Independent PO2 Monitoring - 1 or 2 Cells

**PhilSiswick** · 26th November 2006, 10:18

Nigel's recent post about his Vision handset freezing and the many other examples highlighting how important some form of independent monitoring of your PO2 is have set me thinking about my dependence on the Vision handset.

So, I'm looking for a way of adding PO2 monitoring without breaking the cardinal rule that I've set myself for any mods that I make to my Vision - I'm not going to fiddle with the electronics or the loop, as they are the core of the unit. If I leave them alone, any changes shouldn't impair the operation of the unit if I get them wrong.

I'm tempted by the rEvodream, as I like the idea of running the HUD as a backup to the Vision HUD. I would fly the unit as normal, checking the Vision handset regularly as now. I wouldn't look at the rEvo HUD unless it did something other than burn steady green. That should catch an issue like Nigel's and allow me to determine whether I need to bail out.

I've discounted most of the other options such as the VR£, Explorer and the Sartek PO2 monitor for a variety of reasons. I don't want backup integrated deco, so that knocks most of the computers out and I think that the HUD on the rEvo adds a lot of extra safety, so wouldn't just go with a simple PO2 monitor.

I haven't found an adaptor that allows me to add more than one extra cell to the Vision. Is there one that I haven't spotted? Assuming that there isn't, is it really sensible to add PO2 monitoring using just one cell?

I recognise that something is better than nothing, but is running this off one cell actually adding more risk than running completely without it, as it might cause complacency. Worse, it might lead me to make a bad call in an apparent failure situation, as its readings are based on less information than those on the Vision handset (no validation of readings across cells etc).

Cheers,

***Beanie*** · 26th November 2006, 11:03

Quote: (Originally Posted by PhilSiswick)

I've discounted most of the other options such as the VR£, Explorer and the Sartek PO2 monitor for a variety of reasons. I don't want backup integrated deco, so that knocks most of the computers out and I think that the HUD on the rEvo adds a lot of extra safety, so wouldn't just go with a simple PO2 monitor.

you don't have to have integrated deco to show PPO2 on the VR3 (version 3 up)

***caveseeker7*** · 26th November 2006, 11:32

All three cells.

Use Beanie's cell holder to connect the pO2 monitor from SubseaSystems to the three cells of your rebreather. With or without HUD. No deco.

http://www.deepdiving.net/homebuilt.html

One thought, by the way, "burn steady green" can also happen when the computer freezes while the light is on. That's the reason most manufacturers use a blinking or pulsating light to indicate that the computer is running. If it freezes either with the light on or off you know you have a problem. One that the HUD from SubseaSea Systems would also alert you to (on its own electronics, not your Rebreather's).

paulraymaekers · 26th November 2006, 16:20

Quote: (Originally Posted by caveseeker7)

One thought, by the way, "burn steady green" can also happen when the computer freezes while the light is on. That's the reason most manufacturers use a blinking or pulsating light to indicate that the computer is running. ......

theoretically that can happen, until now we never noticed it, but...

we counter the problem this way: on the rEvo, we always use 2 independant rEvodreams, with each having a hud, mounted side by side on the mouthpiece. The chance that both freese at the same time, AND both with the green steady on.... what's the probability to get struck by lightning??

second, if a processor freeses, the LCD indication on the display keeps working!!! :-)
how?? well, each rEvodream have 2 independant processors: one in the digital voltmeter that shows the PPO2 on the lcd, the other processor takes care of the hud. if the voltmeter/lcd goes down, the hud keeps working. If the processor of the HUD freeses, the LCD-voltmeter keeps on running!

regards
paul

dave t · 26th November 2006, 17:42

I have one extra cell fitted to my vision it runs a simple po2 readout, its there as a second opinion only (if the vision freezes the fourth cell wont ). I have a personal "golden rule" any one of my cells goes outside my safe zone which is 0.4 - 1.5 and I go OC and I stay OC until I have found and rectified the problem.

Why not second deco computer? its a good solution if the primary screw up. If the vision freezes (example) you will loose your deco as well. Its very simple to just refer to the back up one!! In my opinion much better than tables.

just my opinion

Dave

decoweenie · 26th November 2006, 18:08

Quote: (Originally Posted by dave t)

I have one extra cell fitted to my vision it runs a simple po2 readout, its there as a second opinion only (if the vision freezes the fourth cell wont ).

Likewise for me. I think we even have the same source for the independent 4th cell display (i.e. Dave Mager)...

I never had the Vision freezes or goes out on me, but it is just a back-up plan since I have never dived a CCR unit with independent PO2 displays.

Once tested the Sartek secondary 3-cell display (in the next weeks), I will most likely add it to the Vision lid so if the Vision ever goes out on a long trip, I could still dive the unit manually.

**PhilSiswick** · 26th November 2006, 19:26

Quote: (Originally Posted by caveseeker7)

All three cells.

Use Beanie's cell holder to connect the pO2 monitor from SubseaSystems to the three cells of your rebreather. With or without HUD. No deco.

Subsea Systems Homebuilders Display System

Trouble is, that means fiddling with the wiring to the cells, doesn't it? I want to avoid doing that if possible, so that I can return the unit to its natural state if I sell it, or need to return it to APD.

Quote:

One thought, by the way, "burn steady green" can also happen when the computer freezes while the light is on. That's the reason most manufacturers use a blinking or pulsating light to indicate that the computer is running. If it freezes either with the light on or off you know you have a problem. One that the HUD from SubseaSea Systems would also alert you to (on its own electronics, not your Rebreather's).

A good point.

Cheers,

**PhilSiswick** · 26th November 2006, 19:27

Quote: (Originally Posted by paulraymaekers)

theoretically that can happen, until now we never noticed it, but...

we counter the problem this way: on the rEvo, we always use 2 independant rEvodreams, with each having a hud, mounted side by side on the mouthpiece. The chance that both freese at the same time, AND both with the green steady on.... what's the probability to get struck by lightning??

second, if a processor freeses, the LCD indication on the display keeps working!!! :-)
how?? well, each rEvodream have 2 independant processors: one in the digital voltmeter that shows the PPO2 on the lcd, the other processor takes care of the hud. if the voltmeter/lcd goes down, the hud keeps working. If the processor of the HUD freeses, the LCD-voltmeter keeps on running!

regards
paul

Ah, so I will need to check the display on the rEvo periodically, in addition to the HUD, to make sure it really is alive. No issue, really.

Cheers,

**PhilSiswick** · 26th November 2006, 19:39

Quote: (Originally Posted by dave t)

I have one extra cell fitted to my vision it runs a simple po2 readout, its there as a second opinion only (if the vision freezes the fourth cell wont ).

I'm only looking for a second opinion. It seems that in Nigel's case, the Vision carried on running, but the handset froze. I'd hate to bail out and lose the constant PO2 and gas usage advantages if I didn't need to.

Would you say that, in extremis, one cell is enough, or is that just too risky?

Quote:

I have a personal "golden rule" any one of my cells goes outside my safe zone which is 0.4 - 1.5 and I go OC and I stay OC until I have found and rectified the problem.

That makes a lot of sense, I'll put that in my mental rule book too.

Quote:

Why not second deco computer? its a good solution if the primary screw up. If the vision freezes (example) you will loose your deco as well. Its very simple to just refer to the back up one!! In my opinion much better than tables.

just my opinion

Dave

Why no backup deco computer? It's largely a matter of cost - for the kind of diving I'll be doing for a while, I'll be able to safely bail out to tables (and to OC) if the worst happens. My objectives for a backup are more about being able to verify that the Vision is working if I see something strange happening.

The rEvodream is cheap enough to be almost throwaway if I later do go for backup integrated deco. In the meantime, it seems to deliver everything I need.

Cheers,

paulraymaekers · 26th November 2006, 21:21

Quote: (Originally Posted by PhilSiswick)

....The rEvodream is cheap enough to be almost throwaway if I later do go for backup integrated deco. In the meantime, it seems to deliver everything I need.

Cheers,

that sounds .... I should make it more expencive??? does it seem more reliable then ???:-)

paul

26th November 2006, 10:18	#1 (permalink)
PhilSiswick Phil Siswick, Tango Current Rebreather/s: Evolution Other Rebreather/s: Inspiration Vision Join Date: Apr 2006 Location: Oxford, UK Posts: 1,062	Independent PO2 Monitoring - 1 or 2 Cells Nigel's recent post about his Vision handset freezing and the many other examples highlighting how important some form of independent monitoring of your PO2 is have set me thinking about my dependence on the Vision handset. So, I'm looking for a way of adding PO2 monitoring without breaking the cardinal rule that I've set myself for any mods that I make to my Vision - I'm not going to fiddle with the electronics or the loop, as they are the core of the unit. If I leave them alone, any changes shouldn't impair the operation of the unit if I get them wrong. I'm tempted by the rEvodream, as I like the idea of running the HUD as a backup to the Vision HUD. I would fly the unit as normal, checking the Vision handset regularly as now. I wouldn't look at the rEvo HUD unless it did something other than burn steady green. That should catch an issue like Nigel's and allow me to determine whether I need to bail out. I've discounted most of the other options such as the VR£, Explorer and the Sartek PO2 monitor for a variety of reasons. I don't want backup integrated deco, so that knocks most of the computers out and I think that the HUD on the rEvo adds a lot of extra safety, so wouldn't just go with a simple PO2 monitor. I haven't found an adaptor that allows me to add more than one extra cell to the Vision. Is there one that I haven't spotted? Assuming that there isn't, is it really sensible to add PO2 monitoring using just one cell? I recognise that something is better than nothing, but is running this off one cell actually adding more risk than running completely without it, as it might cause complacency. Worse, it might lead me to make a bad call in an apparent failure situation, as its readings are based on less information than those on the Vision handset (no validation of readings across cells etc). Cheers, __________________ Phil (WSKD 0001) I have always felt that the dive I am on is not nearly important as the dives I plan to be on the rest of my life. Tom Rose, 2007 The person who gets the farthest is generally the one who is willing to do and dare. The sure thing boat never gets far from shore. Charles A. Lindbergh www.hugsac.org.uk
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26th November 2006, 11:03	#2 (permalink)
*Beanie* Gallery Administrator Current Rebreather/s: Inspiration Classic Other Rebreather/s: Inspiration Vision Join Date: Jan 2005 Location: In da house! yeah baby! Posts: 3,292	Re: Independent PO2 Monitoring - 1 or 2 Cells Quote: (Originally Posted by PhilSiswick) I've discounted most of the other options such as the VR£, Explorer and the Sartek PO2 monitor for a variety of reasons. I don't want backup integrated deco, so that knocks most of the computers out and I think that the HUD on the rEvo adds a lot of extra safety, so wouldn't just go with a simple PO2 monitor. you don't have to have integrated deco to show PPO2 on the VR3 (version 3 up) __________________ Beanie Gallery Admin & Library Assistant. www.outlawdivers.org.uk www.beandiving.co.uk www.beanengineering.co.uk
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26th November 2006, 11:32	#3 (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: 5,535	Re: Independent PO2 Monitoring - 1 or 2 Cells All three cells. Use Beanie's cell holder to connect the pO2 monitor from SubseaSystems to the three cells of your rebreather. With or without HUD. No deco. http://www.deepdiving.net/homebuilt.html One thought, by the way, "burn steady green" can also happen when the computer freezes while the light is on. That's the reason most manufacturers use a blinking or pulsating light to indicate that the computer is running. If it freezes either with the light on or off you know you have a problem. One that the HUD from SubseaSea Systems would also alert you to (on its own electronics, not your Rebreather's). __________________ 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.!"
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26th November 2006, 16:20	#4 (permalink)
paulraymaekers rEvo's daddy Current Rebreather/s: rEvo Other CCR Home Build Other Rebreather/s: rEvo Other CCR Home Build Join Date: May 2005 Location: belgium Posts: 1,599	Re: Independent PO2 Monitoring - 1 or 2 Cells Quote: (Originally Posted by caveseeker7) One thought, by the way, "burn steady green" can also happen when the computer freezes while the light is on. That's the reason most manufacturers use a blinking or pulsating light to indicate that the computer is running. ...... theoretically that can happen, until now we never noticed it, but... we counter the problem this way: on the rEvo, we always use 2 independant rEvodreams, with each having a hud, mounted side by side on the mouthpiece. The chance that both freese at the same time, AND both with the green steady on.... what's the probability to get struck by lightning?? second, if a processor freeses, the LCD indication on the display keeps working!!! :-) how?? well, each rEvodream have 2 independant processors: one in the digital voltmeter that shows the PPO2 on the lcd, the other processor takes care of the hud. if the voltmeter/lcd goes down, the hud keeps working. If the processor of the HUD freeses, the LCD-voltmeter keeps on running! regards paul __________________ www.rEvo-rebreathers.com .... the earth is flat, Elvis is alive, and radial scrubbers give longer dwell time than axials...
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26th November 2006, 17:42	#5 (permalink)
dave t RBW Member Current Rebreather/s: Inspiration Classic Inspiration Vision Evolution Sport Kiss Classic Kiss Dolphin Ray Azimuth Home Build Other Rebreather/s: Dolphin Ray Azimuth Home Build Join Date: May 2005 Location: UK Posts: 659	Re: Independent PO2 Monitoring - 1 or 2 Cells I have one extra cell fitted to my vision it runs a simple po2 readout, its there as a second opinion only (if the vision freezes the fourth cell wont ). I have a personal "golden rule" any one of my cells goes outside my safe zone which is 0.4 - 1.5 and I go OC and I stay OC until I have found and rectified the problem. Why not second deco computer? its a good solution if the primary screw up. If the vision freezes (example) you will loose your deco as well. Its very simple to just refer to the back up one!! In my opinion much better than tables. just my opinion Dave
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26th November 2006, 18:08	#6 (permalink)
decoweenie Crash Test Dummy Current Rebreather/s: Other CCR Other Rebreather/s: Other CCR Join Date: Feb 2005 Location: Cairo Posts: 5,487	Re: Independent PO2 Monitoring - 1 or 2 Cells Quote: (Originally Posted by dave t) I have one extra cell fitted to my vision it runs a simple po2 readout, its there as a second opinion only (if the vision freezes the fourth cell wont ). Likewise for me. I think we even have the same source for the independent 4th cell display (i.e. Dave Mager)... I never had the Vision freezes or goes out on me, but it is just a back-up plan since I have never dived a CCR unit with independent PO2 displays. Once tested the Sartek secondary 3-cell display (in the next weeks), I will most likely add it to the Vision lid so if the Vision ever goes out on a long trip, I could still dive the unit manually. __________________ "...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
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26th November 2006, 19:26	#7 (permalink)
PhilSiswick Phil Siswick, Tango Current Rebreather/s: Evolution Other Rebreather/s: Inspiration Vision Join Date: Apr 2006 Location: Oxford, UK Posts: 1,062	Re: Independent PO2 Monitoring - 1 or 2 Cells Quote: (Originally Posted by caveseeker7) All three cells. Use Beanie's cell holder to connect the pO2 monitor from SubseaSystems to the three cells of your rebreather. With or without HUD. No deco. Subsea Systems Homebuilders Display System Trouble is, that means fiddling with the wiring to the cells, doesn't it? I want to avoid doing that if possible, so that I can return the unit to its natural state if I sell it, or need to return it to APD. Quote: One thought, by the way, "burn steady green" can also happen when the computer freezes while the light is on. That's the reason most manufacturers use a blinking or pulsating light to indicate that the computer is running. If it freezes either with the light on or off you know you have a problem. One that the HUD from SubseaSea Systems would also alert you to (on its own electronics, not your Rebreather's). A good point. Cheers, __________________ Phil (WSKD 0001) I have always felt that the dive I am on is not nearly important as the dives I plan to be on the rest of my life. Tom Rose, 2007 The person who gets the farthest is generally the one who is willing to do and dare. The sure thing boat never gets far from shore. Charles A. Lindbergh www.hugsac.org.uk
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26th November 2006, 19:27	#8 (permalink)
PhilSiswick Phil Siswick, Tango Current Rebreather/s: Evolution Other Rebreather/s: Inspiration Vision Join Date: Apr 2006 Location: Oxford, UK Posts: 1,062	Re: Independent PO2 Monitoring - 1 or 2 Cells Quote: (Originally Posted by paulraymaekers) theoretically that can happen, until now we never noticed it, but... we counter the problem this way: on the rEvo, we always use 2 independant rEvodreams, with each having a hud, mounted side by side on the mouthpiece. The chance that both freese at the same time, AND both with the green steady on.... what's the probability to get struck by lightning?? second, if a processor freeses, the LCD indication on the display keeps working!!! :-) how?? well, each rEvodream have 2 independant processors: one in the digital voltmeter that shows the PPO2 on the lcd, the other processor takes care of the hud. if the voltmeter/lcd goes down, the hud keeps working. If the processor of the HUD freeses, the LCD-voltmeter keeps on running! regards paul Ah, so I will need to check the display on the rEvo periodically, in addition to the HUD, to make sure it really is alive. No issue, really. Cheers, __________________ Phil (WSKD 0001) I have always felt that the dive I am on is not nearly important as the dives I plan to be on the rest of my life. Tom Rose, 2007 The person who gets the farthest is generally the one who is willing to do and dare. The sure thing boat never gets far from shore. Charles A. Lindbergh www.hugsac.org.uk
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26th November 2006, 19:39	#9 (permalink)
PhilSiswick Phil Siswick, Tango Current Rebreather/s: Evolution Other Rebreather/s: Inspiration Vision Join Date: Apr 2006 Location: Oxford, UK Posts: 1,062	Re: Independent PO2 Monitoring - 1 or 2 Cells Quote: (Originally Posted by dave t) I have one extra cell fitted to my vision it runs a simple po2 readout, its there as a second opinion only (if the vision freezes the fourth cell wont ). I'm only looking for a second opinion. It seems that in Nigel's case, the Vision carried on running, but the handset froze. I'd hate to bail out and lose the constant PO2 and gas usage advantages if I didn't need to. Would you say that, in extremis, one cell is enough, or is that just too risky? Quote: I have a personal "golden rule" any one of my cells goes outside my safe zone which is 0.4 - 1.5 and I go OC and I stay OC until I have found and rectified the problem. That makes a lot of sense, I'll put that in my mental rule book too. Quote: Why not second deco computer? its a good solution if the primary screw up. If the vision freezes (example) you will loose your deco as well. Its very simple to just refer to the back up one!! In my opinion much better than tables. just my opinion Dave Why no backup deco computer? It's largely a matter of cost - for the kind of diving I'll be doing for a while, I'll be able to safely bail out to tables (and to OC) if the worst happens. My objectives for a backup are more about being able to verify that the Vision is working if I see something strange happening. The rEvodream is cheap enough to be almost throwaway if I later do go for backup integrated deco. In the meantime, it seems to deliver everything I need. Cheers, __________________ Phil (WSKD 0001) I have always felt that the dive I am on is not nearly important as the dives I plan to be on the rest of my life. Tom Rose, 2007 The person who gets the farthest is generally the one who is willing to do and dare. The sure thing boat never gets far from shore. Charles A. Lindbergh www.hugsac.org.uk
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26th November 2006, 21:21	#10 (permalink)
paulraymaekers rEvo's daddy Current Rebreather/s: rEvo Other CCR Home Build Other Rebreather/s: rEvo Other CCR Home Build Join Date: May 2005 Location: belgium Posts: 1,599	Re: Independent PO2 Monitoring - 1 or 2 Cells Quote: (Originally Posted by PhilSiswick) ....The rEvodream is cheap enough to be almost throwaway if I later do go for backup integrated deco. In the meantime, it seems to deliver everything I need. Cheers, that sounds .... I should make it more expencive??? does it seem more reliable then ???:-) paul __________________ www.rEvo-rebreathers.com .... the earth is flat, Elvis is alive, and radial scrubbers give longer dwell time than axials...
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