Galileo G2 too short NDL on 2° dive???

[Chris Karrer]

HI!
I bought a Galileo G2 for my friend in Costa Rica and i was testing it diving with it and my own Suunto Eon Steel.
Unfortunately i discovered a massive difference in Non Deco Limit between the 2 computers,both strapped to my arm.

1° Dive after 21 hour surface interval
EON Steel 20 min @ 98ft after 2 minutes
Galileo G2 19 min @ 98ft after 2 minutes

2° dive after 1:26 min surface interval
EON Steel 18 min @ 98ft after 2 minutes
Galileo G2 11 min @ 98ft after 2 minutes

As i kepth my EON Steel as reference i received 4 minutes deco on the Galileo G2 while
the Eon Steel showed no deco after 1 minute deep stop.

Both computers are in air, not in altitude mode and personal setting is zero and
both computers show the same depth

The same behavior (approx 7 minute less botom time on 2nd dive) was confirmed in several other dives.

I understand that the algorithm of the two computers is different,
but half of the bottom time on dive two is a bit too restrictive for what i experience during my work.

Enyone else encountered this behaviour or is it just me?

 

[tbone1004]

different algorithms behave in different ways. Even though personal setting was 0, that doesn't mean the algorithms are set to mimic each other when set to default conservatism. Experiment with the algorithm to find what works or read up on the algorithm to find out why the Galileo cut that second dive short and if that is safer than the Eon's

 

[scrane]

Seems like the Galileo has a better grasp of two adjacent deep dives.

 

[elbig]

Are you sure you are comparing NDL's? Depending on which screen you are using, the G2 may be showing RBT which includes time to surface and 3 min safety stop.

 

[Hatul]

Also make sure the G2 has MB set to 0. Your finding is contrary to my experience with the Suunto Vyper and the Galileo Sol. On repetitive dives the Suunto was much more conservative.

 

[Chris Karrer]

@ Elbig Yes, i am comparing NDL
@ Hatul yes the MB is also on zero and yes, Suunto was more restrictive than the older Scubapro/Uwatec computers
@ tbone1004: i have also a tek computer and i know that they have complete different algorithms and i can't get the tec computer to run similar to a rec computer
I am overweight, 53 years old and made 3500+ dives (300-500 each year and about 30% of them deeper than 90ft ) only with Suunto computers and i never ever had any issues so it seems to me that their algorithm works.

During my work as instructor and guide i dive with people having different computers, but i never experienced a difference like this.
The only dives i had clients with very short NDL's there was either P value high or altitude mode set, so this made me wondering about the strange behaviour of the G2

However,
yesterday i loaded the new firmware and i will test the G2 again today to see if something changed
Also as soon my buddy lend me his Galileo Luna i will confront both together to see if there is some kind of difference or not.

Certainly the 7 minutes NDL on a second dive is safer,
but as guide this not feasible as i have to argue every time under water when i call the group to ascend and they have still 7 minutes of NDL.

Thank you for all your replies, i will keep you updated!

Chris

 

[Chris Karrer]

Well,
i finally made it to check the Galileo G2 together with a Galileo Terra from my buddy.
Both computers where not used for more than 72 hours, mounted on my arm and have same settings

Galileo Terra
MB Level 0
PDIS: On
Altitude set automatic

Galileo G2
MB Level 0
PDIS: Off
Altitude set automatic

1° dive @ 30 meters/98 ft G2 has 1 minute less NDL
1.38 min surface iterval
2° dive @ 30 meters/98ft G2 has 9 minute less NDL

A higher setting in MB Level will lead to a shorter No-Stop / NDL as the manual writes:
When two G2 dive computers are used simultaneously, with one unit set to a MB level of L5 and the other to a MB level of L0, the no-stop time for the L5 unit will be shortened and more level stops will be required before the diver has the obligation of a decompression stop.

There should be no difference in NDL if PDIS is on or OFF as PDIS only change the depth and time of Deep Stops

I'm still wondering where this difference is coming from???

Chris

 

[Hatul]

I'll be going on a dive trip next month and will be using my G2 and Aladin Tec 3G as a backup. These two also should be using the same algorithm so I'll report on my readings.

 

[kelemvor]

They use different algorithms. Both use Bühlmann, G2 uses the ZHL-16 ADT MB variant and Luna/SOL used ZHL8 ADT MB. I couldn't find specifics on Terra, but I would bet that it's based on one of the ZHL8 variants like all the "older" scubapro computers.

Bühlmann decompression algorithm - Wikipedia


There's been a few threads on the topic posted on scubaboard. In general, the new G2 is slightly more conservative.

 

[beaverdivers]

Were the computers at 30 meters for the complete bottom time on both dives?