Coaxial Waveguide Resonators as Sensors of Physical Properties of Dielectric Liquids

Microwave sensors applicable for measurement of physical properties (density, moisture, concentration of mixtures, etc.) of different dielectric liquids located in tanks (technological reservoirs, measurement cells, etc.) are considered. In each of considered sensors electromagnetic oscillations are excited in a coaxial waveguide resonator being the sensitive element. Resonant frequency of electromagnetic oscillations of coaxial waveguide resonator containing a monitored liquid is measured. Lower end of coaxial waveguide resonator is metal wall while its upper end is cut-off coaxial waveguide. Electromagnetic oscillations of
$H_{\text{mlp}}(\mathrm{m}=1,2,3\ldots$
.;
$\mathrm{p}=1,2,3,\ldots)$
types are excited in resonators with reduced diameters of inner or outer conductors of cut-off coaxial waveguides as compared with corresponding diameters of the resonators. Electromagnetic oscillations of
$\mathrm{H}_{\text{mnp}}(\mathrm{m}=0,1,2,\ldots$
;
$\mathrm{n}=2,3,\ldots;\mathrm{p}=1,2,\ldots)$
types or
$\mathrm{E}_{\text{mnp}}(\mathrm{m}=0,1,2,\ldots;\mathrm{n}=1,2,\ldots; =1,2,\ldots)$
types are excited in resonators with increased diameters of inner conductors of cut-off coaxial waveguides as compared with inner diameters of the resonators.