Algorithm question (Perdix AI vs DSAT)

[hammet]

I have many dives under my (weight) belt using a Oceanic Geo2 computer. All my dives are rec dives with almost all of them warm water reef dives.
I was looking at the new Oceanic ProPlus X as I'm familiar with the Oceanic format and desktop software. I posted about it here to find some first hand reviews. Well, everyone suggested the Perdix AI, so, being about $200 cheaper and wireless to boot, I took the plunge.
My question is about the Buhlmann ZHL-16c algorithm it uses versus the DSAT that I've been using all these years. I've read up on the basics of both algorithms but for my type of diving, I'm seeing a big disadvantage of using the Buhlmann even on the LOW conservative setting.
Here's an air dive plan on the perdix vs oceanic:

(sorry the column spacing isn't preserved when posting here)
Depth Oceanic Perdix
50 81 76
60 57 50
70 40 35
80 30 25
90 24 19
100 19 15
110 16 12
120 13 9
130 11 8

As you can see, the Oceanic DSAT times, which come very close to the PADI RDP NDLs, are significantly greater than the Buhlman numbers and that's on the LOW conservative setting.

It would seem I'm limiting my dive times by using a Perdix as long as I am comfortable using the higher limits that DSAT allows.

Any comments are appreciated. (I'm sure this has been beaten to death here on this forum so sorry if I'm duping).

 

[Snoweman]

I'm confused. Following the numbers under the heading make it appear you get more time with the Perdix. I.e. - at 50' Perdix fives you 81 minutes, while Oceanic gives you 76 minutes. Am I reading it wrong?

 

[Joneill]

I have many dives under my (weight) belt using a Oceanic Geo2 computer. All my dives are rec dives with almost all of them warm water reef dives.
I was looking at the new Oceanic ProPlus X as I'm familiar with the Oceanic format and desktop software. I posted about it here to find some first hand reviews. Well, everyone suggested the Perdix AI, so, being about $200 cheaper and wireless to boot, I took the plunge.
My question is about the Buhlmann ZHL-16c algorithm it uses versus the DSAT that I've been using all these years. I've read up on the basics of both algorithms but for my type of diving, I'm seeing a big disadvantage of using the Buhlmann even on the LOW conservative setting.
Here's an air dive plan on the perdix vs oceanic:

(sorry the column spacing isn't preserved when posting here)
Depth Perdix Oceanic
50 81 76
60 57 50
70 40 35
80 30 25
90 24 19
100 19 15
110 16 12
120 13 9
130 11 8

As you can see, the Oceanic DSAT times, which come very close to the PADI RDP NDLs, are significantly greater than the Buhlman numbers and that's on the LOW conservative setting.

It would seem I'm limiting my dive times by using a Perdix as long as I am comfortable using the higher limits that DSAT allows.

Any comments are appreciated. (I'm sure this has been beaten to death here on this forum so sorry if I'm duping).

Maybe you mixed your numbers up - but what you posted seems to show just the opposite: the Perdix #'s look to be better (assuming you listed NDL's )?

 

[hammet]

Sorry ... I mixed up the columns. Should be fixed now.

 

[Joneill]

Sorry ... I mixed up the columns. Should be fixed now.

I would not personally consider those differences very significant, especially since I was trained to never push the limits when diving and that trying to ride the NDL line is a bad idea.

 

[hammet]

20% difference is very significant.

 

[KentB]

3-5 min I wouldn't really worry about.........are you regularly within that range of NDL limits?

 

[scubadada]

I have many dives under my (weight) belt using a Oceanic Geo2 computer. All my dives are rec dives with almost all of them warm water reef dives.
I was looking at the new Oceanic ProPlus X as I'm familiar with the Oceanic format and desktop software. I posted about it here to find some first hand reviews. Well, everyone suggested the Perdix AI, so, being about $200 cheaper and wireless to boot, I took the plunge.
My question is about the Buhlmann ZHL-16c algorithm it uses versus the DSAT that I've been using all these years. I've read up on the basics of both algorithms but for my type of diving, I'm seeing a big disadvantage of using the Buhlmann even on the LOW conservative setting.
Here's an air dive plan on the perdix vs oceanic:

(sorry the column spacing isn't preserved when posting here)
Depth Oceanic Perdix
50 81 76
60 57 50
70 40 35
80 30 25
90 24 19
100 19 15
110 16 12
120 13 9
130 11 8

As you can see, the Oceanic DSAT times, which come very close to the PADI RDP NDLs, are significantly greater than the Buhlman numbers and that's on the LOW conservative setting.

It would seem I'm limiting my dive times by using a Perdix as long as I am comfortable using the higher limits that DSAT allows.

Any comments are appreciated. (I'm sure this has been beaten to death here on this forum so sorry if I'm duping).

Hi @hammet

I've been diving Oceanic computers running DSAT since 2002 (nearly 1400 dives) and used an Oceanic backup until August 2016, when I switched to a Dive Rite Nitek Q, to learn about Buhlmann with GFs. I now have about 22O dives on the Nitek Q and have learned quite a bit, it's not as simple as you would think. I would suggest you run the same NDL tables of DSAT vs Bulhmann, but include EAN32 and EAN36 in addition to air. You might find it interesting to take your Perdix out of rec mode and run GF hi of 90 and 100, in addition to the 95 you ran. After you run the additional comparisons, come back and attempt to explain what you have found.

I have commented previously on this topic in similar threads. I never dive air, only nitrox between about 31 and 37%. If I would like to try to match DSAT, I dive my Nitek Q with a GF hi beween 90 and 100, depending on depth and mix.

Good diving, Craig

 

[Joneill]

20% difference is very significant.

So are you saying you dive purely square profiles and push NDL to it’s limit? If so, I guess it could be considered significant. However, I don’t think most would notice any real impact for typical recreational, multilevel dive profiles.

 

[hammet]

thank you Craig.
I primarily dive nx too but I figured the dive times were adjusted similarly as per the partial pressure of N2. I only quoted the air values for simplicity.