Ubidots Community

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.


I’ve tried to replicate this formula as a synthetic variable, but I’m not getting any results.

The variables are: OG (the first measured density reading) and FG is the last density reading the device takes every 15 minutes.

Can someone help me put this formula as a synthetic variable?

Thank you

Hi @Miguel_M_V,

Could you please share the synthetic formula so I can help you checking what could be wrong?

Looking forward to your response.


Can you show me in screenshots how to do this please as I’m very new to it all thanks
Or could you please share a link please

Many thanks

Hi @Task001,
thank you for sharing your question with the community.

Please refer to the following article that explains how to implement that formula using synthetic variables.


I’m looking a bit thick because I still don’t understand how to do it sorry

If I give someone my account information could you please do it for me please

Thanks in advance