Measuring device for detecting measurement signals during a penetration movement of a penetration body into a surface of a test body, for identifying the scratch resistance of the surface of the test body or during a scanning movement of the penetration body on the surface of the test body, in particular for identifying the surface roughness, having a housing which has a force generating apparatus which is operatively connected to a penetration body for generating a travelling movement of the penetration body along a longitudinal axis of the housing and a controls a penetration movement of the penetration body into a surface to be tested of the test body or positions the penetration body on the surface of the test body for scanning and to at least one first measuring apparatus for measuring the depth of penetration into the surface of the test body or a travelling movement of the penetration body along the longitudinal axis of the housing during a scanning movement on the surface of the test body, characterised in - that the force generating apparatus is controlled by means of a gaseous pressure medium for the penetration movement of the penetration body, - that the force generating apparatus has a pressure chamber having at least one first pressure surface, said force generating apparatus being operatively connected to the penetration body, - that the pressure chamber has a second pressure surface which is opposite the first pressure surface, - that the first and second pressure surfaces (51, 52) are formed as a pressure membrane, which are orientated parallel to each other and are preferably fastened on the peripheral wall of the housing, - that the first and second pressure surfaces (51, 52) have freedom of movement in only one degree of freedom, - that the first measuring device for measuring the travelling movement of the penetration body is provided between the first pressure surface and the penetration body, - that a further measuring device is provided between the first pressure surface and the penetration body for detecting at least one displacement of the penetration body along the axis of the travelling movement of the test body relative to the penetration body, - that the first measuring device and the at least one further measuring device are provided in a housing portion of the housing, said housing portion adjoining the pressure chamber, and - that a holding element which accommodates the penetration body is provided on a lower peripheral region of the housing portion of the housing and at a distance from the first pressure surface. - that the force generating apparatus is controlled by means of a gaseous pressure medium for the penetration movement of the penetration body, - that the force generating apparatus has a pressure chamber having at least one first pressure surface, said force generating apparatus being operatively connected to the penetration body, - that the pressure chamber has a second pressure surface which is opposite the first pressure surface, - that the first and second pressure surfaces (51, 52) are formed as a pressure membrane, which are orientated parallel to each other and are preferably fastened on the peripheral wall of the housing, - that the first and second pressure surfaces (51, 52) have freedom of movement in only one degree of freedom, - that the first measuring device for measuring the travelling movement of the penetration body is provided between the first pressure surface and the penetration body, - that a further measuring device is provided between the first pressure surface and the penetration body for detecting at least one displacement of the penetration body along the axis of the travelling movement of the test body relative to the penetration body, - that the first measuring device and the at least one further measuring device are provided in a housing portion of the housing, said housing portion adjoining the pressure chamber, and - that a holding element which accommodates the penetration body is provided on a lower peripheral region of the housing portion of the housing and at a distance from the first pressure surface.