MCCR two or three oxygen cells ?

decoweenie · 7th October 2005, 17:31

Quote: (Originally Posted by GKAM)

...It is all about personal choice (unless you guys are all DIR

fanatics and want to assimilate us all

)

You know we are all discussing here...

At the end of the day, an informed diver makes his/her own decision knowing all of the options.

GKAM · 7th October 2005, 17:43

Quote: (Originally Posted by decoweenie)

You know we are all discussing here...

Totally with you, Phi

Quote: (Originally Posted by decoweenie)

At the end of the day, an informed diver makes his/her own decision knowing all of the options.

That is my exact point. I was just taking the piss out of the hardcore DIR guys. I hate absolute views.

GKAM

Erik · 8th October 2005, 03:52

The more the merrier as they say...

I have had two cell failures at the same time twice. One time the Inspiration went nuts because two cells froze just below the setpoint and started injecting like mad. They read correct on a diluent flush and below 1.0 but just refused to go above 1.15. The correct sensor was way up around 2.0. The unit was dived and fine on dives the day before (and earlier throughout the dive!)...

It also happened on the KiSS, but at least that unit doesn't try to actively kill you haha

. Easily flew it home on the correct one (with some increased margins)

Sensors just go bad here in the tropics way too fast.

There is actually a new commercial manual unit available called the Pelagian which is designed for and comes with two sensors (but place for a third, or a VR/Explorer hookup). I'll try it next time I go there.

http://www.rebreatherlab.com

silent running · 9th October 2005, 05:28

Quote: (Originally Posted by AD_ward9)

FYI: the probability of two galvanic cells going down with a ceiling fault during a single dive is 85K hours. Replace them at the same time from the same batch, then 5.6K hours. With a ceiling fault, your ears are going to have to be pretty good at integration if you are going to come out alive.

Why are people using galvanic sensors anyway? Because they exist, are easy, do not involve change. Sol-gel and opto sensors are available and are the future. They are already in use in medical O2 and CO2 applications.

In a few years time, the O2 and CO2 sensor will be printed onto the scrubber cartridge. Throw away. Just like on food packaging. I have put a post on this onto the Open Revolution area, with links showing the technologies working.

Alex

Hello Alex, I've been hearing about optical sensors (and used them in one of my many dumb jobs, as a diagnostic sleep technician) as an option for Rebreather's for a while now. I'm not familiar with this Sol-gel stuff, gotta look at your link. And it may be true that they are the way of the future. So what's taking so long? I mean what are the devil's advocate objections? I would think that given the volitile nature of galvanic O2 sensors, one would think that manufaturers would jump at the chance to implement these new technologies. I've been meaning to put this question to Peter Ready of SMI. What say ye?

GKAM · 14th October 2005, 08:11

I found the link to the article!

This is the one I was referring to wrt the # of sensors in a mCCR loop

http://www.airheadsscuba.com/sensors.html

GKAM

***caveseeker7*** · 14th October 2005, 13:29

Quote: (Originally Posted by GKAM)

I think that Kerry once wrote a very good article on why 3 sensors are overkill in mCCR. Look around his site for it.

Kerry has been using two cells in his Dolphin CCR conversion for quite a long time.
But you also have to consider the spots he dives, the waters up there are relatively shallow. Somewhere in the 10 msw range if I remember correctly.

After diving the Sting Ray from a liveaboard with Andy, Kim and Gordon etc he ammended his views, on Dive-Oz I believe. For the depth he was diving there he would feel more comfortable with a third sensor, something like that.

Another consideration is the gas supply and the depth you're diving to. If you have only a 2 ltr loop supply dil flushes can use up relatively large amounts of your gas.

By the way, some of the DIR chaps dive rebreathers and quite successfully at that.
They are as welcome here as anyone diving or wanting to dive a rebreather. You don't have to like their stance, but for their own diving you'll have to accept it.

jdz · 14th October 2005, 13:51

My comment wrt 3 sensors for mCCR is that I dislike having the 3 sensors combined into the one package...like the munro triple. (btw, I would recommend the Munro single units anyday...) see http://www.ppo2.com/Displays_1.htm

If you are going to the extent of 3 sensors, the should be IMO independant of each other.

Cheers, JDZ

decoweenie · 14th October 2005, 14:37

Quote: (Originally Posted by caveseeker7)

...But you also have to consider the spots he dives, the waters up there are relatively shallow. Somewhere in the 10 msw range if I remember correctly...

Exactly! When reading "Internet advice", it is best to recognize and align the type of diving where the advice came from against yours.

Different types of diving have different requirements due the different levels of risk involved.

Someone who doesn't do any deco diving should be a different viewpoint from someone who does, and might see the level of redundancy as unnecessary.

Caveat Emptor applies to advices as well...

7th October 2005, 17:31	#11 (permalink)
decoweenie Crash Test Dummy Current Rebreather/s: Other CCR Other Rebreather/s: Other CCR Join Date: Feb 2005 Location: Cairo Posts: 5,510	Quote: (Originally Posted by GKAM) ...It is all about personal choice (unless you guys are all DIR fanatics and want to assimilate us all ) You know we are all discussing here... At the end of the day, an informed diver makes his/her own decision knowing all of the options. __________________ "...after a while you get bored offering advice to a bull that like to keep butting the fence with its head rather than walking through the open gate..." - Rebreather World PM
(Offline)

7th October 2005, 17:43	#12 (permalink)
GKAM digital nomad Current Rebreather/s: Other CCR Other Rebreather/s: Other CCR Join Date: May 2005 Location: Greece Posts: 251	Quote: (Originally Posted by decoweenie) You know we are all discussing here... Totally with you, Phi Quote: (Originally Posted by decoweenie) At the end of the day, an informed diver makes his/her own decision knowing all of the options. That is my exact point. I was just taking the piss out of the hardcore DIR guys. I hate absolute views. GKAM
(Offline)

8th October 2005, 03:52	#13 (permalink)
Erik no bubble maker Current Rebreather/s: Other CCR Other Rebreather/s: Not Bought Yet Inspiration Classic Evolution Megalodon Sport Kiss Classic Kiss MK 15.X Other CCR Join Date: Apr 2005 Location: Thailand Posts: 21	The more the merrier as they say... I have had two cell failures at the same time twice. One time the Inspiration went nuts because two cells froze just below the setpoint and started injecting like mad. They read correct on a diluent flush and below 1.0 but just refused to go above 1.15. The correct sensor was way up around 2.0. The unit was dived and fine on dives the day before (and earlier throughout the dive!)... It also happened on the KiSS, but at least that unit doesn't try to actively kill you haha . Easily flew it home on the correct one (with some increased margins) Sensors just go bad here in the tropics way too fast. There is actually a new commercial manual unit available called the Pelagian which is designed for and comes with two sensors (but place for a third, or a VR/Explorer hookup). I'll try it next time I go there. http://www.rebreatherlab.com
(Offline)

9th October 2005, 05:28	#14 (permalink)
silent running Mature mouth breather Current Rebreather/s: Prism Topaz Other Rebreather/s: Join Date: Jun 2005 Location: U.S.A. Brooklyn, New York Posts: 1,814	Quote: (Originally Posted by AD_ward9) FYI: the probability of two galvanic cells going down with a ceiling fault during a single dive is 85K hours. Replace them at the same time from the same batch, then 5.6K hours. With a ceiling fault, your ears are going to have to be pretty good at integration if you are going to come out alive. Why are people using galvanic sensors anyway? Because they exist, are easy, do not involve change. Sol-gel and opto sensors are available and are the future. They are already in use in medical O2 and CO2 applications. In a few years time, the O2 and CO2 sensor will be printed onto the scrubber cartridge. Throw away. Just like on food packaging. I have put a post on this onto the Open Revolution area, with links showing the technologies working. Alex Hello Alex, I've been hearing about optical sensors (and used them in one of my many dumb jobs, as a diagnostic sleep technician) as an option for Rebreather's for a while now. I'm not familiar with this Sol-gel stuff, gotta look at your link. And it may be true that they are the way of the future. So what's taking so long? I mean what are the devil's advocate objections? I would think that given the volitile nature of galvanic O2 sensors, one would think that manufaturers would jump at the chance to implement these new technologies. I've been meaning to put this question to Peter Ready of SMI. What say ye?
(Offline)

14th October 2005, 08:11	#15 (permalink)
GKAM digital nomad Current Rebreather/s: Other CCR Other Rebreather/s: Other CCR Join Date: May 2005 Location: Greece Posts: 251	I found the link to the article! This is the one I was referring to wrt the # of sensors in a mCCR loop http://www.airheadsscuba.com/sensors.html GKAM
(Offline)

14th October 2005, 13:29	#16 (permalink)
*caveseeker7* Who loves ya, baby Current Rebreather/s: Sport Kiss Other Rebreather/s: Prism Topaz Join Date: Jan 2005 Location: Too far from Neverland Posts: 5,435	Quote: (Originally Posted by GKAM) I think that Kerry once wrote a very good article on why 3 sensors are overkill in mCCR. Look around his site for it. Kerry has been using two cells in his Dolphin CCR conversion for quite a long time. But you also have to consider the spots he dives, the waters up there are relatively shallow. Somewhere in the 10 msw range if I remember correctly. After diving the Sting Ray from a liveaboard with Andy, Kim and Gordon etc he ammended his views, on Dive-Oz I believe. For the depth he was diving there he would feel more comfortable with a third sensor, something like that. Another consideration is the gas supply and the depth you're diving to. If you have only a 2 ltr loop supply dil flushes can use up relatively large amounts of your gas. By the way, some of the DIR chaps dive rebreathers and quite successfully at that. They are as welcome here as anyone diving or wanting to dive a rebreather. You don't have to like their stance, but for their own diving you'll have to accept it. __________________ Cheers Stefan "Political Correctness is a doctrine, fostered by a delusional, illogical minority, and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a turd by the clean end.'!"
(Offline)

14th October 2005, 13:51	#17 (permalink)
jdz Prism Cave Diver Current Rebreather/s: Prism Topaz Dolphin Home Build Other Rebreather/s: Dolphin Home Build Join Date: Feb 2005 Location: Melbourne Australia Posts: 217	My comment wrt 3 sensors for mCCR is that I dislike having the 3 sensors combined into the one package...like the munro triple. (btw, I would recommend the Munro single units anyday...) see http://www.ppo2.com/Displays_1.htm If you are going to the extent of 3 sensors, the should be IMO independant of each other. Cheers, JDZ
(Online)

14th October 2005, 14:37	#18 (permalink)
decoweenie Crash Test Dummy Current Rebreather/s: Other CCR Other Rebreather/s: Other CCR Join Date: Feb 2005 Location: Cairo Posts: 5,510	Quote: (Originally Posted by caveseeker7) ...But you also have to consider the spots he dives, the waters up there are relatively shallow. Somewhere in the 10 msw range if I remember correctly... Exactly! When reading "Internet advice", it is best to recognize and align the type of diving where the advice came from against yours. Different types of diving have different requirements due the different levels of risk involved. Someone who doesn't do any deco diving should be a different viewpoint from someone who does, and might see the level of redundancy as unnecessary. Caveat Emptor applies to advices as well... __________________ "...after a while you get bored offering advice to a bull that like to keep butting the fence with its head rather than walking through the open gate..." - Rebreather World PM
(Offline)

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