Let's compare our conservatism setting

[zixzax]

But it's weird that this thread never gets into the 'New Posts' list...

 

[outofofficebrb]

Hi guys. I am a newbie and to be honest I don't quite understand your reply which is out of my knowledge. But I am happy to learn.
I guess I might not have explained my intention well enough. I have got my first computer recently and I am curious about whether there is huge gap in terms of NFL between different brands even if they are set with similar conservatism (GF value).
I can do a dive plan (by an app) on my computer and get the result. I just input the depth and GF and oxygen proportion and get the result. I assume that your computers can do the similar thing.
To make it simple, we calculate our first dive only. And maybe Buhlmann GF algorithm computers only..
Cheers

What we are trying to tell you is that many computers may show similar results after the first dive but it is actually after the 2nd, 3rd, 4th, 15th, 25th repetitive dive where you start to see extremely different NDLs which is much more telling. Basing information on 1 dive only is not a good representation of the different brands. My guess is you are trying to establish a level of conservatism based on the gap/differences in NDLs. Our computers allow us to plan a dive based on the residual nitrogen logged on the computer from a previous dive but they don't allow us to plan based on having done a simulated number of dives with that simulated amount of residual nitrogen. My computer would be planning this 1 dive based on no residual (since I have had a very long surface interval) but it won't let me plan the 2nd, 3rd, 4th, 15th, or 25th dive.

I can tell you that on "medium" conservatism on my Perdix and a Suunto at A0P0, after 1 dive, NDLs are quite similar. However, after repetitive diving over a few days, doing 4-5 dives a day, the NDL can differ as much as 25 minutes. I remember this because we were on the Alma Jane wreck in Puerto Galera which is at 80 something feet. I had to go up because my partner's computer only had 5 minutes of NDL left. My partner was diving his Suunto and I was diving my Perdix as buddies and it was really interesting to see it side by side like that.

Your post makes it to "recent" as soon as someone responds and it is in descending order of most recent to least recent.

 

[dmaziuk]

All ZH-L implementations should compute the same gas loading. Give or take a different assumed respiratory quotient and round-offs here and there. You can take any planner (subsurface is free) and run your profiles and see how gradient factors change things -- it should be close enough to any ZH_L16+GF computer out there.

The bit where actual dive computer implementations may not match is calculating the NDL: there are a few assumptions involved, and different vendors can make different ones. You'd still get a difference of couple of minutes at the most. If it's more that that your computer may be broken.

So the answer is no there can't be a huge gap. Especially on the first dive only, and particularly for different implementation of ZHL-16+GF only.

 

[Jay]

To make it simple, we calculate our first dive only. And maybe Buhlmann GF algorithm computers only..
Cheers

Using the same algo with the same GF across different brands will* produce the same NDL results (*=unless the manufacturer has something quirky / some rounding effect etc which I highly doubt but ..blanket statements on SB ... you know).

On repetitive dives with different algos the NDL differences at depth can be quite large (dives #3+) , as in closer between 10-15min depending on SI using 16-C vs. Suunto RGBM. Here a pic:

But it's weird that this thread never gets into the 'New Posts' list...

To see your own post hit the 'Recent' button more than once, it seems to do the trick.

 

[Barnaby'sDad]

Hi guys. I am a newbie and to be honest I don't quite understand your reply which is out of my knowledge. But I am happy to learn.
I guess I might not have explained my intention well enough. I have got my first computer recently and I am curious about whether there is huge gap in terms of NFL between different brands even if they are set with similar conservatism (GF value).
I can do a dive plan (by an app) on my computer and get the result. I just input the depth and GF and oxygen proportion and get the result. I assume that your computers can do the similar thing.
To make it simple, we calculate our first dive only. And maybe Buhlmann GF algorithm computers only..
Cheers

Where the results are going to be algorithm driven, I doubt the brand of the computer is going to matter much. Ex. My Mares Matrix has the Mares “propriety” take on RGBM...which is the same algorithm that’s used in a bunch of different computers. Each applicable brand having their own spin on RGBM.

I would expect a similar outcome with computers with the Buhlmann algorithm.

 

[dmaziuk]

Where the results are going to be algorithm driven, I doubt the brand of the computer is going to matter much. Ex. My Mares Matrix has the Mares “propriety” take on RGBM...which is the same algorithm that’s used in a bunch of different computers. Each applicable brand having their own spin on RGBM.

I would expect a similar outcome with computers with the Buhlmann algorithm.

RGBM has more knobs to tweak, starting with the choice of half-times for tissue compartments. (According to Wienke's published papers anyway.) That's where different implementations could have much more variance than what you'll see in Buhlmann implementations. Additionally, RGBM is computationally intensive so the low-power DCs like mares puck or cressi leo will likely run a simplified "folded" version -- there may be slightly different ways to "fold" it leading to more difference in results.

Still, on a "nice square" profile with no prior loading, the NDL differences should be within a couple of minutes.