Dielectric properties sensor and its application to biofuels

Biofuel characterization using electrical measurements is a promising alternative to conventional techniques, particularly given the increasing use of radio frequency and microwave processing in this field. Accurate measurement of electrical properties, such as permittivity and conductivity, is critical for process control and quality assurance. However, commercially available sensors are often expensive and not fully suited for biofuel applications. This paper presents a novel, low-cost sensor for measuring the electrical properties of liquid biofuels, which is robust and highly accurate for industrial use. The sensor operates at frequencies of up to 60 MHz, including the 13.56, 27.12, and 40.68 MHz industrial, scientific, and medical bands, enabling the characterization of a wide range of biofuels, from low-loss dielectrics to highly polar and conductive liquids. The sensor performance is demonstrated by its high accuracy: a relative uncertainty of 2% for permittivity and 1% for conductivity. We demonstrate its use in two key applications: the accurate verification of commercial gasoline/bioethanol and diesel/biodiesel blends, and the real-time monitoring of electrical properties during biodiesel production via transesterification.