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***jradomski*** · 10th May 2006, 05:41

Quote: (Originally Posted by Johan)

It seems to be common knowledge that the VPM algorithm is freely available but does anyone know:

Which is the reference implementation of VPM-B for rebreather divers?

As far as I know there is the original VPM-B code (Baker). This is straightforward code but it only appears to handle the OC case. Then there are CCR adaptions like Maikens code in VBA and Spaughs CCR adaption of Bakers VPM code in Fortran.

Initially it seems pretty straight forward to port the initial code to the CCR case just by calculating the gas fractions based on setpoint and depth. However, using rebreathers the air should be more humid (right?) so there should be more water vapor in the gas. Shouldn't this be taken into calculation considering the water vapor pressure already is a variable in the OC case? The second thing that may differ is how to use the Schreiner equation which is discussed HERE.

It seems like most people on this forum uses V-Planner but I dont know how it adapts the VPM-B model to CCR (or SCR for that case). Would be interesting to know since then other implementations can use the same approach and together build a better dive database. Maybe Ross can tell us? (btw not looking for the source code just the algorithm)

IMHO I think it would be nice to have a baseline reference implementation that has a set number of input values which produces a predictable deco plan for the CCR case just like the OC case. A bonus would of course be if the implementation would be in a more modern language such as C, Java or C#.

actually no, once inside the lungs the gas reaches 100% humidity.. 100% is 100% no matter how you cook it (on a CCR it just reaches this before it enters your body) .. Ther are some variations in the RQ numbers used by modellers but they make only a slight difference..

when you are on OC the inspired fractions (all gases) are less than the gas in the tank because of the addition of WVP.. On a CCR theoritically the PO2 should be correct based on measurements and only the inerts are reduced..but then again sensor accuracy is +/- 1% anyway

but either way variations in WVP only has small effects on the deco schedules.. There are 3 common RQ numbers, schreiner, buhlman and the us navy.. I user the Navy numbers as they are more conservatibe than buhlmans numbers but still only have a small effect..

10th May 2006, 05:41	#20 (permalink)
*jradomski* Moderator Current Rebreather/s: Inspiration Classic Sport Kiss Optima rEvo Other CCR Other Rebreather/s: Inspiration Vision Evolution Megalodon Classic Kiss rEvo Other CCR Join Date: Mar 2005 Location: "Da" Bronx Posts: 3,093	Re: RGBM Licensing? Quote: (Originally Posted by Johan) It seems to be common knowledge that the VPM algorithm is freely available but does anyone know: Which is the reference implementation of VPM-B for rebreather divers? As far as I know there is the original VPM-B code (Baker). This is straightforward code but it only appears to handle the OC case. Then there are CCR adaptions like Maikens code in VBA and Spaughs CCR adaption of Bakers VPM code in Fortran. Initially it seems pretty straight forward to port the initial code to the CCR case just by calculating the gas fractions based on setpoint and depth. However, using rebreathers the air should be more humid (right?) so there should be more water vapor in the gas. Shouldn't this be taken into calculation considering the water vapor pressure already is a variable in the OC case? The second thing that may differ is how to use the Schreiner equation which is discussed HERE. It seems like most people on this forum uses V-Planner but I dont know how it adapts the VPM-B model to CCR (or SCR for that case). Would be interesting to know since then other implementations can use the same approach and together build a better dive database. Maybe Ross can tell us? (btw not looking for the source code just the algorithm) IMHO I think it would be nice to have a baseline reference implementation that has a set number of input values which produces a predictable deco plan for the CCR case just like the OC case. A bonus would of course be if the implementation would be in a more modern language such as C, Java or C#. actually no, once inside the lungs the gas reaches 100% humidity.. 100% is 100% no matter how you cook it (on a CCR it just reaches this before it enters your body) .. Ther are some variations in the RQ numbers used by modellers but they make only a slight difference.. when you are on OC the inspired fractions (all gases) are less than the gas in the tank because of the addition of WVP.. On a CCR theoritically the PO2 should be correct based on measurements and only the inerts are reduced..but then again sensor accuracy is +/- 1% anyway but either way variations in WVP only has small effects on the deco schedules.. There are 3 common RQ numbers, schreiner, buhlman and the us navy.. I user the Navy numbers as they are more conservatibe than buhlmans numbers but still only have a small effect.. __________________ Joe Radomski CCR Trimix Instructor Trainer ANDI Instructor Trainer Director #10 All posts are personal opinions and DO NOT reflect any affiliated agency unless specifically stated. Last edited by jradomski : 10th May 2006 at 05:43.
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