PURPOSE: To measure the dielectric property of a liquid material that flows to a conduit by providing a non-conductive shell with a bore, an alternate engagement fringe field electrode provided on the inner surface of the shell, and a means for guiding current between the electrodes.

CONSTITUTION: A sensor has a ceramic cylinder with an alternate engagement electrode capacitor that is imitated on an inner wall, an electrode is provided at the recessed part of ceramic, the surface of the electrode is flush with the surface of ceramic, and a protection cover prevents the electrode from being corroded. A gap between electrodes is normally 0.1-10mm and an operation region on a detection surface is normally 5-250cm2. The sensor operates in a fringe field mode. More specifically, the fringe of an electromagnetic field between the electrodes saturates a sample. The gap of the alternate engagement electrode is selected so as to acquire the maximum penetration of the fringe electromagnetic field at a large fraction of a sample volume in the sensor while retaining an easily measurable electrostatic capacity between the electrodes, thus measuring the average dielectric property of the annular capacity of the sample.