Petrel2, Perdix, or Perdix AI?

[gearbow]

I'm purchasing a new computer right away. I'm Full Cave, Sidemout and cave deco certified. I don't have any plans in the near future to do any rebreather training but a few years ago I didn't think I'd be diving caves either.

I realize if I dive rebreather one of my computers at least will need to be a Petrel but could a Perdix run as second computer or both computers would be monitoring breathing gas in real time?

 

[Fathom044]

Abe Davis, wakulla here. Also NACD side mount. Only oc, no desire to move to cc. That's been 30+ yrs. Recently purchased the Perdix. Hands down, best computer I've ever had!! I've owned the HS explorer and Vr3 for trimix. Lots of others for everything else.

 

[KenGordon]

I'm purchasing a new computer right away. I'm Full Cave, Sidemout and cave deco certified. I don't have any plans in the near future to do any rebreather training but a few years ago I didn't think I'd be diving caves either.

I realize if I dive rebreather one of my computers at least will need to be a Petrel but could a Perdix run as second computer or both computers would be monitoring breathing gas in real time?

Your second computer doesn't need to monitor your exact gas mix. You tell it the setpoint change depths and it implies the ppO2 at a given point in the dive. If you bail out or manually change the setpoint you need to tell it.

You do not really even need a CCR aware computer as the backup. An OC one with mixes set for the depths where you will be spending time will do a fair job.

 

[Tug]

I'd go with either a new perdix or a gently used petrel2/perdix depending on your budget. Most rebreathers these days have a hardwired set point controller/computer so any of the shearwaters would work fine for a secondary computer.

Unless you see a need for AI, I don't really see the point in spending the extra for those features.

 

[tstormdiver]

I stared out as full cave DPV Cave & Multi stage cave, then went to CCR (Hollis) for cave & tech diving. My CCR hard wired controller is a Petrel 1. Both of my back- up computers are Petrel 1's. I got them just before the Petrel 2's came out. I am getting a Perdix AI to use for recreational diving (I instruct), as I prefer the Shearwaters, even for rec diving- ease of reading. As for a back- up computer, only the Petrels (if I am correct) have fischer connectors to Monitor (only) a single O2 cell. Only a hardwired controller will control an eCCR. I use my back-up computers (stand alones) as just that. They run a solid PO2 & change PO2's a programmed depths, to match the set point PO2 change on my controlling computer. The readings aree not exactly the same as controller,... but pretty close, overall,.... & tends to be a bit more conservative. Enough to get me out in a pinch, if the controller goes out for some reason.

 

[kensuf]

Umm, the Petrel, Perdix, or Perdix AI you buy will not be controlling the CCR you buy, so it doesn't matter what you buy today.

If you want the computer you buy today to be able to accurately monitor a CCR, you only have one option, and that's the Petrel 2 EXT. However, the EXT is connected to a CCR via a Fischer cable, and there's a lot that can go wrong there, and it's extra bulk on the device.

BTW, to clear up some confusion, the Fischer port will monitor 3 cells accurately and the normal Shearwater voting logic rules apply. You'll also need to calibrate it separately from your controller. If you're diving a Shearwater driven eCCR (JJ, SF2, Prism2) you'll likely have a Shearwater connected via a digital signal cable called CANBUS, if you're diving an mCCR (KISS Explorer) you'll likely just have a Shearwater connected via a Fischer Port (there's no controller on the mCCR).

IMHO, if I was buying a computer today, and not sure I was going to go CCR in the future, I would just buy a standalone Perdix or Perdix AI. Even without the Fischer port, it can be used with a CCR; it won't monitor your PO2 in real time, but it will track your loading based on what you tell it you're running as a setpoint. In over 350 hours of CCR diving, I have found my stand-alone Petrel running in CCR mode to match very close to what a Shearwater connected to the unit was monitoring.

Last thing I'd like to suggest, is if you're in the North Florida / High Springs area the weekend of May 5th, join us for the CCR workshop at Cave Country Dive Shop. We'll spend a day in a classroom discussing CCR design, theory, and function and that should clear up some of the confusion. Then we'll spend a day diving different units.

Ken

 

[Capt Jim Wyatt]

Go for the Perdix.

 

[Fathom044]

Go for the Perdix.

Again, what he said!

 

[Beau640]

I have a normal perdix not an AI, but has anyone with the AI found the transmitters to jut out/be a pain with side mount or mess up house routing/jut out/stick into the wing in back mount doubles? I was looking at my back mount set up and wondering if the transmitter would be too large to incorporate into the set up without sticking out somewhere

 

[tstormdiver]

I have a normal perdix not an AI, but has anyone with the AI found the transmitters to jut out/be a pain with side mount or mess up house routing/jut out/stick into the wing in back mount doubles? I was looking at my back mount set up and wondering if the transmitter would be too large to incorporate into the set up without sticking out somewhere

It is a standard Oceanic transmitter. They stand out no more than any other AI transmitter. Where the placing of the transmitter is, is dependent on the port configuration of the first stage used.