An Improved Microwave Sensor for Qualitative Assessment of Recycled Cooking Oils
An improved planar microwave sensor comprising a resistor-embedded top microstrip line and a ground etched complementary split-ring resonator (CSRR) is presented to assess the quality of recycled cooking oils. The proposed sensor designed on a 1.6 mm Taconic substrate (εr=2.2) exhibits a reasonably higher value of sensitivity and an improved quality factor, thereby facilitating the detection of even slight variations in electrical and chemical properties of low-loss dielectric samples. The enhanced performance of the proposed sensor is attributed to incorporating a specific value of the lumped resistor on the top side of a microstrip line, which helps in coupling the maximum electric field to the CSRR and providing an extreme improvement in the S21 notch (-50 dB) near resonance. The proposed sensor is designed and simulated using the full wave simulator, the CST MWS. The equivalent circuit model is developed using the ADS to understand the behavior of the circuit in detail. An analytical formulation is implemented using MATLAB, which provides a definite relationship between the small value of the resistor connected on the top of the microstrip line, and the S21 value near resonance. After optimizing various parameters of the sensor including the lumped resistor, it is fabricated and tested. Several fresh and recycled cooking oil samples are measured, and it is observed that their acid values get degraded from 1.5 to even 9.4 indicating the toxic nature of the recycled oils and their adverse effect on human health. The acid value of the oil samples in the present situation is obtained under a controlled chemical environment by developing an empirical relationship between this parameter and the normalized frequency and the S21 notch. The proposed sensor provides substantially high sensitivity (fractional sensitivity of 9.5%) for a unit change in oil rancidity in terms of frequency (~25 MHz/mgKOHgm-1) and S21 notch (~ 3.33 dB/mgKOHgm-1).
Email Address of Submitting Authorapala@iitk.ac.in
ORCID of Submitting Author0000-0001-5970-7682
Submitting Author's InstitutionIndian Institute of Technology Kanpur
Submitting Author's Country