In Vinoland, we use degrees °Brix (°B) - the percentage of total solids in solution - to measure the sugar content of our grape juice. As I have mentioned before, this is only a guideline as to when grapes are ready to be harvested and made into wine.
Today was the first time that I have bothered to test our Cabernet Sauvignon to see just exactly where it is on it's little annual journey towards maturity. I took several readings and they all came in exactly the same, (no need to take an average of the readings - which was a first for me), 22.6 °B. Yes, Thomas, I know that that is approximately 12.9% potential alcohol, but look at the squished grapes in the above photograph; seeds are still partially green, pulp is still firmly attached to the seeds, and there is almost no colour extraction. The flavours are quite promising, but merely measuring the sugar content is no indication of phenologic maturity.