Back-up computer on a JJ

Back up computer on a JJ

  • Total voters
    38
  • Poll closed .
mick4707

mick4707

Member
I’m thinking about adding a second computer to my JJ. I can see pro’s and con’s to both stand alone and integrated to read the cells. What are other people doing?
 
Why have it reading the cells. You already have a HUD that's telling you your ppo2. Set back up to 1.25 and it'll be very close to matching primary on deco.
 
I use Liquivision x1. Easy to switch to OC of I'm not diving ccr and can change set points in dive if in ccr mode. It doesn't connect to cells, as said already with HUD and predator that's enough. I dive both on vpm/b. nice option is I can choose fast bail out on Liquivision if needed, add gases in dive etc. deco schedules usually match within a minute.
 
why wouldnt you have it track the cells? the more devices as backup the better.

i dont dive a jj, but i run a meg/pf with predator/petrel integrated in both.

i then have an independent x1 tracking as well, set to +1 consv as a 'get out' bailout computer.
 
It's harder to put another connection into the JJ. The setpoint control is good enough I think to run it standalone at 1.25
Dave
 
Paul r s said:
Why have it reading the cells. You already have a HUD that's telling you your ppo2. Set back up to 1.25 and it'll be very close to matching primary on deco.
Click to expand...
I use a standalone Petrel and there's no need to dial the setpoint back.

I have both Shearwaters auto-switch setpoints at the same depths and, with the PO2 on the Petrel set to the same as I'm using on the unit, the deco is identical.
 
Standalone X1 for me.

Most units hold such a tight setpoint I just can't see any reason to run 2 cell integrated computers.

More cables
More holes
More connections

Just keep it simple and have the backup on the wrist ticking away at the required setpoint.

Cheers
Chriso
 
I just use a Vytec on gauge mode and run ratio deco as back up to my JJ. Works fine and is much cheeper.

Another conection to the cells on a JJ is a lot of work and Id say its a negitave step. If you must run another computer just run it stand alone.

ATB

Mark
 
I've run a backup computer on splitters for about 4 years in both an inspo classic and deep pursuit. never had an issue apart from damaging a cable once by snagging it on a wreck.

Apart from providing another level of redundancy, which probably isn't needed, it lets me run 4 cells and any replacement cell goes into position 4 that's not connected to the controller, until I know it's OK.

I'd rather keep a spare cell in the head where I can see it working than in a spares bag and hope it works when I need it.
 
Just don't do it, the unit has been designed so you don't have any reason too.
If you have reached the point where your primary and HUD have failed, it's bailout time.
 
Chriso said:
Standalone X1 for me.

Most units hold such a tight setpoint I just can't see any reason to run 2 cell integrated computers.

More cables
More holes
More connections

Just keep it simple and have the backup on the wrist ticking away at the required setpoint.

Cheers
Chriso
Click to expand...

I agree, that's exactly what I do with my JJ.
 
I've been using OSTC 3 as a back up on my JJ. It's a cracking little computer, although they are having depth sensor problems at the moment. I'm sure, just like Shearwater, it will get sorted.
 
I also use a Stand alone and the Deco is identical most of the time (except for once i bumped my Stand alone and set it back to 0.7 at 72m).
 
The best reasons I can see for going with a connected back-up are that...

If you lose your main computer holding a steady 1.2 manually is not going to be so perfect as with a solenoid, especially following the HUD to control ppO2, so will calculate deco better.

...and...

If you are on your ascent and realise that you just did the whole dive on 0.7 setpoint your backup is probably of very little use if it was on 1.2 or 1.3.

I currently use an un-connected Petrel as my backup, and at the moment I don't consider these enough of a reason to change. If I was buying a new computer I would probably get one with a fischer connection though so that I could hook it up if I wanted.
 
For years I used a stand alone computer diving a Classic KISS. No issues. then I plumbed a Shearwater in, no issues.

With my JJ, I just have a stand alone backup computer/. It is set to 1.3 ALL the time, no need to change it about and it will normally add a couple of inutes to deco.

I dive my JJ as a hybrid, so have no issues with running it from the HUD. If both go down, it's hihgly likely you would havae lost the signal to a backup computer that is blumbed in as well, so it all becomes a bit academic.

Best thing is to say,

'***k it', and go diving...

cheers

Andy
 
Iain3 said:
If you are on your ascent and realise that you just did the whole dive on 0.7 setpoint your backup is probably of very little use if it was on 1.2 or 1.3.
Click to expand...

Thats why we all carry printed backup tables... we "all" do that don't we? :naughty:
 
30mins at 80m on .7
leave bottom change set piont to 1.5 ,

about 8 mins more deco than running the full dive at 1.3

tho you could all ways do the same deco as your buddy if he had changed his set piont when he should have , backup for your backup , lol
 
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