Compact Multifunctional Five-Wire Line-Based Microwave Sensor for Volumetric Characterization of Liquids

A new microwave sensor system with a five-wire line configuration is developed for volumetric characterization of liquids. Compared with the existing permittivity-based evaluation methods, the sensor is low profile, low-cost, submersible, easy to fabricate and implement (can be inserted into a container through a small access). An analytical model is proposed for accurate permittivity determination, and the effects of the line length and frequency range on the signals are thoroughly studied for optimal setting. The accuracy of the sensor is verified with standard liquids of known permittivity. From the measurement of honey and alcoholic drinks, explicit relationships are found between the permittivity and the constituent content, thereby facilitating liquid discrimination. The potential for the detection of liquid stacking and level change is well demonstrated in the evaluation of oil samples. The sensor offers an alternative solution to assessment of a wide range of liquids in food, oil, agricultural and bio-sensing applications.