pp02/deco computer combined or separate?

Mark Chase

I agree.


Personally I use one PP02 and Deco computer combined and a separate bottom /depth gage. Then I use ratio deco to confirm my ascent time.

If the primary cuts out i use my ratio profile and or my buddy to get out.

I dont like units that also run the CCR. If i were in that position id defo have a seporate computer.

ATB

Mark

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Lancer4545

Easy....compare the output of your 4th cell to what you're unit is showing and make a calculated decission if they are too far apart.

Lance

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Nad

PPO2/Deco on board and Deco with variable PO2 separate.
If possible, a passive PO2 control.
Exactly like Ouroboros or Sentinel.

I usually dive with a separate VR3 without 4th cell, just the computer and I change the setpoint exactly as I do with the onboard unit.
There's sometime a couple of minute of difference because of the variation of the PO2 otherwise is perfect.

Nad

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caveseeker7

I like the idea of the deco computer using the actual pO2 in the loop to calculate.
Preferably using all three sensors rather than a single for redundancy.

Having the setpoint controller and deco computer in a single unit is acceptable as long as both works, however, I like the idea of having them separate. My reasoning behind it is that if there is a failure, it's more likely to be one or the other rather than both. That obviously depends on the implementation of the electronics, and the failure.

I liked the basic layout plan Pete Readey had for the PRISM, having the setpoint controller maintaining the setpoint, and adding a separate deco computer that displays the 3 pO2s and uses the same pO2 that is maintained. Separate displays, separate cables, separate power supplies. The planned implementation using fiber optics for transmission of the pO2 data I also liked, as it would have isolated the setpoint controller from any damage to the deco computer, shorts and the like. The HUD display sounded cool, though impractical without a BOV, and changing settings on the computer remained an open issue. A normal handset would have done it for me, and may actually seen the light of day.

For that unit, and the MK series, the Hammerhead secondary with deco is the only option, and a good one in my opinion. You keep the normal setpoint control as it is, with the LED display either HUD or wrist-mounted, and get triple sensor readout with deco calculation, all in a considerably more robust package. Since the solenoid isn't powered by the handset, battery duration shouldn't be an issue.

The same setup would work with other CCRs like the Meg and AP units, or as they use "normal sensors" the Shearwater Pursuit is an alternative option. For those I would probably prefer the Shearwater due to the larger display and smaller case.

The Hammerhead as a complete system is also a good solution with the optional secondary deco , maybe the best. Two handsets, two cables, two batteries, two pO2 displays, two deco computers. One runs the setpoint controller, one the DIVA HUD. That's great redundancy.

And when the head is Juergensen Marine's design (Inspiration replacement and Optima) you even have the option of hooking up a 4th cell and yet another deco computer if you're the belt, suspender and duct tape kind of guy.

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Dsix36

I should have said it this way. It sounds soooo much better than my post. Have some green!

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silent running

Yes Stefan, for integrated deco/SP control the HH does seem to be a very good package. But 2 Handsets with 2 cables, multiple buttons, menus, etc is more than is necessary to get in the water.

Less buttons, less cables, less handets=less clutter, less cables to kink and entangle and seals to leak and less buttons to fail/break.

For me, another benefit of the seperate SP and deco electronics is that it tends to keep my attention more compartmentalized/focused on the physical functioning of the unit, with occaisional checking of my deco computer. This, as opposed to focusing more attention on a display as the source of info/feedback on what the unit is doing at any given moment. The heightened awareness things like sounds and WOB might be helpful in early detection of a small leak or flood. This is not to say that those diving an integrated deco CCR can't have a similar level of awareness, only that the multi function deco computer/display would tend to focus a bit more of the diver's attention on the displays, menus and button pushing.

Also, when something goes wrong with SP only electronics, you can be sure that you will not lose your deco info and of course, if your stand alone deco computer starts misbehaving, you can be certain that it won't interfere with the SP controller's main, basic task of holding SP. Being able to isolate problems/failures quickly and with certainty buys you time and minimizes stress, 2 very important things in a crisis.

I'm sure the future will bring some progress in ECCR electronics, but for the time being, simpler is better, IMHO.

Of course, if I were diving an MCCR, it's a different story and I'd want my deco computer to read off at least one cell as your PO2 will vary over a long dive. But then, at least something like the Shearwater isn't also tasked with firing a solenoid, voting logic and cell tracking. I'd be more inclined to trust it to give good info than 1 computer which has to do everything...

caveseeker7

Andy, I didn't say the Hammerhead was the best solution, but that it may well be.

I like the simplicity of the PRISM/MK electronics, too, as you know. But most all deco computers need button pushing in the first place, and if you want to have redundancy and use two deco computers, you'll have to do it twice. so you'll be pushing buttons anyway, to change high/low setpoints, gases, CC/OC settings etc. Unless you use a Cochran where you'll tap and curse to set it, and then can't use it during bailout. Or just use tables you generate for every dive you do beforehand ... .

Just like have to calibrate twice, pushing buttons or turning screws.

If you really want simple and less failure points, compressed air OC and a basic dive computer with wet switch can't be beat, I'm afraid.

Don't know why setpoint and deco in one should be less trustworthy than having them separately, either someone can design and build good electronics or not. JM has been building setpoint controllers for a long time, longer than SMI I believe. So the experience is there. And implemented integrated deco a long time ago, too, so far I haven't heard of deco accidents piling up within the established range.

And don't think for a second that simple electronics haven't failed, or separate dive computers.

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silent running

Hi Stefan, didn't mean to imply that you were making a declaration. And yes, time will tell with the latest gen HH, could very well be a winner.

I prefer less button pushing rather than more-on/off unit power and 1 push of the HE before I jump, just to make sure it's ready and I'm airborne. Unless I decide to change SP and fly manually, I won't have to touch a button/switch again untill I'm back on the surface. And since I use tables and a bottom timer for back up, no button pushing there either.

Yes, but the difference with the Prism/MKs is any button pushing is done on the surface, with the 2dry cal screw turning done once per trip.

No, I'm sure SP only electronics have failed also, but I would bet that they fail less often because the programing is simpler-less bugs-and they require less processing power-less hardware problems. I'm sure that somebody can and will make a reliable integrated deco/SP unit, maybe the new HH is it and maybe Boris will continue to wrack up hours without major issues.

The future seems to lie with low power display, rechargable comps like the Liquivision. And IR seems like a much better way to feed data as opposed to electrical current traveling down a cable under thousands of pounds of water.

The low power display and rechargeable battery principle of the Liquivision seems to have no drawbacks other than the limited lifespan of the device. I'd like to see it incorporated into an ECCR.

IR does require another level of complication to convert the info to an optical signal and it seems vulnerable to kinking. Not sure I'd take that means of feeding data over the bone simple means of driving an analog 2dry directly off high current sensors... -Andy