New diver: Suggested conservatism settings for a Petrel?

[Croomrider]

Would love to see the NDL times of your Oceanic, at whatever settings it allows.

OK, I did a comparison between the Oceanic Datamax Pro-Plus (original) and the Petrel for all three settings of conservatism in the recreational mode. These are for air only. My Oceanic DPP does not have any settings to adjust the conservatism. I will list the NDL times in minutes starting at 50 feet in 10 foot increments to 150 feet depth. I wish I could do this in table format, but I don't know how on a forum post.

Oceanic Datamax Pro-Plus:
80, 57, 40, 30, 24, 19, 16, 13, 10, 9, 8

Petrel Rec-OC LO 45/95:
199, 103, 68, 49, 36, 28, 12, 10, 8, 7, 5 (Not correct, don't use)

Petrel Rec-OC MED 40/85:
153, 83, 56, 39, 29, 22, 9, 8, 6, 5, 4 (Not correct, don't use)

Petrel Rec-OC HI 35/75:
117, 69, 45, 31, 22, 17, 7, 6, 5, 4, 3 (Not correct, don't use)

I was actually surprised to see that all modes of the Petrel were less conservative than the Oceanic until you go deeper than 100 feet. When I first got the Petrel, I compared it at about 120 feet and it was less conservative, and I assumed that would be the case all the way through. It was not. I guess the two computers use different models for their algorithms. Very interesting indeed!

Mike

 

[C Dub]

Croomrider, interesting indeed! Thanks for taking the time to do that!

BTW, I think your third Petrel series, you meant to type HIGH instead of LO?

 

[Croomrider]

Croomrider, interesting indeed! Thanks for taking the time to do that!

BTW, I think your third Petrel series, you meant to type HIGH instead of LO?

You're right. I went back and fixed it! thx

Mike

 

[Michael Guerrero]

C Dub, if you want to learn more about this whole gradient factor thing read Erik Baker's papers "Understanding M-Values" and "Clearing up the Confusion About Deep Stops". You can find them with google searches.

 

[C Dub]

Hey Mike, I'm getting some different numbers. I thought I might have changed something by accident, so I reset all settings to factory, and double checked. For Rec Mode, Air, and medium conservatism, I'm getting an NDL time of only 63 minutes at 50 feet.

I'm finding this number by choosing Dive Setup+, NDL Planner+, then Plan for a dive starting right now. It shows all the NDL's starting at 50 feet, in 10 foot intervals. The full table is:
63,40,27,2015,11,8,7,6

I'm wondering how you are getting 153 minutes?

OK, I did a comparison between the Oceanic Datamax Pro-Plus (original) and the Petrel for all three settings of conservatism in the recreational mode. These are for air only. My Oceanic DPP does not have any settings to adjust the conservatism. I will list the NDL times in minutes starting at 50 feet in 10 foot increments to 150 feet depth. I wish I could do this in table format, but I don't know how on a forum post.

Oceanic Datamax Pro-Plus:
80, 57, 40, 30, 24, 19, 16, 13, 10, 9, 8

Petrel Rec-OC LO 45/95:
199, 103, 68, 49, 36, 28, 12, 10, 8, 7, 5

Petrel Rec-OC MED 40/85:
153, 83, 56, 39, 29, 22, 9, 8, 6, 5, 4

Petrel Rec-OC HI 35/75:
117, 69, 45, 31, 22, 17, 7, 6, 5, 4, 3

I was actually surprised to see that all modes of the Petrel were less conservative than the Oceanic until you go deeper than 100 feet. When I first got the Petrel, I compared it at about 120 feet and it was less conservative, and I assumed that would be the case all the way through. It was not. I guess the two computers use different models for their algorithms. Very interesting indeed!

Mike

 

[Agility]

I do not know about the Datamax but most Oceanic DCs use the DSAT algorithm (or they let you choose betwenn DSAT and Pelagic Z+ which uses a Bühlmann ZH-L16 table) The Petrel uses the well documented ZH-L16C algorithm with Gradient Factors.
Please keep in mind that all these algorithms are purely theoretical mathematical models. They have all been tested on thousands of dives but they may not describe what really goes on in a divers body.

 

[DuboisP]

Hey Mike, I'm getting some different numbers. I thought I might have changed something by accident, so I reset all settings to factory, and double checked. For Rec Mode, Air, and medium conservatism, I'm getting an NDL time of only 63 minutes at 50 feet.

I'm wondering how you are getting 153 minutes?

63 minutes at 50 feet is the correct value.
don't try 153 minutes without stop, but if you want be nominated to Darwin Awards
for 153 minutes at 50, you need a stop of 30 minutes.

 

[Croomrider]

63 minutes at 50 feet is the correct value.
don't try 153 minutes without stop, but if you want be nominated to Darwin Awards
for 153 minutes at 50, you need a stop of 30 minutes.

Yeah, I obviously did something wrong, I'll have to figure that out. I haven't had the petrel very long and so far on all dives I've used both computers and been well within the NDL limits for both. It does worry me that I have come up with erroneous numbers so easily in the rec mode. I know the computer was set to air when I went into the NDL planning section, and I assumed that it would use what the computer was set for, but I think I had a nitrox gas enabled as well, so it must have used that in the planning mode. Other than that, I would hope it would show the actual correct NDL time during the dive for the gas I had it set to. I don't think I will have to worry about staying down for 153 minutes with the air I have available anyway!

Mike

---------- Post added August 14th, 2014 at 08:36 AM ----------

 

[packrat12]

When I compared my computers, I was using the default CF which on the Oceanic Pro Plus 3 is 0 and used DSAT. I also have an older veo 100 which I compared to, which previously I compared to my ancient Oceanic (1996 era). Those 3 computers compared similar. I then was trying to match my Shearwater in Rec mode to the rest of my family. I found that in all settings (even Low CF on Shearwater), the Shearwater was more conservative. I also found that using Z+ (CF 0) on PP3, the Shearwater was closest, differing by a minute or 2 to the conservative side.

I will need to go home tonight and run the numbers like croomrider.

 

[C Dub]

I'm guessing you have nitrox gasses entered and turned on. The planner appears to default to the highest active mix.