Franken-Rig PP02 Measurement

 

PP02 measurement has been the bane of home-builders since we began to build rebreathers.

I decided to use an off-the-shelf system to begin with, and will add a 3-sensor system later.

 

The first issue in converting to CCR is to add a PP02 measurement system. Taking the path of least resistance, I took a few minutes to add a Draeger Oxyguage port and now use an Oxyguage as the PP02 measurement system. I'll probably add a 3 sensor PP02 system shortly, but will make the sensor probe to fit this same port. Actually, I'd feel pretty comfortable with the single sensor, just doing a manual diluent flush every now and then, and I do like the audible alarm feature. But the new system will probably have a Heads-Up LED display and will be even better. Stay tuned!

 

With the Oxygauge port added, the rig is not a lot different that it was to begin with, only we can now measure loop PP02 and press on with the balance of the work.

 

That was easy, wasn't it? I told you the whole thing took 3 hours to build! How long did you expect me to fool with adding PP02 measurement?

WARNING: Nobody in their right mind would rely only on a single sensor PP02 measurement system for complete control of a CCR.

Strategy for survival on ALL CCR's: You ought to KNOW the PP02 of the diluent at any depth where you plan to use a system like this, and do frequent diluent flushes to confirm the reliability of the sensor. Plus you ought to be aware that if the auto-add valve triggers without a depth increase, it means that you have used-up more 02 volume than has been replaced by the add-system. If the auto-add valve triggers and you have not descended deeper in the last minute, you DO need to investigate the PP02 and probably need to manually add more 02 to the loop. If you understand the constant loop volume method of 02 addition (a bailout mode for use with electronically controlled CCR's) you know what I am talking about.

If this is all Greek, it means one thing and one thing only: YOU SHOULD NOT BE DIVING WITH OR MAKING A SYSTEM LIKE THIS. If in doubt, seek instruction from someone who KNOWS what he's talking about! People like that are few and far between, so remember: It's YOUR ass out there!

Just as a note: I'll be adding a redundant PP02 measurement system as soon as I can get time to do so. If you copy this rig, you ought to do likewise.

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