Petrel 2 NDL Planner

[eweingarden]

I recently purchased a Shearwater Petrel 2 and I'm learning the OC Recreational mode right now. My question pertains to the gas that shows on the NDL Plan screen. Within "Select Gas", the active gas is 21%, although 32% is on and 40% off. I next go into "Dive Setup" then "Define Gas" and again I have 21% selected with 32% turned on and 40% off. When I next go into "NDL Planner", the "Gas" is shown as Nx32. I would have expected the "Gas" to show as Air. Can anyone tell my why the "Gas" defaults to Nx32 in the "NDL Planner" when I have 21% selected within "Select Gas" and "Define Gas"? Thanks.

 

[tcoen]

I recently purchased a Shearwater Petrel 2 and I'm learning the OC Recreational mode right now. My question pertains to the gas that shows on the NDL Plan screen. Within "Select Gas", the active gas is 21%, although 32% is on and 40% off. I next go into "Dive Setup" then "Define Gas" and again I have 21% selected with 32% turned on and 40% off. When I next go into "NDL Planner", the "Gas" is shown as Nx32. I would have expected the "Gas" to show as Air. Can anyone tell my why the "Gas" defaults to Nx32 in the "NDL Planner" when I have 21% selected within "Select Gas" and "Define Gas"? Thanks.

Hi eweingarden,

That is the intended operation. If 32% is turned on, the the Petrel expects that you will be using it for predication purposes. The Petrel will never automatically switch the active gas on you, but for forward looking operations, all gases that are on are used.

So in the NDL planner it chooses the best gas of those that are on. At deeper depths the NDL planner will be showing air. During the dive, NDL is always calculated based on the currently active gas. However, once deco stops are needed, the schedule planning will assume that the best gas of the depth will be used.

As a rule for Shearwater products, if you are not planning to use a gas on a dive, make sure that gas is OFF before starting the dive.

Best regards,
Tyler Coen
Shearwater Research

 

[eweingarden]

Thank you for the concise reply.