Measurement method and system in the manufacture of paper or paperboard

In a measurement method in the manufacture of paper or paperboard, different forces prevailing in a nip between a roll and a counter roll of an apparatus conveying a paper or paperboard web are measured. In the method there are several measurement points implemented with one or more film sensors ( 3 ) placed in the roll ( 1 ) in the transverse direction of the paper or paperboard web. The measurement information obtained from the measurement points by means of the sensor or sensors ( 3 ) is utilized to determine the pressure distribution of the nip. The film sensor ( 3 ) is a piezo- and pyroluminescent sensor from which the measurement information can be received optically at least in the initial stage, or a sensor comprising an electromechanical film (EMFi). The sensors ( 3 ) placed in the calender roll ( 1 ) can be utilized to measure the pressure distribution of the calender nip (N).