A method for determining the compression level of a node by compacting and welding electrical lines inserted into a compression chamber of an ultrasonic welding system, the compression chamber having an adjustable height and width. The method includes inserting the lines into the compression chamber, compacting the lines, determining the compacting cross section of the compacted lines, determining the actual total cross section via a correlation function taking the compacting cross section into account, welding the compacted node with a welding parameter set, determining the welding dimension from the height (h2) and width (b) of the compression chamber after welding, and calculating the compression level based on the actual total cross section and the welding dimensions.