Abstract: The measuring device comprises at least one measuring head having a reference part, which comprises a reference surface against which the moving web is supported. The reference surface comprises a measuring area in the inside of which the property of the web is measured. The reference part is arranged in connection with the measuring head in such a way that below the reference part, there is a substantially open air space. The measuring head comprises means for generating negative pressure in the air space below the reference part, and the reference part comprises holes formed through it, in such a way that the negative pressure generated in the air space affects through the reference part the space between the reference surface and the moving web in such a way that the web is supported against the reference surface substantially over the whole area of the measuring area.

Abstract: The measuring device comprises at least one measuring head having a reference part, which comprises a reference surface against which the moving web is supported. The reference surface comprises a measuring area in the inside of which the property of the web is measured. The reference part is arranged in connection with the measuring head in such a way that below the reference part, there is a substantially open air space. The measuring head comprises means for generating negative pressure in the air space below the reference part, and the reference part comprises holes formed through it, in such a way that the negative pressure generated in the air space affects through the reference part the space between the reference surface and the moving web in such a way that the web is supported against the reference surface substantially over the whole area of the measuring area.

Abstract: The invention relates to a method and an apparatus for measuring properties of a moving web, a sensor (1) being arranged on a first side of the moving web (7), the sensor comprising a differential coil (3), which comprises at least two coils, and a reference plate (4). A sensor plate (6) is arranged on a second side of the moving web (7). Electric current is used to induce a voltage to the differential coil (3). The voltage of the differential coil (3) varies as the web (7) changes the effect caused by the sensor plate (6) to the differential coil. The properties of the web (7) are determined by measuring the voltage of the differential coil (3).

Abstract: The invention relates to a method and apparatus for measuring the caliper of paper substantially continuously during papermaking. A sensor (3a, 3b) is arranged above and/or under the paper (2), the sensor (3a, 3b) measuring the caliper of the paper (2) at least on one side of the paper (2) mainly without contacting the surface of the paper (2). At given intervals the sensor (3a, 3b) measuring mainly without contact is brought into momentary contact with the surface of the paper (2).