Accession Number : ADA306048

Title :   A Prototype Microwave Probe and Reflectometer for In Situ Measurement of Soil Electrical Properties.

Descriptive Note : Final rept.,

Corporate Author : ARMY ENGINEER WATERWAYS EXPERIMENT STATION VICKSBURG MS ENVIRONMENTAL LAB

Personal Author(s) : Everett, Joel B. ; Curtis, John O.

PDF Url : ADA306048

Report Date : FEB 1996

Pagination or Media Count : 84

Abstract : A number of simple experiments were performed on a microwave reflectometer, operating at 60 MHz, to test the feasibility of its use as a tool for accurately measuring the complex electrical properties of soils. Such knowledge could be used to predict electromagnetic wave attenuation, the volumetric moisture contained within soil near the probe surface, and, through the relative changes in soil properties either over surface areas or as a function of depth below the surface, the presence of harmful contaminants. Background information contained within this report includes a review of similar microwave sensor applications and a description of the basic relationships used to convert sensor voltage measurements into relative dielectric permittivity and conductivity. Experiments were conducted to investigate the volume of soil that would be measured by the soil and to determine the sensitivity of the instrument. While permittivity measurements appeared to be quite good, conductivity measurements in low conductivity materials were not as reliable. A simple analytical study indicated that the conductivity measurements would be quite sensitive to the accuracy of the voltmeter being used by the reflectometer. In most soils, the frequency of operation and the sensitivity of this system will allow the field lines to extend about 1 cm away from the probe surface, making the probe ideal for surface measurements and well suited to being placed in a borehole or cone penetrometer environment to obtain vertical profiles of soil properties. Numerous improvements to the measurement system were recommended to improve its sensitivity and utility.

Descriptors :   *DIELECTRIC PROPERTIES, *REFLECTOMETERS, *SOIL TESTS, PROBES, DETECTORS, ACCURACY, PENETROMETERS, MICROWAVE EQUIPMENT, SENSITIVITY, ELECTRICAL CONDUCTIVITY, SOILS, PROFILES, RADIATION ATTENUATION, ELECTROMAGNETIC RADIATION, INSTRUMENTATION, MOISTURE, ELECTRICAL MEASUREMENT, VOLTMETERS.

Subject Categories : Geology, Geochemistry and Mineralogy

Distribution Statement : APPROVED FOR PUBLIC RELEASE