The surface roughness measurement of metals using microwaves

A principle of surface roughness measurement for metals using relations between the surface roughness and reflected microwave power is developed. A single-chip microcomputer is used for processing and displaying the results. This method features noncontact inspection and real-time operation as well as high accuracy and ease of application. The apparatus includes a microstrip disk radiator and a cubic dipole antenna, which is used for receiving microwave power reflected from the metal surface and converting it to DC voltage. Nine standard steel samples which have different contour arithmetic mean deviations (roughness) Ra were measured. The range of Ra is 0.01-2.00 mu m. An error of less than 5% was achieved.<>