MICROWAVE THICKNESS MEASURING DEVICE UTILIZING TWO RESONANT CAVITIES ON EITHER SIDE OF THE TEST PIECE

摘要

A device for measuring a displacement or the thickness of a sheet comprises a microwave test cavity resonator whose resonance frequency is controlled by said displacement or thickness and a microwave reference cavity resonator. A saw tooth modulated microwave generator supplies microwave energy to both cavities. First and second detector means detect the transmission of power by the test cavity and the reference cavity respectively and the volume and resonance frequency of the reference cavity are automatically adjusted in order to cause said transmissions to coincide in time.