The paper aims to present a new method measuring the belt friction coefficient by the original computer-controlled measuring set. The essential elements of this semi-automated assembly are a digital force gauge and a digital servomotor. The Dynamixel MX64T servomotor with the externally installed shaft is a reliable, accurate and affordable instrument for examining frictional force and the belt friction coefficient, in dependence on the set constant rotational speed of the shaft. The new measurement method is realized by a double arrangement of the measuring assembly by winding the fibre onto the roller surface of the external shaft of the digital servo-motor and pulling the fibre over the external roller surface by the digital servomotor. The paper is intended for accurate engineering measurements or university scientific-research measurements, especially when it is necessary to declare the coefficients of unknown combinations of contacting materials of fibre and the roller surface, or the need to explore the properties of new types of fibres. The view of the tribological issues is physical-technical because virtually the relationships between the coupled physical phenomena of the same measuring set and the influences of the parameters of the sophisticated technical equipment on these phenomena are used.