Let's compare our conservatism setting
- Thread starter zixzax
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outofofficebrb
HARRO HUNNAYYY
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.
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.
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
Need to dive more!
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:
To see your own post hit the 'Recent' button more than once, it seems to do the trick.
Barnaby'sDad
Contributor
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.
SCUBA-MOON
Registered
Very interesting post so far. I just got a Garmin descent G1 in March and I took it to St. Lucia in April. My wife was using an old suit mosquito I had. She just started diving last year so we haven’t got her a new computer yet. I had the Garmin set to low conservatism (45/95). The first dive she had a little longer NDL than I did. We went to 100 feet and I had about 15 minutes of NDL, but hers was 17. However, after around a 40 minute surface interval, we went back down to 82 feet for a wreck dive, and her NDL was far less than mine. By the end of the dive I had no decompression obligation, but the Suunto was telling her to spend 10 minutes at 10 feet. This was actually much better than what the computer initially said she needed to do, which was 20 minutes at 10 feet!. Half of it cleared before we got to the safety stop. I never even got close to deco.
I’ve owned a cobra, cobra three, a stinger, and a mosquito. I enjoyed them all, but after having used the Garmin, I don’t think I could ever go back. I learned to dive on an orca edge, but it’s been most of my youth using an oceanic VEO 250, which if I’m not mistaken uses DSAT. I got into Suunto as I got older because I was told they’re more conservative. Having used a variety of computers ranging from Sherwood, oceanic, Suunto, and Garmin, I personally have enjoyed the Garmin descent G1 more than any of them. It’s so easy to use and I love using it in my every day life for its smart watch and fitness tracker capabilities. To be honest, I didn’t mind having the extra stop, but it could’ve been a real problem. Had I not known how Suuntos behave. I think a Shearwater peregrine is on the menu for my wife.
I’ve owned a cobra, cobra three, a stinger, and a mosquito. I enjoyed them all, but after having used the Garmin, I don’t think I could ever go back. I learned to dive on an orca edge, but it’s been most of my youth using an oceanic VEO 250, which if I’m not mistaken uses DSAT. I got into Suunto as I got older because I was told they’re more conservative. Having used a variety of computers ranging from Sherwood, oceanic, Suunto, and Garmin, I personally have enjoyed the Garmin descent G1 more than any of them. It’s so easy to use and I love using it in my every day life for its smart watch and fitness tracker capabilities. To be honest, I didn’t mind having the extra stop, but it could’ve been a real problem. Had I not known how Suuntos behave. I think a Shearwater peregrine is on the menu for my wife.
TrimixToo
Contributor
I know this will sound a bit harsh, but:
Let's not. The plural of "anecdote" is not "data." The sample size here is too small to be meaningful. Read things like studies from reputable sources...Deco for Divers...and anything at all from Simon Mitchell.
Let's not. The plural of "anecdote" is not "data." The sample size here is too small to be meaningful. Read things like studies from reputable sources...Deco for Divers...and anything at all from Simon Mitchell.
Comparing different dive computer high, medium, low conservatism settings really isn’t very interesting to me. I’m more interested in the qualitative aspects behind the community’s choices of gradient factors. I was diving 50/85, which worked fine for me, until a dive buddy got mild subcutaneous emphysema. He attributed it to his substantial reserves of “bioprene.” Regardless, he decided he wanted a bit more conservatism, so I’m now using 50/75. Since any gradient factor lower than 100/100 is, by definition, conservative, and you can’t know if it is conservative enough until it fails, I’m curious how different people arrived at their personal value.
I also had a buddy get subQ DCS after a no-stop dive in warm water with ~GF45/80. Profile was fine. No overexertion, controlled ascent, etc. The dive MD found nothing out of line in the profile. Unfortunately, lightening can strike for unknown reasons at times. I would propose that the most likely cause is often related to dehydration in similar cases.
As far as settings, I go with 55/95 for average sport diving, 55/80 for trimix. For the sport profile, the 55 doesn't really come into play for non-stop dives, but it keeps me changing the settings less between the 2 profiles. The rational for the 95 high is it gets me more NDL time with multilevel diving, and the final high GF # is generally much lower by the time you surface unless making a fairly direct ascent. With today's computers (I dive a Shearwater PerdixAi and Garmin MK2i) you can monitor the GF Surface % in real time, so I tend to be under 80 anyway by the time shallower portion of the dive and 3 min. safety stop is over.
The rationale for the 55/80 is to diminish the deeper stops for deco, which is when the GF low really matters anyway, and to add some conservatism for planned trimix/deco profiles on the high side. Again, with the GF Surface % ability, it's easy to hang out on O2 a few extra minutes and bring the high GF # down even more with a little extra deco gas.
This has worked for me for the last couple of years. I started back in the "deep stop" and RGBM days (which were done with deco software) and with computers that didn't allow for all of the personalization (NitekHe) and this seems to be the closest to a comfortable middle ground based on what I have looked into so far. I understand bringing the GF low even higher to ditch the deeper stops completely (but I am still hesitant to go with an 80/80 for some reason), and adjusting to the first gas change (for me would be EAN50 @ 70'), which would probably bring the low # up even a bit more from 55. For the purpose of repetition 55/80 is where I am at now, as I am a little hesitant to "go all in", since it worked for us in the old days, but it is evolving continuously and I am open to what you all think on eiither the sport or tech. sides.
As far as settings, I go with 55/95 for average sport diving, 55/80 for trimix. For the sport profile, the 55 doesn't really come into play for non-stop dives, but it keeps me changing the settings less between the 2 profiles. The rational for the 95 high is it gets me more NDL time with multilevel diving, and the final high GF # is generally much lower by the time you surface unless making a fairly direct ascent. With today's computers (I dive a Shearwater PerdixAi and Garmin MK2i) you can monitor the GF Surface % in real time, so I tend to be under 80 anyway by the time shallower portion of the dive and 3 min. safety stop is over.
The rationale for the 55/80 is to diminish the deeper stops for deco, which is when the GF low really matters anyway, and to add some conservatism for planned trimix/deco profiles on the high side. Again, with the GF Surface % ability, it's easy to hang out on O2 a few extra minutes and bring the high GF # down even more with a little extra deco gas.
This has worked for me for the last couple of years. I started back in the "deep stop" and RGBM days (which were done with deco software) and with computers that didn't allow for all of the personalization (NitekHe) and this seems to be the closest to a comfortable middle ground based on what I have looked into so far. I understand bringing the GF low even higher to ditch the deeper stops completely (but I am still hesitant to go with an 80/80 for some reason), and adjusting to the first gas change (for me would be EAN50 @ 70'), which would probably bring the low # up even a bit more from 55. For the purpose of repetition 55/80 is where I am at now, as I am a little hesitant to "go all in", since it worked for us in the old days, but it is evolving continuously and I am open to what you all think on eiither the sport or tech. sides.
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