controls model supported controls multiple magnitude controls or decoupling controls the following are preferred controls p controls pi controls pid controls two point controls with or without hysteresis adaptive controls condition controls non linear controls model supported controls and multiple magnitude controls pi controls two point controls with or without hysteresis condition controls and model supported controls are particularly preferred the temperature measuring sensors may be thermometers thermoelectric elements resistance thermometers pt100 or infra red measuring devices thermoelectric elements resistance thermometers and pt100 are preferred temperature measuring devices the temperature measurement above the side discharge and below the side discharge may in principle be located in any position provided it is situated at least one plate removed from the head or sump respectively of the column the measuring locations are preferably chosen as follows a typically about 4 to 5 plates above the side discharge and below the side discharge or b by an empirical process for determining the measuring location in which disturbances are introduced into the column and the resulting changes in the quantity of side discharge and or the amount of intermediate boiling component are determined at sensitive temperature measuring points by 34 sensitive 34 is meant in this context that the temperatures at the measuring points react rapidly and with sufficient amplitude to the above mentioned changes one or more measuring points may be selected from these sensitive measuring points to serve as measuring control magnitude when more than one measuring point is used above or below the side discharge a suitable average should be calculated for the given region c alternatively the position of the material exchange zones may be determined by means of measurements or simulations and the measuring probes for determining the temperature may be arranged in regions of large material exchange streams.