Thickness measuring device for indicating the mean value of a pre-set number of measurements of the thickness of a layer

Claim 1

Device for measuring the mean value of a pre set number of measurements of the thickness of a layer on a substrate for use in combination with a thickness measuring probe that is positioned on said layer, said probe generating a signal which decreases as said probe is Brought into measuring position adjacent the layer and data output means comprising comparator means connected to said probe and controlled by measuring signals from said probe, said comparator means having a threshold at a probe signal level higher than the maximum thickness to be measured to thereby generate a control signal as said probe approaches said layer, time delay means controlled by said comparator means control signal and providing a delay signal that permits the proper placement of the measuring probe on the layer, means controlled by the delay signal of said time delay means for generating a signal which establishes the beginning and the end of the measuring time interval, gate means having an input connected to said probe for receiving the measurement signals and a control input connected to said last named means for receiving a control signal from said means for establishing the measuring time interval, said latter signal opening and closing said gate means during the measuring time interval, adding means connected to the output of said gate means having an input for receiving input signals during measuring time intervals, dividing means connected to said adding means for dividing the measurement signals by the amount of said pre set number of measurement, pre-settable counter means set to said pre set number of measurements and connected to be controlled by said comparator means control signals coupled with said dividing means for counting said comparator means control signals, one signal being generated for each individual measurement, said counter means being connected to said adding means for automatically controlling the release of output data from said means to said data output means upon counting said pre-set number of measurements, and reset means connected to reset various means of the device for further use following the release of output data.