For the $15.00, I decided to experiment. Got one with a 0-25% scale. I will check it against known (commercial wine, or ??) and see how close it is. I'm not sure if these things can be calibrated. After 10-15 tests, I should have a fairly good idea how close and the amount of variation. I'm curious how it will vary between white and red wine. I'll post back here about it but it will probably be a couple months.
Seems fairly unnecessary unless you don’t already measure the gravity on both ends? The only benefit I can envision is that sometimes juice buckets seem to have already started fermenting by the time you get them so you don’t really know the starting gravity.