Bottom Timer and dive computer

[gcbryan]

(I don't know if I should start this new on the DIR forum or continue it here -- which I shall -- in hopes of getting a "proper" answer.)

PF replied to my question regarding the SPG that it is the only non-redundant piece of equipment the team has. If true (and I believe it is) then, by my understanding of the rule of redundantcy, the SPG is a non-critical device and the redundant information about tank pressure comes from a knowledge of three things, diver's RMV/SAC, time and depth (which is consistent with the training of being able to estimate one's pressure at any time during the dive).

BUT, if the SPG IS a non-critical device, then why would it matter so much that it be of only one kind -- chrome plated brass with glass cover?

I don't believe it is a non-critical device. If there is a leak, knowing SAC/time/depth will not tell you tank pressure.

 

[PerroneFord]

I think it is non-essential in the sense that if gas management is done correctly, it is an unneded resourts. However, it's failure necessitates the dive be terminated. So in that sense, it is really simply a backup to the gas plan.

I think it stands to reason that we use the most reliable SPG we can so that we do not have to prematurely end the dive.

Again, these are just my thoughts.

 

[Peter Guy]

PF -- or anyone else -- Is there any "objective" evidence that a brass SPG is any more, or less, reliable than any other pressure sensing device?

Honest, I'm not trying to pick a fight here -- I'm just trying to determine if this is one of those "This is the way it is" things or if there is actually something factual to back up the "rule"

 

[PerroneFord]

I think that the heavy construction of the brass and glass units are a bit more robust than the plastic units. But of course that really is subjective, at least for me. Perhaps there is some objective evidence one way or the other.

Frankly, I think it comes down to what you're most comfortable with.