Optical measuring device (also refraction meter, refraction = refraction) with which the concentration of liquids or solid bodies can be determined by means of light refraction. A variant of such a device was developed by the German physicist Ernst Abbe (1840-1905), who was the owner of the Zeiss company. In viticulture, the sugar content in the form of the must weight and therefore the potential alcohol content can already be determined in the grapes in the vineyard or in the grape must. In a drop of grape must enclosed between two prisms, the light is diffracted according to the sugar content and the value is usually displayed together on a scale on the eyepiece in a different unit of measurement depending on the wine-growing country (for example Brix, Oechsle and KMW = Klosterneuburger Mostwaage). The more concentrated the sugar solution, the more the light is refracted.
This is used to determine the degree of ripeness or physiological ripeness as a decision-making aid for the ideal time to harvest the grapes. To obtain a representative value, at least 100 berries must be taken from different grape zones and necessarily also from several grapes from different locations in the vineyard. These berries are crushed together in a container and then some grape must is taken for measurement. The must weight development is determined by taking several measurements on different days in succession. The must weight is also determined using other devices such as areometer or pycnometers. For other measurement methods, see analytical testing and a list of relevant keywords under units of measurement.
Refractometer: by Jacek Halicki - Own work, CC BY-SA 4.0, Link
Eyepiece: by Robert Roßkopf - Own work, CC BY-SA 4.0, Link
Graphic: Vvon Gottsleben - Anton Paar GmbH, CC BY-SA 3.0, Link
