A vinometer is used for determining the alcohol content of a finished wine.
They can only be used on dry wines with no residual sugar content present.
The funnel is filled with wine until a small amount of wine exits the base. Then rotate the tube 180 degrees and sit on a flat plate. Watch where the wine in the tube stops and that is your approximate alcohol reading. A more specific reading can be obtained by mixing 5mls of wine to 5mls of water and proceeding as above. your final reading should be multiplied by two to give the alcohol percentage. e.g. if the vinometer shows 5% than your wine would have an alcohol percentage of 10%