Abstract: A method and a device that performs the method for measuring the flatness of a metal product traveling on a path, the method includes measuring a first longitudinal tension measurement value (T1) with a measuring roller, determining a model of stress over the thickness of the metal product as a function of plastic or elastoplastic deformation of the product, calculating a correction factor for the longitudinal deformation according to the stress model, calculating a corrective value (T1?, T2?) for the first longitudinal tension measurement value (T1) at at least one evaluation point (M1, M2) as a function of the longitudinal deformation correction factor (Z1), and calculating a corrected flatness measurement value (PC) at at least one of the evaluation points.

Abstract: A method and device for measuring the flatness of a metal product traveling on a path. The product has at least plastic or elastoplastic deformation properties. The metal product (1) is in the form of a strip that travels (D) under tension over a flatness measurement assembly (2) that deflects the product, such as at least one measuring roller (RM) that deflects the product. Measure flatness by measuring the longitudinal tension over a deflection zone.