Logging how far I pushed the nitrogen (now a Perdix AI; was a Oceanic DataTrans)

[lairdb]

Looking back through my logs, I realize I miss a feature from my Oceanic.

On the Oceanic, there was a single bar graph, representing (iirc) the highest loaded compartment.

You had 12 tick marks of "green" and 3 more of "yellow" before getting into deco status, and if you ascended slowly enough to offgas, at the end it would show both the max and the end-of-dive.

I used to scribble these in my log, just as a measure of how hard I had been pushing, etc. A 70 minute dive with "N=5" is one thing; a 25 minute dive with "Nmax=14; end=12" was a whole different thing.

With the Perdix, I don't see anything comparable -- not in what's available in log mode, and not really even from downloading the logging. (I could run the mouse across the dive graph and look for the lowest NDL, but that's fairly ugly.)

Am I missing something?

("You shouldn't be thinking about it that way; think of it this way" is a valid comment. "Load your data into SubSurface and then..." is valid, but disappointing.)

 

[Whitrzac]

There's a bar graph on the perdix that shows all 13 compartments

 

[lairdb]

There's a bar graph on the perdix that shows all 13 compartments

Can you view that in log mode? Or just during the dive?

 

[Mergulhador do Delray]

Can you view that in log mode? Or just during the dive?

This might help.

Question on NDL vs Graph

Greetings! I did my first 2 dives on a new Perdix AI. However, I was confused over what appeared to me to be conflicting info. Both dives were shallow, ~50 ft, first on 35% Nitrox, the second on 32% Nitrox. Both gasses were programmed and selected. Only one enabled at a time. I was surprised...

scubaboard.com

 

[scubadada]

Hi @lairdb

I dived a Oceanic Pro Plus 2 from 2002-2010, it had 10 segments on the nitrogen loading graph, 11 was deco. I have been diving a Oceanic VT3 from 2010 and it has 7 segments on the loading graph and 8 is deco. To be honest, I have never paid any attention to the nitrogen loading graph and have only paid attention to my NDL, of course the two are correlated. Since 2019, I have dived the VT3 along with a Shearwater Teric, off a single transmitter. Sorry if some of my comments are not correct for a Perdix AI. I'm assuming that all or most of your dives are no stop. About 5% of my dives are light deco.

Your DataTrans ran the DSAT decompression algorithm. Though not perfect, a GF high of 95 is similar to DSAT, is that what you run? A lower GF high would generally be more conservative that what you were used to. I find the information available to me on the Teric to be more valuable than that from my VT3. Specifically, I'm talking about SurfGF. If you dive right up to your NDL and then do a normal direct ascent to the surface at 30 ft/min, you will surface with a GF very near your GF high. A safety stop will decrease your surfacing GF. The SurfGF tells you what your GF would be if you were instantaneously on the surface, from any depth. Your ascent and/or your safety stop will decrease the SurfGF and your actual surfacing GF. I dive at a GF high of 95, but have become a bit more conservative at my increasing age. I use the SurfGF to adjust my safety stop or last deco stop so that my surfacing GF is no higher than about 80-85.

On this dive my NDL got down to 1 min. My GF when arriving at the safety stop was 54%. The GF at the end of the safety stop was 36%. My surfacing GF was 75%, what I expected from following my SurfGF. The large increase in the GF during the final ascent should be duly noted. The surfacing GF is shown in the dive stats under computer, or can be taken off the graph, where I got the other GF values. The surfacing GF is a fairly good measure of the decompression stress at the end the dive.

 

[crofrog]

I dive at a GF high of 95, but have become a bit more conservative at my increasing age. I use the SurfGF to adjust my safety stop or last deco stop so that my surfacing GF is no higher than about 80-85.

I don’t understand the widespread use of surface gf in this fashion. Just set your GF high to what you want to get out of the water at.

What your doing is just a “deco” dive with extra steps

 

[scubadada]

I don’t understand the widespread use of surface gf in this fashion. Just set your GF high to what you want to get out of the water at.

What your doing is just a “deco” dive with extra steps

I get a fair amount more bottom time at at GF high of 95 than at 85, but can still make a safe direct ascent to the surface at any time. Many do an adaptive safety stop or pad their deco stop to reduce risk. SurfGF takes away all the guesswork and allows you to surface with whatever safety factor you want. On many/most dives, no additional time is needed, good to know that.

 

[crofrog]

I get a fair amount more bottom time at at GF high of 95 than at 85, but can still make a safe direct ascent to the surface at any time. Many do an adaptive safety stop or pad their deco stop to reduce risk. SurfGF takes away all the guesswork and allows you to surface with whatever safety factor you want. On many/most dives, no additional time is needed, good to know that.

Changing your gradient factors doesn’t magically give you more bottom time. If you set your computer to a gf high of 75 it would just tell you have a stop if you dove the same profile

 

[tursiops]

Just set your GF high to what you want to get out of the water at.

Actually, my GF-high is the worst I want to get out of the water at. Preferably, I'll get out at a lower GF. That's what SurfGF allows me to do.

 

[crofrog]

Actually, my GF-high is the worst I want to get out of the water at. Preferably, I'll get out at a lower GF. That's what SurfGF allows me to do.

Sure but you could just set it to what you want to get out of the water at like 75, and then if you need to get our sooner look at your surface gf and see how much risk you’re going to take on.

You’re doing a bunch of extra work to avoid having your computer tell you you’re in deco.