Scr/vsc

anton610 · 27th January 2008, 15:17

Hello!

can anyone explain me the method of SCR/VSC very simple?

i've read a few posts but i can make nothing out of it.

thanks!!

***caveseeker7*** · 27th January 2008, 18:48

Will Smithers' VSC Calculations and a recent thread on the subject here at Rebreather World:
SCR - VSC as CCR bailout method

Hanssing · 27th January 2008, 20:33

Quote: (Originally Posted by caveseeker7)

Will Smithers' VSC Calculations and a recent thread on the subject here at Rebreather World:
SCR - VSC as CCR bailout method

The thread pointed to by CaveSeeker7 is very interesting, but I'm afraid I have to object to the link provided.

Concerning VSC by Will: If you're trying to understand VSC, thats NOT the place to start. The Excel-sheet linked has a dangerous error, and it does not tell wich method is used, nor does it implement it correctly for others to use.
If used by a newbie without complete understanding, one wich is unable to see the errors in the sheet, and possibly the method, this could lead to hypoxia and death - BEWARE!

From the last line, I can sadly tell that the author is no longer among us, and I therefor truely wish I did not have critizise his work but I'll list my objections:

Firstly the Excel-sheet implements VSR by scaling counts to absolute pressure, wich gives constant end/avg. FO2 - this is not stated but is clear from the excel-file. See the thread for further info.
The "algoritm" works by lowering the FO2 of the Dil used by a fixed amount. As far as I can tell it's 0.2, ie. makes a 40% used down to say 20%. But due to the error in the sheet this is not easy to detect.
The number of breaths are calculated WRONGLY. The colum H has a critical error, since it's formula should not be '300*Gx', but something like 'Gx/0.2*$B$2' ie. a FO2-drop of 0.2 SCALED by the meassured drop-count. Incidently for the numbers in the sheet is matches, but not if your drop is different from 60.
Does not advise against meassuring with to high FO2, where drop-count becomes non-linear, and therefor TOO HIGH.
Does not include any 25% safety-factor as stated in the text.
If used with diluents below 40% in the config, it could render one unconsius due to hypoxia near the shallows.

I would not dare use that sheet - sorry

Safe Dives
Nicolai

27th January 2008, 15:17	#1 (permalink)
anton610 toni the strange Current Rebreather/s: Evolution Other CCR Other Rebreather/s: Other CCR Join Date: May 2006 Location: austria Posts: 179	Scr/vsc Hello! can anyone explain me the method of SCR/VSC very simple? i've read a few posts but i can make nothing out of it. thanks!! __________________ "Das Übel kommt nicht von der Technik, sondern von denen, die sie mißbrauchen." Jacques-Yves Cousteau (1910-1997)
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27th January 2008, 18:48	#2 (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: 5,496	Re: Scr/vsc Will Smithers' VSC Calculations and a recent thread on the subject here at Rebreather World: SCR - VSC as CCR bailout method __________________ 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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27th January 2008, 20:33	#3 (permalink)
Hanssing flap-flop ..... flap-flop Current Rebreather/s: rEvo Other Rebreather/s: rEvo Join Date: Nov 2005 Location: Denmark Posts: 407	Re: Scr/vsc Quote: (Originally Posted by caveseeker7) Will Smithers' VSC Calculations and a recent thread on the subject here at Rebreather World: SCR - VSC as CCR bailout method The thread pointed to by CaveSeeker7 is very interesting, but I'm afraid I have to object to the link provided. Concerning VSC by Will: If you're trying to understand VSC, thats NOT the place to start. The Excel-sheet linked has a dangerous error, and it does not tell wich method is used, nor does it implement it correctly for others to use. If used by a newbie without complete understanding, one wich is unable to see the errors in the sheet, and possibly the method, this could lead to hypoxia and death - BEWARE! From the last line, I can sadly tell that the author is no longer among us, and I therefor truely wish I did not have critizise his work but I'll list my objections: Firstly the Excel-sheet implements VSR by scaling counts to absolute pressure, wich gives constant end/avg. FO2 - this is not stated but is clear from the excel-file. See the thread for further info. The "algoritm" works by lowering the FO2 of the Dil used by a fixed amount. As far as I can tell it's 0.2, ie. makes a 40% used down to say 20%. But due to the error in the sheet this is not easy to detect. The number of breaths are calculated WRONGLY. The colum H has a critical error, since it's formula should not be '300Gx', but something like 'Gx/0.2$B$2' ie. a FO2-drop of 0.2 SCALED by the meassured drop-count. Incidently for the numbers in the sheet is matches, but not if your drop is different from 60. Does not advise against meassuring with to high FO2, where drop-count becomes non-linear, and therefor TOO HIGH. Does not include any 25% safety-factor as stated in the text. If used with diluents below 40% in the config, it could render one unconsius due to hypoxia near the shallows. I would not dare use that sheet - sorry Safe Dives Nicolai __________________ Woohooo - I can change my rEvo! Its going to be bitchin' tricked out piece of gear Last edited by Hanssing : 27th January 2008 at 20:37.
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