[vrantist]

Lo vedo un po' inutile se usato durante la fermentazione messo dentro il fermentatore, a meno ché non abbia un sistema per compensare l'anidride carbonica creata dal lievito, senza contare la schiuma che si va a creare in superficie che asciugandosi si andrebbe ad attaccare allo strumento appesantendelo e falsando le letture

Dubbi legittimi, ma andrebbe provato. Ecco cosa dicono loro su questi temi:

Q. How accurate is the Brewometer? 
A. The specific gravity is accurate +/- 0.002.The thermometer is accurate +/- 2 degrees F (+/- 1 degree C). 
Q. How is the Brewometer affected by foam?  
A. There is no noticeable interference from foam. Foam plays a minimal role since it is significantly less dense than the beer and 95% of the device is submerged in the beer. 
Q. How do bubbles from CO2 affect the Brewometer?
A. We recommend putting the Brewometer in your beer prior to pitching yeast, this will ensure any bubbles will not affect initial readings. Bubbles from dissolved CO2 may cause higher than expected readings for a short time if placed in an active fermenting brew. However, this can be sped up if washed with alcohol (i.e. Everclear).