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

[Belzelbub]

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.

They should definitely be clear on this up front. If they say it's Buhlmann ZH-L16C, then it should track like it. This is less important for me as my dives don't involve extensive deco planning. However, it could be a significant issue for divers that do extensive planning on gas use and deco times.

One of the main draws for running Buhlmann is that it is well known and open source, so when planning the dive, the diver can input their settings, planned switches etc. using one of the deco planning software available. Then doing the dive, they set the computer the same, dive the plan and come up with some longer than expected deco stops.

If they state it is Buhlmann ZH-L16C with GFs, then it should behave as such.

 

[BoltSnap]

They should definitely be clear on this up front. If they say it's Buhlmann ZH-L16C, then it should track like it. This is less important for me as my dives don't involve extensive deco planning. However, it could be a significant issue for divers that do extensive planning on gas use and deco times.

One of the main draws for running Buhlmann is that it is well known and open source, so when planning the dive, the diver can input their settings, planned switches etc. using one of the deco planning software available. Then doing the dive, they set the computer the same, dive the plan and come up with something longer than expected deco stops.

If they state it is Buhlmann ZH-L16C with GFs, then it should behave as such.

I agree from technical diving point of view. Standardization is very important for dive planning using planning software, conformity among buddy teams and dive execution.

I'll reach out to Scubapro once I back home in few days to get more definitive information from them.

 

[stuartv]

Thank you @Sevenrider860 for posting about this.

It coincides with what I have observed.

I had a tech student for a week in Cozumel at the beginning of this year. My student has been using a G2 for recreational diving and already had a SP AI transmitter, so bought 2 brand new G2 Tek computers to use for class and future tech diving.

On the second day of class, our 2nd dive was to 80 feet. There were 3 of us, all with the same GF settings. My student with the G2 Tek went into deco (well, according to her computer) and she didn't tell me, and then she had 17 minutes of deco (according to her computer) while we were hanging at 10 feet. Myself and the other diver did not have any deco.

I was never able to figure out why her computer did that. Her and the other diver were both on air. It was not that her computer was set to air and the other diver was set to a rich Nitrox. I was on CCR, so not directly comparable. We all had the same GF set in our computers.

The rest of the week, her G2 Teks seemed to track pretty well with my and the other diver's Shearwaters.

My friend that owns the shop where I teach had told me that he will only accept students for tech training that are using a Shearwater. I had thought that any computer running GF would be fine. I think I am now on the Shearwater-only boat.

 

[BoltSnap]

The rest of the week, her G2 Teks seemed to track pretty well with my and the other diver's Shearwaters.

Doesn't this part seem contradictory?

 

[Kendall Raine]

Anyone wanna bet that its some proprietary nonsense cause they dont trust their customers?

Agreed.

Reminds me of Irvine's rants against computers in general: you don't know what your deco is because when the engineers went home at night the lawyers went to work on the code.

FWIW I've found my Shearwater tracks very closely to to Multi-Deco ZHL16-C. Padding a GF enabled model is asinine. Claiming it's ZHL16-C is actionable; except in Hollywood of course where everything is "based on a true story."

 

[stuartv]

Doesn't this part seem contradictory?

Absolutely! So, the G2 Tek is unpredictable AND inconsistent.

Disclaimer: I did not mess with my student's G2 Teks at all. I looked over her shoulder as she/we tried to make them do what I wanted. And, she had not dived with them prior to the start of class. So, it is *possible* that it was some setting that she changed after that one dive with the long deco that "fixed" it. I do not know.

What I DO know (also) is that watching her navigate the menus on the G2 Tek showed it to be - to ME - a, well, sh1tty(!) user interface compared to the Shearwater Perdix or Teric. It was not intuitive at all - to me or to her (or so it appeared to me as I watched her). She has been using a G2 for a while and even she was looking all over trying to figure out where stuff was and how to change some things.

 

[BoltSnap]

Absolutely! So, the G2 Tek is unpredictable AND inconsistent.

Disclaimer: I did not mess with my student's G2 Teks at all. I looked over her shoulder as she/we tried to make them do what I wanted. And, she had not dived with them prior to the start of class. So, it is *possible* that it was some setting that she changed after that one dive with the long deco that "fixed" it. I do not know.

What I DO know (also) is that watching her navigate the menus on the G2 Tek showed it to be - to ME - a, well, sh1tty(!) user interface compared to the Shearwater Perdix or Teric. It was not intuitive at all - to me or to her (or so it appeared to me as I watched her). She has been using a G2 for a while and even she was looking all over trying to figure out where stuff was and how to change some things.

I'm going to reserve judgement until I hear back from SP guys when I get home. I'm planning to get the G2 Tek at some point but I need to get the HUD first.

 

[stuartv]

The thing that I was wondering about what happened with my student is if there is some setting for the G2Tek that tells it to apply SP's adaptive algorithm junk to the ascent plan that is calculated using GFs. I.e. it calculates your ascent based on your chosen GFs, but then, if the adaptive setting is turned on, it will make your ascent more conservative based on whatever parameters it monitors (e.g. SAC rate, water temp, etc.).

In order to answer that question, I found the G2 Tek manual and looked. What I found says that the G2 Tek will log your heart rate and skin temp, if you connect those sensors, but it doesn't use that data for the ascent algorithm. So, in theory, my theory is not the explanation. I still don't know why my student's G2Tek gave her all that deco on that one dive.

BUT, in reading through the manual I found these other things:

This is from page 13 of the G2 Tek manual, available here:

https://scubapro.johnsonoutdoors.com/sites/default/files/2022-10/SP_G2TEK_manual_EN.pdf

So, if you skip a deco stop, the G2Tek will lock you out for 24 hours.

Not today, Satan!

And this is from page 36:

WHAAAT?!? It will change your gradient factors during a dive?!?!

Well, what could possibly go wrong there?

And this is from page 70:

It calculates your deco based on a variable ascent rate? W. T. F?!?!

Anybody got any suggestions on what deco planning software you could use before your dive to calculate your dive plan - so that it will match what your G2Tek actually does in the water?

I mean, I use Subsurface for dive planning. It will allow me to specify 4 different ascent rates, if I want to, based on:

Below 75% avg depth
75% to 50% avg depth
50% avg depth to 20ft
20ft to surface

But, as my actual dive computer doesn't have the same options, I use the same ascent rate for all 4 parameters, so that my plan matches what my Shearwater says during the dive.

I don't know of any software that will plan with a variable ascent rate like the G2Tek manual shows.

Bottom line: In my personal opinion, the ScubaPro G2Tek dive computer absolutely SUCKS as a technical diving computer. I sure hope they at least get it sorted out so the GF implementation actually works correctly (i.e. like Shearwater computers and all the dive planning software everyone uses work). Including at least an option for it to calculated based on a more standard ascent rate.

 

[lexvil]

 

[inquis]

Anybody got any suggestions on what deco planning software you could use before your dive to calculate your dive plan - so that it will match what your G2Tek actually does in the water?

It won't match, but planning for 20 ft/min ascent rate across the board will have you carry more gas than it thinks you need and is probably more realistic to boot.