Larry D Hendrickson

US Patent:

20130200905, Aug 8, 2013

Filed:

Feb 3, 2012

Appl. No.:

13/365388

Inventors:

Michael L. Rhodes - Richfield MN, US
Clayton S. Morton - Elkton MD, US
James A. Chambers - Hawthorn Wds IL, US
Graeme L. Jarvis - Marblehead MA, US
Larry L. Hendrickson - Savoy IL, US

International Classification:

G01R 27/26

US Classification:

324667

Abstract:

A capacitance-based moisture sensor may include a sleeve having an internal cavity, a container filled with soil or other material inserted into the internal cavity, and a pair of ring-shaped conductive bands around the exterior of the sleeve forming a capacitor and providing a frequency output. The rings positioned around a perimeter of the sleeve may be connected to a fixed inductor to form an oscillator with a variable frequency output. The sensor may be calibrated from the frequency output for each of a plurality of substances, measuring the volumetric water content for saturation of the material, and determining at least one fitting constant in an equation wherein volumetric water content is a function of the frequency output and a plurality of fitting constants.