potential alcohol by volume?

Can someone explain to me how potential alcohol by volume works? Or maybe what I'm really wondering if how accurate the PAV readings on a hydrometer really are? For example, tonight I bottled up a batch of apfelwein and just for the heck of it decided to take a hydrometer reading. 0.999 was the reading. If I go by my hydrometer that puts the potential alcohol by volume at 0%. Now I know that's not the case. Or am I misinterpreting something?

Thanks,

Jeff

The key word is "potential." Measure your unfermented wort or must, and it will attempt to tell you how much alcohol could potentially be fermented from it.

I'd ignore that scale, without knowing your final gravity it's just guesswork. Better yet, subtract your final gravity from your original gravity, and multiply by 131. That will get you quite close to the actual ABV.