When is ZH-L16C GF not ZH-L16C GF? When it is a G2 Tek computer

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Sevenrider860

Contributor
Scuba Instructor
Messages
1,162
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Location
Newnan, GA
# of dives
1000 - 2499
I had high hopes for the G2 Tek computer. I thought that Scubapro finally released a computer that used a non-proprietary algorithm and it would make a nice backup to my Shearwater. The ability to load CCR checklists and other reference data into the computer as pictures was a nice feature. Unfortunately this does not seems to be the case. Since diving the G2 Tek I noticed that it never seemed to track with my Garmin or my Shearwater when running identical GF values. I finally had a chance to compare the deco algorithm implementation of the Garmin Descent Mk2i, Shearwater Peregrine, and G2 Tek this weekend. I mounted them all on a piece of PVC and took them for a dive. The conditions for each were identical.

They were all set on Air with a GF of 50/75. While it is not expected that the computers will track exactly, my experience with the Garmin, Shearwater and Scubapro HUD running ZH-L16C GF is that they were always within a minute or 2 of each other. The G2 Tek is way outside this 1 to 2 minute range.

Example...

At 88 feet / 61 minutes both the Garmin and Sheawater were showing about a 6 minute stop at 30 feet. The G2 Tek showed a 3 minute stop at 40 feet. I ensured I cleared each stop on ascent based on the deepest/longest times (it was always the Scubapro G2 Tek). In the end, on the same dive, the G2 Tek took 11 minutes longer than the Shearwater to clear the final stop (The Garmin cleared the final stop a little less than 2 minutes before the Shearwater).

I mentioned my concerns to Scubapro in October about how the G2 Tek was not tracking the ZH-L16C GF implementations of the other computers...in fact it did not even track the ZH-L16C GF implementation of the Scubapro HUD. They said they would contact R&D. Of course I never heard back. I followed up again after this test and the response from Scubapro was "our unit is more conservative intentionally".

Shearwater states that they implement ZHL-16C, Garmin state they implement ZHL-16C, and Scubapro state they use ZH-L16C. One expects that identical algorithms would track similar to each other. Based on the response from Scubapro, it seems what they have really done is release another proprietary algorithm based on ZH-L16C GF. My expectation is that when you implement ZH-L16C GF, the computer should be made more conservative by adjusting the GF settings, not by the manufacturer changing the underlying algorithm. What is funny is that Scubapro does seem to have a good ZH-L16C GF algorithm in their HUD.

If you are only doing recreational diving and your are not trying to use a standard algorithm that is run by offline dive planner software, I think the standard G2 is a great dive computer. I was hoping to see all the benefits of the hardware but using a standard ZH-L16C GF algorithm in the G2 Tek. That is not what Scubapro is delivering in the G2 Tek.
 
Any justifications from them on why and what their intended benefits were?
Just a guess, a layer of liability protection. I find it interesting that the G2 tec differs from the HUD version, my older G2 with MB only set to MB L0 differs wildly from the HUD in GF 40/80 but nothing dive limiting.

By the way, tried GPS and really cont come up with a use for it for me all it seemed to do was use up 4 dives worth of charge, I’m sure it’s nice for some but for my diving it’s pretty useless.

I wonder if the Luna 2 GF matches the HUD or the tec?
 
Tec Services said they will reach out to R&D again.
They are yanking your chain again. I will never buy another scubapro computer for this exact reason
 
The rumor I heard, and it has not been confirmed or acknowledged by ScubaPro, is that the HUD algorithm was implemented by the SeaBear development team. I am guessing the G2, G3, and I am guessing the Luna 2.0, ZH-L16C code is another team.

I acknowledge this is just a rumor and my speculation based on that rumor.
 
I wonder if the Luna 2 GF matches the HUD or the tec?
My guess is that the G2 Tek, G3, and Luna 2.0 are running the same code. I have not dived them or compared, but that is my guess.
 
I've heard mentioned (though I don't know if that applies to the Scubapro G2 TEK) that some manufacturers will automatically increase the conservatism if a deco or safety stop is missed or has not been completed. In theory this would improve diver safety, but this can get you into trouble if you now don't have enough breathing gas to fulfill your new deco obligations.

If the G2 is more conservative from the get go, and maintains that conservatism throughout the dive without screwing with it on the fly, I don't really mind it (unless you're using it as a backup for a ZH-L16C computer from a different manufacturer), but they should be clear about this up front.
 

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