ANOTHER ALTERNATIVE FOR REBREATHER SENSORS

[rock92]

another two hours today, no issues.

 

[Dusty123]

Well mines not looking good so far calibrated 46ma in 100% 9ma at 10% just like my others and was consitently 0.2po2 off the others when dived. Got out of the water and put 100% in and it was reading 38 ma the other cells still reading what I calibrated at 46ma. I know someone with two ast cells and not having issues.

 

[telemonster]

Resurrecting a zombie thread, since now I have a good answer to Ken's question! No idea when the JJ Vandagraph sensors will be available, and neither does the JJ manufacturer or the US distributor. DGX has no AI cells either.

SO, I was wondering if anyone had any real world experience with OxyCheq / AST cells since we last discussed this in December. It looks like I can get some of them.

Fairly new CCR diver, but an electronics geek. Finished Prism2 cert last summer, I am at maybe 30 hours now.

My original DGX (AI?) were due for replacement so I picked up a set of 3 from OxyCheq.

First, no born on / death by date printed on the label unlike the DGX ones. This could be implemented in the assembly line with a thermal ribbon based label printer.

Second, the DGX ones I bought last year had closer readings out of the box and during their lifespan with regards to mV readings. One of the three OxyCheq ones I received sits down at 8.8mV and the other two are above 10mV. Per mfgr spec on my Hollis Prism 2, above 8.3 is within spec @ 21% at sea level. But it made me wonder a bit about the build consistency of these. I haven't re-seated the Molex connectors to make sure it isn't line loss, but I think I swapped the connectors to the sensors around around and verified the lower reading stayed with the one cell.

I calibrated it with 99%, swapped gas out for air and things settled back to .21 on the dot.

I do recall the DGX ones had some sort of testing output printout from the factory as well, to demonstrate some kind of QA process during mfgr. Nothing like that was included with the cells sold by OxyCheq.

I have mostly been doing shallow dives at Lake Phoenix this summer, and on one of them messing around I was trying to check for current limiting and was having a difficult time getting the ppo2 high while sitting at 20ft freshwater. But can't blame it on the sensors, it might of been residual air in the loop. Will try again this weekend. It has me thinking about building a DIY pressure pot and cable extender though.

Case build quality seems fine.

Shipping happened pretty quick via USPS.

Good communications.

I emailed and suggested the born on date on the decal and got a response right after I received them.

Anyone else?

 

[beester]

Also interested... just received 3 AST cells for my JJ as well. Always used Vandergraphs. Not diving until next Tuesday, but will check as well... hopefully they don't act up, because I have no spares and on a full week of tech diving.

 

[Dusty123]

Talked to several divers using them they seem to have problems with humidity or temp. They have the same issue i have they are linear when you calibrate but not when you dive them. Then wait 24hrs and let them dry out and are back to being linear again. Checked them in a cell checker and when they are room temp and dry no issues so not sure what the problem is

 

[JahJahwarrior]

Shearwater computers log the mv reported at each reading, it seems like it would be relatively easy to fill your tray with a variety of cells, take them for a dive, then export that data so someone smarter than me can statistically compare the readings from each cell in real life, and give us some value for reliability, linearity, etc.

I'm a little alarmed about the inconsistent start voltages and the lack of test data with each cell, and I think I will go back to AI when they are in good stock, but I don't have any data that shows the AST cell has any issues at all and in my limited experience it seems ok.

 

[rock92]

Shearwater computers log the mv reported at each reading, it seems like it would be relatively easy to fill your tray with a variety of cells, take them for a dive, then export that data so someone smarter than me can statistically compare the readings from each cell in real life, and give us some value for reliability, linearity, etc.

I'm a little alarmed about the inconsistent start voltages and the lack of test data with each cell, and I think I will go back to AI when they are in good stock, but I don't have any data that shows the AST cell has any issues at all and in my limited experience it seems ok.

not quite as elaborate as your parameters, but to your point. here is the download of my last two dives where i have two AI cells and one AST cell. both of these dives where close to an hour each and in 50* water with depths down to around 90'

 

[rock92]

Anyone have any additional data, feedback, or inputs? I am a couple of weeks away from putting the second AST cell in the mix.

 

[Dusty123]

Out of the four ast cells I have used one is in agreement with my vandagraph cells. One cell wont stay linear (output drops to 38mv )when dived but check out ok after a dive and drying out. I had one cell that was 7.2mv in air and 32mv in o2, dived fine then died and wont calibrate. I have another that was particularly strong at 12mv in air 60mv in o2 (new been out of bag a few days)after diving output dropped and is at 7.8mv in air.

 

[rock92]

wow, that's all over the place. fortunately, the one AST cell has been right in alignment with the two AI cells on mine. I'm diving the O2ptima. what about you @Dusty123 ?