RB80 Math ?

se2schul · 14th May 2008, 13:26

Hi guys,

Thanks for the responses so far. Please keep them coming. I'm a little busy with work and life at the moment, but I'm looking forward to following the links and putting in some research in the near future.

For those that are interested in my motivations.... I'm just trying to get a better understanding of how the RB80 works. I had a very thorough course, however they can only cram so much info into my brain in a short amount of time. I understand that there can be wild PO2 swings in the shallows, and I've seen a simulation of this, and I know how to avoid this in practice, but I really don't have a thorough understanding of this. I'd like to measure some of my personal values (like my metabolic rate) and run a little simulation. I would use the simulation software I was given, except it's not working well for me. In fact, it won't even install on my computer. I've had to extract the files from the CAB file manually to get things running. Now that things are running, I'm not convinced that I'm using this properly. The software is part German (I think?) and part English, and although it's very simple, the user interface isn't presented very professionally, and the user interface is a bit buggy, which doesn't give me good confidence in the validity of the software. Anyway, I figure it will be a bit of a fun project to be able to create my own simulation from first principles - and an excellent learning experience.

I'll share any progress I make with this.

Thanks,
Steve

frankstoop · 14th May 2008, 13:34

Quote: (Originally Posted by se2schul)

Can anyone help me out with the algorithm used to calculate the loop stabilization on the RB80?

I'm also interested in how to calculate when the loop will go hypoxic during a depth change.

I am trained on the RB80, and I'm aware of the "rules" to follow to avoid hypoxia while diving the unit.
I'm also aware of a battlefield calculation to calculate at approximately what depth a gas becomes hypoxic.
I also have some simulation software that is supposed to calculate these things for me, however, the software is half German - half English, the interface is a bit "clunky", and I'm not always sure what it's doing. I'm not sure if there's a newer version of this software available.

Anyway, if anyone can help me with the loop stabilization algorithm, and the hypoxia algorithm, it would be much appreciated.

Isn't this a 'Contradictio in terminis'. On pscr hypoxia is most an item for ascend; so during dynamic ambitial conditions. Loop stabilization algorithm is valid for static ambient. I've done some algorithm for this item, but it is very, very complex. As simple pscr functions, as complex is it's algorithm.
For example in the dynamics, time of ascend and descend are important factors. So you need time factors in the algorithm.
There is also the problem, it is not a linear system. f.e. active scr is continuous injecting; pscr injection is dependant from the position of the end of the bellows in comparison with the levers. So dependant from the position, you have digital injection. The position at a certain moment is also the result of the historie before.

After some evening huzzling formula's from Karl's i've found that stabilized the ppO2 drop is equal to the athmosferic preasure of the inert gas / factor 2.5
Factor 2.5 is calculated as the fraction of used oxygen in breathing gas, multiplied by the bellows factor. So 4% used O2, CO2 = 1/25 part of the gas and this multiplied by 10 ( most used bellows factor ) = 2.5

regards, Frank

davy · 14th May 2008, 14:33

Like Frank mentions, there is the "magical factor" 2.5 which is valid for a 4% surface O2 consumption and 1:10 bellows which matches my situation very well.
This results in a quite simple formula that can even be used on-the-fly.
On verification during actual dives it was spot on at predicting pO2.

The pO2 drop is actually the partial pressure of the inert gas / 2.5
to know the pO2 during the dive, just subtract the pO2 drop from the pO2 you would have on OC.

I created a little excel sheet to easily play with it and learn.
the user interface is not that great, but if you want I can send it...

Also there is the V-planner which incorporates a full blown decompression planning for pSCR which works well.
Very cool to compare "actual" profiles Vs. OC reference plans.

frankstoop · 14th May 2008, 15:09

Quote: (Originally Posted by davy)

Like Frank mentions, there is the "magical factor" 2.5 which is valid for a 4% surface O2 consumption and 1:10 bellows which matches my situation very well.
This results in a quite simple formula that can even be used on-the-fly.
On verification during actual dives it was spot on at predicting pO2.

The pO2 drop is actually the partial pressure of the inert gas / 2.5
to know the pO2 during the dive, just subtract the pO2 drop from the pO2 you would have on OC.

I created a little excel sheet to easily play with it and learn.
the user interface is not that great, but if you want I can send it...

Also there is the V-planner which incorporates a full blown decompression planning for pSCR which works well.
Very cool to compare "actual" profiles Vs. OC reference plans.

i agree with you davy. Just calculate this ppO2 and subtract it from actual ppO2. BUT, ONLY in STABALIZED conditions. On descend, there is lots of gas injected in the belows and the ppO2 drop can decrease to 0. On the other hand on ascend ( if not right operated ) there isn't any injection and the ppO2 drop will increase rapidly.

regards, Frank

mixgas · 19th May 2008, 17:21

I also did some work on this when I first started on the PSCR.
I got 2 different spreadsheets, both in German I think, I culd share if it's of any interest.

It got 5 parameters depending on unit spec, mix and personal metabolism wich I put in last after monitoring Po2 on a fiew dives.

I also discovered that Po2 increases together with work load.

Jan

14th May 2008, 13:26	#11 (permalink)
se2schul New Member Current Rebreather/s: RB80 / Clone Other Rebreather/s: RB80 / Clone Join Date: Oct 2007 Location: Ottawa Posts: 65	Re: RB80 Math ? Hi guys, Thanks for the responses so far. Please keep them coming. I'm a little busy with work and life at the moment, but I'm looking forward to following the links and putting in some research in the near future. For those that are interested in my motivations.... I'm just trying to get a better understanding of how the RB80 works. I had a very thorough course, however they can only cram so much info into my brain in a short amount of time. I understand that there can be wild PO2 swings in the shallows, and I've seen a simulation of this, and I know how to avoid this in practice, but I really don't have a thorough understanding of this. I'd like to measure some of my personal values (like my metabolic rate) and run a little simulation. I would use the simulation software I was given, except it's not working well for me. In fact, it won't even install on my computer. I've had to extract the files from the CAB file manually to get things running. Now that things are running, I'm not convinced that I'm using this properly. The software is part German (I think?) and part English, and although it's very simple, the user interface isn't presented very professionally, and the user interface is a bit buggy, which doesn't give me good confidence in the validity of the software. Anyway, I figure it will be a bit of a fun project to be able to create my own simulation from first principles - and an excellent learning experience. I'll share any progress I make with this. Thanks, Steve
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14th May 2008, 13:34	#12 (permalink)
frankstoop New Member Current Rebreather/s: Other SCR Other Rebreather/s: Other SCR Join Date: Nov 2006 Location: holland Posts: 3	Re: RB80 Math ? Quote: (Originally Posted by se2schul) Can anyone help me out with the algorithm used to calculate the loop stabilization on the RB80? I'm also interested in how to calculate when the loop will go hypoxic during a depth change. I am trained on the RB80, and I'm aware of the "rules" to follow to avoid hypoxia while diving the unit. I'm also aware of a battlefield calculation to calculate at approximately what depth a gas becomes hypoxic. I also have some simulation software that is supposed to calculate these things for me, however, the software is half German - half English, the interface is a bit "clunky", and I'm not always sure what it's doing. I'm not sure if there's a newer version of this software available. Anyway, if anyone can help me with the loop stabilization algorithm, and the hypoxia algorithm, it would be much appreciated. Isn't this a 'Contradictio in terminis'. On pscr hypoxia is most an item for ascend; so during dynamic ambitial conditions. Loop stabilization algorithm is valid for static ambient. I've done some algorithm for this item, but it is very, very complex. As simple pscr functions, as complex is it's algorithm. For example in the dynamics, time of ascend and descend are important factors. So you need time factors in the algorithm. There is also the problem, it is not a linear system. f.e. active scr is continuous injecting; pscr injection is dependant from the position of the end of the bellows in comparison with the levers. So dependant from the position, you have digital injection. The position at a certain moment is also the result of the historie before. After some evening huzzling formula's from Karl's i've found that stabilized the ppO2 drop is equal to the athmosferic preasure of the inert gas / factor 2.5 Factor 2.5 is calculated as the fraction of used oxygen in breathing gas, multiplied by the bellows factor. So 4% used O2, CO2 = 1/25 part of the gas and this multiplied by 10 ( most used bellows factor ) = 2.5 regards, Frank
(Offline)

14th May 2008, 14:33	#13 (permalink)
davy New Member Current Rebreather/s: RB80 / Clone Home Build Other Rebreather/s: RB80 / Clone Home Build Join Date: Aug 2005 Location: Belgium Posts: 21	Re: RB80 Math ? Like Frank mentions, there is the "magical factor" 2.5 which is valid for a 4% surface O2 consumption and 1:10 bellows which matches my situation very well. This results in a quite simple formula that can even be used on-the-fly. On verification during actual dives it was spot on at predicting pO2. The pO2 drop is actually the partial pressure of the inert gas / 2.5 to know the pO2 during the dive, just subtract the pO2 drop from the pO2 you would have on OC. I created a little excel sheet to easily play with it and learn. the user interface is not that great, but if you want I can send it... Also there is the V-planner which incorporates a full blown decompression planning for pSCR which works well. Very cool to compare "actual" profiles Vs. OC reference plans. Last edited by davy : 14th May 2008 at 14:37.
(Offline)

14th May 2008, 15:09	#14 (permalink)
frankstoop New Member Current Rebreather/s: Other SCR Other Rebreather/s: Other SCR Join Date: Nov 2006 Location: holland Posts: 3	Re: RB80 Math ? Quote: (Originally Posted by davy) Like Frank mentions, there is the "magical factor" 2.5 which is valid for a 4% surface O2 consumption and 1:10 bellows which matches my situation very well. This results in a quite simple formula that can even be used on-the-fly. On verification during actual dives it was spot on at predicting pO2. The pO2 drop is actually the partial pressure of the inert gas / 2.5 to know the pO2 during the dive, just subtract the pO2 drop from the pO2 you would have on OC. I created a little excel sheet to easily play with it and learn. the user interface is not that great, but if you want I can send it... Also there is the V-planner which incorporates a full blown decompression planning for pSCR which works well. Very cool to compare "actual" profiles Vs. OC reference plans. i agree with you davy. Just calculate this ppO2 and subtract it from actual ppO2. BUT, ONLY in STABALIZED conditions. On descend, there is lots of gas injected in the belows and the ppO2 drop can decrease to 0. On the other hand on ascend ( if not right operated ) there isn't any injection and the ppO2 drop will increase rapidly. regards, Frank
(Offline)

19th May 2008, 17:21	#15 (permalink)
mixgas New Member Current Rebreather/s: RB80 / Clone Other Rebreather/s: RB80 / Clone Join Date: Sep 2005 Location: Norway Posts: 27	Re: RB80 Math ? I also did some work on this when I first started on the PSCR. I got 2 different spreadsheets, both in German I think, I culd share if it's of any interest. It got 5 parameters depending on unit spec, mix and personal metabolism wich I put in last after monitoring Po2 on a fiew dives. I also discovered that Po2 increases together with work load. Jan __________________ http://www.reelactiondiving.com
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