We report, for the first time, a low-cost and robust homemade hollow coaxial cable Fabry-Pérot resonator (HCC-FPR) for measuring liquid dielectric constant. In the HCC design, the traditional dielectric insulating layer is replaced by air. A metal disk is welded onto the end of the HCC serving as a highly reflective reflector, and an open cavity is engineered on the HCC. After the open cavity is filled with the liquid analyte (e.g., water), the air-liquid interface acts as a highly reflective reflector due to large impedance mismatch. As a result, an HCC-FPR is formed by the two highly reflective reflectors, i.e., the air-liquid interface and the metal disk. We measured the room temperature dielectric constant for ethanol/water mixtures with different concentrations using this homemade HCC-FPR. Monitoring the evaporation of ethanol in ethanol/water mixtures was also conducted to demonstrate the ability of the sensor for continuously monitoring the change in dielectric constant. The results revealed that the HCC-FPR could be a promising evaporation rate detection platform with high performance. Due to its great advantages, such as high robustness, simple configuration, and ease of fabrication, the novel HCC-FPR based liquid dielectric constant sensor is believed to be of high interest in various fields.


Electrical and Computer Engineering


University of Missouri Research Board


The work was supported by University of Missouri Research Board

Keywords and Phrases

Coaxial cables; Dielectric materials; Dielectric properties of liquids; Ethanol; Evaporation; Liquids; Mixtures; Reflection; Resonators; Thermal variables measurement, Air liquid interfaces; Dielectric insulating layers; Ethanol/water mixtures; Evaporation rate; High robustness; Highly reflective; Impedance mismatch; Liquid dielectrics, Phase interfaces

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Article - Journal

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Final Version

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