Abstract: A system (10) accurately measures the resistivity of a material (12) via capacitive coupling without contact with the material (12). A transmission electrode (14a) sends signals through the material (12) to a reception electrode (14b). An oscillation mechanism (16) forwards a periodic signal at a predetermined frequency f to the electrode (14a), and a detection mechanism (18) receives a resistivity signal from the electrode (14b), which signal is proportional to the resistivity of the material (12), and translates the resistivity signal into a resistivity value for the material (12). The oscillation mechanism (16) comprises an oscillator (21) connected through a transformer (T1) to a quarter-wavelength stub (24), which feeds an excitation signal to the transmission electrode (14a). The detection mechanism (18) comprises a detector (31) connected via a transformer (T2) to a quarter-wavelength stub (26), which is directly connected to the reception electrode (14b).
Type:
Grant
Filed:
August 23, 1993
Date of Patent:
January 31, 1995
Assignee:
Denmar, Inc.
Inventors:
Dennis R. Jones, James E. Lutz, Richard H. Campbell, Denys D. Overholser