Help with simple deco algorithm project

[scubadada]

Thanks @Jay

I initially thought iterations of Buhlmann ZH-L16C would be the same. The experience with my Nitek Q and Teric proved that to be incorrect. Actually, it appears that each is a little, or more, different that the others. I would love to see Buhlmann computers put through a standard repetitive dive routine like the ScubaLab test. Of course, then I would like to see how they handle light deco, then.....

 

[stepfen]

Hmmm... I tried to help using my divecomputer.eu but apparently this dive computer's planner doesn't give you NDL times for a given depth.

Instead the planner works this way: you give it depth and time and gives you a dive table (deco depth and times) if based on the inputs your dive is a deco one - otherwise nothing.

I didn't know so far because I've been using subsurface for such calculations (NDL at given depth).
I'll have to triple check this because I just got it few weeks ago and it might be hidden somewhere, but so far I can't find it. Nothing is mentioned in the manual either.

 

[scubadada]

Hi @stepfen

I believe you are correct, @LandonL sent me a PM that the Deep 6/divecomputer.eu did not have an NDL planner.

 

[stepfen]

Hi @stepfen

I believe you are correct, @LandonL sent me a PM that the Deep 6/divecomputer.eu did not have an NDL planner.

Good to have a confirmation. Something to add in my suggestions/feature requests e-mail I am preparing for them.

 

[scubadada]

Not related to my initial question, but does anyone know why the NDLs vary a little when run on the same computer over various times? I first noticed this with my Nitek Q, it applies to my Teric also.

I just ran NDLs on my Teric for air, 32%, and 36%, once per day, for four days in a row. NDLs varied from between 0 and 3 minutes, depending on depth and mix. The biggest differences were at lower depths, where the NDLs were longer. These were all clean, 1st dive, at a GF high of 95.

Try it yourself, I'd be interested in what you find.

 

[FreeFlyFreak]

Not related to my initial question, but does anyone know why the NDLs vary a little when run on the same computer over various times? I first noticed this with my Nitek Q, it applies to my Teric also.

I just ran NDLs on my Teric for air, 32%, and 36%, once per day, for four days in a row. NDLs varied from between 0 and 3 minutes, depending on depth and mix. The biggest differences were at lower depths, where the NDLs were longer. These were all clean, 1st dive, at a GF high of 95.

Try it yourself, I'd be interested in what you find.

Probably related to Atmospheric pressure at the time of testing. (surface pressure)

Lower surface pressure shorter NDL's, like being at altitude.
Higher surface pressure longer NDL's

 

[scubadada]

Probably related to Atmospheric pressure at the time of testing. (surface pressure)

Lower surface pressure shorter NDL's, like being at altitude.
Higher surface pressure longer NDL's

Thanks, I thought of that. When I was using my Nitek Q, I did not know the atmospheric pressure. With the Teric, I know the atmospheric pressure and this argument does not appear to hold up. I will record the atmospheric pressure with the NDLs for future measurements to make sure.

I don't know how Dive Rite and Shearwater adjust NDL for atmospheric pressure, perhaps continuously? Oceanic's 1st change is at 3,000 feet, that would be about a 10% reduction in atmospheric pressure

 

[FreeFlyFreak]

Thanks, I thought of that. When I was using my Nitek Q, I did not know the atmospheric pressure. With the Teric, I know the atmospheric pressure and this argument does not appear to hold up. I will record the atmospheric pressure with the NDLs for future measurements to make sure.

I don't know how Dive Rite and Shearwater adjust NDL for atmospheric pressure, perhaps continuously? Oceanic's 1st change is at 3,000 feet, that would be about a 10% reduction in atmospheric pressure

If atmospheric pressure doesnt correlate then I'm out of ideas.
I presume the tissues were clear in the computers

 

[scubadada]

If atmospheric pressure doesnt correlate then I'm out of ideas.
I presume the tissues were clear in the computers

Yes, clean, 1st dive. I'll do some more "research"

 

[scubadada]

Hi @FreeFlyFreak

I apologize, it turns out you were correct, The minor variations in NDL seen in the planner are due to differences in barometric pressure. I made additional observations, making careful note of the pressure. Due to a recent storm, I had a reasonably broad range from 986-1006 mbar. The shortest NDLs were at the lowest barometric pressure and the longest were at the highest pressure. There was a nice gradation between the two. I contacted Shearwater technical assistance, they confirmed this to be the case. Here is a summary table of my recent observations.

Thanks, and good diving,

Craig