A Microwave instrument for Measurement of Small Inbomogeneties in Supercalendar Rollers and Other Dielectric Cylinders*

A microwave instrument for non-destructive testing of the homogeneity of supercalendar rollers used in paper mills is described. The sensor consists of a flat coaxial transmission line a half wavelength long. A sensitivity of more than 0,1% is achieved in measuring small changes in the dielectric constant. Measurement of absolute values of the dielectric constant is also possible.