Redundant Dive Computer

[caruso]

I know I had gotten into deco a couple of times with the Zoops when my air consumption was greater than it is now. I haven't had a problem since, and my air consumption is better

This sounds backwards.

 

[dmaziuk]

This sounds backwards.

I think for a computer that calculates EAN21 differently from air, that might be just right.

 

[Doby45]

Petrel2 EXT controller for my rebreather is primary, Perdix AI is backup, same GF on both. Rec NDL diving, Perdix AI only.

 

[Graveyarddiver]

I have used 4 different computers.
Shearwayer perdix
Mares quad
Suunto zoop
Dive rite ni tek 3

I’ve been using a combinationsof perdix/mares quad; quad/zoop, and perdix/ni tek and am at my wits end.

I’m buying a second perdix and callingbit a day, the headache of adjusting conservatism, computers putting me in “time out” and the struggle of switching gasses on different computers is not worth the money saved, or the headache of showing a worried, teenage, divemaster that you complete you obligation based on you plan and your primary computer, when you come out and the second is beeping like hell.

 

[TrimixToo]

I have used 4 different computers.
Shearwayer perdix
Mares quad
Suunto zoop
Dive rite ni tek 3

I’ve been using a combinationsof perdix/mares quad; quad/zoop, and perdix/ni tek and am at my wits end.

I’m buying a second perdix and callingbit a day, the headache of adjusting conservatism, computers putting me in “time out” and the struggle of switching gasses on different computers is not worth the money saved, or the headache of showing a worried, teenage, divemaster that you complete you obligation based on you plan and your primary computer, when you come out and the second is beeping like hell.

Heh. I used to routinely "bend" my backup, a recreational computer, on the first dive of the day. I got worried questions from crew about the beeping once in a while when they didn't glance at my other wrist or know what I was doing. The second dive usually had the computer in gauge mode, and ended quietly.

Not just for that reason, two computers that actually know what you're breathing are better than one that does and one that doesn't. But it takes time to get funds to buy all this stuff, so in the meantime, we all do what we can.

 

[Marie13]

Perdix AI primary, Geo 2.0 as backup. I pretty much ignore the Geo. It’s only there if the Perdix goes wonky.

 

[Manatee Diver]

I finally replaced my Suunto Cobra 3 with a second Teric and a SPG.

I got annoyed by my second dive being limited by my Cobra 3 or it going into deco.

 

[Blue Quaker]

Still using 2 Diverite He computers...one on each wrist.

 

[Asheron]

I run a 2 - Petrel EXT 2, what i will do is stagger firmware updates in them so i am never running the same firmware on both in case of a problem.

This is just something i copy from the Power Utility Industry where we stagger some Relay and Equipment Firmware on redundant equipment where the Primary and Backup are the same make and model.

 

[saxman242]

Interesting. I used to dive with a Suunto primary and backup. My partner always has and still continues to do so. After a certain number of back to back dives over a week's time (4-5 a day), the NDL started catching up with him on his Suunto even on the most liberal setting and while I was only on medium for my Perdix. Call me stupid for asking this, but I don't see how setting it to 21% nitrox vs air really changes how liberal or conservative the computer will be...Bueller? Anyone care to explain this one to me?

Thanks.

It has to do with how rounding is done in the computer where only 2 significant figures can be inputted. Suunto has you round down your measured value; for 21.1% or 21.9%, you would input "21%". It then does its calculations based off of 1% + the O2 percentage indicated. In the case of inputting 21% nitrox, it'd be calculating off of 22%.

From the zoop manual:
"The dive computer will not accept fractional percentage values of oxygen concentration. Do not round up fractional percentages. For 43example, 31.8% oxygen should be entered as 31%. Rounding up will cause nitrogen percentages to be understated and will affect decompression calculations. If there is a desire to adjust the com -puter to provide more conservative calculations, use the personal adjustment feature to affect decompression calculations or reduce the PO2 setting to affect oxygen exposure according to the entered O2% and PO2 values.

NOTE As a safety precaution the oxygen calculations in the computer are made with an oxygen percentage of 1% + set O2% ."


Some of the Suuntos seem to have addressed this work around though, as the Zoop manual goes on to say:

"In the NITROX Mode, when set to standard air (21% O2), the instrument can be used as an air dive computer. It remains in this air mode until the O2% setting is adjusted to any other percentage of oxygen (22% - 50%)."

My guess is that that wasn't always the case.