[rEvo] Petrel 2 controller intermittently shows 0.0/low PPO2 for all sensors

[mr_v]

I have seen it recommended to coat them in Christo Lube. Problem is it dries out, and it is conductive. So you have to balance water protection with shorting your cells. Haven't found any dielectric grease that is compatible with a breathing environment.

All surfaces must be completely clean and dry. Before applying silicone sealant.

Cover the backend of the connector to make a seal around the wires. Also put some Christo Lube into the holes on the side where the pins clip in. This allows the air inside to compress, but shouldn't short the wires. Be careful not to get any on the connector face. Put a thin film of silicone sealant on the face and plug it in. Don't dive it until the silicone is dry (24 hours).

This is food grade 100% silicone sealant. Do not use silicone grease as this is a 100% oxygen environment. Let the sealant dry completely before use.

I have the KISS splitter board so mine plug in to it, but same concept. I have cut out "o-rings" from old silicone wrist seals and placed around the board receptacle where the cells plug in to seal the back of the cells. This allows me to change cells on the fly without waiting for silicone sealant to dry. The board is already waterproof from the factory.

This has greatly increased the stability of readings during long dives/trips. I no longer expect the cells to get more erratic as time goes on during a trip. They typically get more stable after day one then stay that way for the entire trip.

@J-Vo, well thank you the tip. I followed your advice - what a difference! I got a very stable cell performance after 2 hours on the loop. Will do more tests over the weekend!

 

[Dsix36]

I am late to this party and do not want to red all the posts so this may have already been said. I have to assume that your unit has some sort of cell isolation and that makes a single connection or short very unlikely to effect all 3 cell readings. Basically the only thing that can effect all 3 cells is the common ground wire in the cable. If that wire is broken inside the insulation it may very well still make connection and only act up intermittently. I have had this happen with more than one cable over the years.

 

[mr_v]

I am late to this party and do not want to red all the posts so this may have already been said. I have to assume that your unit has some sort of cell isolation and that makes a single connection or short very unlikely to effect all 3 cell readings. Basically the only thing that can effect all 3 cells is the common ground wire in the cable. If that wire is broken inside the insulation it may very well still make connection and only act up intermittently. I have had this happen with more than one cable over the years.

Yep, all been resolved and fixed.

I have a custom cable batch coming in to simplify field repairs, and J-Vo's tips seem to have resolved the intermittent moisture issues in Molex connectors.

 

[LFMarm]

I was able to complete the built and test both the sensors I am currently using and all the spares. Sharing some of the results for anybody interested:

(A) Here are 3 sensors in use. They all have good linear behavior, 1 and 2 lower deviations than 3 but all well in the ±1% range that I consider safe for diving.

(B) Here are 1 sensor in use and 2 spares. They are all in the accepted ±2% range of linearity but start to show some signs of aging / deviation at higher pO2. I would still consider these usable in case of need.

(C) Here are 2 old sensors. They show significant non-linearity and would be dangerous to use (only keeping them around for testing but would never dive with them).

I plan to test sensors every few months to monitor their aging and be ready to swap them as soon as they show signs of non-linearity.

Thanks everyone who helped me putting this together.