Mathematical Model of a High-Frequency Hygrometer for Cotton Seeds Based on Substitution Circuits

This is a review of high-frequency methods for measuring and controlling the humidity of various materials. The moisture of cotton seeds is a major factor affecting their qualitative and quantitative characteristics in technologies for their storage, transport, and processing. Thus, direct humidity measurements of cotton seeds during processing is an important problem. A mathematical model of a high-frequency hygrometer for cotton seeds is constructed in which the test material is represented as a complicated dielectric in an electric field. A substitution circuit containing a capacitance between electrodes is proposed, along with capacitances and resistances corresponding to different forms of polarization. Four variants of the substitution circuit are examined which approximately describe the dependence of the tangent of the dielectric loss angle on the frequency of the electromagnetic field. It is shown that the simplest parallel two-component RC substitution circuit corresponds most closely to the actual object of measurement at frequencies of 10⁵–10⁸ Hz.