Eliminating measurement errors when determining thickness of electrically conducting film applied to ferromagnetic body enables accurate measurement in presence of relatively large base material quality fluctuations

摘要

Inductance of measurement coils carrying a.c. current is evaluated. The method involves evaluating the inductance of at least one measurement coil (14) carrying an a.c. current, whereby a dimensionless parameter is determined using the equation K = e asterisk (LSA - L0)/(Linfinity asterisk - LSA), where LSA is the inductance of the coil with respect to air; L0 is the inductance of the sensor coil when positioned on the uncoated metal surface of the base material; Linfinity asterisk is the coil inductance measured only with respect to the film material, e is a numerical factor and K is converted with an adjustment characteristic into a correction factor and the measured thickness DM is converted into a real thickness DW with DW = DM/F.