know whether this difference between uwatec and suunto is normal or is it outside of normal variance. 18 mins does seem to be quite a lot.[/quote]

Having dived with a few different buddies who are using uwatec models I would say that was typical. As you were both in none stop time I would not be too concerned when one computer Indicates 20 mins of stops and one says 20min non stop time then I would worry.

I dive CCR using Vytecs and the difference between them and proper CCR computers is frightning.

[liamm]

cheers for the info guys, ill probably just watch it over the next few dives.

[Mal Bridgeman]

Liam

Been thinking some more about this.

First thing is to check the NDLs for each computer for each depth when they are "clean". Variance at this point will indicate likelihood of difference later.

Next is to compare the depth readings. It's unlikely they read exactly the same ..... the one that reads slightly deeper will use up ND time more quickly, obviously. Does the variance differ the deeper you get?

Finally when you compared the remaining NDLs were you at *exactly* the same depth. Depending on where you are in the computer's model of your dive and what was the controlling "compartment" will have a bearing. If you went up or down a metre, would the NDL change significantly?

It's why diving to the limits of a computer is really not to be recommended, especially when the decompression algorithms are ...well .... rudimentary

HTH
Mal

[serp]

Originally Posted by liamm

Just spent a week in the red sea - superb, the highlight of which was the thistlegorm. I was diving with a mate who was on a sunto D6 and i was on an alladin smart pro (18months old).
Most of the profiles were fairly conservative - about an hour run time fairly shallow and the last twenty mins spent at 10m or less. On the last dive on the thistlegorm we spent a bit of time at 28ish nosed about and then got gradually shallower as we worked throuigh the wreck. after about 40mins we had worked up to 20m and my comp was still allowing me 30min no stop time, my friends d6 had 12 mins left and the guide had 8mins. There wouldnt have been much of a difference in profiles between us and we were all on 31% - is there a problem with the computer or does this seem normal?

I had intended on selling it and getting something that could do three mixes but i'm now unsure about selling it if its not working.

Ant help appreciated

Hi Liamm,

Suunto computers are notoriously conservative when it comes to calculating no decompression limits and the length of the decompression stops. Personally I dive a Suunto Vytec and have no problem with that (better safe then sorry), but some people don't use Suuntos just because of that.

Hope this helps,
Josef

[liamm]

After a bit of reading around and geeking i think i've sorted out the problem. It seems that the smart pro is more conservative on the first dive but that the suunto would tend to be more conservative on the ascent. In particular the suunto would be much more conservative on repeat/consecutive dives - this is probably where the difference arose.

Anyway i'm now happy that the computer isnt faulty but dont think ill stick with it. The nice people at uwatec/scubapro wanted me to trade it in for a tek2G but wern't really offering much by way of incentive so i think i'll sell it myself.
As for a replacement ....... i'm drawn to a VR3 as it appears that it'll manage my diving now and for a long time to come but i might need to sell everything in the house on ebay first . .

[scuba steve irl]

the suntos hav a deep stop function , can be set to be mor conservative and are worked of a different algrithm . the sunto works off a reduced micro bubble algrithm . this when set will and can be very conservative .