GB555211A - Apparatus for electrically determining the moisture content of granular or powdery materials - Google Patents

Abstract

555,211. Inductance capacitance and powerfactor measurements determining physical qualities of material. MARCONI INSTRUMENTS, Ltd., and BARTLEY, W. B. Feb. 6, 1942, No. 1611. [Class 37] The moisture content of a given volume of granular or powdery substance such as grains of wheat is determined by measuring the electrical properties such as the dielectric constant or the power factor and automatically compensating for the change in density that occurs with change in moisture content. Four condensers a, a<SP>1</SP>, a<SP>11</SP>, a<SP>111</SP>, and a variable resistor a<SP>1111</SP> are arranged to form a Wheatstone bridge. Across the condenser a<SP>1</SP> is connected a reactor, shown as a condenser B consisting of a container b and an electrode b<SP>1</SP>, the substance under test being placed within the container to form the dielectric of the condenser. The condenser a is adjusted by means of a dial e<SP>1</SP> until balance is obtained. The container b with its contents is then placed on the arm c of a spring balance and thereby moves a cursor e in accordance with the weight. The scale is calibrated in terms of dielectric constant and the scale reading indicated by the cursor is corrected for the weight of the substance relative to the given volume. Alternatively the weighing means may operate an auxiliary control, such as a small variable air condenser, so that the measuring circuit is adjusted to read the true value.