This is the OG to Plato formula I started with:
=(-0,003829+WORTEL((0,003829*0,003829)-4*0,00001572*(1-(L205/1000))))/(2*0,00001572)
Eventually I managed to derive this Plato to OG formula from it.
=2000-(((0,003829*0,003829)-(((2*P205*0,00001572)+0,003829)*((2*P205*0,00001572)+0,003829)))/(4*0,00001572))+1)
Don't ask me why the 2000- is at the start of it. I added that so that the right number came out at the end. If you're wondering what the L205 and P205 are, they are the cell numbers of respectively the OG in specific gravity and Plato. I'm using the formula in a spreadsheet, you see.Rather naively, after leaving school I never expected to have to manipulate complex arithmetic formulae again. Then along came brewing. Converting between Plato and OG and vice versa is a pain. As is calculating alcohol content from OG and FG. At least I only have to do this once. Embedded in the spreadsheet, the calculation occurs automatically. I pity any poor bastard who has to do this by hand.
Why was I doing this? For my mega-gravity table. I've just been incorporating some analyses (is this the correct plural form of analysis? I keep using it) from German sources, where all the gravities are in Plato. Well, Balling, really. I'm aware that it isn't a 100% identical to Plato, but I've already spent several hours playing around with Plato conversions. It'll have to do.
5,360. There's another number for you. How many entries I now have in my mega-gravity table. Now I've added the continental ones.
It would be interesting to see the definition of the wortel function, and also an explanation of the original OG->PLATO formula. I'm thinking of things like what the 0,003829 and 0,00001572 constants are.
ReplyDeleteIt's actually possible to simplify both formulas quite a bit, but I don't know if you're interested in that.
Still, an explanation would be interesting. To me, anyway.
(OG - 1000)/4 = plato. Well, near enough for brewers so ought to be near enough for geeks. Perhaps not, actually.
ReplyDeleteLars, it's all to do with the way sugar breaks down into alcohol and CO2. I can't remember the precise explanation and too knackered to look it up.
ReplyDeleteFatman, the reason I'm so fussed about the OG to Plato conversion is because that's the first step in getting an accurate ABW calculation from a gravity drop. Maybe I'm thick and there's a much simpler way.