Ratio Dive Computers Announces New iX3M 2!! Our Best Dive Computer yet!

[scubadada]

I have to admit that I did not understand much of that post, as I don't know much about the inner workings of dive computers. As someone interested in the iX3M2, and so far always doing no-deco dives (but might be interested in some light deco like you describe), would you mind dumbing that down for me to help me understand what the concern might be? I was leaning toward the iX3M2 Pro as my next computer, but want to understand any concerns/limitations.

Hi @Rob9876

The Pro model runs only Buhlmann ZH-L16C, you do not have be concerned with the other 3 deco algorithms. This is the only deco algorithm you need for your planned diving.

 

[L13]

I have to admit that I did not understand much of that post, as I don't know much about the inner workings of dive computers. As someone interested in the iX3M2, and so far always doing no-deco dives (but might be interested in some light deco like you describe), would you mind dumbing that down for me to help me understand what the concern might be? I was leaning toward the iX3M2 Pro as my next computer, but want to understand any concerns/limitations.

Most modern dive computers are based on the Buhlmann ZHL-16C model for inert gas physiology. The other models mentioned are predecessors in the history of 16C, except VPM-B which is based on a different "bubble model" for inert gas physiology.

For all the ZHL algorithms, the number represents the number of "tissue compartments" tracked by the model. The last letter represents the set of a/b parameters in the model which sets the limit for inert gas(nitrogen) supersaturation in each "tissue compartment." The A and B sets were targeted at dive tables. The C set is the newest, and targeted at dive computers.

GFs is short for Gradient Factors. GFs are an addition to the Buhlmann model proposed by Baker. a GF is a new more conservative supersaturation limit represented as a percent of the Buhlmann limit. GF-High is the new limit used for NDL dives and for surfacing on Deco dives. GF-Low is the new limit for the first and deepest deco stop on a Deco dive, and isn't used for NDL dives.

Many previous popular dive computer models use some of these other models, often with proprietary modifications. Some divers would like their new computer to emulate a previous computers algorithm that they were comfortable with, so companies like Ratio provide those options, in addition to ZHL-16C+GFs. Other companies, like Shearwater, provide only ZHL-16C+GFs.

 

[scubadada]

I would bet that computers running RGBM algorithms (Suunto, Mares, Cressi) outnumber computers running Buhlmann by a considerable margin

PZ+ is a good example of a popular proprietary deco algorithm derived from Buhlmann ZH-L16C

DSAT, another popular deco algorithm, was not derived from Buhlmann

Shearwater offers VPM and DCIEM on the Perdix 2 and the Petrel 3

 

[Rob9876]

I would bet that computers running RGBM algorithms (Suunto, Mares, Cressi) outnumber computers running Buhlmann by a considerable margin

Another quick question since y'all have been so helpful: my current computer is a Mares Puck Pro+, so would the iX3M2 Pro algorithm would be more or less conservative than the Mares (assuming RGBM) algorithm?

 

[L13]

I would bet that computers running RGBM algorithms (Suunto, Mares, Cressi) outnumber computers running Buhlmann by a considerable margin

True, but most people buying these computers don't even question the algorithm running. Why change something that is working unless customers demand different. The higher end models are adding ZHL-16C for the more discerning customers.

PZ+ is a good example of a popular proprietary deco algorithm derived from Buhlmann ZH-L16C

But the PZ+ is based on Buhlmann ZH-L16C with proprietary changes.

DSAT, another popular deco algorithm, was not derived from Buhlmann

DSAT is a Haldane algorithm that, while not derived from Buhlman, is informed by Buhlmann work.

Shearwater offers VPM and DCIEM on the Perdix 2 and the Petrel 3

Yes, but I was under the impression you had to pay more for those algorithms. I could be wrong on that.

 

[L13]

Another quick question since y'all have been so helpful: my current computer is a Mares Puck Pro+, so would the iX3M2 Pro algorithm would be more or less conservative than the Mares (assuming RGBM) algorithm?

It would be hard to know for sure since RGBM and its various implementations are proprietary. But likely there are settings on each computer that match fairly closely.

Since I'm not a fan of the bubble models (they are good, but I think the modern Haldane models are better), you should probably rely on someone else for the answer to this.

Maybe @scubadada or @BoltSnap can give a definitive answer?

 

[scubadada]

Another quick question since y'all have been so helpful: my current computer is a Mares Puck Pro+, so would the iX3M2 Pro algorithm would be more or less conservative than the Mares (assuming RGBM) algorithm?

That depends entirely on how the iX3M 2 is set. The computer has 6 presets, 93/93, 90/90, 80/80, 75/75, 50/85, and 45/80.

A GF high of 93 or 90 will most certainly be more liberal than Mares RGBM. The RGBM computers are often more conservative on repetitive dives than on the first clean dive. Somewhere between the GF high of 75 and 85 will be a fair match for the Mares. I have a very good idea of how Buhlmann and DSAT track, I have never dived a RGBM computer.

 

[Puppeteer]

If you are not doing decompression diving, then you really don't need to worry about gradient factors. The factors determine the calculation of your decompression stops, and don't impact your NDL.

Just correcting what I said above, in case someone happens upon this in the future. Thanks to Belzelbub.
The gradient factors are used for calculating decompression stops. GF Hi can impact no decompression dives as it adjusts the percentage of the maximum nitrogen levels your computer will allow compared to theoretical maximum allowed with a particular diving algorithm. The lower number this is, the shorter your NDL will be, but the further from theoretical maximum nitrogen saturation you will be.

 

[Belzelbub]

If you are not doing decompression diving, then you really don't need to worry about gradient factors. The factors determine the calculation of your decompression stops, and don't impact your NDL.

That’s not correct. GFLo is not used during No Stop dives, but GFHi is. GFLo determines the depth of the first deco stop. GFHi is very similar to conservatism settings with many dive computers. The GFHi number provides a buffer against the theoretical maximum of the algorithm.

For No Stop dives GF settings of 30/70 and 70/70 would yield the same NDL. 70/70 and 70/95 would yield different NDLs.

 

[scubadada]

I received a prompt reply from Ratio regarding additional questions regarding ZH-L12. Ratio service was very responsive:

"Yes, ZH-L12 is adjusted with GF as well.
Well, as dive computer manufacturer we choose to give as many choices as possible to the diver on which algorithm to use.
Plus our units are used for algorithm research purposes by some hyperbaric medical associations that sometimes needed to switch between the different versions of BUL"