Design and performance of a capacitor sensor and impedance analyzer for nondestructive moisture content determination

Abstract

In this work, the design and performance of a low-cost impedance analyzer, called the CI Meter, that was assembled and calibrated to measure impedance and phase angles at 1, 5 and 9 MHz is given. A cylindrical sample holder with a single set of parallel-plate electrodes embedded inside along its length that can hold samples (100–150 g) of peanut pods (in-shell peanuts) was built and used with this instrument. The measured values of impedance and phase angle with this experimental setup were used in an empirical equation to obtain the average moisture content values of peanut samples with moisture contents in the range of 6–23%. The moisture content values determined by this system and a commercial impedance meter were compared with those obtained by a standard method. For over 90% of the samples tested in the moisture range between 6 and 23% the moisture content values were found to be within 1% of the standard values for both systems. Ability to determine the average moisture content of in-shell peanuts without shelling and cleaning them, with a low-cost instrument, will be of considerable use in the peanut industry. This method could be extended to other types of in-shell nuts.