VR3 and 4° Cell DCS Problems

mapko

Hi everybody,

A couple of months ago I had a DCS Problem using my VR3 with external Ox Cell in my EDO04 loop. VR3 was set to CCR with an internal Set Point to 1.2, the external sensor reading was enabled and Safety Factor was 0.

I made a short dive to 70 meters to waste some trimix I had into my 7 liters tanks. I planned a 10 minutes @ 80 meters dive, but at 70 meters I aborted cause my 2nd computer got creazy , I surfaced with a speed of about 5 m/min and I did few minutes of deco as my VR3 told me. After some minutes (10) from surfacing I got first DCS symptoms to my right elbow, I cured it with 45 min of O2 during my trip back home.

After this bad experience I modify VR3 Safety Factor to 20 and I’m doing more aggressive dives without problem .

I don’t have cardiac forame (I don’t know the correct English world) opened.

A guy told me this is because VR3 PO2 reading frequency is too low, can be true?

Have you heard about VR3 get less conservative with external sensor enabled?



Thanks



Marco

EBT

An obvious question. have you converted the EDO04 to CCR then?

If not, using the VR3 in this way is not going to give you a valid deco.

If so, just ignore me

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mapko

External PO2 reading enabled.

Padowan

Do you still have to set a PPO2 setpoint when using an external cell then?

I would think that a pointless step, the external cell is giving the actual PPO2.

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mapko

I believe that with external PPO2 reading, internal set point has no mining on deco calc. For similar dives but different set point (0.8, 1.4), VR3 gives close deco.



The main question is:

Does anybody experimented a less conservative deco with VR3 and external PPO2 reading enabled?


Marco

Scuba_Vixen

As long as everything's working, it's pretty pointless, but if you see the computer's cell dropping off (or some other issue), for example, and switch over to "no external cell' enabled, ( so you don't generate some errant deco profile) but stay on the loop using other PO2 monitoring and control, (at the original setpoint) the computer has to have a setpoint to reasonably predict deco on.

I don't think I explained that very well, but I think you'll get the idea.


Darlene

Mark Chase

The post is confusing but I am assuming you mean the VR3 is tracking your PP02 and you’re running your unit on something like a 1.2 set point.

Question.. Were you decoing out on Trimix or doing an 02 flush at 6m?

We found decoing out on trimix using the 1.3 set point was just not working and my buddy and I were definitely sub clinical. 15mins at the end of deco on pure 02 sorted this problem out.

Apart from that I can say that I have been involved with a bunch of divers all using the VR3 on 0 safety and doing dives up to 90m in the UK without getting bent. Then suddenly one of them got bent on a 60m dive. Helium bend treated with 02 on the boat so no big problem but it shows how conditions and diver preparation on any given day can result in a bend.

ATB

Mark Chase

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