Karl Deutsch Pruf - Und Messgeratebau Gmbh+co. Kg

Werner F Roddeck

Volker K Deutsch

Heinz-Peter Schafer

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. In the semiconductor store of the micro-computer, the non-linear relationship between the coil inductance of at least one probe and the distance between the probe and the parent material is being or has been stored in the form of at least one values table and in which the layer thickness values of the foils are being or have been stored. The microcomputer calculates the thickness values of the layer material from the measurement data fed to it and from the stored data.

Method of and apparatus for layer thickness measurement

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. This method and apparatus make possible high accuracy of measuring while avoiding the disadvantages of analog circuit arrangements and while using a counting frequency usable by very low current CMOS components which can be used in portable battery-operated devices.

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Velbert, Germany

Werner F Roddeck