Miniaturized nondestructive microwave sensor for chickpea moisture measurement

A miniaturized microstrip ring resonator (MRR) 1 in.x1 in. resonating at f( ro)=10.27 GHz was used as a nondestructive moisture sensor for chickpea ker nels (Cicer arietinum L.) for ease in loading and unloading. The change in the resonant frequency (Delta f(r)) of the MRR is a measure of the amount o f moisture in the overlaid kernel. The percentage of moisture (M) was varie d from 0% (dry) to similar to 50% (fully soaked) calculated on a wet weight basis. Delta f(r) increased with M, although not linearly. Three regions w ere observed in the sensitivity curve. The first region extended from 0%-12 %, the central region from 12%-43%, and the saturation region from 43%-50% in moisture content. In the central region the observed Delta f(r) was 574 MHz, whereas in the first and third regions it was 44 and 55 MHz, respectiv ely. The regions in the sensitivity curves indicate different dominant phen omena. A small scatter was observed in the first region, which increased wi th the increasing percent of moisture content. (C) 1999 American Institute of Physics. [S0034-6748(99)04207-0].