Permittivity models for determination of moisture content in Hevea Rubber Latex

The commercial open-ended coaxial probe (Agilent 85070E) is the most commonly used sensor to determine the permittivity of wet materials. This paper extends the usability and applicability of the sensor to the estimation of moisture content in Hevea Rubber Latex. The dielectric constant and loss factor were measured using the commercial probe whilst the moisture contents were obtained using the standard oven drying method. Comparison results were obtained between the different dielectric models to predict moisture content in latex. Both the dielectric constant and the loss factor of rubber latex linearly increased with moisture content at all selected frequencies. Calibration equations were established to relate both the dielectric constant and the loss factor with moisture content. These equations were used to predict moisture content in Hevea latex from measured values of the dielectric constant and the loss factor. The lowest mean relative error between actual and predicted moisture contents was 0.02 at 1 GHz when using the Cole-Cole dielectric constant calibration equation.