Abstract: A method of and apparatus for measuring the layer of coating thickness of non-magnetic substances on a ferromagnetic parent material by the magneto-inductive method or of non-metallic substances on a conductive parent material by the eddy current method. This is done with the use of a probe whose coil inductance is evaluated as a criterion for the thickness of the layer to be measured. An adjustment to the geometry and the magnetic properties of the specimen are made before the first measurement. In the adjustment, at least one non-magnetic or non-conductive foil is disposed or are consecutively disposed between the probe and the surface of the coated specimen and the measured data obtained then and in the subsequent measurements are fed to a microcomputer.

Abstract: A method of measuring the thickness of test articles by pulse reflection ultrasonics, the length of time period as determined by the signal triggering the ultrasonic transmission and by an ultrasonic signal reflected at the end of the measurement path length being used to determine the distance travelled by the ultrasonics. In the method, the triggering signal for the ultrasonic transmitter is generated in phase with a measuring oscillation of a high and known frequency, whereafter the integral number of measuring oscillation pulses or waves which fit into a time period corresponding to measurement path length are counted, whereafter the measuring oscillation is so detuned that the residual measuring oscillation or wave found over and above that in the time period is reduced to zero and a correction value is derived from the amount of frequency detuning for the measurement path length resulting from the integral number of measuring oscillation pulses or waves.