With the help of a phertometer, the surface of a sample is scanned with a needle of defined geometry and standardized roughness parameters are calculated. While usually only the average roughness Ra is considered, there are many other parameters, such as contact ratio, roughness depth, etc., which allow a more meaningful description of the surface, depending on the problem.
Hardness is the mechanical resistance that a material offers to the mechanical penetration of a harder test specimen. Depending on the material, a distinction is made between different hardness measurement methods. While for metals the Vickers hardness or the Rockwell hardness correspond to the permanent deformations in the surface, the Shore hardness A and D are used for elastomers and plastics (DIN ISO 48-4).