Developing and testing of a cylindrical dielectric sensor for measuring sugar concentration of sugar beet syrup

Continuous (on-line) measuring and monitoring of sugar concentration of sugar beet syrup at different stages of cooking and concentrating processes is one of the fundamental needs of sugar industry. In this study, a cylindrical dielectric sensor was developed and evaluated for measuring the sugar concentration of sugar beet syrup in terms of %Brix. The sensor consists of a cylindrical steel tube and a central core as the capacitor electrodes connected to function generator and spectrum analyzer by coaxial cable. For the laboratory tests, sugar beet syrups at five different concentrations of sugar (i.e. %Brix of 26.5, 37.9, 48.7, 54.1 and 62) were tested using the sensor where frequency was swept between 0-150 MHz. Amplitude-frequency spectra at different %Brix were further analyzed. The results showed strong positive correlations between the first (R2= 0.99) and second (R2= 0.98) resonance frequency and %Brix. Calculated dielectric constants decreased with increasing %Brix of the syrup samples. It was concluded that the dielectric sensor is a promising instrument for measuring the %Brix of sugar beet syrup. The development of this sensor for online measurement of sugar concentration in sugar factory is recommended.