Hygrometer for use with cereal grains - measures permittivity and includes capacitor with flat internal plate and parallelepiped external plate

摘要

The hygrometer for cereal grains and other similar loose material operates by measuring the permittivity of the moist grains and comprises a measurement capacitor between whose plates the grains are placed and there is a means of measuring the reactance of the capacitor system at a known frequency. The capacitor (3) has an external plate in the form of a parallel epiped cavity with a base which is approximately horizontal and a flat internal plate (32) at equal distances from the two lateral faces of the external plate. One or more of the plates is covered with an electrically insulating coating opposite the other plate. Reactance is measured using a sinusoidal signal generator (1) connected to the capacitor by a variable capacitor (2) and a voltmeter device (6) across the terminals of the measurement capacitor (3).