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From: Josep M- Torrents Dolz (torrents) >Bruce Metelerkamp wrote: > Josep > Perhaps you could introduce yourself to sowacs by sending a >brief abstract of your PhD work to the list? Hello list-friends, I'm a lecturer in Politechnical University of Catalonia. As you see, Bruce invited me to introduce myself to sowacs. I apologize for my not english mother tonge (and I'm always pleased to constructive corrections). My address is as follows, -- Josep Maria Torrents-Dolz, Departament d'Enginyeria Electr_nica, Universitat Polit_cnica de Catalunya, c/. Gran Capit_ s/n edifici C4, 08034 Barcelona, Spain, tel. 34-3-401 67 58, fax 34-3-401 67 56, e-mail torrents@eel.upc.es Here it is a brief abstract of my PhD work titled Development of Electrical Impedance Measurement Techniques Applied to Soil Characterization. Directed by: Dr. Ramon Pallas-Areny Soil moisture quantification is of great interest in different engineering areas. This moisture knowledge through electrical impedance, carries on an accurate study of measurement techniques, in order to know the real measured factors. Moreover, you have to know if electrical measurements corresponds to moisture presence or to interferent phenomenon, as ionic-electronic transductions due to electrode polarization, local electrical charge accumulations or instrumentation limitations, often ill solved in literature. The theoretical study of electrical properties (conductivity and permittivity) from mixtures give us soil as a particles system with three phases: the solid one, the electrolytic one and voids. You can study soil system as a high loss composite dielectric material. Phase interaction modify electrical properties of theoretical mixtures. This behavior force us to use pseudoempirical laws and our own model. Classical electrical impedance techniques have been analyzed, validated, ranged and applied to soil medium material. If electrical drawbacks are not considered or forgot, they will give probably erroneous interpretations. In addition, these measurement techniques and electrical soil moisture materials studies carry us on some cells development. They have been matched to different frequencial measurement strategies, combining instruments and right connections among different parts with some original solutions. The soil conductivity is not frequency dependent in the studied range (1 Hz to 100 MHz). Instead, it is function of electrolytic concentration. Beyond a threshold, there is a lineal relationship between conductivity and moisture content in sand soil. In clay and lime type soil this relationship is a potential one till near saturation. At low frequency, it is not possible to measure permittivity-moisture relationship due to conductivity masking effect. At higher frequency (at least 1 MHz), the permittivity-moisture relationship has the same shape behavior to conductivity-moisture curves. These results have been successfully compared with modified literature models. The development and analyses of measurement techniques and the electrical models of soils allow us to know soil moisture but you must know previous information about soil type and initial electrolyte concentration. The development techniques aid quick and cheap the classical non electrical techniques and the developed ones may substitute classical ones if we accept a 5% uncertainty. Will be in touch! Josep Maria Barcelona, 11-XII-96