Chris Stock
Contributor
Really? EVERY computer is safe in any mode. Not one is having you standing in a lightning storm.
Buddy Dive's Using Different Algorithms (computers)
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Really? EVERY computer is safe in any mode. Not one is having you standing in a lightning storm.
Two dives a day strikes me as very conservative so I'd be surprised if either computer has a problem with it. I did 39 dives in Palau last fall over 9 days with my Perdix set to Medium, using 32%, and never came close to a problem with it. One of the nicest things about your Perdix is the tissue loading graph. It will provide a lot of information as to how the model is actually reacting to multiple dives over multiple days.
(I have put it a couple of minutes into deco on some deeper dives at Cocos Island, but it cleared before or during the safety stop in each case.)
(I have put it a couple of minutes into deco on some deeper dives at Cocos Island, but it cleared before or during the safety stop in each case.)
scrane
Contributor
I think Oceanic’s Z+ will be a closer match to Shearwater’s GFHi set at 95.
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scrane
Contributor
Here's what I get directly from my OCi and my Perdix, both of which are sitting at about 2500' elevation. The OCi matches the Oceanic table for sea level. I don't know if the Perdix took a hit for the elevation. Oceanic is set for Z+ and the Perdix GFHi 95:
Depth: Perdix/OCi 50:70/65 60:47/48 70:33/35 80:24/26 90:19/19 100:15/16 110:12/12 120:10/10
Here's what I get for Perdix GFHI 85 and Z+:
Depth: Perdix/OCi 50:58/65 60:37/48 70:26/35 80:19/26 90:15/19 100:12/16 110:10/12 120:8/10
Obviously, this is only for the first dive with no residual N2.
So, if the purpose of the exercise is to match algorithms and calling the dive when the first diver hits NDL there's not a lot of difference between GFHi 85 vs. 95 and Z+ at deeper depths. The spread is larger in shallower water where there's a better match between GFHi 95 and Z+.
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Hi @scrane
First, clean dive NDLs do an incomplete job of illustrating deco algorithm performance in the conservative to liberal spectrum. You may want to take a look at the 2017 dive computer testing by ScubaLab, where computers were subjected to 4 standard dives in a hyperbaric chamber. There is a link to the full test results in the beginning of this article 11 New Dive Computers Tested By ScubaLab In 2017
Included in the testing was a Perdix AI running 45/95 or 40/85, an Aqua Lung i200 running PZ+, and an Oceanic PPX running DSAT. On the 1st dive PZ+ was not much different than 45/95 until ascent to 40 feet, where it had half the NDL. On the 2nd dive PZ+ was more conservative than 40/85. On the 3rd dive, after a longer SI, PZ+ was similar to 40/85. On the 4th dive PZ+ was similar to more conservative than 40/85.
On the 1st dive DSAT was considerably more liberal than 45/95. On the 2nd and 4th dives 45/95 was more liberal than DSAT. They were quite similar on the 3rd dive. See my posts #s 5 and 8 regarding my experience with DSAT and Buhlmann ZH-L16C with GF. I have about 200 dives using the 2 side by side.
Good diving, Craig
First, clean dive NDLs do an incomplete job of illustrating deco algorithm performance in the conservative to liberal spectrum. You may want to take a look at the 2017 dive computer testing by ScubaLab, where computers were subjected to 4 standard dives in a hyperbaric chamber. There is a link to the full test results in the beginning of this article 11 New Dive Computers Tested By ScubaLab In 2017
Included in the testing was a Perdix AI running 45/95 or 40/85, an Aqua Lung i200 running PZ+, and an Oceanic PPX running DSAT. On the 1st dive PZ+ was not much different than 45/95 until ascent to 40 feet, where it had half the NDL. On the 2nd dive PZ+ was more conservative than 40/85. On the 3rd dive, after a longer SI, PZ+ was similar to 40/85. On the 4th dive PZ+ was similar to more conservative than 40/85.
On the 1st dive DSAT was considerably more liberal than 45/95. On the 2nd and 4th dives 45/95 was more liberal than DSAT. They were quite similar on the 3rd dive. See my posts #s 5 and 8 regarding my experience with DSAT and Buhlmann ZH-L16C with GF. I have about 200 dives using the 2 side by side.
Good diving, Craig
scrane
Contributor
Craig,
Thanks for the link. I looked at it a little yesterday on my phone. I will look at it today a little closer on the big screen. It's nice to have raw data.
Sandy.
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Hi Sandy,
If there's one thing I've learned since I started diving with computers in 2002, it is that comparing various deco algorithms for no stop dives is often not a simple matter. I have dived DSAT continuously, first with an Oceanic Pro Plus 2, and then switching to my Oceanic VT3 in 2010. My first backup computer was a Cochran EMC-14. It ran a modified Haldanean, 14 compartment, adaptive algorithm that was slightly more liberal than DSAT on both 1st and repetitive dives. It made a good backup computer, but was quite difficult to use due to a coin operated button system (bridging contacts). It still works and I dive it every once in a while, just for fun. Someone gave me a Dive Rite Nitek Duo, it was simple to program and use. Unfortunately, it ran a proprietary, 9 compartment, Bulhmann ZH-L16 variant that was more conservative than PZ+ and proved of no use to me. It also still works and I have loaned it out a couple of times. When I switched to my VT3, I went to a Geo 2 backup, they run essentially identically. I bought my Dive Rite Nitex Q in 2016, with a goal of learning how Buhlmann ZH-L16C with gradient factors worked. At that time, the Q was available, totally unlocked, from Dive Gear Express, for only $400. It was a relatively inexpensive way for me to get my experience, unfortunately, now discontinued. I dived the Nitek Q for a couple hundred dives before I went back to my Geo 2 backup. I dive the Nitek Q every so often to further test what I have learned.
As you have, I have spent a fair amount of time comparing 1st dive NDLs of various computers and deco algorithms. In fact, I have spreadsheets full of values. This information is valuable but gives no information on handling of repetitive dives. One way to get this information is to dive the computers side by sides dives as I have done over the years. There is very little controlled data comparing the various deco algorithms on repetitive dives. The ScubaLab testing I cited in my previous post is one of the few sources. I have found this data quite interesting and it illustrates the phenomena I pointed out in other, prior posts, in comparing DSAT and Buhlmann.
I am very visually oriented, so took the time to graph the depth leaving NDL times for the 4 dives in the 2017 ScubaLab computer tests. Perhaps you and others will enjoy taking a look. DSAT, PZ+, 45/95, 40/85, Scubapros's 16 ADT MB, Mares RGBM, and Cressi RGBM are included. No Suunto computers were tested in 2017.
Good diving, Craig
If there's one thing I've learned since I started diving with computers in 2002, it is that comparing various deco algorithms for no stop dives is often not a simple matter. I have dived DSAT continuously, first with an Oceanic Pro Plus 2, and then switching to my Oceanic VT3 in 2010. My first backup computer was a Cochran EMC-14. It ran a modified Haldanean, 14 compartment, adaptive algorithm that was slightly more liberal than DSAT on both 1st and repetitive dives. It made a good backup computer, but was quite difficult to use due to a coin operated button system (bridging contacts). It still works and I dive it every once in a while, just for fun. Someone gave me a Dive Rite Nitek Duo, it was simple to program and use. Unfortunately, it ran a proprietary, 9 compartment, Bulhmann ZH-L16 variant that was more conservative than PZ+ and proved of no use to me. It also still works and I have loaned it out a couple of times. When I switched to my VT3, I went to a Geo 2 backup, they run essentially identically. I bought my Dive Rite Nitex Q in 2016, with a goal of learning how Buhlmann ZH-L16C with gradient factors worked. At that time, the Q was available, totally unlocked, from Dive Gear Express, for only $400. It was a relatively inexpensive way for me to get my experience, unfortunately, now discontinued. I dived the Nitek Q for a couple hundred dives before I went back to my Geo 2 backup. I dive the Nitek Q every so often to further test what I have learned.
As you have, I have spent a fair amount of time comparing 1st dive NDLs of various computers and deco algorithms. In fact, I have spreadsheets full of values. This information is valuable but gives no information on handling of repetitive dives. One way to get this information is to dive the computers side by sides dives as I have done over the years. There is very little controlled data comparing the various deco algorithms on repetitive dives. The ScubaLab testing I cited in my previous post is one of the few sources. I have found this data quite interesting and it illustrates the phenomena I pointed out in other, prior posts, in comparing DSAT and Buhlmann.
I am very visually oriented, so took the time to graph the depth leaving NDL times for the 4 dives in the 2017 ScubaLab computer tests. Perhaps you and others will enjoy taking a look. DSAT, PZ+, 45/95, 40/85, Scubapros's 16 ADT MB, Mares RGBM, and Cressi RGBM are included. No Suunto computers were tested in 2017.
Good diving, Craig
scrane
Contributor
Craig,
Yah, no kidding!
I took a little time to look at the numbers and was impressed on how much the times for the second dive virtually exploded across algorithms after a deeper dive followed by a short safety stop. What really surprises me is how GF95 leaves DSAT in the dust, and more or less leaves it there.
I, too, have been diving DSAT for over 5 years, and as time has gone on (I'll be 70 in May!) I have been giving DSAT NDLs a wider and wider margin.
I am planning a liveaboard trip in June, and having gotten a Perdix I thought I'd be pretty safe with a GF95, but thanks to you, having seen the data I think I'l start off with GF85. I'll also be carrying my OCi in DSAT as a benchmark and a backup. Four dives/day, but it looks like 2 hr SI between dives which should make a big difference.
I recently got the Shearwater because I am intrigued by the Tissues Loading display. Also, the well documented Buhlmann algorithm.
I think it would be worthwhile, since you went to the trouble, and because there seems to be some interesting things happening, that you start a seperate thread. Judging from other recent threads there seems to be a lot of interest in this subject.
Thanks for your effort.
Sandy
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