These devices work according to the hydrometric principle and react to the relative density of the liquid. With a residual sugar spindle including a thermometer according to Dr. Kielhöfer, the content of unfermented sugar, i.e. the residual sugar in wine, can be determined quite accurately. However, this requires the original must weight in Oechsle or KMW of the wine in question. The residual sugar spindle reading applies when the thermometer reads exactly 20 °Celsius. For each degree above this, 0.2 sugar degrees are to be added, for each degree below this, 0.2 sugar degrees are to be subtracted. With the temperature-corrected sugar value and the original must weight, the sugar content of the wine in g/l can be taken from a table (the sugar table). These devices are calibrated for wines of average extract and alcohol content. Deviations from this result in a different immersion depth. They are therefore relatively inaccurate and cannot provide exact readings. See the taste directions (dry to sweet) under sugar content.
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