System for measuring a property of a dielectric material by applying signals at two different frequencies to a capacitance probe through tuned input circuits

Claim 1

IN A SYSTEM FOR DETERMINING A PROPERTY OF A DIELECTRIC MATERIAL, SAID SYSTEM COMPRISING A FIRST SOURCE OF ELECTRICAL INPUT SIGNALS AT A HIGH FREQUENCY, A SECOND SOURCE OF ELECTRICAL INPUT SIGNALS AT A LOW FREQUENCY, DETECTING MEANS, A MEASURING PROBE HAVING SPACED ELECTRODES ARRANGED FOR APPLYING SAID INPUT SIGNALS TO AT LEAST PORTION OF SAID MATERIAL AND COUPLING SAID DETECTING MEANS TO SAID PORTION, AND A BALANCING CAPACITOR CONNECTED TO SAID PROBE: THE IMPROVEMENT COMPRISING A FIRST INPUT CIRCUIT COUPLED TO SAID FIRST SOURCE, A SECOND INPUT CIRCUIT COUPLED TO SAID SECOND SOURCE, MEANS COUPLED BETWEEN SAID FIRST INPUT CIRCUIT AND SAID PROBE AND SAID BALANCING CAPACITOR FOR COUPLING SAID FIRST SOURCE TO SAID PROBE AND SAID BALANCING CAPACITOR WHILE SUBSTANTIALLY DECOUPLING SAID SECOND SOURCE FROM SAID FIRST SOURCE, AND MEANS COUPLED BETWEEN SAID SECOND INPUT CIRCUIT AND SAID PROBE TO SAID BALANCING CAPACITOR FOR COUPLING SAID SECOND SOURCE TO SAID PROBE AND SAID BALANCING CAPACITOR WHILE SUBSTANTIALLY DECOUPLING SAID FIRST SOURCE FROM SAID SECOND SOURCE, SAID FIRST INPUT CIRCUIT AS SO COUPLED, INCLUDING SAID PROBE CAPACITANCE AND SAID BALANCING CAPACITOR, BEING SUBSTANTIALLY RESONANT AT SAID HIGH FREQUENCY, AND SAID SECOND INPUT CIRCUIT AS SO COUPLED, INCLUDING SAID PROBE CAPACITANCE AND SAID BALANCING CAPACITOR, BEING SUBSTANTIALLY RESONANT AT SAID LOW FREQUENCY.