Cell Checker questions

[doctormike]

Hey,

I dive a JJ, and I'm thinking of getting a cell checker, given the recent discussions about the accuracy of the O2 flush, the question of linearity at the high end of the operational range, etc...

I have been in contact with John from Narked at 90, who was very helpful in describing the Cell Checker vs the Mini-Check. Just wondering if any of the experienced rebreather divers here have any thoughts about this.

The MC is about half the cost of the CC, and I don't see the big downside of using the JJ's electronics to get the data, but maybe I'm missing something. Is the standalone unit much easier to work with? How about other options? I see the DE-OX unit that is even more expensive than the CC, and goes up to 10 bar.

 

[tbone1004]

@Bobby and @DA Aquamaster will hopefully weigh in on this.

having looked at them, there really is no downside other than time to using the mini checker. If anything using the full electronics that will ultimately be reading the cell is arguably better.

Now, Bobby has some information about some cells that behaved at the 1.6ata check on O2, but stopped behaving under extreme pressure.
If you can afford it, I think the De-Ox is worth the extra money. Able to do the 1.6 check with air so you know that it's truly air as well as getting it to behave under extreme pressure. It's negligible over the N90 big checker and is a no brainer for that, but is 2.5x as expensive as the baby one.

 

[JohnnyC]

I’ve got the mini and will check my cells up to a PO2 of 2.0. The spreadsheet that comes with it is pretty good and does all the math for you. I use my Predator for PO2 and mV readings, I put them into the spreadsheet and drive on. No need to overthink it. I might see if John can make me a back cap with SMB’s and a Fischer so I can check with my SF2 head and my Predator at the same time.

If a cell will get me to 2.0 in the pot and it’s linear within a couple percent, IDGAF if it’s linear at 3.8..... Decompression isn’t that precise, and I always extend my shallow O2 stop anyway so a couple percent over the whole range doesn’t worry me, and I don’t dive my PO2 on the bleeding edge. I can afford .8 to actually be 1.0, and I’m never at 1.6 unless i’m at 6m doing deco.

Obviously if this doesn’t correlate to your style of diving, do what best fits to keep you safe. You’d feel pretty damn stupid dying on the loop because you wanted to save a couple bucks on a fancy pressure pot.

Shoot me your e-mail address if you want me to send you the excel files that Narked supplies with their cell checkers so you can see how it works.

 

[rjack321]

The mini check is fine. I would recommend NOT using the volt meter adapter, use your own head to record the mVs. I have found that when the cells are not all capable of delivering a current that you can find induced currents created in the adjacent cable wires. Its best to have them all hooked up and delivering their mV and amps simultaneously.

 

[abnfrog]

I have a de ox Im willing to part with, has all the fittings plus a needle valve , selling my ccr so I wont need it any more , just o2 cleaned

 

[macado]

Shoot me your e-mail address if you want me to send you the excel files that Narked supplies with their cell checkers so you can see how it works.

I don't suppose you're able to share that Excel file? I started making my own to graph linearity with my homemade cell checker but I really liked the one Narced at 90 supplied from what I briefly saw.

 

[billgraham]

My unscientific observation is that sensors usually behave ok when you calibrate/test the rig and then go wonky on the dive. It seems to me that they fail during the dive more often in cold water. Even forgetting about which ones get the gas first, you can see the one that's going away acting differently when you view them all. For the wreck divers, boat vibration and pounding can shake connections loose in your harness and cause a working/not working cell on the dive. As my friend Edd would say, "Everything was going great, until I got in the water..."

 

[Divermikey]

I have constructed a "under $50" cell checker. If someone would be willing to share the Excel program so I can chart them I would be very appreciative.