Impedimetric Sensor System for Edible Oil Quality Assessment

The repeated usage of frying oil is hazardous due to the degradation caused by chemical reactions, which happen while heating. The total polar compounds and the free fatty acids are the main two chemical parameters affected by frying. These parameters increase significantly with the use of oil for frying and are reported as reasons for causing serious illnesses like heart diseases. For this purpose, sensor systems for oil quality assessment are necessary. In fact, changes of the composition due to frying leads to variation of its dielectric parameters. This can be measured using a capacitive sensor and the measurement of its impedance change. The main challenge thereby is that the impedance changes are very small and stray capacitances have a big influence on the measurements. In this context, this work proposes a sensor system with high accuracy able to detect the small changes that occur in the resistance and capacitance under influence of stry capacitances. Theoretical and simulation studies are carried out for different cap acitive sensors as well as meas urement procedures of its cornp lex imp edance. The sensor should provide a high sensitivity to relative perrnittivity and the electrical conductiv ity, and at the same time a small size and a high reproducibility. Interdigital electrodes sensor with a suitable design fulfils all these requirements. A deep consideration of stray capacitances is needed to realize an accurate sensor system. For t hese reasons, the design of the measurement circuit is crucial within this work. We propose, a measurernent circuit based on a combinat ion of the method of capacitance to voltage conversion and the phase shift measurement method. By cornbining both rnethods together it is possible to rneasure accurate ly the complex irnpedance of edible oil. Experimental results show that measurement systern is capable to detect small changes of dielectric parameters, which are correlated to the chemical parameters.

Level thesis:degree_level

thesis.doctoral

Grantor dc:publisher

Technische Universität Chemnitz

Year

2019

Author dc:creator

• Fendri, Ahmed

Contributors dc:contributor

• Kanoun, Olfa
• Ghariani, Hamadi
• Thomas, Ulrike
• Derbel, Faouzi

• Polare Komponenten
• freie Fettsäuren
• dielektrische Parameter
• Widerstand
• parasitäre Kapazitäten
• komplexe Impedanz
• interdigitale Elektroden
• relative Permittivität
• Polar compounds
• free fatty acids
• dielectric parameters
• Capacitance
• resistance
• capacitive sensor
• parasitic capacitances
• complex impedance
• interdigital electrodes
• relative permittivity
• electrical conductivity