Impedance-Based Water-Quality Monitoring Using the Parallel-Plate Method

The application of electromagnetic (EM) waves to measure the electrical properties (dielectric constant and loss tangent) of materials is a well-known approach. The electrical properties can be used to indirectly measure several physical properties of solutions in water such as the concentration and chemical composition of contaminants in water, as a representative of the liquid phase in soil. A capacitive method of measuring dielectric properties of solutions is proposed to detect and determine low-concentration chemical and biological contaminations in water. The primary objective of this project is to design a low-cost sensor that would require small volumes of samples to detect low concentrations of dissolved contaminants in water. A forward model was developed using a finite-element method (FEM) to simulate the experimental setup (EXP). A calibration function was also developed to minimize deviations between FEM and EXP results for benchmark/reference solutions with known dielectric properties. The validated, calibrated forward model was then inverted to calculate the electrical properties of unknown solutions using the corresponding EXP results

Relaxation diélectrique de solutions aqueuses d'éthylène glycol aux micro-ondes

Les auteurs présentent des séries de résultats de mesures en hyperfréquences concernant les permittivités diélectriques de l'éthylène-glycol et de ses solutions aqueuses à 20 ○C, pour diverses concentrations, entre 100 MHz et 20 GHz. Ils ont utilisé trois techniques différentes : des mesures précises à trois fréquences fixes parfaitement stabilisées en guides d'ondes 1,20 ; 3,26 et 9,45 GHz par une méthode réflectométrique ; des mesures utilisant l'analyseur de réseau vectoriel HP 8510 B fonctionnant entre 45 MHz et 20 GHz ; et des mesures par réflectométrie en domaine de temps (R.D.T.). Ils montrent que l'analyse de la relaxation peut être représentée par la superposition de deux domaines de dispersion de type “Debye" pour l'éthylène glycol et ses solutions aqueuses. Par décomposition spectrales, ils déduisent la permittivité statique, les temps de relaxation et la permittivité à fréquence infinie à 20 ○C? Ils proposent que ces mélanges soient de type associé-associé suivant le concept de Schallamach, qui montre que pour des mélanges de ce type, il existe des relaxations d'agrégats contenant les deux types de molécules plutôt que des relaxations de molécules individuelles.

A comparison of ocean emissivity models using the Advanced Microwave Sounding Unit, the Special Sensor Microwave Imager, the TRMM Microwave Imager, and airborne radiometer observations

[1] New measurements of the permittivity of saline water at millimeter wavelengths have the potential to improve the accuracy of ocean surface emissivity models for use with microwave and millimeter-wave imaging and sounding instruments. Recent radiative transfer models employing a range of different treatments of surface ocean emissivity are compared with observations from the following microwave radiometers: Advanced Microwave Sounding Unit, Special Sensor Microwave Imager, TRMM Microwave Imager, Microwave Airborne Radiometer Scanning System, and Deimos. Emissivity models using the new permittivity model fit these observations more closely than those models which use the Klein and Swift extrapolation model. INDEX TERMS: 333

A comparison of ocean emissivity models using the Advanced Microwave Sounding Unit, the Special Sensor Microwave Imager, the TRMM Microwave Imager, and airborne radiometer observations

International audienceNew measurements of the permittivity of saline water at millimeter wavelengths have the potential to improve the accuracy of ocean surface emissivity models for use with microwave and millimeter-wave imaging and sounding instruments. Recent radiative transfer models employing a range of different treatments of surface ocean emissivity are compared with observations from the following microwave radiometers: Advanced Microwave Sounding Unit, Special Sensor Microwave Imager, TRMM Microwave Imager, Microwave Airborne Radiometer Scanning System, and Deimos. Emissivity models using the new permittivity model fit these observations more closely than those models which use the Klein and Swift extrapolation model