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

[Sevenrider860]

Thanks @Sevenrider860

I can't understand why Scubapro would use an elevation of 1000 m when diving at sea level with the G2 Tek rather than the actual barometric pressure as used with the HUD. Does the Luna 2.0 work like the G2 Tek?

Shearwater uses the actual barometric pressure. This can easily be demonstrated by using the NDL planner at different barometric pressures. I was interested in this when I first got my Teric and constructed a spreadsheet covering between 985 and 1028 mbar.

View attachment 831593

G2 Tek, G3, and LUNA 2.0 all use the same ZH-L16C + GF algorithm.

 

[Sevenrider860]

What is their justification for this?

To be honest, the video call I had with Scubapro was not arranged by them to justify anything on their part, but it was to explain why I was seeing differences between Shearwater, Garmin, G2 Tek and the Scubapro HUD.

I did appreciate their willingness to engage with me and explain things.

 

[cerich]

OK, I officially need a day off. I did of course mean "more" when I typed "less", and it took me three -- count 'em -- re-reads to see that.

you may also wish to consider adding the word "theoretical" . Because changing settings ion a dive computer does NOT in any manner change what is going on in your body. Your posts make it sound like you think it does.

 

[dmaziuk]

you may also wish to consider adding the word "theoretical" . Because changing settings ion a dive computer does NOT in any manner change what is going on in your body. Your posts make it sound like you think it does.

There was a context to the post Stuart commented on, which he ignored as usual. The context was the computer "adaptively" changing your chosen conservatism setting (GF in this case) mid-dive without you asking. There is nothing theoretical about that being a bad idea, whichever way it changes: more conservatism can push the TTS past diver's gas supply, less conservatism can push the diver's surfacing gas loading out of their comfort zone. That design stems form a very practical problem between designer's chair and keyboard.

 

[cerich]

, less conservatism can push the diver's surfacing gas loading out of their comfort zone.

how does the computer "push" the surfacing gas loading" . It is subcutaneous, attached to the regulator. I am intensely curious to the mechanism.

I have only had dive computers that no matter what I set them on are theoretical and have no actual ability to increase or reduce gas loading. Your posts have been saying they do, and I feel like I missed some new technological development somehow.

 

[dmaziuk]

I have only had dive computers that no matter what I set them on are theoretical and have no actual ability to increase or reduce gas loading. Your posts have been saying they do, and I feel like I missed some new technological development somehow.

My posts are written with the ass-umption that when I turn my conservatism knob to 95 and get the longer bottom time as a result, that is because I actually plan to stay at the bottom longer.

You are of course welcome to set your computer up the way you read on The Internet and then ignore it on the dive. That option has always been available, no new developments here.

 

[Deeply Safe Labs]

Hi Divers,

We have conducted testing that might interest you and may answer some of your questions. More details are available here: Info - Deeply Safe Labs: A website for dive computer testing

On the subject, we have not tested either the G2 Tek nor the G3. However, we have tested the Luna 2.0, which we can confirm computes higher decompression times than theoretical unmodified ZH-L16 C. You can find the test results here: Deeply Safe Labs

@Sevenrider860 I have gone over the manual you quoted, but couldn't find any mention that altitude classes use the upper bound for calculations. This would be in contradiction with previous Uwatec and Scubapro computers, up since the first Aladin, in 1987. Could you please indicate where you found that information? Thanks in advance.

Best regards,
Eric Frasquet,
Deeply Safe Labs.

 

[cerich]

My posts are written with the ass-umption that when I turn my conservatism knob to 95 and get the longer bottom time as a result, that is because I actually plan to stay at the bottom longer.

You are of course welcome to set your computer up the way you read on The Internet and then ignore it on the dive. That option has always been available, no new developments here.

so, you think your computer magically makes your actual tissue loading change? What is that mechanism?

 

[stuartv]

@Sevenrider860 I have gone over the manual you quoted, but couldn't find any mention that altitude classes use the upper bound for calculations. This would be in contradiction with previous Uwatec and Scubapro computers, up since the first Aladin, in 1987. Could you please indicate where you found that information? Thanks in advance.

Best regards,
Eric Frasquet,
Deeply Safe Labs.

I don't know that it explicitly says exactly that.

But, Section 2.5 (p.33) is where it says:

Dive algorithms use altitude classes which are directly derived from barometric pressure

And if the algorithm uses a "altitude class" instead of the actual barometric pressure, then what should we expect it to use? Using the lower bound would be the least conservative approach. Using the upper bound would be the most conservative approach.

By using an "altitude class", I don't see how we could expect anything OTHER than using the upper bound.

I think nobody would say that it is acceptable to know the diver is at 950m altitude (with C0 being the lowest altitude class, covering 0 to 1000m) and the algorithm to treat that the same as being at sea level. By using "altitude class", it seems like it pretty much HAS to use the upper bound.

 

[dmaziuk]

so, you think your computer magically makes your actual tissue loading change? What is that mechanism?

I use the computer to track my dives so when my computer tells me my tissue loading changed, it is because I spent some time at some pressure.

As I said before, you may use yours differently.