Shearwater Perdix AI

[savsuds]

So does the Hollis do anything to account for the ascent + stops or does it leave that up to you to factor into your reserve? It sounds like it just tells you when you reach your preset reserve pressure only?

It leaves it up to you. I generally leave 1000 PSI for my ascent/stop. I change the value depending upon my planned dive.

I always dive with a pony for those oh **** moments.

 

[RayfromTX]

I don't know much about scuba diving but I have years of judging correctly when a socially challenged person should be ignored rather than encouraged. I wish I could justify trying one of these new wrist gadgets. I'll probably regret ordering one for 150$ instead but it is definitely a cheaper roll of the dice at this point in my diving progression. It is cool to see where it has gotten in the last few decades and there is still a long way to go to integrate the technologies that already exist into scubatech. The logging programs are even further from where they should be but that is another topic.

 

[Joneill]

@Joneill,

RMV by definition is a diver's personal breathing rate of volume per minute at one atmosphere absolute (1 ATA at the surface): It does not change with different tank sizes and is independent of cylinder size. The only way it varies is with hard physical exertion resulting in an increased breathing rate, or an easy relaxed activity state that results in a lesser breathing rate. Also pressure SAC rates are not transferable to different tank sizes. (See p.16 of the Shearwater Perdix AI user's manual).

By convention you first determine and then pick one RMV value -either relaxed activity or exertion- and evaluate it over different tank sizes to give you a different pressure SAC rate for each particular cylinder -->NOT pick one SAC rate evaluated over different cylinders to give different RMV's because this contradicts the definitions above which state that RMV does not change over tank sizes, and SAC rates are not transferable to other tank sizes.

Therefore, it is incorrect to say:
This is like claiming:

• 25 psi/min from an AL80 is a lower RMV than 25psi/min in Double AL80's. If your SAC is 25 psi/min and you're using an AL80, then you are consuming a RMV 0.64 cuft per minute; so if you use 25psi/min in Double AL80's you are consuming a RMV 1.28 cuft per minute?? No! This would imply your breathing rate doubles when you use double manifolded tanks. This is obviously not true by definition!

Properly applied per definition and convention:

For an exertion RMV of 1cf/min per ATA:

Pressure SAC rate for an AL80 is 1cf/min divided-by 80cf/3000psi equals 37.5psi/min.
Pressure SAC rate for Double 80's is 1cf/min divided-by 160cf/3000psi equals 18.7psi/min.

Clearly, it makes more sense that Double AL80's last twice as long and have a pressure that moves at a slower rate per minute, which is half of a single tank AL80 pressure rate per minute, because the Doubles have twice the volume capacity for a given RMV of 1cf/min.

As proof, for any constant breathing rate evaluated over an AL80 and then over Double manifolded AL80's: A Perdix AI can directly measure this, and will always show this 1:2 ratio of Double AL80's vs Single AL80 pressure SAC rates.

---->Try it out for yourself!

I give up!

 

[Joneill]

Double post - forum issues, it appears...

 

[buddhasummer]

I think there's bigger issues afoot in this thread than just forum issues.

 

[luscioman]

I think a good note is too see how many Petroleum and Perdix are for sale in the classifieds. It seems like every other post. I assume they are selling to get the AI.

 

[Compressor]

I dive with a group of GUE divers (nicest people you would ever want to meet). They do not use AI but have no problem with my using it. I might be wrong but I don't think GUE would object to AI for recreational dives so long as the SPG was also in place on left waist D-ring. I do this.

I dive with GUE folks sometimes. They use AI. When they take a GUE class, they take it off.

 

[buddhasummer]

I'm missed the release of the "Petroleum" was that before or after the Perdix...

 

[WarrenZ]

If a Petrel plunges hard enough into the mud in the bottom of the bay it can turn into Petroleum eventually.

 

[chillyinCanada]

I only recently learned that Shearwater provided a diver recall display on their Petrel and NERD computers for the Diver6 system. Unfortunately, the receiver for that system is an enormous tube installed on the back of the tank.
Diver6 - System Hardware

I would love to see a collab between Desert Star and Shearwater on a compact homing receiver to find your boat or buddy (although that might cross too far out of tech computer territory and alienate the fundamentalist conservative base )

Yes, get an EPIRB equivalent in there too!