For the production of quality wine it is necessary to control each single step of the production. In addition to monitoring the filtration stages prior to and after maturing, the automatic control of the pre-clarifying using photometric turbidimeters is of interest. When the pre-clarification tank is emptied, the clear must is drained while the sludge, which has collected in the lower and upper portion of the tank, is avoided. In case of light-coloured juices (white wine, rosé wine), it can be detected with the naked eye, when the solids appear in the free-run must. However, the continuous measurement of turbidity allows a fast and reliable optimization of the process. In case of coloured juices (red wine), visual detection is impossible and the measurement of the turbidity value is essential. Photometer