公开(公告)号：US3684954A

公开(公告)日：1972-08-15

申请号：US3684954D

申请日：1970-12-21

Applicant: INDUSTRIAL NUCLEONICS CORP

Inventor： JAGGERS HENRY T ,  THEADO DONALD R

IPC: G01N27/22 ,  G01R27/26

CPC classification number: G01N27/223

Abstract: For quantitively determining a property of a dielectric material, in particular its relative moisture content, an alternating current electrical signal at a constant frequency is applied to a capacitive probe coupled to the material. The effect of the capacitance of the empty probe is balanced out, and a detection signal is produced from the imbalance occasioned by the dielectric material. A first logarithmic signal is derived logarithmically related to the detection signal and used to vary the applied signal in a direction opposite to changes in the detection signal to reduce the demands upon the dynamic range of system components. A second logarithmic signal is derived logarithmically related to the applied signal. The first and second logarithmic signals are then combined to produce a third logarithmic signal logarithmically related to the ratio of said detection and applied signals, and indicative of the property of the material.