A four terminal measurement system for measuring the dielectric properties of clay at low frequencies

摘要

Recently there has been increasing interest in theuse of the frequency dependent dielectric properies of clay soilsas a potential method of contaminant detection. The study ofdielectric properties of contaminated clays at lower frequencies isof particular importance as this has been theoretically argued tobe the range in which the interfacial polarisation and double layerpolarisation occurs. These are phenomena which providevaluable information on the physical and chemical properties ofclays and how these will change in the presence of contaminants.However, dielectric measurements are more difficult to obtainat low frequencies due to a number of phenomena that can causemeasurement errors. Four terminal measurement systems aretheoretically capable of reducing the error due to thephenomenon of electrode polarisation. A commercial probe thatis normally used to measure the biomass of biologicalsuspensions has been tested for its suitability to make dielectricmeasurements in clays. Preliminary results highlight some of theproblems with calibrating such a system for this type ofmeasurement and indicate that the problems of electrodepolarisation can still persist.