MV reading on cell

**Dsix36** · 9th February 2008, 01:02

Quote: (Originally Posted by Gilles)

The easier and more reliable way to tell is to observe where your PO2 reading falls to in air after you have done your oxygen cal (I'm assuming your system uses a 1-point calibration protocol). If it falls back to somewhere substantially above .21, then you a have a more positive indication of cell failure. I'll only elaborate further if requested.

I agree with this totally!

Quote: (Originally Posted by Gilles)

The above mentioned 6mv change can be due to a ~1.2mV (6/4.8) change in the ambient mV of your cell, easily caused by dampness, or other.

It should have the same effect on all 3 cells then.

Quote: (Originally Posted by Gilles)

mV readings are only of any use in 2-point cal systems. They are redundant in 1-point cal systems, and 1-point cal systems are a more simple and superior method of controller calibration, IMHO.

I really agree with most of this. I am just stating what I was taught.

Gilles · 9th February 2008, 05:00

Quote: (Originally Posted by Dsix36)

It should have the same effect on all 3 cells then.

No because the effect of moisture on cells is rather random (in my observations). One thing is certain is that humidity causes a mV attenuation across its response function, causing an "current-limitation-like" effect.

Personally, my preference is to perform post-dive calibrations (when cells are damp from usage), and only re-cal if any indication of cells changing. My argument

here is that it may be better to calibrate the cells in the state that they are normally operating in. I have observed much better and prolonged good behaviours this way

.

edit: PLEASE ENSURE CELLS ARE OPERATING AS EXPECTED WITH AIR AND KNOWN PURITY OF OXYGEN AND ALSO PERFORM IN-WATER TESTS.

Quote:

I really agree with most of this. I am just stating what I was taught.

Sometimes, important things are learned on the internet more effectively than during instruction

. In my own training experience, I/we were only taught the process of cell calibration, and very little about the purpose and/or how the whole cal process works. This has taken a little research on my own part.

**Dsix36** · 10th February 2008, 21:11

Quote: (Originally Posted by Gilles)

No because the effect of moisture on cells is rather random (in my observations). One thing is certain is that humidity causes a mV attenuation across its response function, causing an "current-limitation-like" effect.

Personally, my preference is to perform post-dive calibrations (when cells are damp from usage), and only re-cal if any indication of cells changing. My argument

here is that it may be better to calibrate the cells in the state that they are normally operating in. I have observed much better and prolonged good behaviours this way

.

edit: PLEASE ENSURE CELLS ARE OPERATING AS EXPECTED WITH AIR AND KNOWN PURITY OF OXYGEN AND ALSO PERFORM IN-WATER TESTS.

Now I understand what you mean! I always cal about a week after diving and all sensors are dryed out. I have noticed some sensor drift during dives from moisture so this makes sense to do the cal post dive and then just check it pre dive.

I will experiment with this procedure and see how it works for me. Thanks for the patience with me

9th February 2008, 01:02	#31 (permalink)
Dsix36 Going Down? Current Rebreather/s: Optima Other Rebreather/s: Join Date: Aug 2007 Location: florida Posts: 857	Re: MV reading on cell Quote: (Originally Posted by Gilles) The easier and more reliable way to tell is to observe where your PO2 reading falls to in air after you have done your oxygen cal (I'm assuming your system uses a 1-point calibration protocol). If it falls back to somewhere substantially above .21, then you a have a more positive indication of cell failure. I'll only elaborate further if requested. I agree with this totally! Quote: (Originally Posted by Gilles) The above mentioned 6mv change can be due to a ~1.2mV (6/4.8) change in the ambient mV of your cell, easily caused by dampness, or other. It should have the same effect on all 3 cells then. Quote: (Originally Posted by Gilles) mV readings are only of any use in 2-point cal systems. They are redundant in 1-point cal systems, and 1-point cal systems are a more simple and superior method of controller calibration, IMHO. I really agree with most of this. I am just stating what I was taught. __________________ THE MORE THAT I LEARN, THE MORE THAT I STILL NEED TO LEARN!!!!!!
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9th February 2008, 05:00	#32 (permalink)
Gilles Worship the feminine Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Sep 2005 Location: Den Haag (Netherlands) Posts: 761	Re: MV reading on cell Quote: (Originally Posted by Dsix36) It should have the same effect on all 3 cells then. No because the effect of moisture on cells is rather random (in my observations). One thing is certain is that humidity causes a mV attenuation across its response function, causing an "current-limitation-like" effect. Personally, my preference is to perform post-dive calibrations (when cells are damp from usage), and only re-cal if any indication of cells changing. My argument here is that it may be better to calibrate the cells in the state that they are normally operating in. I have observed much better and prolonged good behaviours this way. edit: PLEASE ENSURE CELLS ARE OPERATING AS EXPECTED WITH AIR AND KNOWN PURITY OF OXYGEN AND ALSO PERFORM IN-WATER TESTS. Quote: I really agree with most of this. I am just stating what I was taught. Sometimes, important things are learned on the internet more effectively than during instruction. In my own training experience, I/we were only taught the process of cell calibration, and very little about the purpose and/or how the whole cal process works. This has taken a little research on my own part. __________________ Gilles http://www.dirrebreather.com Last edited by Gilles : 9th February 2008 at 05:04.
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10th February 2008, 21:11	#33 (permalink)
Dsix36 Going Down? Current Rebreather/s: Optima Other Rebreather/s: Join Date: Aug 2007 Location: florida Posts: 857	Re: MV reading on cell Quote: (Originally Posted by Gilles) No because the effect of moisture on cells is rather random (in my observations). One thing is certain is that humidity causes a mV attenuation across its response function, causing an "current-limitation-like" effect. Personally, my preference is to perform post-dive calibrations (when cells are damp from usage), and only re-cal if any indication of cells changing. My argument here is that it may be better to calibrate the cells in the state that they are normally operating in. I have observed much better and prolonged good behaviours this way. edit: PLEASE ENSURE CELLS ARE OPERATING AS EXPECTED WITH AIR AND KNOWN PURITY OF OXYGEN AND ALSO PERFORM IN-WATER TESTS. Now I understand what you mean! I always cal about a week after diving and all sensors are dryed out. I have noticed some sensor drift during dives from moisture so this makes sense to do the cal post dive and then just check it pre dive. I will experiment with this procedure and see how it works for me. Thanks for the patience with me __________________ THE MORE THAT I LEARN, THE MORE THAT I STILL NEED TO LEARN!!!!!!
(Offline)

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