Implementación de un sensor de permitividad para fluidos utilizando el método de terminación coaxial abierta

Abstract

This Project focuses on the implementation of an open-ended coaxial probe capable of measuring the complex permittivity on liquids using the MegiQ VNA, which is available in the School of Engineering of the University of Cuenca. First, the ENA Keysight Technology equipment, available in ARCOTEL, was used to do measurements and to have a global idea about the measurement process using the open-ended coaxial probe method. Later, the design and implementation of the probe and three mathematical models that relate to the permittivity with the reflection coefficient are described according a little bibliographic and theoretical review about the propagation of electromagnetic waves in the transmission lines and previous experiments on the permittivity measurement using similar methods. The reference data is used for the selection of the analyzed liquids (water, butanol, ethanol, methanol, propan-1-ol, propan-2-ol), which were arranged by the Chemical engineering lab of the University of Cuenca. A second task described in this thesis is the conversion and registry of the measurement of the reflection coefficient of each liquid. When comparing obtained results with theorical data, the following parameters were defined: the proper mathematical model (Capacitive Model), reference liquid (propan-1-ol), and analysis frequency range (500 – 2500 MHz). Finally, after performing data adjustment, the results that evaluate precision and accuracy of the probe according the average and standard deviation of the error rate produced in repetitive measurements on each liquid (exactly 10 measurements) are exposed. The probe has a margin of error of 15% and a degree of accuracy of 3-6% in most of the frequencies analyzed.