Menetelmä ja laitteisto paperin, kartongin tai vastaavan rainamaisen tai arkkimaisen tuotteen laadun valvomiseksi

The invention relates to a process and a plant for quality control of a web-shaped, sheet-shaped or equivalent product, such as paper, cardboard or equivalent. The quantity of the coating material, surface glue or equivalent which is spread on top of or amongst the product W to be examined, to which product W optical brightener has been added in order to obtain the required quality of the product W, is checked and measured during the production process of the product which is examined. The quantity of coating material, surface glue or equivalent is measured from the product W or from a wet film on top of the roller surface in such a way that the web-shaped, sheet-shaped or equivalent product W is radiated with ultraviolet light 2 in order to generate fluorescent light 4 in the optical brightener and the intensity and/or colour of the said fluorescent light 4 is determined locally in order to determine the quantity of optical brightener and the quantity of coating material, surface glue or equivalent proportional thereto.