SOLVED - Derived expression - using first value



I have set up a a device to help with brewing and to determine the fermentation of wort to alcohol.

I’m trying to set up a derived expression to calculate the alcohol by volume measurement as a % the formulae is.

ABV =(76.08 * (og-fg) / (1.775-og)) * (fg / 0.794)

OG= Originating gravity before fermentation - i.e. the very first reading
FG= Final gravity - i.e. when the wort has finished fermenting, this will decline until the beer is finished

Is there a way using my data to take the first ubidot value for SG (it would literally be the first entry) and use this within a derived expression?

I can edit the expression manually each time i.e. 1.040 being the starting gravity, but this will vary from beer to beer.


FG wouldn’t need to be changed as this will be the most recent value.

Can anyone give me any pointers please?




Solved, needed to add in OG as a rolling variable over a predetermined timescale.