Calibration Question

diverrob · 14th July 2008, 04:12

I have new AI cells in my Evo and have been having trouble with the cells when diving in warm H2O (25C). I do all of the pre-dive checks and calibrate just prior to diving and all goes well. During the dive around the 35-45min mark I get a cell warning when I manually inject O2 and then they are all reading a bit off from each other. I am diving in 20-40FSW so I decided to surface on one of the dives and turn off the set and re-calibrate. After a successfully calibration I resume the dive and have no further problems. I did a dill flush and all cells were spot on and then assessed to 20fsw and did an O2 flush and again all of the cells were spot on. What I suspect is that the cells were calibrated when they were dry and after they get some moisture in them they start to go to shit. I was hoping to get some input from others who may have had similar problems. I don't plan to ever get AI cells again but I have 2.5 weeks here and want to continue to dive when I can get away from work. Any input would be appreciated, thanks

Rob

***ScubaDadMiami*** · 14th July 2008, 04:19

Same issue with my cells here in South Florida. If I first calibrate at home and then take the unit from my air conditioned home to my air conditioned car and then take out into the heat on the dive boat, if I check the reading after a while, it is already off even before starting the dive. Recalibrate before the dive, dive for an hour in the warm water, and it is off again. Calibrate after the first dive, and it holds after that.

I find that if I let the rebreather stay out in the hot weather for long enough (at least a few hours) before doing the first calibration, I am not having the issue. Not always exactly convenient.

diverrob · 14th July 2008, 08:55

Quote: (Originally Posted by ScubaDadMiami)

Recalibrate before the dive, dive for an hour in the warm water, and it is off again. Calibrate after the first dive, and it holds after that.

I find that if I let the rebreather stay out in the hot weather for long enough (at least a few hours) before doing the first calibration, I am not having the issue. Not always exactly convenient.

Thanks for that, I did have the same thing happen during a dive charter. The first dive the cells were all messed up and the second one they were great. My buddy also had the same problems with his meg

**wedivebc** · 14th July 2008, 12:49

I had a set of cells that seemed overly sensitive to moisture. I found if I calibrated between dives they held calibration better than if they were dry calibrated.

diverrob · 14th July 2008, 17:38

Quote: (Originally Posted by wedivebc)

I had a set of cells that seemed overly sensitive to moisture. I found if I calibrated between dives they held calibration better than if they were dry calibrated.

were they AI cells??

**wedivebc** · 14th July 2008, 19:58

Quote: (Originally Posted by diverrob)

were they AI cells??

No teledyne but I bet they share many characteristics

**Dsix36** · 14th July 2008, 20:30

I have had the same problem with both AI & Tele sensors. I no longer keep the sensors inside the house with AC, they stay in the garage now. The problem has not gone away completely, but it seems to be working out good enough for a 3 hr dive with no problems.

mempilot · 15th July 2008, 00:56

Quote: (Originally Posted by Dsix36)

I no longer keep the sensors inside the house with AC, they stay in the garage now.

Don,

Were you sleeping with your sensors in bed next to you, or did you have one of those little hamster cages on the night stand for them?

Put'n em out in the garage with the dog now are ya?

I started a thread about climate controlled calibrations vs. real world. I truly believe it is the reason for many of the cell drop off issues I have.

scuba_phil · 15th July 2008, 04:11

Rob,
Here is my experience. Meg came with TD OS, settled out after 2 weeks, remained stable for the next year. Changed them out after 13 months (1 year rule) with AI OS. I bought 4. They settled out after 2 weeks and remained stable for 4 months, then one failed. I then put in the redundant unit and it lasted 2 weeks. I did notice that the replacement sensor was very sensitive to moisture before it died. Currently, I have 2 AIs and 1 old TD in my unit. The old TD still puts out 10.2 mv in air. I will only buy the TD OS in the future.

Phil

diverrob · 15th July 2008, 08:59

Quote: (Originally Posted by scuba_phil)

Rob,
Here is my experience. Meg came with TD OS, settled out after 2 weeks, remained stable for the next year. Changed them out after 13 months (1 year rule) with AI OS. I bought 4. They settled out after 2 weeks and remained stable for 4 months, then one failed. I then put in the redundant unit and it lasted 2 weeks. I did notice that the replacement sensor was very sensitive to moisture before it died. Currently, I have 2 AIs and 1 old TD in my unit. The old TD still puts out 10.2 mv in air. I will only buy the TD OS in the future.

Phil

Thanks for that I am just trying to get through the next few weeks until I get back home. They did not seem to mind the cold H2O I normally dive in. I will be replacing them with the TD ones as well in the future

Rob

14th July 2008, 04:12	#1 (permalink)
diverrob The Evolution of Diving Current Rebreather/s: Evolution Other SCR Other Rebreather/s: Not Bought Yet Other SCR Join Date: May 2005 Location: Victoria BC Canada Posts: 329	Calibration Question I have new AI cells in my Evo and have been having trouble with the cells when diving in warm H2O (25C). I do all of the pre-dive checks and calibrate just prior to diving and all goes well. During the dive around the 35-45min mark I get a cell warning when I manually inject O2 and then they are all reading a bit off from each other. I am diving in 20-40FSW so I decided to surface on one of the dives and turn off the set and re-calibrate. After a successfully calibration I resume the dive and have no further problems. I did a dill flush and all cells were spot on and then assessed to 20fsw and did an O2 flush and again all of the cells were spot on. What I suspect is that the cells were calibrated when they were dry and after they get some moisture in them they start to go to shit. I was hoping to get some input from others who may have had similar problems. I don't plan to ever get AI cells again but I have 2.5 weeks here and want to continue to dive when I can get away from work. Any input would be appreciated, thanks Rob
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14th July 2008, 04:19	#2 (permalink)
*ScubaDadMiami* Moderator Current Rebreather/s: Optima Other Rebreather/s: Join Date: Sep 2005 Location: Florida, USA Posts: 2,076	Re: Calibration Question Same issue with my cells here in South Florida. If I first calibrate at home and then take the unit from my air conditioned home to my air conditioned car and then take out into the heat on the dive boat, if I check the reading after a while, it is already off even before starting the dive. Recalibrate before the dive, dive for an hour in the warm water, and it is off again. Calibrate after the first dive, and it holds after that. I find that if I let the rebreather stay out in the hot weather for long enough (at least a few hours) before doing the first calibration, I am not having the issue. Not always exactly convenient. __________________ Howard Packer IANTD CCR Instructor Miami Beach, Florida CCRDiveTraining.com
(Online)

14th July 2008, 08:55	#3 (permalink)
diverrob The Evolution of Diving Current Rebreather/s: Evolution Other SCR Other Rebreather/s: Not Bought Yet Other SCR Join Date: May 2005 Location: Victoria BC Canada Posts: 329	Re: Calibration Question Quote: (Originally Posted by ScubaDadMiami) Recalibrate before the dive, dive for an hour in the warm water, and it is off again. Calibrate after the first dive, and it holds after that. I find that if I let the rebreather stay out in the hot weather for long enough (at least a few hours) before doing the first calibration, I am not having the issue. Not always exactly convenient. Thanks for that, I did have the same thing happen during a dive charter. The first dive the cells were all messed up and the second one they were great. My buddy also had the same problems with his meg
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14th July 2008, 12:49	#4 (permalink)
wedivebc FIGJAM Current Rebreather/s: Megalodon Other CCR Other Rebreather/s: Not Bought Yet Inspiration Classic Sport Kiss Other CCR Join Date: Feb 2005 Location: Vancouver Island BC Canada Posts: 1,411	Re: Calibration Question I had a set of cells that seemed overly sensitive to moisture. I found if I calibrated between dives they held calibration better than if they were dry calibrated. __________________ Cheers, Dave.... Man is the only animal burdened with the knowledge he will eventually die
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14th July 2008, 17:38	#5 (permalink)
diverrob The Evolution of Diving Current Rebreather/s: Evolution Other SCR Other Rebreather/s: Not Bought Yet Other SCR Join Date: May 2005 Location: Victoria BC Canada Posts: 329	Re: Calibration Question Quote: (Originally Posted by wedivebc) I had a set of cells that seemed overly sensitive to moisture. I found if I calibrated between dives they held calibration better than if they were dry calibrated. were they AI cells??
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14th July 2008, 19:58	#6 (permalink)
wedivebc FIGJAM Current Rebreather/s: Megalodon Other CCR Other Rebreather/s: Not Bought Yet Inspiration Classic Sport Kiss Other CCR Join Date: Feb 2005 Location: Vancouver Island BC Canada Posts: 1,411	Re: Calibration Question Quote: (Originally Posted by diverrob) were they AI cells?? No teledyne but I bet they share many characteristics __________________ Cheers, Dave.... Man is the only animal burdened with the knowledge he will eventually die
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14th July 2008, 20:30	#7 (permalink)
Dsix36 Going Down? Current Rebreather/s: Optima Other Rebreather/s: Join Date: Aug 2007 Location: Deerfield Beach, Florida Posts: 976	Re: Calibration Question I have had the same problem with both AI & Tele sensors. I no longer keep the sensors inside the house with AC, they stay in the garage now. The problem has not gone away completely, but it seems to be working out good enough for a 3 hr dive with no problems. __________________ THE MORE THAT I LEARN, THE MORE THAT I STILL NEED TO LEARN!!!!!!
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15th July 2008, 00:56	#8 (permalink)
mempilot What is this..terrafirma? Current Rebreather/s: Megalodon Other Rebreather/s: Megalodon Join Date: Aug 2006 Location: Ft. Lauderdale Posts: 1,269	Re: Calibration Question Quote: (Originally Posted by Dsix36) I no longer keep the sensors inside the house with AC, they stay in the garage now. Don, Were you sleeping with your sensors in bed next to you, or did you have one of those little hamster cages on the night stand for them? Put'n em out in the garage with the dog now are ya? I started a thread about climate controlled calibrations vs. real world. I truly believe it is the reason for many of the cell drop off issues I have. __________________ MEM "Da Pilot" Black holes are where God divided by zero. "If at first you don't succeed, don't dive silent." "Would you mind not shooting at the thermo-nuclear weapons." ~ Vic Deakins "Donkey's kill more people annually than plane crashes."
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15th July 2008, 04:11	#9 (permalink)
scuba_phil New Member Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Jun 2006 Location: Orange County, CA Posts: 33	Re: Calibration Question Rob, Here is my experience. Meg came with TD OS, settled out after 2 weeks, remained stable for the next year. Changed them out after 13 months (1 year rule) with AI OS. I bought 4. They settled out after 2 weeks and remained stable for 4 months, then one failed. I then put in the redundant unit and it lasted 2 weeks. I did notice that the replacement sensor was very sensitive to moisture before it died. Currently, I have 2 AIs and 1 old TD in my unit. The old TD still puts out 10.2 mv in air. I will only buy the TD OS in the future. Phil
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15th July 2008, 08:59	#10 (permalink)
diverrob The Evolution of Diving Current Rebreather/s: Evolution Other SCR Other Rebreather/s: Not Bought Yet Other SCR Join Date: May 2005 Location: Victoria BC Canada Posts: 329	Re: Calibration Question Quote: (Originally Posted by scuba_phil) Rob, Here is my experience. Meg came with TD OS, settled out after 2 weeks, remained stable for the next year. Changed them out after 13 months (1 year rule) with AI OS. I bought 4. They settled out after 2 weeks and remained stable for 4 months, then one failed. I then put in the redundant unit and it lasted 2 weeks. I did notice that the replacement sensor was very sensitive to moisture before it died. Currently, I have 2 AIs and 1 old TD in my unit. The old TD still puts out 10.2 mv in air. I will only buy the TD OS in the future. Phil Thanks for that I am just trying to get through the next few weeks until I get back home. They did not seem to mind the cold H2O I normally dive in. I will be replacing them with the TD ones as well in the future Rob
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