Ein Verfahren zur Messung der komplexen Dielektrizitätszahl an kleinen Flüssigkeitsmengen im Frequenzbereich von 0,7–25 GHz mit Hohlraumresonatoren

A method is described for measuring the complex relative permittivity of liquids. Circular cylindrical TE₀₁₁-, TM₀₁₀- and coaxial-line-resonators are used. The liquid under test is contained in a narrow glass tube (volume<0.5 ml) which is placed concentrically along the axis of the cavity resonator. Besides the knowledge of the diameter of the glass tube and the dimensions of the resonator only frequency measurements are required. The accuracy of the method (error±5% of the absolute value for both, the real- and imaginary part of the permittivity) is comparable to other methods requiring a larger amount of liquid. Furthermore, permittivity variations can be measured very sensitively because these are indicated by shifts of the resonance frequency as well as changes of the quality constant, which can both be determined with an error smaller than 0.5%. Some experimental results for water and an aqueous phospholipid suspension are given to demonstrate the accuracy of the method.