1. Welding apparatus, having a current source for supplying electrical power to at least one electrode at a welding torch and a control system co-operating with the current source, linked to an input device for entering settings for different welding parameters, several sensing means being provided for detecting various actual values of a welding process, characterised in that at least one measuring system ( 31 ) for sensing a movement, in particular a welding wire displacement and/or a welding torch displacement or similar is provided, which detects a surface structure of an object.