Abstract: The invention comprises a measuring device and method for the pressing zone width pressure per unit area of this zone and/or additional characteristic variables of a roll of material depending on the pressing surface area. A time interval measured directly or indirectly in which the distance a sensor from the roll of material is either above or below a certain limiting value is obtained by a plurality of sensors positioned on the surface of a roller pressed against the roll. The pressing zone width is automatically computed from this time interval and the speed of the web of sheet material and, if necessary, additional information including the radius of the roll, the weight of the roll of material and the like. The winding of the sheet of material is controlled based upon the ascertained pressing zone width.

Abstract: A measuring device for determining the pressure zone width and/or surface pressure between a web roll for a web and a further roll of a winding apparatus includes at least one reflex sensor emitting a radiation towards the web roll and receiving radiation reflected from the web roll. The reflex sensor is provided with a source emitting the radiation towards the web roll and a receiver which picks up beams reflected from the web roll. Source and receiver are embedded within the peripheral area of the further roll and are arranged adjacent to each other. During winding of the web, the reception of the radiation is interrupted when the web roll covers the source and/or the receiver. This interruption of the reception is a measure for the pressure zone width and in connection with other variables and constants for the roll firmness.